WO2007052375A1 - Method for controlling gas supply mechanism for respirator and controller - Google Patents

Abstract

A method for controlling a respirator having a gas supply mechanism controlled with a stability having an increased margin. The flow F of an assist gas is measured, and an estimated flow ^F of the assist gas is determined by an observer (54). The flow difference F between the measured flow F and the estimated flow ^F is determined. Information on the spontaneous respiration pressure Pmus of a patient is collected, and a target pressure Pin to control the gas supply mechanism (20) is computed from the information. By thus computing the target pressure Pin from the flow difference F and adequately selecting a parameter by a regulation transfer function, the margin of the stability limit of the entire system (14) can be increased. Hence, even if the actual entire system varies, a run-away hardly occurs. Compared to the conventional PAV type, the assist response can be improved.

Description

 Specification

 Method and apparatus for controlling gas supply mechanism for ventilator

 Technical field

 The present invention relates to a control device and a control method for a gas supply mechanism used for a ventilator.

 Background art

 [0002] Proportional Assist Ventilation (Proportional Assist Ventilation, abbreviated PAV method) is a method of controlling the ventilator's gas supply mechanism during the inspiratory period when patients breathe spontaneously .

 FIG. 22 is a block diagram showing the entire system 5 including a prior art ventilator 1 and a patient 2. A ventilator 1 that realizes the PAV method includes a gas supply mechanism 3 and a control device 4 that controls the gas supply mechanism 3. The control device 4 detects the flow rate of the support gas, and determines the discharge pressure of the gas supply mechanism 3 based on the detected flow rate.

 The control device 4 calculates the first calculated value (K * F) obtained by multiplying the flow rate F of the assist gas by the flow rate gain K.

 fa fa

, Second gain of volume gain K multiplied by volume V of support gas delivered into the patient's lungs

 va

 (K 'FZs) and add the first calculation value (K * F) and the second calculation value (K' FZs) to obtain va fa va

 Calculate the target pressure Pin. The flow gain K is the estimated airway resistance "

 fa

 The volume gain K is calculated by multiplying the estimated lung elastance “E” by the assist rate.

 vg

 Multiplyed value. Here, let A be the assist rate when R = R and "E = E".

 The control device 4 gives a signal representing the calculated target pressure Pin to the gas supply mechanism 3. The gas supply mechanism 3 to which the signal representing the target pressure Pin is given discharges the support gas at the support pressure Pvent based on the target pressure Pin. Appropriate flow gain K and volume gain K

 By setting to fa va, the gas supply mechanism 3 gives a support pressure Pvent that is proportionally increased to the patient's spontaneous breathing pressure Pmus (see, for example, Japanese Patent Publication No. 2714288).

FIG. 23 is a graph showing the relationship between the ventilation volume Vmus during spontaneous breathing and the ideal ventilation volume Vast during assist breathing in the entire system 5 of the prior art. Support pressure Pvent is spontaneous Amplification is performed at an amplification factor of 1 / (1 A) times that of the spontaneous breathing pressure Pmus according to the time change of the breathing pressure Pmus. As a result, the ventilation volume Vast during the assisted breathing by the ventilator is amplified to 1 / (1-A) times the ventilation volume Vmus by the spontaneous breathing alone.

 In the above-described prior art, it is necessary to determine the flow rate gain K and the volume gain K after accurately determining the airway resistance “R and lung elastance” E of the patient. There

 fa fg

As another conventional technique, a configuration for determining a patient's airway resistance R and pulmonary elastance E is disclosed (see, for example, Japanese Patent Publication No. 11-502755).

 The entire prior art system 5 supplies support gas to the patient at a pressure (Pvent + Pmus) calculated by adding the support pressure Pvent and the spontaneous breathing pressure Pmus in a positive feedback configuration. In the positive feedback configuration, the entire system may become unstable, and the assist pressure Pvent may amplify without converging, so-called “runaway” may occur.

 For example, a runaway can be used if the flow gain K and volume gain K are not appropriate.

 fa va

This may occur when there is an excessive delay from the time when the reference pressure pin is input until the gas supply mechanism 3 operates, when the patient's condition fluctuates, or when other disturbances are applied. When runaway occurs, the pressure of the support gas becomes excessive, which may damage the patient's lungs and airways. In the conventional technology, the assist must be forcibly stopped. The reason why runaway tends to occur is that the transient response of the entire system 5 of the conventional technology is small and the transient response tends to become unstable. If the stability margin of the entire system 5 is small, even if the entire system is slightly changed, the stability limit may be exceeded and runaway may occur. In addition, it is necessary to set the flow gain K and volume gain K fa va so that the entire system 5 does not become unstable, so the degree of freedom in gain selection is low and it is difficult to adjust the appropriate gain. There's a problem.

Disclosure of the invention

 Accordingly, an object of the present invention is to provide a control device and method for a gas supply mechanism of a ventilator that can increase the stability margin in the entire system including the ventilator and a patient.

In response to a signal representing the target pressure Pin, the present invention applies a support gas containing oxygen to the support pressure. With the power Pvent, the control device that controls the gas supply mechanism for the ventilator that supplies the patient's airway via the inspiratory line,

 A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,

 A delay compensation means for calculating the output according to a predetermined adjustment transfer function capable of parameter adjustment as a delay compensation pressure “Pm” with the target pressure Pin as an input;

 In response to the lag compensation pressure 'Pm calculated by the lag compensation means, the pulsation support pressure "Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimating means for calculating the flow rate of the support gas as an estimated flow rate "F, a flow rate difference detected between the flow rate F detected by the flow rate detecting means, and an estimated flow rate F calculated by the flow rate estimating means" F Computing means;

 In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. It is a control device of a gas supply mechanism characterized by including. According to the present invention, the flow rate detection means detects the support gas flow rate F, and the flow rate estimation means calculates the support gas estimated flow rate 'F. Detected support gas flow rate F is the force that changes depending on the patient's spontaneous breathing pressure Pmus Estimated support gas flow rate F is not affected by the patient's spontaneous breathing pressure Pmus. By obtaining the flow rate deviation AF from the flow rate F and the estimated assist gas flow rate F, information on the patient's spontaneous breathing pressure Pmus can be obtained. Here, the spontaneous breathing pressure Pmus is a value obtained by converting the respiratory effort, which is the force a patient spends on breathing, into a pressure, and an accurate value cannot be measured unless a special method is used. In the present invention, the spontaneous expiratory pressure Pmus that may be generated by breathing effort is virtually determined based on the flow rate deviation A F without using a special method.

The control amount calculation means calculates a target pressure Pin for controlling the gas supply mechanism in response to the flow rate deviation AF. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure P mus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, a support corresponding to the spontaneous breathing pressure Pmus that changes sequentially is provided. Supporting pressure With Pvent, supporting gas can be supplied to the patient's airways.

 Further, by calculating the target pressure Pin based on the flow rate deviation AF, the patient and the ventilator can be compared with the prior art that calculates the target pressure Pin based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to cause the divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced.

 In the present invention, the delay compensation means calculates the delay compensation pressure “Pm” according to the adjustment transfer function based on the target pressure Pin. The flow rate estimation means calculates the delay compensation pressure calculated by the delay compensation means. Calculate the estimated flow F based on Pm.In this case, by adjusting the meter of the adjustment transfer function, the control characteristics of the entire system including the ventilator and the patient can be adjusted. Even when the organ model is inaccurate, it is possible to make it difficult to achieve a positive feedback configuration for the entire system, thereby reducing the occurrence of runaway water and making the actual respiratory organ state relative to the respiratory organ model. Even if it fluctuates, the support pressure Pvent can be stably amplified proportionally.

For example, by appropriately selecting the parameters of the adjustment transfer function, the responsiveness of the support pressure Pv ent can be improved, and the support pressure Pvent can be amplified in proportion to the spontaneous breathing pressure Pmus with high accuracy. It is possible to suppress an asynchronous state in which the inhalation period in which the patient sucks the support gas and the supply period in which the gas supply mechanism supplies the support gas to the patient's airway are shifted. In addition, by appropriately selecting the parameters of the adjustment transfer function, it is possible to prevent the support pressure Pvent from becoming oscillating, and so-called robust stability can be improved. In this way, the parameters of the adjustment transfer function can be appropriately selected, so that the responsiveness and robustness of the support pressure Pvent regardless of the amplification factor of the support pressure Pvent and the accuracy of the respiratory organ model. Stability and Support pressure Pvent can be amplified in proportion to accuracy. As a result, the load imposed on the patient by the ventilator can be reduced.

 Further, the present invention is characterized in that the adjustment transfer function includes a control element approximating a transfer function of a gas supply mechanism actually measured with a target pressure Pin as an input and an assist pressure Pvent as an output.

 According to the present invention, the adjustment transfer function has a control element approximating the transfer function of the gas supply mechanism, so that the support pressure Pvent at which the gas supply mechanism discharges the support gas after the target pressure Pin is given. The delay compensation pressure "Pm can be set according to the time change of the pressure. By this, the value obtained by dividing the adjustment transfer function by the transfer function of the gas supply mechanism can be made close to 1, and the support pressure Pmus As for the amplification factor of the support pressure for Pvent, the difference between the amplification factor set by the control amount calculation means and the actual amplification factor can be reduced.

 In addition, the present invention controls a gas supply mechanism for a ventilator that supplies a support gas containing oxygen to a patient's airway via an inspiratory line at a support pressure Pvent in response to a signal representing a target pressure Pin. To the control device that

 A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,

 A delay compensation means for calculating an output according to a predetermined adjustment transfer function as a delay compensation pressure 'Pm with the target pressure Pin as an input;

 In response to the lag compensation pressure "Pm calculated by the lag compensation means, the pulsation assist pressure" Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimating means for calculating the flow rate of the support gas as an estimated flow rate "F, a flow rate difference detected between the flow rate F detected by the flow rate detecting means, and an estimated flow rate F calculated by the flow rate estimating means" F Computing means;

 In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. Including

The adjustment transfer function includes a first-order lag element, and the temporary delay element The time constant Tm is a control device for a gas supply mechanism characterized in that the time constant Tm is set larger (Tm> Tc) than a time constant Tc approximating a first-order lag element included in the transfer function of the gas supply mechanism.

According to the present invention, the flow rate detection means detects the support gas flow rate F, and the flow rate estimation means calculates the estimated support gas flow rate F. The detected support gas flow rate F is the patient's spontaneous breathing pressure. The estimated flow rate of the support gas varies depending on the _Pmus "F", which is not affected by the patient's spontaneous breathing pressure Pmus. Therefore, by obtaining the flow rate deviation AF from the detected assist gas flow rate F and the estimated assist gas flow rate F, information on the patient's spontaneous breathing pressure Pmus can be obtained. Is a value obtained by converting the respiratory effort, which is the power a patient spends on breathing, into pressure, and an accurate value cannot be measured unless a special method is used. In response to the flow rate deviation AF, the spontaneous breathing pressure Pmus that is likely to be generated by the breathing effort is virtually determined.

 The control amount calculating means calculates a target pressure Pin for controlling the gas supply mechanism in response to the flow rate deviation A F. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure P mus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, the support gas can be supplied to the patient's respiratory tract with the support pressure Pvent corresponding to the spontaneous breathing pressure Pmus that changes sequentially. .

Further, by calculating the target pressure Pin based on the flow rate deviation AF, the patient and the ventilator can be compared with the prior art that calculates the target pressure Pin based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to cause the divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced. In the present invention, the delay compensation means calculates the delay compensation pressure “Pm” according to the adjustment transfer function based on the target pressure Pin. The flow rate estimation means calculates the delay compensation pressure calculated by the delay compensation means. Calculate the estimated flow rate F based on Pm, in which case the time constant Tm of the first-order lag element constituting the adjustment transfer function is larger than the time constant Tc approximating the first-order lag element included in the gas supply mechanism (Tm > Tc) When the transfer function of the entire system including the ventilator and the patient is expressed in the frequency domain, the differential gain in the high-frequency response part must be approximately expressed in proportion to Tm. Can do.

 Therefore, an increase in the time constant Tm of the transfer function for adjustment corresponds to an increase in the differential gain in the high-frequency response part. Increasing the differential gain in the high-frequency response part can improve the responsiveness of the support pressure Pvent during the patient's inspiration start period. By improving the responsiveness in this way, the support pressure Pvent can be accurately amplified in proportion to the spontaneous breathing pressure Pmus that changes over time, and the asynchronous state between the ventilator and the patient. Can be suppressed. Here, the time constant Tm of the adjustment transfer function is preferably set lower than the value at which the transient response of the support pressure Pvent becomes oscillating. As a result, the burden imposed on the patient by the ventilator can be further reduced. Further, according to the present invention, the adjustment transfer function includes a time delay element, and the time delay element is substantially equal to a time delay Lc approximating the time delay element included in the transfer function of the gas supply mechanism. The same dead time Lm is set.

According to the present invention, the dead time Lm included in the transfer function for adjustment and the dead time Lc included in the transfer function of the gas supply mechanism are set to approximately the same value (Lm Lc or Lm = Lc). When the time constant of the first-order lag element of the transfer function is changed, the stable region can be increased. In other words, it is possible to maintain a stable state and increase the variable time constant. As a result, the time constant can be increased as much as possible within the stable range where the response of the support pressure Pvent does not vibrate or diverge, and the speed response of the support pressure Pvent can be further improved. If the respiratory organ model is not accurate with respect to the actual respiratory organ, even if the amplification factor is large, the dead time Lm included in the adjustment transfer function and the waste time included in the transfer function of the gas supply mechanism Compared to the case where the time Lc is excessively different, the time constant can be increased as much as possible in the stable range, further increasing the responsiveness of the support pressure Pvent. Can be improved.

 In addition, the present invention controls a gas supply mechanism for a ventilator that supplies a support gas containing oxygen to a patient's airway via an inspiratory line at a support pressure Pvent in response to a signal representing a target pressure Pin. To the control device that

 A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,

 A delay compensation means for calculating the output according to a predetermined adjustment transfer function as a delay compensation pressure “Pm” with the target pressure Pin as an input;

 In response to the lag compensation pressure 'Pm calculated by the lag compensation means, the pulsation support pressure "Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimating means for calculating the flow rate of the support gas as an estimated flow rate "F, a flow rate difference detected between the flow rate F detected by the flow rate detecting means, and an estimated flow rate F calculated by the flow rate estimating means" F Computing means;

 In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. Including

 The adjustment transfer function is configured to include a first-order lag element and a time delay element, and the time delay Lm in the time delay element is set as zero. It is a control device.

According to the present invention, the flow rate detection means detects the support gas flow rate F, and the flow rate estimation means calculates the support gas estimated flow rate 'F. The detected support gas flow rate F _varies depending on the patient's spontaneous breathing pressure _Pmus , but the estimated support gas flow rate F is not affected by the patient's spontaneous breathing pressure Pmus. By obtaining the flow rate deviation AF from the estimated support gas flow rate F and the flow rate AF of the assist gas, information on the spontaneous breathing pressure Pmus of the patient can be obtained. Here, the spontaneous breathing pressure Pmus is a value obtained by converting the respiratory effort, which is the force a patient spends on breathing, into a pressure, and an accurate value cannot be measured unless a special method is used. In the present invention, spontaneous breathing that may have occurred due to respiratory effort in response to flow deviation AF without using a special method. Pressure Pmus is virtually determined.

 The control amount calculating means calculates a target pressure Pin for controlling the gas supply mechanism in response to the flow rate deviation A F. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure P mus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, the support gas can be supplied to the patient's respiratory tract with the support pressure Pvent corresponding to the spontaneous breathing pressure Pmus that changes sequentially. .

 Further, by calculating the target pressure Pin based on the flow rate deviation AF, the patient and the ventilator can be compared with the prior art that calculates the target pressure Pin based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to make it difficult for divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced.

In the present invention, the delay compensation means calculates the delay compensation pressure “Pm” according to the adjustment transfer function based on the target pressure Pin. The flow rate estimation means calculates the delay compensation pressure calculated by the delay compensation means. The estimated flow rate F is calculated based on Pm.In this case, the dead time Lm of the dead time element constituting the adjustment transfer function is set to zero, and the first order with the dead time Lm set to zero. By appropriately setting the time constant Tm of the delay element, the stable region can be increased when the time constant of the first-order delay element of the adjustment transfer function is changed. The time constant can be increased as much as possible in a stable range where the response of the support pressure Pvent does not oscillate or diverge, and the speed response of the support pressure Pvent can be increased. Power S If the respiratory organ model is not accurate with respect to the actual respiratory organ, the time constant can be increased as much as possible within the stable range even if the amplification factor is large, and the speed of the support pressure Pvent can be increased. Responsiveness can be further improved and dead time factor By setting the dead time Lm to zero, the parameters required for the adjustment transfer function can be reduced. Compared to adjusting both the dead time Lm and the time constant Tm, the adjustment transfer function is more appropriate. A simple time constant Tm can be obtained easily. For example, the value obtained by calculating the time constant Tm and the dead time Lm in the adjustment transfer function (Tm + Lm) is the time constant Tc approximating the first-order lag element included in the transfer function of the gas supply mechanism and the dead time element Is set to be smaller than the value obtained by adding the approximate dead time Lm (Tc + Lc).

 The time constant Tm of the first-order lag element of the adjustment transfer function is characterized in that an upper limit is set according to an amplification factor for proportionally amplifying the spontaneous breathing pressure Pmus. According to the present invention, when the time constant Tm of the first-order lag element of the adjustment transfer function becomes excessively large and exceeds a predetermined upper limit value, the response of the support pressure Pvent becomes oscillatory. As the amplification factor for proportionally amplifying the spontaneous call suction pressure Pmus increases, the upper limit value decreases. Therefore, the upper limit value of the time constant Tm is determined according to the amplification factor, and the response of the support pressure Pvent becomes oscillatory regardless of the amplification factor by setting the time constant Tm below the upper limit value. Can be prevented.

 The present invention also provides a control of a gas supply mechanism for a ventilator that supplies a support gas containing oxygen at a support pressure Pvent to a patient's airway in response to a signal representing a target pressure Pin. How to do it

 A flow rate detection step for detecting the flow rate F of the support gas flowing through the intake pipe;

 A delay compensation pressure calculation process in which the target pressure Pin is input and the output according to the adjustment transfer function with adjustable parameters is calculated as the delay compensation pressure “Pm”.

 In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;

 A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step;

In response to the flow rate deviation ΔF calculated by the deviation calculation step, the target pressure Pin is And a control amount calculation step of calculating and giving a signal representing the target pressure Pin to the gas supply mechanism.

 According to the present invention, the support gas flow F is detected in the flow detection process, and the support gas estimated flow F is calculated in the flow estimation process. The detected support gas flow F is the patient's spontaneous breathing pressure. The estimated support gas flow rate 'F varies depending on Pmus, but is not affected by the patient's spontaneous exhalation pressure Pmus, so the detected support gas flow rate F and the estimated support gas flow rate F By obtaining the flow rate deviation AF, information on the patient's spontaneous breathing pressure Pmu s can be obtained.

 In the control amount calculation process, a target pressure Pin for controlling the gas supply mechanism is calculated based on the flow rate deviation A F. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure Pmus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, the support gas can be supplied to the patient's airway with the support pressure Pvent corresponding to the spontaneous breathing pressure Pmus that changes sequentially.

 Further, by calculating the target pressure Pin in response to the flow rate deviation, the patient and the ventilator are connected with each other as compared with the conventional technique in which the target pressure Pin is calculated based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to make it difficult for divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced.

In the present invention, in the delay compensation pressure calculation step, the delay compensation pressure “Pm” is calculated according to the adjustment transfer function based on the target pressure Pin. In the flow rate estimation step, the delay compensation calculated in the delay compensation pressure calculation step is calculated. Calculate the estimated flow rate F based on the pressure Pm. In this case, adjust the control characteristics of the entire system including the ventilator and the patient by adjusting the parameters of the adjustment transfer function. Even if the respiratory model is accurate Therefore, the entire system can be configured to have a positive feedback configuration. This reduces runaway and allows the respiratory model to vary with respect to the actual respiratory condition.

, Support pressure Pvent can be amplified stably and proportionally.

 For example, by appropriately selecting the parameters of the adjustment transfer function, the responsiveness of the support pressure Pv ent can be improved, and the support pressure Pvent can be amplified in proportion to the spontaneous breathing pressure Pmus with high accuracy. It is possible to suppress an asynchronous state in which the inhalation period in which the patient sucks the support gas and the supply period in which the gas supply mechanism supplies the support gas to the patient's airway are shifted. In addition, by appropriately selecting the parameters of the adjustment transfer function, it is possible to prevent the support pressure Pvent from becoming oscillating, and so-called robust stability can be improved. In this way, the parameters of the adjustment transfer function can be appropriately selected, so that the responsiveness and robustness of the support pressure Pvent regardless of the amplification factor of the support pressure Pvent and the accuracy of the respiratory organ model. The stability can be improved, and the supporting pressure Pvent can be proportionally amplified with high accuracy. As a result, the load imposed on the patient by the ventilator can be reduced.

 The present invention also provides a control of a gas supply mechanism for a ventilator that supplies a support gas containing oxygen at a support pressure Pvent to a patient's airway in response to a signal representing a target pressure Pin. How to do it

 A flow rate detection step for detecting the flow rate F of the support gas flowing through the intake pipe;

 The target pressure Pin is input, and the delay compensation pressure calculation step for calculating the output according to the predetermined adjustment transfer function as the delay compensation pressure “Pm”;

 In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;

 A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step;

In response to the flow rate deviation ΔF calculated by the deviation calculation step, the target pressure Pin is A control amount calculation step for calculating and providing a signal representing the target pressure Pin to the gas supply mechanism,

 The adjustment transfer function includes a first-order lag element, and a time constant Tm larger than the time constant Tc that approximates the first-order lag element included in the transfer function of the gas supply mechanism is set in the temporary delay element. This is a control method of the gas supply mechanism. According to the present invention, the support gas flow F is detected in the flow detection process, and the support gas estimated flow F is calculated in the flow estimation process. The detected support gas flow F is the patient's spontaneous breathing pressure. The estimated support gas flow rate 'F varies depending on Pmus, but is not affected by the patient's spontaneous exhalation pressure Pmus, so the detected support gas flow rate F and the estimated support gas flow rate F By obtaining the flow rate deviation AF, information on the patient's spontaneous breathing pressure Pmu s can be obtained.

 The control amount calculating means calculates a target pressure Pin for controlling the gas supply mechanism based on the flow rate deviation A F. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure P mus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, the support gas can be supplied to the patient's respiratory tract with the support pressure Pvent corresponding to the spontaneous breathing pressure Pmus that changes sequentially. .

 Further, by calculating the target pressure Pin in response to the flow rate deviation, the patient and the ventilator are connected with each other as compared with the conventional technique in which the target pressure Pin is calculated based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to cause the divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced.

In the present invention, in the delay compensation pressure calculation step, the delay compensation pressure “Pm” is calculated according to the adjustment transfer function based on the target pressure Pin. In the flow rate estimation step, the delay compensation pressure calculation is performed. Based on the delay compensation pressure Pm calculated in the process, the estimated flow rate F is calculated. In this case, the time constant Tm of the first-order lag element constituting the adjustment transfer function is included in the primary supply included in the gas supply mechanism. It is set larger than the time constant Tc approximating the delay element (Tm> Tc) When the transfer function of the entire system including the ventilator and the patient is expressed in the frequency domain, the differential in the high frequency response part The gain can be expressed in a form approximately proportional to Tm, so an increase in the time constant Tm of the adjustment transfer function corresponds to an increase in the differential gain in the high-frequency response part. When the differential gain at the point increases, the responsiveness of the assist pressure Pvent during the patient's inhalation start period can be improved, and by improving the responsiveness in this way, spontaneous changes that change over time can be achieved. For respiratory pressure Pmus Therefore, the support pressure Pvent can be proportionally amplified with high accuracy and the asynchronous state between the ventilator and the patient can be suppressed, where the time constant Tm of the adjustment transfer function is the transient response of the support pressure Pvent. It is preferable to set the value lower than the value that becomes vibrational, which can further reduce the burden of the ventilator on the patient.The present invention responds to a signal representing the target pressure Pin. Then, in the control method of the gas supply mechanism for the ventilator that supplies the support gas containing oxygen with the support pressure Pvent to the patient's airway through the inspiratory line,

 A flow rate detection step for detecting the flow rate F of the support gas flowing through the intake pipe;

 The target pressure Pin is input, and the delay compensation pressure calculation step for calculating the output according to the predetermined adjustment transfer function as the delay compensation pressure “Pm”;

 In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;

 A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step;

In response to the flow rate deviation ΔF calculated by the deviation calculation step, a target pressure Pin is calculated, and a signal representing the target pressure Pin is given to the gas supply mechanism. Including

 The adjustment transfer function is configured to include a first-order lag element and a time delay element, and the time delay Lm in the time delay element is set as zero. This is a control method.

 According to the present invention, the support gas flow F is detected in the flow detection process, and the support gas estimated flow F is calculated in the flow estimation process. The detected support gas flow F is the patient's spontaneous breathing pressure. The estimated support gas flow rate 'F varies depending on Pmus, but is not affected by the patient's spontaneous exhalation pressure Pmus, so the detected support gas flow rate F and the estimated support gas flow rate F By obtaining the flow rate deviation AF, information on the patient's spontaneous breathing pressure Pmu s can be obtained.

 The control amount calculating means calculates a target pressure Pin for controlling the gas supply mechanism based on the flow rate deviation A F. Therefore, the target pressure Pin is also a pressure corresponding to the patient's spontaneous breathing pressure P mus. By supplying a signal representing the target pressure Pin calculated in this way to the gas supply mechanism, the support gas can be supplied to the patient's respiratory tract with the support pressure Pvent corresponding to the spontaneous breathing pressure Pmus that changes sequentially. .

 Further, by calculating the target pressure Pin in response to the flow rate deviation, the patient and the ventilator are connected with each other as compared with the conventional technique in which the target pressure Pin is calculated based only on the detected flow rate F of the assisting gas. The entire system including it can be made a positive feedback configuration, and the margin for the stability limit of the entire system can be increased. If this causes disturbances, there is an excessive time delay in the gas delivery system, the patient's respiratory model cannot be set correctly, the patient's lung and airway conditions change, and the patient's call Even when the suction state changes, it is possible to cause the divergence of the support pressure Pvent, so-called runaway. By providing the support pressure Pvent proportional to the patient's spontaneous breathing pressure Pmus in this way, pressure support according to the patient's breathing timing can be performed, and the burden on the patient can be reduced.

In the present invention, in the delay compensation pressure calculation step, the delay compensation pressure “Pm” is calculated according to the adjustment transfer function based on the target pressure Pin. In the flow rate estimation step, the delay compensation calculated in the delay compensation pressure calculation step is calculated. Calculate the estimated flow rate F based on the pressure "Pm. In this case The dead time Lm of the dead time element constituting the adjustment transfer function is set to zero. When the time constant of the first-order lag element of the adjustment transfer function is changed by appropriately setting the time constant Tm of the first-order lag element while the dead time Lm of the time delay element is zero as described above The stable area can be increased. In other words, it can maintain a stable state and increase the variable time constant. As a result, the time constant can be increased as much as possible in a stable range where the response of the support pressure Pvent does not vibrate or diverge, and the speed response of the support pressure Pvent can be further improved. In addition, if the respiratory organ model is not accurate with respect to the actual respiratory organs, the time constant can be increased as much as possible within the stable range even if the amplification factor is large, and the responsiveness of the support pressure Pvent Can be further improved. Furthermore, by setting the dead time Lm of the dead time element to zero, the parameters required for the adjustment transfer function can be reduced, and the adjustment transmission is compared to the case of adjusting both the dead time Lm and the time constant Tm. An appropriate time constant Tm for the function can be easily obtained. For example, the value obtained by adding the time constant Tm and the dead time Lm in the adjustment transfer function (T m + Lm) is the time constant Tc approximating the first-order lag element included in the transfer function of the gas supply mechanism and the dead time element. It is set smaller than the value obtained by adding the approximate dead time Lm (Tc + Lc).

Brief Description of Drawings

 Objects, features and advantages of the present invention will become more apparent from the following detailed description and drawings.

 FIG. 1 is a block diagram showing a ventilator 17 and a patient 18.

 FIG. 2 is a block diagram specifically showing the entire system 14 according to the embodiment of the present invention. FIG. 3 is a diagram showing the ventilation volume Vmus during spontaneous breathing and the assist breathing in the entire system 14 according to the present invention. It is a graph which shows the relationship with ideal ventilation volume Vast.

FIG. 4 is a block diagram showing the entire system 14 when the improved estimation PAV method is used. FIG. 5 is a block diagram showing the entire system 14 when the estimation PAV method is used. FIG. 6 is a block diagram showing the entire system 14 when the conventional PAV method is used. Figure 7 is a graph showing the experimental results using the improved estimation PAV method.

 Figure 8 is a graph showing the experimental results using the estimated PAV method.

 Figure 9 is a graph showing the experimental results using the conventional PAV method.

 Figure 10 shows the experimental results comparing the support pressure Pvent response waveforms of the improved estimation PAV method and the conventional PAV method.

 Figure 11 shows the experimental results comparing the flow rate F response waveforms of the improved estimation PAV method and the conventional PAV method.

 Figure 12 shows the simulation results showing the response of the support pressure Pvent when the amplification factor for the spontaneous breathing pressure Pmus and the time constant Tm of the adjustment transfer function are changed in the improved estimation PAV method.

 FIG. 13 is a block diagram showing an example of the ventilator 17.

 FIG. 14 is a flowchart showing the operation of the control device body 33.

 FIG. 15 is a graph showing the concept of changes in the evaluation value F of robust stability and rapid response when the time constant Tm of the first-order lag element and the time delay Lm of the time delay element are changed.

 FIG. 16 is a graph showing the support pressure Paw and the ventilation flow rate Qi using the time constant Tm and the dead time Lm constituting the second maximum point M2.

 FIG. 17 is a block diagram showing an entire system 13 according to still another embodiment of the present invention. FIG. 18 is a block diagram showing an entire system 12 according to still another embodiment of the present invention. FIG. 19 is a block diagram showing the entire system 10 of still another embodiment of the present invention. FIG. 20 is a graph for explaining the airway resistance R.

 FIG. 21 is a graph for explaining lung compliance.

 FIG. 22 is a block diagram showing the entire system 5 including a prior art ventilator 1 and a patient 2.

Fig. 23 shows the ventilation volume Vmus and the assist call during spontaneous breathing in the entire system 5 of the prior art. It is a graph which shows the relationship with the ideal ventilation volume Vast at the time of inhalation.

BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a block diagram showing a ventilator 17 and a patient 18. The ventilator 17 includes a gas supply mechanism 20 of a human respirator and a control device 21 that controls the gas supply mechanism 20. The gas supply mechanism 20 supplies a support gas 16 containing oxygen to the patient's airway 15. The support gas 16 is, for example, pressurized air in the atmosphere. The gas supply mechanism 20 is a gas supply means such as a pump and can control the pressure of the assisting gas to be discharged. When the patient 18 performs spontaneous breathing, the gas supply mechanism 20 is controlled during the inspiration period. Proportional assist ventilation method (proportional support ventilation method, Proportional

Assist Ventilation (abbreviated as PAV method). The control device 21 of the present embodiment controls the gas supply mechanism 20 in accordance with the original purpose of the PAV method. The gas supply mechanism 20 supplies the support gas 16 to the patient's airway 15 at the support pressure Pvent proportional to the spontaneous exhalation pressure Pmus. Spontaneous breathing pressure Pmus is a value obtained by converting respiratory effort, which is a force acting from the outside of the lungs caused by movement of respiratory muscles such as the diaphragm, into pressure. In the present embodiment, the support pressure Pvent is treated as being approximately equal to the discharge pressure of the gas supply mechanism 20.

The gas supply mechanism 20 controlled according to the PAV method supplies the support gas 16 to the patient at a higher pressure as the patient 18 sucks the support gas 16 more strongly. Further, as the suction power of the patient 18 becomes weaker, the pressure of the support gas 16 to be supplied is lowered, and the supply of the support gas 16 is stopped when the patient finishes the suction of the support gas. By controlling the gas supply mechanism 20 in this manner, the support gas 16 can be supplied at a pressure corresponding to the respiratory effort of the patient 18, and the burden on the patient 18 in the breathing motion can be reduced.

The control device 21 calculates a target pressure Pin corresponding to the patient's spontaneous breathing pressure Pmus and gives the target pressure Pin to the gas supply mechanism 20. The gas supply mechanism 20 provided with the target pressure Pin supplies the support gas 16 to the patient's airway 15 at the support pressure Pvent corresponding to the patient's spontaneous breathing pressure Pmus. In the embodiment of the present invention, the transfer function to which “(” is attached is , Indicating a transfer function in the Laplace region, a value given with “′” indicates an estimated value or a calculated value, not an actual value, and “s” indicates a Laplace operator.

 The control device 21 includes a flow rate detection means 50, an estimation means 51, a deviation calculation means 52, and a control amount calculation means 53. The flow rate detection means 50 detects the flow rate F of the support gas 16 actually supplied to the patient's airway 15. Hereinafter, the flow rate detected by the flow rate detection means 50 is referred to as a detected flow rate F. The detected flow rate F is a flow rate of gas flowing from the gas supply mechanism 20 through the inspiratory conduit 25, and is approximated to be equal to the flow rate of gas flowing through the patient's airway. Since the detected flow rate F varies depending on the influence of the spontaneous breathing pressure Pmus, it becomes the flow rate of the respiratory system with the spontaneous breathing pressure Pmus applied.

 The flow rate detection means 50 measures the flow rate of the support gas 16 flowing through the intake pipe line 25. The intake pipe 25 is a pipe that leads the support gas 16 to the patient's airway as well as the pressure source force of the gas supply mechanism 20. When the flow rate detecting means 50 detects the flow rate F of the support gas, it gives the detected flow rate F to the deviation calculating means 52. The estimation means 51 has an observer 54 indicating a respiratory organ model that is modeled by simulating a patient's respiratory tract. The observer 54 serves as a flow rate estimating means for calculating the flow rate 'F of the support gas that will be supplied to the patient. Specifically, the observer 54 supports the support gas flowing through the intake pipe 25 when the support gas having a predetermined delay compensation pressure “Pm” is supplied to the intake pipe 25 in the absence of the spontaneous breathing pressure Pmus. Hereinafter, the flow rate estimated by the estimation means 51 is referred to as an estimated flow rate “F”. The estimated flow rate F is the delay compensation pressure “Pm” described later, and is the flow rate of the inhaler system when the assist gas is given to the respiratory system. A signal representing the estimated flow rate “F” is supplied to the deviation calculating means 52.

 The deviation calculating means 52 calculates a flow deviation Δ F that is a value obtained by subtracting the estimated flow rate F from the detected flow F, and gives the calculation result to the controlled variable calculating means 53. The controlled variable calculating means 53 Is given a preset gain (K + K / s) to support pressure Pvent

 FG VG

Calculate the target pressure Pin to generate.

The control amount calculation means 53 gives signals representing the calculated target pressure Pin to the estimation means 51 and the gas supply mechanism 20, respectively. The gas supply mechanism 20 starts from the control amount calculation means 53. A support gas 16 is supplied to the patient's airway 15 at a discharge pressure based on a signal representing a given target pressure Pin, that is, a support pressure Pvent. Further, the estimating means 51 sequentially calculates the estimated flow rate F based on the signal representing the target pressure Pin given from the control amount calculating means 53.

 FIG. 2 is a block diagram specifically showing the entire system 14 according to the embodiment of the present invention. The estimation means 51 further includes a delay compensation unit 55 in addition to the observer 54. The delay compensation unit 55 is used to compensate for delay elements such as a delay element of the gas supply mechanism 20 and a delay element of the air circuit, such as a primary delay element and a dead time element of each component constituting the entire system 14. Provided. The delay compensation unit 55 is a delay compensation unit that calculates an output according to an adjustment transfer function that can be adjusted with a target pressure Pin as an input. The entire system including the ventilator 17 and the patient 18 14 It is provided to improve the control characteristics. The delay compensation unit 55 takes the target pressure Pin as an input, and calculates an output according to an adjustment transfer function with adjustable parameters as the delay compensation pressure Pm. The delay compensation unit 55 gives a signal representing the calculated delay compensation pressure Pm to the observer 54. In the present embodiment, the adjustment transfer function includes a control element approximating the transfer function of the gas supply mechanism 20 that is measured with the target pressure Pin as an input and the support pressure Pvent as an output. Have different parameters for determining the control element.

In the present embodiment, the transfer function of the gas supply mechanism 20 is represented by the product of the first-order lag element Gc (s) and the dead time element ^e_I ^. The adjustment transfer function ^{_{Gm (s) 'e _IJn'}} s also a first-order lag element Gm (s), represented by the product of the dead time element e- L ^{m 's.} The time constant Tm of the first-order lag element of the adjustment transfer function is set to be larger than the time constant Tc of the first-order lag element of the gas supply mechanism 20 (Tm> Tc). Further, the dead time Lm of the adjustment transfer function is set to substantially the same value (Lm Lc or Lm = Lc) as the dead time Lc of the gas supply mechanism 20. In the present invention, “substantially the same” includes the same case.

The observer 54 estimates the estimated flow rate F of the support gas when the support gas is supplied to the airway 15 of the patient 18 with the delay compensation pressure “Pm” based on the respiratory organ model of the patient. The observer 54 includes a subtractor 56, an estimated flow rate calculator 57, a support gas volume calculator 58, and an alveolar pressure calculator 59. The subtractor 56 is supplied with a signal representing the delay compensation pressure Pm from the delay compensator 55 and a signal representing the calculated alveolar pressure 'Palv from the alveolar pressure calculator 59. The subtractor 56 subtracts the calculated alveolar pressure Palv from the delay compensation pressure “Pm” and provides a signal representing the value to the estimated flow rate calculator 57. The calculated alveolar pressure 'Palv will be described later. The estimated flow rate calculator 57 divides the subtracted value subtracted by the subtractor 56 by a preset estimated airway resistance “R” and calculates the divided value as an estimated flow rate “F”. The estimated flow rate calculator 57 gives a signal representing the calculation result to a deviation calculation means 52 and a support gas volume calculator 58 which will be described later.

 The estimated airway resistance “R” is an estimated value of the patient's airway resistance R, and is preset by, for example, a medical staff. The estimated airway resistance “R” is preset by a detected value detected by the measuring device. You can do it. Further, in the entire system 14 of the present embodiment, the estimated airway resistance “R” does not have to exactly match the actual patient airway resistance R. The support gas volume calculator 58 is configured to supply the support gas. The estimated flow rate “F” calculated by the estimated flow rate calculator 57 is sequentially accumulated from the start time, and the integrated value is calculated as the support gas volume “V. The support gas volume calculator 58 is a so-called integrator. The volume of the support gas calculated by the support gas volume calculator 58 is referred to as “calculation volume” V, and is distinguished from the actual volume V of the support gas.

 The alveolar pressure calculator 59 multiplies the calculated volume V by a preset estimated lung elastance 'E', and calculates the multiplied value as the calculated alveolar pressure 'Palv. The alveolar pressure calculator 59 gives the calculated calculated alveolar pressure 'Palv to the subtractor 56. The calculated alveolar pressure “Palv” is an estimated pressure in the alveoli and is distinguished from the actual alveolar pressure Palv. Estimated lung elastance “E” is the elastance representing the elasticity of the patient's lungs. E is an estimated value, and is preset by, for example, medical personnel. Further, the estimated lung elastance “E” may be set in advance by a detection value detected by a measuring instrument such as a ventilation mechanics inspection apparatus. In the entire system 14 of the present embodiment, “Elastans” E does not have to match the elastance E of the actual patient's lungs exactly.

When the support gas 16 flows through the airway 15, a pressure loss almost proportional to the flow rate F of the support gas 16 occurs, and the pressure in the lung becomes lower than the airway pressure Paw. Airway resistance R This represents the relationship between the flow rate F and pressure loss. The value (F'R) obtained by multiplying the flow rate F of the support gas 16 by the airway resistance R is the pressure loss due to the duct resistance of the airway 15. For example, a typical airway resistance R is 5 to 30 (cmH0) / (liter / second). However, airway resistance R is

 2

It varies greatly depending on the patient's condition.

 When the support gas 16 is supplied into the lung, the alveolar pressure Palv increases almost in proportion to the increase in the volume V of the support gas 16 supplied into the lung. The lung elastance E represents the relationship between the volume V of the support gas 16 and the alveolar pressure Palv. The value (V'E) obtained by multiplying the volume V of the support gas 16 by the lung erastance E is the alveolar pressure Palv. This alveolar pressure Palv is a pressure against the inflow of the support gas 16. For example, typical lung elastance E is 1/20 to 1/50 (milliliter) / (cmH0). However, lung elastance E is

 2

It varies greatly depending on the patient's condition.

 Based on such characteristics of the respiratory tract, the respiratory organ model possessed by the observer 54 is set. The respiratory organ model possessed by the observer 54 is set to the following relationship.

[Number 1]

"P a w-" P a l v = "R-" F (1) j "F--V… (2)

"P a 1 V =" E ■ "V… (3) In other words, the respiratory organ model of the observer 54 is the patient's respiratory organ model when the spontaneous breathing pressure Pmus is zero. The value obtained by subtracting the calculated alveolar pressure 'Palv from the pressure "Pm" is equal to the value obtained by multiplying the estimated flow rate' F and the estimated airway resistance 'R. Also, the value obtained by integrating the estimated flow rate from the support gas supply start time is calculated. The volume is equal to V. The calculated alveolar pressure, Palv, is equal to the estimated lung elastance 'E' multiplied by the calculated volume 'V.

 Therefore, when the calculated airway pressure Paw is an input value and the estimated flow rate “F” is an output value, the transfer function G (s) of the observer 54 is expressed as follows.

 54

G (s) = s / (^ Rs + "E) · '· (4) Where is the estimated airway resistance and is the estimated lung elastance. The other symbols have the same meaning as the symbols shown in the above equation. The respiratory organ model possessed by such an observer 54 is an example of implementation, and may be another model that models the respiratory organ of the patient.

 The control amount calculation means 53 includes a first calculation value (K * A F) obtained by multiplying the flow rate deviation A F calculated by the deviation calculation means 52 by a flow rate gain K that is a preset coefficient, and the support gas.

 FG FG

The second calculated value (K * A FZs) obtained by multiplying the value obtained by sequentially integrating the flow rate deviation ΔF from the supply start time and the volume gain K, which is a preset coefficient, is obtained, and the first calculated value (K-AF )

 VG VG FG

And the second calculated value (K ∆ F / s) to add the target pressure Pi related to the support pressure Pvent

 VG

Calculate n. When the flow deviation A F is an input value and the target pressure Pin is an output value, the transfer function G (s) of the control amount calculation means 53 is shown below.

 53

 G (s) = K + Κ / s --- (5)

 53 FG VG

 Here, K represents the flow gain, and Κ represents the volume gain. For other formulas

 FG VG

Represents the same meaning for the symbols shown in the above formula. For example, the flow gain Κ

 FG

The value obtained by multiplying the determined airway resistance R by the predetermined flow amplification gain i3 (R

 FG'iS)

 FG

The volume gain K is defined as the predetermined volume gain gain for the estimated lung elastance “E”.

 VG

Value ΓΕ ·) multiplied by β. The flow amplification gain and volume amplification

VG VG FG

When the gain β is set to the same value, they are simply referred to as amplification gain β. More

VG

-R = R and "" = 増 幅, the amplification gain is represented by Β. By adjusting the flow rate gain in this way, the rapid response to spontaneous breathing pressure Pmus can be further improved.

FG

The steady gain of the target pressure pin can be adjusted by adjusting the volume gain K.

 VG

You can. The flow gain κ and volume gain κ can be individually adjusted.

 FG VG

In addition, the target pressure Pin can be set by improving the control characteristics such as quick response and damping in combination with the steady gain.

The estimation unit 51, the deviation calculation unit 52, and the control amount calculation unit 53 described above have been individually described for easy understanding, but the transfer functions may be equivalently converted and arranged. Further, the estimation means 51, the deviation calculation means 52, and the control amount calculation means 53 may be realized by a computer capable of numerical calculation executing a predetermined operation program. In one embodiment of the present invention, the transfer function of the gas supply mechanism 20 includes a dead time element. In FIG. 2, the transfer function Gc (s) excluding the dead time element in the transfer function of the gas supply mechanism 20 and the transfer function e- ¹ ^ of the dead time element are individually illustrated. The transfer function G (s) that approximates the characteristics of the gas supply mechanism 20 when the target pressure Pin is the input value and the support pressure Pvent is the output value is shown below.

 20

G (s) = Gc ( _S ) 'e— ^Lc ' ^s — (6)

 20

 Here, Gc (s) represents the transfer function of the gas supply mechanism 20 excluding the dead time element, and means a first-order lag element in the present embodiment. Therefore, Gc (s) indicates lZ (Tc's + l), and Tc is the time constant of the first-order lag element. E indicates the base of natural logarithm, and Lc indicates the time required for the gas supply mechanism 20 to start adjusting the support pressure Pvent after the target pressure Pin is given. The other symbols have the same meaning as the symbols shown in the above equation.

 The adjustment transfer function G (s) of the delay compensation unit 55 when the target pressure Pin is an input value and the delay compensation pressure “Pm” is an output value is shown below.

 55

G (s) = Gm (s) -e " ^Lm ' ^s --- (7)

 55

Here, Gm (s) represents a transfer function excluding the time delay element, and means a first-order lag element in this embodiment. Therefore, Gm (s) indicates l / (Tm's + l), and Tm is the time constant of the first-order lag element. Lm represents the dead time in the adjustment transfer function. Also, in the actual patient's respiratory tract, the spontaneous breathing pressure P mus is given in addition to the support pressure Pvent, which is different from the force observer 54 respiratory organ model. In the embodiment of the present invention, since the pressure loss in the intake pipe is small, the support pressure Pvent as the discharge pressure of the gas supply mechanism 20 and the actual patient airway pressure Paw are treated as being approximated. FIG. 3 is a graph showing the relationship between the spontaneous ventilation rate Vmus and the ideal ventilation rate Vast during assist breathing in the entire system 14 of the present invention. When the transfer functions of the gas supply mechanism 20 and the delay compensation unit 55 are considered to be equal to each other, the support pressure Pvent is (1 + B) times the spontaneous breath pressure Pmus according to the time change of the spontaneous breath pressure Pmus. Amplified with amplification factor. Ventilation is equal to the volume of support gas flowing into the lungs. Where B is as described above The amplification gain j3 when “R = R and“ E = E ”is shown. Ventilation volume Vast during assisted breathing by ventilator 17 of the present embodiment is amplified to (1 + B) times ventilation volume Vmus during spontaneous breathing.

 When the patient's condition switches from the expiration period to the inspiration period, the patient activates respiratory muscles such as the diaphragm. As a result, the ventilation volume Vmus and the spontaneous breathing pressure Pmus during spontaneous breathing gradually increase over time, and gradually decrease when they reach a certain peak value P1. The patient's condition is switched from the inspiration period to the expiration period.

 Normally, during the inspiration period, the patient's ventilation volume Vmus and spontaneous breathing pressure Pmus during spontaneous breathing first draws a gently increasing curve as a waveform over time, and then rapidly increases from the local maximum to the expiration period. Draw a declining curve. However, depending on the patient's condition, the patient's ventilation volume Vmus and spontaneous breathing pressure Pmus fluctuate significantly, and its peak value P1 and inspiratory period W1 vary.

 The gas supply mechanism 20 controlled by the control device 21 discharges the support gas at the support pressure Pvent so that the airway pressure Paw is proportionally amplified based on the amplification gain predetermined for the spontaneous breathing pressure Pmus of the patient. For example, if the inspiratory period W1 when the peak value P1 of the spontaneous breathing pressure Pmus is small and the inspiration period W1 is short, the support pressure Pvent is set so that the period W2 during which the support gas is supplied when the peak value P2 of the airway pressure Paw is small is supplied. Is controlled. Similarly, when the inspiratory period W1 in which the peak value P1 of the spontaneous breathing pressure Pmus is large is long, the support pressure is set so that the period W2 in which the support gas is supplied in which the peak value P2 of the airway pressure Paw is large is supplied. Pvent is controlled.

As described above, according to the control device 21 of the present embodiment, the support pressure Pvent is determined based on the flow rate deviation AF. Detected flow rate F is the force that changes depending on the patient's spontaneous breathing pressure Pmus Estimated flow rate "F is not affected by the patient's spontaneous breathing pressure Pmus. Therefore, the flow deviation is the value obtained by extracting the change in the spontaneous breathing pressure Pmus As a result, the spontaneous breathing pressure Pmus, which is usually difficult to detect, can be estimated, and can be configured as a disturbance observer when the spontaneous breathing pressure Pmus is regarded as a disturbance. By calculating the target pressure Pin according to the flow rate deviation ΔF related to Pmus, the support gas is calculated with the support pressure Pvent that follows the spontaneous breathing pressure Pmus in almost real time. Can be supplied to the patient.

 Hereinafter, the control method of the gas supply mechanism 20 of the present embodiment, which is a method of inputting a signal indicating the delay compensation pressure “Pm calculated using the delay compensation unit 55 to the observer 54, is referred to as an improved estimated PAV method. In contrast, the control method of the gas supply mechanism 20 of the comparative example, in which the assist pressure Pvent is detected by the pressure detection means and the detection result is input to the observer 54 without using the delay compensation unit 55, is estimated PAV The control method of the gas supply mechanism 20 using the transfer function shown in Fig. 20 is called the conventional PAV method.

Fig. 4 is a block diagram showing equivalent conversion of the entire system 14 when the improved estimation PAV method is used. Figure 4 shows the transfer function with the spontaneous breathing pressure Pmus as input and the support pressure Pvent as output. As shown in Fig. 4, the improved estimation PAV method uses [{Gm (s) -e " ^Lm ' ^s

} / {Gc (s) -e} X {R's + E} / 厂 R's + 'E} — When the feedback gain of 1] is positive, a negative feedback configuration is used, and the feedback gain is negative There is a correct return structure.

Thus, even if {R's + E} / {'R's +' E} is less than 1, {Gm (s) -e " ^Lm ' ^s } / {Gc (s) -e" ^Lc ' ^s } X {R's By adjusting the adjustment transfer function Gm (s) 'e— ¹ ^ so that + E} / {'R's + 'E} exceeds ¹ , the negative feedback configuration can be maintained. For example, in this embodiment, even if the airway resistance R and lung elastance E change significantly due to changes in the patient's condition, and {R's + E} / {'R's +' E} is less than 1, positive feedback configuration Can be expanded and the area of the negative feedback configuration can be expanded.

 The entire system 14 using the improved estimation PAV method takes the spontaneous breathing pressure Pmus as the input value, and the sum of the spontaneous breathing pressure Pmus and the support pressure Pvent as the output value. ) Is expressed by the following equation.

 14

 [Equation 2]

 Pmu s + P v

G (s) ₁₄ =

(8) Here, each symbol corresponds to the symbol described above.

 Gc (s) = l, 'R = R,' E = E, K = 'R'B, K =' Ε · Ε

 FG VG

 In the whole system 14 using the V method, the pressure (Pmus + Pvent) obtained by adding the spontaneous breathing pressure Pmus and the support pressure Pvent is amplified to (1 + C) times the spontaneous breathing pressure Pmus. Here, C is expressed by the following equation.

推定気道抵抗" Rおよび推定エラスタンス" Eを正確に推定可能な場合、すなわち（ R's + E)Z('R's + E)が 1となる場合には、 {Gm(s) 'e— ^Lm'^s}Z{Gc(_S)'e— ^L，が 1 より大きい限り、 自発呼吸圧力 Pmusに対して、支援圧力 Pventを必ず負帰還増幅 すること力 Sできる。また {Gm(s) -e~^Lm'^s}/{Gc(s) 'e^_I"'^s}が可及的に 1に近い値と なることによって、予め入力される増幅ゲイン Bから決定される増幅率（1 + B)とほぼ 等しレ、増幅率を得ることができる。

If the estimated airway resistance "R and estimated elastance" E can be accurately estimated, that is, (R's + E) Z ('R's + E) is 1, {Gm (s)' e— ^Lm ' ^{As long as s} } Z {Gc ( _S ) 'e— ^L , is greater than 1, it is possible to always negatively amplify the support pressure Pvent with respect to the spontaneous breathing pressure Pmus. Also, {Gm (s) -e ~ ^Lm ' ^s } / {Gc (s)' e ^_I "' ^s } is as close as possible to 1 and is determined from the amplification gain B input in advance. The gain is almost equal to the gain (1 + B).

Even if the estimated airway resistance 'R and the estimated elastance' E cannot be accurately estimated and (R's + E) / ('R's + E) is less than 1, as described above, Gm (s) • e " ^Lm ' ^s } / {Gc (s) -e" ^Lc-s } X {R's + E} / 厂 R's +' Ε} By adjusting the constant Tm and the dead time Lm, the support pressure Pvent can be stably controlled while maintaining the negative feedback configuration.

Fig. 5 is a block diagram showing equivalent conversion of the entire system 14 when the estimated PAV method is used. In the estimated PAV method, a signal indicating the assist pressure Pvent detected by the pressure detection means is input to the observer 54. In this case, in FIG. 2, when the transfer function of the gas supply mechanism 20 and the adjustment transfer function are equal (Gm (s). _E " ^Lm " ^s = Gc (s) 'e— be able to.

Figure 5 shows the transfer function with the spontaneous breathing pressure Pmus as input and the support pressure Pvent as output. As shown in Fig. 5, the estimated PAV method has a negative feedback configuration when the feedback gain of [{R's + E} / s R's + ~ E} _1] is positive, and the feedback gain is If it is negative, a positive feedback configuration is used. For example, if the airway resistance R and lung elastance E change significantly due to changes in the patient's condition, and {R's + E} / {R's + 'E} is less than 1, a positive feedback configuration will result, System 14 cannot have a negative feedback configuration. The entire system 14 using the estimated PAV method takes the spontaneous respiration pressure Pmus as an input value, and the sum of the spontaneous respiration pressure Pmus and the support pressure Pvent as an output value.

... (10) As described above, when the estimated PAV method is used, if R> R and "E> E, then {R's + E} Z 厂 R's + E} is less than 1 and is positive In contrast, when the improved estimation PAV method of this embodiment is used, {R • s + E} / 厂 R's + E} Even if is less than 1, adjust the parameters of the transfer function for adjustment to {Gm (s) -e ~ ^Lm ' ^s } / {Gc ( _S ) -e " ^Lc-s } By exceeding X {Rs + E} / {"R-s +" E}, the negative feedback configuration can be maintained and the stability S can be improved.

 The estimated airway resistance “R” and the estimated elastance “E” cannot be exactly the same for the actual airway resistance R and the actual elastance E, and in general these values Usually there is a deviation ("R ≠ R, 'Ε ≠ Ε).

 In the overall system 14 using the improved estimation PAV method, the time constant Tm and the dead time Lm, which are the parameters of the adjustment transfer function, are selected appropriately, so that the overall system 5 using the estimation PAV method is obtained. In comparison, the negative feedback configuration area can be further increased, and the positive feedback configuration can be established, so that even if the estimated values 'R and' E are not accurate, the entire system 14 is stable. The margin to become high.

In this way, the improved estimated PAV method has a more stable margin than the estimated PAV method. Even if there is a change in the patient's condition, there is an error in setting the estimated values "R," E, even if the gain is set large, even if a disturbance is applied, the runaway is further increased. It can be made difficult to occur.

 In the present embodiment, the adjustment transfer function has a first-order lag element and a dead time element, which are control elements approximating the transfer function of the gas supply mechanism 20. Therefore, the delay compensation pressure “Pm” can be set according to the change in the support pressure Pvent over time. This makes it possible to bring the value obtained by dividing the adjustment transfer function by the transfer function of the gas supply mechanism closer to 1. As for the amplification factor of the support pressure Pvent relative to the support pressure Pmus, the difference between the amplification factor set by the control amount calculation means as the amplification gain and the actual amplification factor can be reduced.

 Fig. 6 is a block diagram showing the equivalent transformation of the entire system 5 using the conventional PAV method. Figure 6 shows the transfer function with the spontaneous breathing pressure Pmus as input and the support pressure Pvent as output. As shown in Figure 6, the conventional PAV method always has a positive feedback configuration, and if the flow gain K and volume gain K are not appropriate, the support pressure Pvent may diverge.

There is.

 The entire system 5 using the conventional PAV method has the transfer function G (s) when the spontaneous breathing pressure Pmus is the input value and the sum of the spontaneous expiratory pressure Pmus and the support pressure Pvent is the output value.

 5 is expressed by the following equation.

 [Equation 5]

Shi

… (ID In the whole system 5 using the conventional PAV method, the pressure (Pmus + Pvent), which is the sum of the spontaneous breathing pressure Pmus and the support pressure Pvent, is amplified to 1 / (1 _A) times the spontaneous breathing pressure Pmus. In this case, if A> 0 or A> 1, the spontaneous breathing pressure Pmus cannot be amplified. On the other hand, in the improved estimation PAV method, the parameters of the adjustment transfer function are set appropriately even if the estimation of the respiratory organ model is not a little accurate, and the adjustment transfer function is transferred to the transfer function of the gas supply mechanism 20. By changing the function differently, as long as the amplification gain B is greater than 0, it can be amplified. Therefore, the entire system 14 using the improved estimation type PAV method can increase the degree of freedom in gain selection.

 FIG. 7 is a graph showing experimental results using the improved estimation type PAV method according to the present embodiment. FIG. 8 is a graph showing the experimental results using the estimated PAV method as a comparative example. Figure 9 is a graph showing the experimental results using the conventional PAV method. In the experiments shown in Fig. 7 to Fig. 9, measurements were taken when a ventilator was connected to a simulation device that simulated the patient's respiratory organs, and the simulator simulated the respiratory motion of the patient. The measurement result of spontaneous breathing pressure Pmus and support pressure Pvent is shown. In FIG. 7 to FIG. 9, the spontaneous breathing pressure Pmus is indicated by a solid line, the assist pressure Pvent is indicated by a broken line, and the simulator is operated under the same conditions as the patient's inspiratory period and the time change of the spontaneous breathing pressure.

 Table 1 shows the various parameters used in the experiment. As shown in Table 1, the estimated airway resistance R and estimated elastance "E force are set to be the same as the actual airway resistance R and actual elastance E, and the time constant Tm of the adjustment transfer function is the gas supply The experiment is performed assuming that the transfer function time constant Lc is larger than the time constant Tc of the transfer function of mechanism 20 (Tm> Tc), and the dead time Lm of the transfer function for adjustment is the same as the dead time Lc of the transfer function of the gas supply mechanism 20 (Lm = Lc). went.

[table 1]

図 7〜図 9に示すように、改良推定型 PAV法を用いた場合には、従来型 PAV法お よび推定型 PAV法を用いた場合に比べて、吸気開始時期における速応性を向上す ること力 Sでき、支援圧力 Pventを自発呼吸圧力 Pmusの変化に好適に追従させること ができる。具体的には、 自発呼吸圧力' Pmの増加を開始してから立ち上がり時の任 意の時間 W2が経過した場合において、改良推定型 PAV法の支援圧力 Pventの増 加量 11を、推定型1^¥法ぉょび従来型？八¥法の支援圧カ1^61^の増加量 12 , 13よりち大きくすることができる。

As shown in Figs. 7 to 9, when the improved estimation PAV method is used, the quick response at the intake start timing is improved compared to the conventional PAV method and the estimation PAV method. The support pressure Pvent can suitably follow the change in the spontaneous breathing pressure Pmus. Specifically, the spontaneous breathing pressure ' When the desired time W2 has elapsed, increase of the support pressure Pvent of the improved estimated PAV method 11 is estimated to be the estimated 1 ^ ¥ method and the conventional type. The increase in the support pressure 1 ^ 61 ^ of the eight-way method can be made larger than 12, 13.

 If R = R, E = E, and the high-frequency response part in the frequency domain, that is, s is very large, transforming Eq. (8), the transfer function G (s) of the entire system becomes Tm 's Proportionally

 14

Can be approximated.

 In this case, the time constant Tm acts as the differential action of the proportional integral derivative (PID) feedback action, and the differential gain is proportional to Tm / Tc. Therefore, by increasing the time constant Tm and setting Tm> Tc, the differential gain can be increased, and as a result, the rapid response at the rise of the spontaneous breathing pressure Pmus can be improved. In the low-frequency response part, the differential gain decreases due to the influence of parameters other than the time constant Tm. As a result, the differential gain at the end of the intake period can be reduced, and overshoot can be suppressed.

 In addition, due to the improved speed response, the asynchronous periods W31 and W32 when using the estimated PAV method and the improved estimated PAV method are smaller than the asynchronous period W33 when using the conventional PAV method. can do. Here, the asynchronous period is the difference between the time when the spontaneous breathing pressure Pm us begins to decrease and the time when the support pressure Pvent begins to decrease. Furthermore, in the conventional PAV method and the estimated PAV method, the support pressure Pvent increases rapidly from the time when the spontaneous breathing pressure Pmus begins to decrease (X22, X23). On the other hand, in the improved estimated PAV method, the increase in the support pressure Pvent is small from the time when the spontaneous breathing pressure Pmus starts to decrease (X21).

 As described above, the improved estimation PAV method can improve the quick response at the time of the rise of the spontaneous breathing pressure Pmus, shorten the asynchronous period W3, and reduce the increase in the support pressure Pvent after inspiration. Therefore, the burden on the patient by the ventilator can be reduced.

Also, by setting the dead time Lm included in the transfer function for adjustment and the dead time Lc included in the transfer function of the gas supply mechanism to almost the same value (Lm Lc or Lm = Lc), the first-order delay of the transfer function for adjustment If the time constant of the element is changed, the stable area can be increased. it can. In other words, the range of variable time constants can be expanded while maintaining a stable state. As a result, the response time of the support pressure Pvent can be increased as much as possible in a stable range where the response of the support pressure Pvent does not vibrate and diverge, and the speed response of the support pressure Pvent can be further improved.

 Furthermore, in the estimated PAV method, the support pressure Pvent increases while vibrating, whereas in the improved estimated PAV method, the vibration of the support pressure Pvent can be suppressed. This can further reduce the load that the ventilator places on the patient. The improved estimated PAV method also eliminates the need for pressure detection means, reduces manufacturing costs, eliminates failures due to failure of the pressure detection means, and improves the reliability of ventilators. Can be improved.

 Figure 10 shows the experimental results comparing the support pressure Pvent response waveforms of the improved estimation PAV method and the conventional PAV method. Figure 11 shows the experimental results comparing the gas flow F response waveforms for the improved estimation PAV method and the conventional PAV method. Figures 10 and 11 show the experimental results when the dead time Lm of the adjustment transfer function used in the improved estimated PAV method is 10 msec and the time constant Tm is 5, 10, and 20. The values set in Table 1 are used for the time constant Tc and dead time Lc of the gas supply mechanism 20.

 As is clear from Fig. 10, the improved estimation PAV method can improve the speed response compared to the conventional PAV method. In the improved estimation-type PAV method, the speed response is further improved in proportion to the increase of the time constant Tm. If the time constant Tm is excessive, the support pressure P vent becomes oscillating.

 As is clear from Fig. 11, in the improved estimation PAV method, the time constant Tm is increased and the flow rate F of the support gas becomes oscillatory. When the flow rate F of the support gas becomes oscillating, it means that the load on the patient becomes large, which is not preferable. If the response of the assist gas flow F is oscillating, the assist gas flow F is oscillated by decreasing the flow gain K.

 FG

It can be prevented from becoming dynamic. As a result, the amplification factor can be increased without causing the flow rate of the support gas to oscillate.

In addition, the entire system 14 of this embodiment can be configured as a positive feedback configuration and has improved stability, so that an amplification gain with a large degree of freedom in parameter selection is amplified. Or change the flow gain K and volume gain Κ, runaway may occur.

FG VG

It can be adjusted suitably.

 Figure 12 shows the simulation results showing the response of the support pressure Pvent when the amplification factor for the spontaneous breathing pressure Pmus and the time constant Tm of the adjustment transfer function are changed in the improved estimation PAV method. A respiratory model and a model that simulates the respiratory organ model are constructed by a program, and the gain and the time constant Tm of the transfer function for adjustment are changed.

 The simulation results shown in FIG. 12 are similar to the experimental results shown in FIG. Specifically, in the improved estimation PAV method, the time constant Tm can be increased and the quick response can be improved. If the time constant Tm of the adjustment transfer function is excessive, the support pressure Pvent is oscillating. Become.

 When the amplification factor is large, the time constant Tm of the adjustment transfer function that makes the support pressure Pvent oscillate is smaller than when the amplification factor is small. For example, in the simulation result of this implementation, when the amplification factor is 4, the response of the support pressure Pvent becomes oscillating when the time constant Tm is 33 msec, and when the amplification factor is 6 When the time constant Tm of the adjustment transfer function is 25 msec, the response of the support pressure Pvent becomes oscillatory.

 When the time constant Tm of the adjustment transfer function that makes the support pressure Pvent vibrate is the vibration time constant Tml, the vibration time constant Tml generally has the following relationship.

 Amplification gain i3 X (Tml / Tc)> D… （12）

 Here, D is a predetermined constant, and is 6 in the present embodiment. If the time constant Tm of the adjustment transfer function that does not make the support pressure Pven t vibrate is the non-vibration time constant Tm2, the non-vibration time constant Tm2 generally has the following relationship.

 Tm2 <D XTc / Amplification gain / 3 (1) (13)

 In the present embodiment, the time constant Tm of the adjustment transfer function is determined so as to satisfy the equation (13). In other words, the upper limit of the time constant Tm of the first-order lag element of the adjustment transfer function is set according to the amplification factor for proportionally amplifying the spontaneous breathing pressure Pmus. By setting the upper limit time constant Tm that satisfies Eq. (13), the responsiveness that does not cause the response of the support pressure Pvent to become oscillating can be improved as much as possible.

For example, the time constant Tm of the transfer function for adjustment is adopted as the vibration time constant Tml Set to 1/2. In this embodiment, the time constant Tm of the adjustment transfer function is set to 1.5 to 2 times the time constant Tc of the gas supply mechanism 20.

 When pressure detecting means for detecting the supporting pressure Pvent is provided, the estimating means 51 is given a signal indicating the supporting pressure Pvent from the pressure detecting means, and the supporting pressure Pvent is determined to be oscillatory based on the signal. If it is determined, it may be adjusted to lower the time constant Tm of the adjustment transfer function, and if it is determined not to be oscillatory, it may be adjusted to increase the time constant Tm of the adjustment transfer function. This can more reliably prevent the support pressure Pvent from becoming vibrational.

 It is also possible to change the time constant Tm of the adjustment transfer function at the start and end of intake. For example, by increasing the time constant Tm at the start of intake and decreasing the time constant Tm at the end of intake, it is possible to improve the speed response at the start of intake and reduce the overshoot at the end of intake.

 As described above, when the improved estimation type PAV method according to the embodiment of the present invention is used, in the entire system 14, the estimated airway resistance 'R, estimated elastance "for determining the state of the patient's respiratory period" The parameters for adjusting the control characteristics of the entire system are set to be adjustable according to the gain of E and the assist pressure Pvent.

 As numerical values input to the controller, estimated airway resistance 'R and estimated elastance E are values determined according to the patient's condition, and flow gain K and volume gain K are

 VG VG

This means how much assistance is given to the patient and is a medically determined constant according to the pathological condition. In the present embodiment, the control characteristics of the entire system 14 can be improved by further changing the adjustment transfer function meter.

Specifically, the time constant Tm of the primary transfer element of the adjustment transfer function and the dead time Lm of the dead time element can be set. In this case, by setting the time constant Tm and the dead time Lm appropriately to increase the negative feedback area, the stability margin can be improved and it becomes difficult to become unstable. Therefore, even if the conventional PAV method and the estimated PAV method have a positive feedback configuration, the improved estimated PAV method of the present embodiment stabilizes the control system as a negative feedback configuration. Can do. As a result, runaway can be prevented. This realizes a control method for the gas supply mechanism that further reduces the burden on the patient. The power to do S.

 In addition, by appropriately selecting the parameters of the transfer function for adjustment, the responsiveness of the support pressure Pvent can be improved, and the support pressure Pvent can be amplified in proportion to the spontaneous breathing pressure Pmus with high accuracy. Can suppress the asynchronous state between the ventilator and the patient. In addition, the support pressure Pvent can be prevented from vibrating. In this way, the responsiveness and robust stability of the support pressure Pvent can be improved, and the load on the patient can be reduced.

 For example, estimated airway resistance "R and estimated elastance" E force Even if there is a slight deviation from actual airway resistance R and elastance E, the stability margin of the entire system can be increased as described above. Therefore, the entire system 14 is prevented from becoming unstable, and the amplification gains K and K for amplifying the support pressure Pvent can be increased. Especially as mentioned above

 FG VG

Thus, even when 'R> R, E> E, a negative feedback configuration can be achieved, and the stability margin can be set larger. Therefore, even if the airway resistance R and elastance E are not accurately determined, the possibility of runaway is reduced, and the gas supply mechanism 20 can be controlled. In the present embodiment, the parameters of the adjustment transfer function are set to be adjustable. As a result, even if the control characteristics vary for each gas supply mechanism 20, even if the control characteristics change due to changes over time, the control characteristics can be stabilized by adjusting the parameters as appropriate. .

 FIG. 13 is a block diagram showing an example of the ventilator 17. The control device 21 includes a control device main body 33 including a converter, a flow rate detection means 50, an input means 39, a display means 40, and servo amplifiers 47 and 48 which are amplifier circuits. The control device 21 may further include airway pressure detection means 61.

The flow rate detection means 50 converts the flow rate of the gas flowing through the intake pipe 25 of the gas supply mechanism 20 into an electrical signal, and gives the electrical signal to the control device body 33. Input means 39 includes estimated airway resistance IT and estimated elastance E, amplification gain j3, time constant Tm of delay compensation unit 55, and dead time from doctors and nurses or the administrator who manages gas supply mechanism 20. Lm etc. are input. The input means 39 gives a signal indicating the input information to the control device body 33. The display means 40 is an informing means for informing the patient's airway pressure. Based on the display command signal received from the control device main body 33, the display means 40 displays a waveform indicating a temporal change in the spontaneous breathing pressure Pmus of the patient on the display screen.

 The amplifying circuit 48 gives a signal indicating the target pressure Pin calculated by the control device body 33 to the pump actuator 31. The pump actuator 31 controls the pump based on a signal indicating the target pressure Pin, and the control device main body 33, in which the discharge pressure of the gas supply mechanism 20 is feedback controlled, includes the interface 101, the arithmetic unit 102, Temporary storage unit 103 and storage unit 104 are included. The interface 101 receives a signal from the connected flow rate detection means 50 and gives the signal to the calculation unit 102. The storage unit 104 stores a program to be executed by the control device body 33, and the calculation unit 102 reads out and executes the program stored in the storage unit 104, whereby the estimation unit 51, the deviation calculation unit 52, the control unit Quantity calculation means 53 can be realized. Thereby, the control device main body 33 can control the gas supply mechanism 20 described above. The storage unit 104 may be a computer-readable recording medium such as a compact disk. The arithmetic unit 102 is realized by an arithmetic processing circuit such as a CPU, and executes an operation according to an operation program stored in the storage unit 104.

 FIG. 14 is a flowchart showing the operation of the control device body 33. First, in step sO, the control device main body 33 receives parameters such as the estimated airway resistance “R”, the estimated elastance “E”, the transfer function of the gas supply mechanism 20, the flow rate gain K, and the volume gain K in step sO.

 FG VG

When the data is input and the target pressure Pin and the estimated flow rate “F” can be calculated, the process proceeds to step si.

In step si, the control device main body 33 executes the operation of the deviation calculating means 52, and the deviation AF between the estimated flow F obtained from the previously calculated target pressure Pin and the flow F given from the flow detecting means 50 is AF. Is calculated. When the flow rate deviation AF is calculated, proceed to step s2. In step s2, the control device main body 33 executes the operation of the control amount calculation means 53, and calculates the target pressure Pin based on the flow rate deviation. When the target pressure Pin is calculated, a signal representing the target pressure Pin is given to the gas supply mechanism 20, and the process proceeds to step s3. In step s3, the control device main body 33 executes the operation of the estimating means 51, performs the operation corresponding to the delay compensation unit 55 and the observer 54 based on the signal representing the target pressure Pin, and the spontaneous breathing pressure. Calculate the estimated flow rate F that would be delivered to the patient in the absence of Pmus and proceed to step s4.

 In step s4, the control device body 33 determines whether or not a predetermined end condition is satisfied. For example, when the end command is not given by the input means 39, it is determined to continue the control of the gas supply mechanism 20, and the process returns to step si. In step si, the flow rate deviation AF is calculated again using the estimated flow rate “F calculated in step s3” and the flow rate F given from the flow rate detection means 50. In step s4, the control device body 33 is determined in advance. If it is determined that the termination condition is satisfied, the process proceeds to step s5, and the control operation is terminated.

 As described above, the delay compensation unit, the flow rate estimation unit, the deviation calculation unit, and the control amount calculation unit described above may be realized by executing software predetermined by a computer. Further, the gas supply mechanism 20 is not particularly limited as long as the pressure of the assisting gas to be discharged can be controlled by the control device 21 and an intake pipe 25 for guiding the assisting gas to the patient's airway 15 is formed. . For example, the gas supply mechanism 20 may be a ventilator having a bellows type pump as shown in FIG. 13, or may be an artificial respirator that supplies support gas through a pipe.

 The embodiment of the present invention described above is an example of the present invention, and the configuration can be changed within the scope of the invention. For example, the above-described block diagram is merely an example of the present invention, and may be equivalently converted if the same effect can be obtained. Further, the time constant Tm and the dead time Lm of the adjustment transfer function described above are merely examples, and are not limited to these values. For example, the dead time Lm of the transfer function for adjustment and the dead time Lc of the transfer function approximating the gas supply mechanism 20 may be different values. The time constant Tm of the transfer function for adjustment may be smaller than the time constant Tc of the transfer function approximating the gas supply mechanism 20.

Among the adjustment transfer functions set in the delay compensation unit 55, the time constant Tm and the dead time Lm can be adjusted as parameters, and the time is adjusted according to the amplification rate / 3 that amplifies the spontaneous breathing pressure Pmus. An upper limit value of the constant Tm may be set. In addition, among the transfer functions for adjustment set in the delay compensation unit 55, the time constant Tm and the dead time Lm can be adjusted as parameters, and the time constant Tm is larger than the time constant Tc of the gas supply mechanism (Tm> Tc ) May be set. In this case, an upper limit value of the time constant Tm may be set according to the amplification factor for amplifying the spontaneous breathing pressure Pmus.

 Also, among the adjustment transfer functions set in the delay compensation unit 55, the dead time Lm is almost the same as the dead time Lc of the gas supply mechanism (Lm ^ Lc), and the time constant Tm can be adjusted as a meter. Good. In this case, the time constant Tm may be set to be larger than the time constant Tc of the gas supply mechanism (Tm> Tc). Furthermore, the upper limit value of the time constant Tm may be set according to the amplification factor β for amplifying the spontaneous breathing pressure Pmus.

 In the present embodiment, the parameters in the adjustment transfer function can be changed. However, the present invention includes a case in which some or all of the parameters of the adjustment transfer function are fixed. In this case, the adjustment transfer function is determined so that the entire system has a negative feedback configuration. As a result, the same effect as the above-described embodiment can be obtained. In this case, the transfer function for adjustment includes a control element approximating the transfer function of the gas supply mechanism, so that the value obtained by dividing the transfer function for adjustment by the transfer function of the gas supply mechanism can approach 1 and the support pressure Supporting pressure against Pmus Regarding the amplification factor of Pvent, the difference between the amplification factor set by the control amount calculation means and the actual amplification factor can be reduced.

In addition, the time constant Tm of the first-order lag element constituting the adjustment transfer function is set larger (Tm> Tc) than the time constant Tc approximating the first-order lag element included in the gas supply mechanism. As a result, the rapid response can be improved and the asynchronous state can be suppressed. In addition, the support pressure Pvent can be accurately amplified in proportion to the spontaneous breathing pressure Pmus that changes over time. Furthermore, by setting the dead time Lm included in the transfer function for adjustment and the dead time Lc included in the transfer function of the gas supply mechanism to approximately the same value (Lm Lc or Lm = Lc), the first order delay of the transfer function for adjustment When the time constant of the element is changed, the stable area can be increased. In other words, it can maintain a stable state and increase the variable time constant. As a result, the time constant can be increased as much as possible within the stable range where the response of the support pressure Pvent does not vibrate or diverge, and the speed response of the support pressure Pvent can be further improved. The upper limit of the time constant Tm of the transfer function for adjustment is determined based on equation (13) so that the support pressure P vent does not diverge according to the amplification factor of the support pressure P vent determined by the ventilator administrator. It is preferred that As a result, even if the amplification factor is changed, it is possible to prevent the support pressure Pvent from becoming oscillating and improve the responsiveness as much as possible.

In the present embodiment, the adjustment transfer function includes the first-order lag element Gm (s) and the dead time element _e − Lm ′s. However, the present invention is not limited to this. For example, the adjustment transfer function may have a multi-order delay element that approximates the transfer function of the gas supply mechanism with a rational function. In this case, the multi-order delay element Gm (s) of the adjustment transfer function is expressed by the following equation.

[Equation 6]

1 + a, · s + a ₂ · s + a. 's +-s ⁿ "+ a _n ■ s ⁿ Also, the adjustment transfer function may include a proportional element k in the equation (14). In this case, the adjustment transfer function is expressed by the following equation. By setting the elements, the amplification factor can also be set with the adjustment transfer function.

[Equation 7]

1 + as + a ₂ 's ² + a. · S ³ … + a _n-1 -s ⁿ — ¹ + a _n · s ^{n The} proportional factor k may be set to 0.8. Further, the adjustment transfer function may include a dead time element in the above-described equation (14) or (15).

 FIG. 15 is a graph showing the concept of changes in the evaluation value F of robust stability and rapid response when the time constant Tm of the first-order lag element and the time delay Lm of the time delay element are changed. As the evaluation value F, for the control of the support pressure Pvent, a value obtained by evaluating the two controllability of mouth bust stability and rapid response, which are in a trade-off relationship, is adopted. Here, Fig. 15 makes it easy to understand the change in the evaluation value F of robust stability and rapid response when the time constant Tm of the first-order lag element and the time delay Lm of the time delay element are changed. It is used to do this and does not match the actual change state.

As shown in Fig. 15, the time constant Tm, dead time Lm, and evaluation value F are applied to the three-dimensional coordinate axes. When each is set, the patient's respiratory organs were simulated, although there was a deviation from the calculation results by simulation when the entire system using the improved PAV method of the present embodiment shown in Equation (2) was used. It was estimated that there were two points where the evaluation value F had the maximum value, along with the experimental results using the simulator.

 Therefore, by setting the combination of the time constant Tm and the dead time L m constituting the first maximum point Ml or the second maximum point M2 as parameters of the transfer function for adjustment, the robust stability and rapid response are balanced. And each can be made relatively good.

 In the present embodiment, in the vicinity of the first maximum point Ml, the value (Tm + Lm) obtained by adding the time constant Tm and the dead time Lm in the adjustment transfer function is the first order lag included in the transfer function of the gas supply mechanism. It is set smaller than the value obtained by adding the time constant Tc approximating the element and the dead time Lc approximating the dead time element (Tc + Lc).

 In addition, the dead time Lc and the time constant Tc that approximate the dead time element included in the transfer function of the gas supply mechanism are set to Lc = 10 msec and Tc = 24 msec, respectively. Estimated airway resistance R is 20 (cmH0) / (liter / second), and estimated elastance is 1/30 (milliliter) / (cmHO)

 Assuming 2 2 and an amplification factor of four, in the experimental results of this embodiment using the improved PAV method, the dead time Lm of the adjustment transfer function was 4 msec and the time constant Tm was 10 msec. Similarly, in the vicinity of the second maximum point M2, the value (Tm + Lm) obtained by adding the time constant Tm and the dead time Lm in the adjustment transfer function is the primary delay element included in the transfer function of the gas supply mechanism. It is set smaller than the value obtained by adding the approximate time constant Tc and the time delay Lc approximating the time delay element (Tc + Lc). In the vicinity of the second maximum point M2, the dead time Lm included in the adjustment transfer function is set to zero as described above. As described above, the dead time Lc and the time constant Tc approximating the dead time element included in the transfer function of the gas supply mechanism are set to Lc = 10 msec and Tc = 24 msec, respectively. Estimated airway resistance R is 20 (c mH〇) Z (liter / second), and estimated elastance is 1Z30 (milliliter) / (cmH〇).

In this embodiment using the improved PAV method, the dead time Lm of the adjustment transfer function is 0 msec and the time constant Tm is 10 msec. As the time constant Tm constituting the second maximum point M2, a value larger than the time constant Tm constituting the first maximum point Ml is adopted as the time constant Lm is made zero. Here, the combination of the dead time Lm and the time constant Tm changes at the first maximum point Ml as the parameters of the entire system including the patient and the ventilator change. On the other hand, at the second maximum point M2, the value of the time constant Tm varies with the dead time Lm kept at zero even if the parameters shown in Table 1 change.

 In this way, by setting the parameters of the adjustment transfer function to the time constant Tm and dead time Lm that constitute the first maximum point Ml or the second maximum point M2, the time constant of the primary delay element of the adjustment transfer function is changed. In this case, the stable area can be increased. In other words, it can maintain a stable state and increase the variable time constant. As a result, the time constant can be increased as much as possible within a stable range in which the response of the support pressure Pvent does not vibrate or diverge, and the speed response of the support pressure Pvent can be further improved. In addition, if the respiratory organ model is not accurate with respect to the actual respiratory organ, even if the amplification factor is large, the dead time Lm included in the adjustment transfer function and the dead time Lc included in the transfer function of the gas supply mechanism The time constant can be increased as much as possible in the stable range, and the responsiveness of the support pressure Pvent can be further improved.

 Furthermore, for the time constant Tm and dead time Lm that constitute the second maximum point M2, the dead time Lm of the dead time element is set to zero regardless of changes in the parameters of the entire system including the patient and the ventilator. Compared to adjusting both the dead time Lm and the time constant Tm, the appropriate time constant Tm can be calculated manually or by calculation using a computer, etc. Can be requested.

 In this embodiment, the evaluation value F is defined as a linear sum (F = F1 + F2) of the robust stability evaluation value F1 related to robust stability and the rapid response evaluation value F2 related to rapid response. In the present embodiment, the robust stability evaluation value F1 related to robust stability is expressed by equation (16).

[Equation 8]

Fl ^-| S | — ¹ (16) where F1 is a robust stability evaluation value. A is the robust stability evaluation value F1

 1

Is a robust stability weight constant for determining Also multiplied by robust stability A The other term | s | is a value for evaluating the stability margin, and is set as a modular margin in the present embodiment. The modulus margin is expressed by Eq. (17) when the loop transfer function in the entire system including the ventilator and the patient is expressed by L (jω). In other words, in the Nyquist diagram, the vector trajectory of the loop transfer function in the entire system and the stability limit are represented by the closest distance. In the present embodiment, the robust stability evaluation value F1 related to robust stability is determined based on the equations (16) and (17). Yo!

… (17)

 In the present embodiment, the quick response evaluation value F2 related to the quick response is expressed by the equation (18).

[Equation 10]

 Here, F2 is a rapid response evaluation value. A is used to determine the rapid response evaluation value F2.

 2

This is a quick response weight constant. Also, another term (1 / Tr

 2

esp) is a value for evaluating rapid response. In this embodiment, when step response is considered, the value obtained by dividing the support pressure Pvent by the spontaneous breathing pressure Pmus (= Pvent / Pmus) is , Time to reach 0.632 is represented by the inverse of Tresp (1 / Tresp). In the present embodiment, the rapid response evaluation value F2 related to rapid response is determined based on such a relationship, but may be determined based on other evaluation formulas.

 As described above, since robust stability and rapid response are in a trade-off relationship, if the oral robustness is improved, the rapid response decreases. For example, if a comprehensive evaluation value F is obtained that improves robustness by weakening robust stability, the rapid response weight constant A should be made larger than the robust stability weight constant A described above. Makes the robust stability weaker

 1 2

It is possible to obtain a balanced and comprehensive evaluation value with high responsiveness. By appropriately allocating the balance of the weight constants A and A in this way, robust stability and rapid response are achieved. An evaluation value in consideration of the balance can be obtained. In this embodiment, the above-described (

Force determined based on Eqs. 16) to (18) This determination is an example, and according to other arithmetic expressions, a value that combines the evaluation value related to robust stability and the evaluation value related to rapid response is used. As a comprehensive evaluation value.

 When the improved PAV method is used with the time constant Tm and the dead time Lm constituting the first maximum point Ml and the second maximum point M2 obtained in this way, it is more stable than the simple estimation type PAV. As well as improving the stability and responsiveness, it can improve the robust stability and responsiveness compared to the improved PAV method using a randomly selected time constant Tm and dead time Lm. it can.

 Table 2 is a table showing experimental comparison results when the time constant Tm and the dead time Lm constituting the first maximum point Ml and the second maximum point M2 are used. In Table 2, the dead time Lc and the time constant Tc that approximate the dead time element included in the transfer function of the gas supply mechanism are set to Lc = 10 msec and Tc = 24 msec, respectively. Estimated airway resistance R is 20 (cmH O) /

 2

(Liter / second), estimated elastance is 1/30 (milliliter) / (cmH 2 O), and amplification factor

 2

The airway resistance R and pulmonary elastance E were varied using a simulation device. In this case, the two local maximum points Ml and M2 are both the first-order lag included in the transfer function of the gas supply mechanism (Tm + Lm), which is the sum of the time constant T m and the dead time Lm in the adjustment transfer function. It is set smaller than the value obtained by adding the time constant Tc approximating the element and the time delay Lm approximating the time delay element (Tc + Lc).

[Table 2]

As shown in Table 2, in this embodiment, the time constant Tm and the dead time Lm constituting the second maximum point M2 (Lm = 0, Tm = 20) constitute the first maximum point Ml. More robust stability and quick response than using time constant Tm and dead time Lm (Lm = 4, Tm = 10) It can be seen that it has improved. That is, in the present embodiment, robust stability and quick response can be further improved when the dead time Lm is zero.

 FIG. 16 is a graph showing the support pressure Paw and the ventilation flow rate Qi using the time constant Tm and the dead time Lm constituting the second maximum point M2. Figure 16 compares the improved PAV method with the conventional PAV method.

 In Fig. 16, the dead time Lc approximating the dead time element included in the transfer function of the gas supply mechanism and the time constant Tc are set to Lc = 10 msec and Tc = 24 msec, respectively. Also, the airway resistance R and the estimated airway resistance R in the simulated device are 20 (cmH〇)

 2 / (liters / second), and the elastance E and the estimated elastance in the simulator are 1/30 (milliliter) / (cmH O

 2

), The amplification factor was tripled, the time constant Tm of the adjustment transfer function was 20 msec, and the dead time Lm of the adjustment transfer function was Omse c.

 The first set time ΔΤ1, which is the time difference from the time T2 when the patient ends spontaneous inspiration to the time when the ventilation flow Qi transitions to the state before reaching the value Q0 of the time T1 before starting the spontaneous inspiration, is exhaled. Assuming the degree of asynchrony, the first set time ΔΤ 1 in the improved estimation PAV method according to the present embodiment is equal to the first set time in the conventional PAV method new

It can be made smaller than the interval ΔΤ1. This shortens the period of exhaled breath org

Can reduce the load on the patient.

 In addition, the airway pressure Paw can be approximated to a waveform shape amplified by 3 times, which is a predetermined amplification factor of the patient's spontaneous breathing pressure Pmus. Specifically, the improved estimation PAV method can improve the rapid response of the airway pressure Paw to the patient's spontaneous breathing pressure Pmus compared to the conventional PAV method. In addition, the second set time Δ Τ2, which is the time difference from the time T2 when the patient ends spontaneous inspiration to the time when the airway pressure Paw starts to decrease, is also estimated as an exhalation asynchronous degree according to this embodiment. The second set time ΔΤ 2 in the conventional PAV method is smaller than the second set time ΔΤ 2 in the conventional PAV method.

You can power s. This also makes it possible to shorten the period of exhaled breath and reduce the load on the patient.

In the present embodiment, the time constant Tm and the dead time Lm of the adjustment transfer function constituting either the first maximum point Ml or the second maximum point M2 are used in this way. The parameter of the transfer function for use is not limited to this.

 For example, in an evaluation function for obtaining an evaluation value for evaluating stability and rapid response, the extreme values Ml and M2 change depending on whether the stability is weighted or the rapid response is weighted. Therefore, depending on the evaluation function, zero can be adopted as the dead time Lm, and other than zero can be adopted as the dead time Lm. In addition, it is preferable to follow one of the setting criteria described above for the time constant Tm.

 For example, as described above, the time constant Tm of the adjustment transfer function may be larger (Tm> Tc) than the time constant Tc approximating the first-order lag element included in the transfer function of the gas supply mechanism. The dead time Lm of the transfer function is almost the same as the dead time Lc (Lm Lc or Lm = Lc) approximating the dead time element included in the transfer function of the gas supply mechanism. In addition to the determination method described above, the time constant Tm and dead time Lm of the adjustment transfer function may be appropriately determined according to changes in the parameters of the entire system including the patient and the ventilator. Also, other forms of the adjustment transfer function can be used.

 Of the adjustment transfer functions set in the delay compensation unit 55, the dead time Lm may be zero (Lm = 0), and the time constant Tm may be adjustable as a parameter. In this case, the upper limit of the time constant Tm may be set according to the amplification factor that amplifies the spontaneous breathing pressure Pmus. The time constant Tm may be larger than the time constant Tc of the gas supply mechanism (Tm> Tc). Further, the upper limit value of the time constant Tm may be set and adjusted to be larger than the time constant Tc of the gas supply mechanism and adjusted.

 Of the transfer functions for adjustment set in the delay compensation unit 55, the sum of the time constant Tm and the dead time Lm (Tm + Lm) force The time constant Tc of the gas supply mechanism larger than zero and the dead time Lc The time constant Tm and the dead time Lm may be adjustable after setting (0 <(Lm + Tm) ≤ (Lc + Tc)) smaller than the sum (Tc + Lc). Furthermore, an upper limit value of the time constant Tm may be set according to the amplification factor for amplifying the spontaneous breathing pressure Pmus. Also, the sum of the time constant Tm and the dead time Lm (Tm + Lm) The time constant Tm and the time constant Tm within the range smaller than the sum of the time constant Tc and the dead time Lc (Tc + Lc) The dead time Lm may be fixed.

FIG. 17 is a block diagram showing the entire system 13 according to still another embodiment of the present invention. . The entire system 13 shown in FIG. 17 has the same configuration as the entire system 14 shown in FIG. 2 except that a part of the configuration of the estimation means 51 is different. Therefore, the description of the same configuration is omitted, and the reference numerals corresponding to the entire system 14 in FIG.

 The estimation means 51 further includes a detection delay calculator 60. The detection delay calculator 60 has a detection means model modeled by simulating the flow rate detection means 50. In this case, when the estimated flow rate “F” is given from the observer 54, the detection delay calculator 60 calculates the estimated flow rate “F based on the detection delay of the flow rate detection means 50, and the calculation result is sent to the deviation calculation means 52. give. The deviation calculator 52 subtracts the detected flow detected by the flow detector 50 from the estimated flow “F” calculated by the detection delay calculator 60 to calculate the flow deviation AF. The flow rate of the support gas to be supplied to the patient's airway based on the time characteristics from when the flow rate F of the support gas supplied to the patient's airway is detected until the flow rate detection means 50 outputs the detection result F Can be calculated with higher accuracy. Therefore, the asynchronous state can be prevented more reliably.

 FIG. 18 is a block diagram showing the entire system 12 of still another embodiment of the present invention. The entire system 12 shown in FIG. 18 has the same configuration as the entire system 14 shown in FIG. 2 except that a part of the configuration of the estimation means 51 is different. Therefore, the description of the same configuration is omitted, and the reference numerals corresponding to the entire system 14 in FIG.

Instead of the delay compensation unit 55, a pressure detection means 61 is provided. The pressure detection means 61 detects an airway pressure Paw which is a pressure in the patient's airway. Then, the pressure detection means 61 gives the detected airway pressure Paw to the predetermined delay compensation unit 55. The delay compensation unit has an adjustment transfer function for improving the responsiveness of the support pressure P vent. When the airway pressure Paw is given as an input, the delay compensation unit calculates the delay compensation pressure “Pm” and gives the calculated delay compensation pressure “Pm” to the observer 54. Compensation pressure "Pm lag here is have use the symbols as described above, is set to _{{Gm (S) 'e _} Lms} / {Gc (S)' e _ Les}. Even in this case, the above-described The effect can be achieved.

FIG. 19 is a block diagram showing the entire system 10 according to still another embodiment of the present invention. The entire system 10 shown in FIG. 19 is the same as the entire system 14 shown in FIG. 2 except that the estimated airway resistance “R” and the estimated elastance “E” set in the estimating means 51 are different. Have a success. Therefore, the description of the same configuration is omitted, and the reference numerals corresponding to the entire system 14 in FIG.

 FIG. 20 is a graph for explaining the airway resistance R. When the support gas flowing in the airway is laminar, the flow velocity changes linearly in proportion to the airway pressure Paw. In fact, the airway repeats branching and the thickness is not uniform, so the flow of support gas becomes turbulent. Therefore, the estimated airway resistance R is set considering the turbulent resistance.

 The estimated airway resistance “R” set in the estimation means 51 is the first resistance coefficient “R” that is set constant regardless of the flow rate of the support gas, and the support gas calculated by the estimated flow rate calculator.

 T

This is a value obtained by adding the second flow coefficient "K depending on F". 1st resistance coefficient "R and

 T T

And the second resistance coefficient “K” is set to a coefficient according to the patient's airway resistance.

 T

Alternatively, the resistance of the entire respiratory organ including the thorax may be set as the estimated airway resistance “R. The estimated airway resistance R represented by another approximate expression may be used to approximate the airway resistance R. FIG. 21 is a graph for explaining lung compliance. The estimated elastance “E” set in the estimating means 51 is a value based on the assist gas volume “V” calculated by the assist gas volume calculator, and is the reciprocal of lung compliance C. Compliance C increases nonlinearly with the increase of the support gas volume V during the patient's inspiratory period, and has saturation and hysteresis characteristics.

 The alveolar pressure calculator 59 obtains in advance information indicating the relationship between the compliance C and the volume of the support gas, so that even if the case where the compliance is nonlinear is taken into account, the alveolar pressure Palv Can be calculated.

 In this way, the observer has a model of the respiratory tract that becomes non-linear, so that the estimated flow rate “F” can be estimated with higher accuracy. This makes it possible to accurately estimate the spontaneous respiratory pressure Pmus, The support pressure Pvent can be determined according to the estimated spontaneous breathing pressure Pmus.

Estimated airway resistance R and estimated elastance E may be set appropriately by the doctor, but airway resistance R and elastance E measured in advance by a measuring instrument may be used. In addition, airway resistance R calculated by the estimation method disclosed in JP-T-11-502755 And elastance 'E

 The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects, and the scope of the present invention is shown in the scope of claims, and is not limited to the text of the specification. Further, all modifications and changes belonging to the scope of claims are within the scope of the present invention.

Industrial applicability

 According to the present invention, since the parameters of the adjustment transfer function can be adjusted, the entire system including the human respiratory apparatus and the patient can be adjusted so as to increase the area where the negative feedback configuration is formed. By adopting a negative feedback configuration for the entire system, the stability margin can be increased compared to when the entire system has a positive feedback configuration, and the support pressure Pvent can be prevented from diverging. For example, by appropriately selecting the parameters, it is possible to improve the responsiveness of the transient response of the support pressure and to prevent the support pressure from becoming oscillating. This reduces the load on the patient from the ventilator.

 According to the present invention, regarding the amplification factor of the support pressure Pvent with respect to the support pressure Pmus, the difference between the amplification factor set by the control amount calculation means and the actual amplification factor can be reduced. As a result, the support gas of the support pressure Pvent amplified at an amplification factor close to the desired amplification factor can be given to the patient, and the burden on the patient can be reduced. In addition, the support pressure Pvent can be prevented from becoming an undesirable value.

According to the present invention, the responsiveness of the support pressure Pvent can be improved, the support pressure Pvent can be proportionally amplified with high accuracy, and the asynchronous state can be suppressed. This makes it possible to give the patient support pressure that is close to ideal. That is, when the patient's spontaneous breathing pressure is low, the support pressure is reduced. When the spontaneous breathing pressure is large, the force S can be increased, and the burden on the patient can be reduced. The time constant T m of the transfer function for adjustment is preferably set lower than the value at which the transient response of the support pressure Pvent becomes oscillating. As a result, the burden imposed on the patient by the ventilator can be further reduced. According to the present invention, the dead time Lm included in the adjustment transfer function and the transmission of the gas supply mechanism. By setting the dead time Lc included in the reaching function to almost the same value (Lm Lc or Lm = Lc), even if the respiratory organ model is not accurate with respect to the actual respiratory organ, even if the amplification factor is large Compared to the case where the dead time Lm included in the transfer function for adjustment and the dead time Lc included in the transfer function of the gas supply mechanism are excessively different, the time constant can be made as large as possible in the stable range. This can further improve the responsiveness of the support pressure Pvent. As a result, the load exerted on the patient by the ventilator can be further reduced. According to the present invention, the responsiveness of the support pressure Pvent can be improved, and the support pressure Pvent can be proportionally amplified with high accuracy. Asynchronous state can be suppressed. This makes it possible to give the patient support pressure that is close to ideal. That is, when the patient's spontaneous breathing pressure is low, the support pressure is reduced. When the spontaneous breathing pressure is large, the force S can be increased, and the burden on the patient can be reduced. The time constant T m of the transfer function for adjustment is preferably set lower than the value at which the transient response of the support pressure Pvent becomes oscillating. As a result, the burden imposed on the patient by the ventilator can be further reduced. In addition, by setting the dead time Lm included in the adjustment transfer function to zero, if the respiratory model is not accurate relative to the actual respiratory organ, the time constant can be set within a stable range even if the amplification factor is large. It can be increased as much as possible, and the responsiveness of the support pressure Pvent can be further improved. As a result, the load exerted on the patient by the ventilator can be further reduced. Furthermore, by setting the dead time Lm of the dead time element to zero, it is possible to reduce the parameters required for the transfer function for adjustment, which is more appropriate than when adjusting both the dead time Lm and the time constant Tm. The time constant Tm can be easily obtained.

According to the present invention, even if the amplification factor is amplified, the time constant can be increased as much as possible to improve the responsiveness of the support pressure Pvent, and the response can be prevented from becoming oscillatory. The As a result, the load imposed on the patient by the ventilator can be further reduced. According to the present invention, by adjusting the parameters of the adjustment transfer function, the entire system including the ventilator and the patient can be adjusted so as to increase the area where the negative feedback configuration is provided. By adopting a negative feedback configuration for the entire system, it is possible to increase the stability margin compared to when the entire system is a positive feedback configuration, and to prevent the support pressure Pvent from diverging. Can do. For example, by appropriately selecting the parameters, it is possible to improve the responsiveness of the transient response of the support pressure and to prevent the support pressure from becoming oscillating. As a result, the load applied to the patient by the ventilator can be reduced. According to the present invention, by increasing the time constant Tm of the adjustment transfer function, the responsiveness of the support pressure Pvent can be improved, and the support pressure Pvent can be proportionally amplified with high accuracy and in an asynchronous state. Can be suppressed. This can provide the patient with an ideal support pressure. That is, the support pressure can be reduced when the patient's spontaneous breathing pressure is low, and the support pressure can be increased when the spontaneous breathing pressure is large, thereby reducing the burden on the patient. The time constant Tc is preferably set lower than the value at which the transient response of the support pressure Pvent becomes oscillating. This can further reduce the burden of the ventilator on the patient.

 According to the present invention, by adjusting the parameters of the adjustment transfer function, the entire system including the ventilator and the patient can be adjusted so as to increase the area where the negative feedback configuration is provided. By using a negative feedback configuration for the entire system, the stability margin can be increased compared to when the entire system is a positive feedback configuration, and the support pressure Pvent can be prevented from diverging. For example, by appropriately selecting the parameters, it is possible to improve the responsiveness of the transient response of the support pressure and to prevent the support pressure from becoming oscillating. As a result, the load applied to the patient by the ventilator can be reduced. In addition, by setting the dead time Lm included in the adjustment transfer function to zero, if the respiratory model is not accurate relative to the actual respiratory organ, the time constant can be set within a stable range even if the amplification factor is large. It can be increased as much as possible, and the responsiveness of the support pressure Pvent can be further improved. As a result, the load exerted on the patient by the ventilator can be further reduced. Furthermore, by setting the dead time Lm of the dead time element to zero, it is possible to reduce the parameters required for the transfer function for adjustment, which is more appropriate than when adjusting both the dead time Lm and the time constant Tm. The time constant Tm can be easily obtained.

Claims

The scope of the claims  [1] A control device that controls a gas supply mechanism for a ventilator that supplies a support gas containing oxygen to the patient's airway via an inspiratory line in response to a signal representing the target pressure Pin. In  A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,  A delay compensation means for calculating the output according to a predetermined adjustment transfer function capable of parameter adjustment as a delay compensation pressure “Pm” with the target pressure Pin as an input;  In response to the lag compensation pressure "Pm calculated by the lag compensation means, the pulsation assist pressure" Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimating means for calculating the flow rate of the support gas as an estimated flow rate "F, a flow rate difference detected between the flow rate F detected by the flow rate detecting means, and an estimated flow rate F calculated by the flow rate estimating means" F Computing means;  In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. A control device for a gas supply mechanism comprising: [2] The control function according to claim 1, wherein the transfer function for adjustment includes a control element approximating a transfer function of a gas supply mechanism that is measured with the target pressure Pin as an input and the support pressure Pvent as an output. Control device for gas supply mechanism. [3] In response to a signal representing the target pressure Pin, a control device that controls the gas supply mechanism for the ventilator that supplies the support gas containing oxygen to the patient's airway via the inspiratory line with the support pressure Pvent. In  A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,  A delay compensation means for calculating an output according to a predetermined adjustment transfer function as a delay compensation pressure 'Pm with the target pressure Pin as an input; In response to the lag compensation pressure "Pm calculated by the lag compensation means, the pulsation assist pressure" Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimation means for calculating the flow rate of the support gas as an estimated flow rate F; Deviation calculation means for calculating a flow deviation ΔF between the flow rate F detected by the flow rate detection means and the estimated flow rate “F calculated by the flow rate estimation means;  In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. Including  The transfer function for adjustment includes a first-order lag element, and the time constant Tm of the temporary delay element is larger than the time constant Tc that approximates the first-order lag element included in the transfer function of the gas supply mechanism (Tm > Tc) A control device for a gas supply mechanism which is set. [4] The adjustment transfer function includes a dead time element, and the dead time element includes a dead time Lc that is approximately the same as the dead time element Lc included in the transfer function of the gas supply mechanism. 4. The control device for a gas supply mechanism according to claim 3, wherein Lm is set.  [5] In response to a signal representing the target pressure Pin, a control device that controls the gas supply mechanism for the ventilator that supplies the support gas containing oxygen to the patient's airway via the inspiratory line with the support pressure Pvent. In  A flow rate detecting means for detecting the flow rate F of the support gas flowing through the intake pipe,  A delay compensation means for calculating an output according to a predetermined adjustment transfer function as a delay compensation pressure 'Pm with the target pressure Pin as an input;  In response to the lag compensation pressure "Pm calculated by the lag compensation means, the pulsation assist pressure" Pm assist gas will flow through the inspiratory line using a respiratory organ model that models the patient's respiratory organ. A flow rate estimating means for calculating the flow rate of the support gas as an estimated flow rate "F, a flow rate difference detected between the flow rate F detected by the flow rate detecting means, and an estimated flow rate F calculated by the flow rate estimating means" F Computing means; In response to the flow rate deviation ΔF calculated by the deviation calculating means, a target pressure Pin is calculated, and a control amount calculating means for giving a signal representing the target pressure Pin to the gas supply mechanism and the delay compensating means. Including The adjustment transfer function is configured to include a first-order lag element and a time delay element, and the time delay Lm in the time delay element is set as zero. Control device. [6] The time constant Tm of the first-order lag element of the adjustment transfer function is set to an upper limit according to an amplification factor for proportionally amplifying the spontaneous breathing pressure Pmus. The control device for the gas supply mechanism according to one of the above described forces. [7] In response to the signal representing the target pressure Pin, the support gas containing oxygen is supplied by the support pressure Pvent. In the method of controlling the gas supply mechanism for a ventilator that supplies the patient's airway via the inspiratory line,  A flow rate detection step for detecting the flow rate F of the branch gas flowing through the intake pipe;  A delay compensation pressure calculation process in which the target pressure Pin is input and the output according to the adjustment transfer function with adjustable parameters is calculated as the delay compensation pressure “Pm”.  In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;  A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step;  And a control amount calculation step of calculating a target pressure Pin in response to the flow rate deviation ΔF calculated by the deviation calculation step and providing a signal representing the target pressure Pin to the gas supply mechanism. Control method of the gas supply mechanism. [8] In response to a signal representing the target pressure Pin, in the control method of the gas supply mechanism for the ventilator that supplies the support gas containing oxygen at the support pressure Pvent to the patient's airway via the inspiratory line,  A flow rate detection step for detecting the flow rate F of the support gas flowing through the intake pipe; The target pressure Pin is input, and the delay compensation pressure calculation step for calculating the output according to the predetermined adjustment transfer function as the delay compensation pressure “Pm”; In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;  A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step;  A control amount calculation step of calculating a target pressure Pin in response to the flow rate deviation ΔF calculated by the deviation calculation step and giving a signal representing the target pressure Pin to the gas supply mechanism,  The adjustment transfer function includes a first-order lag element, and a time constant Tm larger than the time constant Tc that approximates the first-order lag element included in the transfer function of the gas supply mechanism is set in the temporary delay element. A control method for a gas supply mechanism.  In response to the signal representing the target pressure Pin, in the control method of the gas supply mechanism for the ventilator that supplies the support gas containing oxygen at the support pressure Pvent to the patient's airway via the inspiratory line,  A flow rate detection step for detecting the flow rate F of the support gas flowing through the intake pipe;  The target pressure Pin is input, and the delay compensation pressure calculation step for calculating the output according to the predetermined adjustment transfer function as the delay compensation pressure “Pm”;  In response to the calculated delay compensation pressure Pm by the delay compensation pressure calculation process, the support gas of the delay compensation pressure “Pm will flow through the inspiratory line using a respiratory organ model that models the respiratory organ of the patient. A flow rate estimation step for calculating the flow rate of the support gas as an estimated flow rate F;  A deviation calculating step for calculating a flow deviation ΔF between the flow rate F of the support gas detected by the flow rate detection step and the estimated flow rate F of the support gas calculated by the flow rate estimation step; In response to the flow rate deviation ΔF calculated by the deviation calculation step, a target pressure Pin is calculated, and a signal representing the target pressure Pin is given to the gas supply mechanism. Including  The adjustment transfer function is configured to include a first-order lag element and a time delay element, and the time delay Lm in the time delay element is set as zero. Control method.