WO2021066003A1 - Cardiac output measurement device - Google Patents

Abstract

[Problem] To enable measurement of cardiac output in a state in which a subject is breathing. [Solution] The present invention has: a heartbeat waveform measurement unit 112 that measures the waveform of microwaves transmitted through a subject; and a frequency calculation unit 115 and a cardiac output calculation unit 116 that numerically analyze the waveform of the microwaves, thereby calculating a waveform that establishes the cardiac output.

Description

Cardiac output measuring device

The present invention relates to a cardiac output measuring device capable of measuring cardiac output while the subject is breathing.

In order to know whether the subject's heart is functioning normally, it is important to measure the cardiac output, which indicates how much blood is being pumped from the heart.

Examination of heart failure, follow-up after heart surgery, verification of medication effect of heart disease, etc. can be performed by measuring cardiac output. As a device for measuring cardiac output, for example, as shown in Patent Document 1 and Patent Document 2, there are various devices.

Japanese Unexamined Patent Publication No. 2016-20516 International Publication 2018/194093

However, since the measurement of cardiac output is usually performed while the subject is breathing, the effect of respiration cannot be ignored for accurate measurement of cardiac output. Since the devices of Patent Document 1 and Patent Document 2 do not consider the influence of respiration, it is difficult to easily measure the cardiac output with high accuracy in facilities such as hospitals and long-term care.

An object of the present invention is to provide a cardiac output measuring device capable of measuring cardiac output while the subject is breathing.

The cardiac output measuring device of the present invention for achieving the above object has a measuring means and a calculating means.

The measuring means measures the waveform of microwaves that have passed through the living body. The calculation means calculates the waveform for which the cardiac output is obtained by numerically analyzing the waveform of the microwave.

According to the present invention, since the influence of the subject's respiration can be removed, the cardiac output can be accurately measured even when the subject is breathing.

It is a block diagram of the cardiac output measuring device of this embodiment. It is a figure which shows the waveform of the microwave measured by the heart rate waveform measuring part. It is a figure which shows the waveform after applying the filter which matches the frequency of the respiratory component waveform. It is a figure which shows the heartbeat waveform after applying the filter which matches the frequency of the apnea component waveform. It is an operation flowchart for calculating the cardiac output by the cardiac output measuring device of this embodiment. It is a figure which shows the waveform (respiratory component waveform + apnea component waveform) of the microwave measured by the heart rate waveform measuring unit. It is a figure which provides the explanation of the method which the frequency calculation part calculates the frequency of the respiratory component waveform. It is a figure which provides the explanation of the method which the frequency calculation part calculates the frequency of the apnea component waveform. It is a figure which shows an example of the heartbeat waveform after molding (the waveform which obtains the cardiac output) used by the cardiac output calculation part for calculating the cardiac output.

An embodiment of the cardiac output measuring device of the present invention will be described below.

(Configuration of cardiac output measuring device)
FIG. 1 is a block diagram of the cardiac output measuring device of the present embodiment. The cardiac output measuring device 100 includes a control unit 110, a transmitting unit 122, a receiving unit 128, a measurement start switch 140, a notification unit 152, a display unit 154, and an input unit 160.

The control unit 110 uses the waveform of the microwave transmitted through the chest of the subject (living body) received by the receiving unit 128 to obtain the cardiac output of the subject, in other words, the heart of the subject. Calculate the amount of blood (liters / minute) pumped from the left ventricle per unit time.

When microwaves pass through the subject's heart, the blood absorbs the microwaves, so the diastole, when blood flows into the heart, is more pronounced than the systole, when blood is drained from the heart. The waveform is attenuated. Cardiac output can be calculated from the amplitude of the microwave waveform that is attenuated by changes in blood. This microwave cardiac output measurement has the advantage that the cardiac output can be measured non-invasively and non-invasively, and that the device can be miniaturized. The measuring device is non-invasive and small in size for heart failure medical treatment, follow-up after heart surgery, verification of medication effect for heart disease, etc., and it is possible to measure cardiac output anytime, anywhere, any number of times. It is important to be. Therefore, it is very important to accurately calculate the attenuation of the microwave waveform so that the cardiac output can be calculated accurately.

When measuring the cardiac output of a subject, microwaves are emitted toward the subject's heart, so the waveform of the microwave that has passed through the human body is the respiratory change and cardiac output of the subject. Since each volume change is included, the cardiac output calculation cannot ignore the effects of respiration. The subject takes various breaths such as shallow breathing, deep breathing, slow breathing, fast breathing, regular breathing, and irregular breathing depending on the measurement environment and condition. Since the relative position of the transmitting antenna and the receiving antenna installed on the body surface of the chest changes with each respiration, respiration hinders the accurate calculation of the attenuation of the microwave waveform. In addition, since microwaves are also absorbed by the lungs, changes in lung capacity due to respiration also hinder the accurate calculation of the attenuation of the microwave waveform. The control unit 110 removes the influence of the subject's respiration and accurately calculates the amount of attenuation of the microwave waveform. The control unit 110 includes various components for accurately calculating the attenuation amount of the microwave waveform, which will be described later.

Especially in heart failure, signs and symptoms are likely to appear in the respiratory state, it becomes difficult to breathe when it worsens, and it becomes possible to breathe normally when it improves. Since the number, depth, and pattern of breathing change from moment to moment as symptoms and signs change, it is very important to realize cardiac output measurement that does not depend on the respiratory state for measurement accuracy. is there.

As a patient flow during hospitalization, many patients after cardiac surgery and patients with heart failure are managed in a centralized management area with abundant monitoring equipment such as ICU and CCU and medical staff immediately after hospitalization, and as they improve, monitoring equipment After being managed in a general ward area where medical staff and medical staff are scarce, the patient is discharged from the hospital. In this patient flow, there may be a device that can evaluate the respiratory status in the centralized control area, but it is common that there is no device that can evaluate the respiratory status in the general ward area. In patients after cardiac surgery and patients with heart failure, it is important to continuously control cardiac output from admission to discharge. Therefore, realizing cardiac output measurement whose measurement accuracy does not depend on the respiratory state makes it possible to measure cardiac output regardless of the location such as the ICU, CCU, and general ward, and it is possible to measure the cardiac output in the entire hospitalized patient flow. It is very important to realize cardiac output control.

Since heart failure is a disease in which re-exacerbation and re-hospitalization are repeated, it is necessary to grasp the cardiac output not only in the hospital where the patient is hospitalized but also at home, a long-term care facility, and a family clinic. Therefore, it is important to easily measure the cardiac output with high accuracy regardless of respiration.

The transmission unit 122 receives an instruction from the control unit 110 and transmits a signal for irradiating a microwave of a predetermined frequency from the transmission antenna 124. As the frequency of the microwave, it is preferable to set the frequency at which the waveform for which the cardiac output is obtained can be obtained most clearly. In this embodiment, microwaves having a frequency of 0.4 GHz to 1.0 GHz are used.

The receiving unit 128 amplifies the microwave signal received by the receiving antenna 126. The subject's chest is located between the transmitting antenna 124 and the receiving antenna 126. In the present embodiment, the transmitting antenna 124 is arranged on the back side of the subject, and the receiving antenna 126 is arranged on the chest side of the subject. The transmitting antenna 124 and the receiving antenna 126 may be configured such that the transmitting antenna 124 is arranged on the chest side of the subject and the receiving antenna 126 is arranged on the back side of the subject. Further, the transmitting antenna 124 and the receiving antenna 126 may be arranged in close contact with the body surface of the subject, or may be arranged at a certain distance from the body surface of the subject. It is preferable that the transmitting antenna 124 and the receiving antenna 126 are arranged around the subject's heart, particularly so as to sandwich the left ventricle. Therefore, the receiving antenna 126 receives the microwave of the received waveform as shown in FIG. 2A, which is irradiated from the transmitting antenna 124 and transmitted through the chest of the subject. The subject is exposed to microwaves while breathing. Therefore, in the received waveform of the microwave in FIG. 2A, the waveform obtained when the subject is breathing (when the chest is up and down) and the waveform when breathing is stopped for a moment (purely). It includes both waveforms and the waveforms during aspiration obtained from the heartbeat only).

The measurement start switch 140 is configured so that a user such as a medical worker such as a doctor or a nurse can instruct the start of measurement of cardiac output. The specific mode of the measurement start switch 140 is not particularly limited as long as it is a switch that can be switched on and off. For example, a toggle type or button type mechanical switch or an electronic switch displayed on the display screen can be mentioned.

The notification unit 152 notifies a message indicating the start of measurement or the end of measurement. The notification unit 152 may notify a message indicating the start of measurement or the end of measurement by sound or light, or may display characters on the screen to notify the notification.

The display unit 154 displays various waveforms calculated by the control unit 110 and the calculated cardiac output. The display unit 154 is a display using a liquid crystal or an organic EL.

The input unit 160 allows a user such as a medical worker to input information about the subject (sex, age, name, weight, height, etc. of the subject) to the control unit 110 and input measurement contents. It is configured as follows. The input unit 160 can be configured by any one of pointing devices such as a push button, a keyboard, and a mouse, or a combination thereof in whole or in part. In the present embodiment, the input unit 160 is provided in the cardiac output measuring device 100, but the cardiac output measuring device 100 may be externally attached.

The external terminal 170 is configured to be able to communicate with the cardiac output measuring device 100 via the communication unit 118. The external terminal 170 is composed of a known tablet, personal computer, or the like.

The control unit 110 includes a heart rate waveform measurement unit 112, a frequency calculation unit 115, a cardiac output calculation unit 116, a storage unit 117, and a communication unit 118. The heart rate waveform measurement unit 112, the frequency calculation unit 115, and the cardiac output calculation unit 116 are configured in the processor 111.

FIG. 2A is a diagram showing a microwave waveform measured by the heart rate waveform measuring unit 112. The heart rate waveform measuring unit 112 functions as a measuring means for measuring the waveform of the microwave transmitted through the subject.

The heart rate waveform measuring unit 112 measures a microwave waveform composed of a composite waveform of a respiratory component waveform and an apnea component waveform as shown in FIG. 2A from the microwave transmitted through the subject. In the example of FIG. 2A, the frequency of the respiratory component waveform is lower than that of the apnea component waveform, the overall shape of the synthetic waveform is obtained from the respiratory component waveform, and the apnea component waveform appears as fine irregularities. In the example of FIG. 2A, the main component of the apnea component waveform includes a change in the microwave waveform due to the inflow and outflow of blood into the heart due to the beating of the heart. The heart rate waveform measuring unit 112 measures the received waveform of the microwave as shown in FIG. 2A amplified by the receiving unit 128. This microwave waveform includes the respiratory component waveform when the subject is breathing and the apnea component waveform when not breathing, but strictly speaking, the respiratory component waveform also includes the apnea component waveform. It has been.

FIG. 2B is a diagram showing a microwave waveform after filtering to match the frequency of the respiratory component waveform. FIG. 2C is a diagram showing a waveform after filtering to match the frequency of the apnea component waveform. The frequency calculation unit 115 and the cardiac output calculation unit 116 function as calculation means for calculating the waveform for obtaining the cardiac output by numerically analyzing the waveform of the microwave.

The frequency calculation unit 115 calculates the frequencies of the respiration component waveform and the apnea component waveform of the microwave reception waveform as shown in FIG. 2A, which are measured by the heart rate waveform measurement unit 112. The frequency calculation unit 115 calculates the frequency of the respiratory component waveform based on the number of variation points of the respiratory component waveform appearing in the unit time in the received waveform of the microwave, and determines the frequency of the aspirating component waveform appearing in the unit time. From the number, the frequency of the aspiratory component waveform, that is, the frequency of the heartbeat caused by the change in the waveform of the microwave due to the inflow and outflow of blood into the heart is calculated. The method of calculating the frequency of the respiratory component waveform and the apnea component waveform performed by the frequency calculation unit 115 will be described in detail later.

The cardiac output calculation unit 116 forms a heartbeat waveform using the frequencies of the respiratory component waveform and the aspiratory component waveform in the microwave waveform calculated by the frequency calculation unit 115, and the cardiac output as shown in FIG. 2C. Calculate the cardiac output from the waveform for which the amount is calculated. A general known method is used to calculate the cardiac output. The cardiac output calculation unit 116 generates a filter that matches the frequency of the respiratory component waveform included in the heartbeat waveform when forming the heartbeat waveform as shown in FIGS. 2B and 2C. The specific method of generating the filter will be described later. When the heartbeat waveform is formed by applying a filter matching the frequency of the respiratory component waveform generated by the heart rate output calculation unit 116 to the microwave waveform as shown in FIG. 2A, the respiratory waveform component as shown in FIG. 2B is formed. A heartbeat waveform is obtained in which is removed to some extent. In addition, the cardiac output calculation unit 116 generates a filter that matches the frequency of the apnea component waveform, that is, the frequency of the waveform component caused by the beating of the heart, when forming the heartbeat waveform. The specific method of generating the filter will be described later. A filter that matches the frequency of the waveform component caused by the heartbeat generated by the cardiac output calculation unit 116 is added to the received waveform of the microwave as shown in FIG. 2A and the heartbeat waveform as shown in FIG. 2B. When applied, a waveform for obtaining the cardiac output as shown in FIG. 2C, specifically, a waveform in which the amplitude for obtaining the cardiac output is accurately reproduced can be obtained. The cardiac output calculation unit 116 calculates the amount of blood delivered by the subject's heart per unit time, that is, the cardiac output from the waveform for obtaining the cardiac output in FIG. 2C. Cardiac output can be calculated from both amplitude changes in FIGS. 2B and 2C, but is compatible with filters that match the frequency of the respiratory component waveform and the frequency of the apneic component waveform (heartbeat). It is possible to calculate more accurately by using the heartbeat waveform as shown in FIG. 2C, which is obtained by applying both filters. In this embodiment, after applying a filter that matches the frequency of the respiratory component waveform, a filter that matches the frequency of the apnea component waveform (heartbeat) is applied, but a filter that matches the frequency of the heartbeat is used. After applying, a filter suitable for the frequency of respiration may be applied. Also, before applying a filter that matches the frequency of the respiratory component waveform or aspiratory component waveform (heartbeat), after applying a general high frequency filter to remove biological noise, the frequency of the respiratory component waveform. It is also possible to perform a filtering process suitable for the frequency of the aspiration component waveform (heartbeat).

The storage unit 117 calculates a filter coefficient for generating a filter that matches the frequency of the respiratory component waveform included in the microwave reception waveform and a filter that matches the frequency of the aspiratory component waveform included in the microwave reception waveform. Store expressions and filters. The cardiac output calculation unit 116 stores filters matching the frequencies of the respiratory component waveform and the apnea component waveform included in the microwave reception waveform as shown in FIG. 2A in the storage unit 117, respectively. It is generated from the coefficient calculation formula and each frequency. Examples of the filter include a digital filter such as a low-pass filter or a band-pass filter.

Therefore, the heart rate output calculation unit 116 uses the frequency of the respiratory component and the frequency of the apnea component represented by the heartbeat calculated by the frequency calculation unit 115, and the filter coefficient stored in the storage unit 117. From the calculation formula, a filter that matches the frequency of the respiratory component waveform included in the microwave waveform and a filter that matches the frequency of the apneic component waveform included in the microwave waveform are generated.

In this way, the reason why the filters suitable for each of the frequencies of the respiratory component waveform and the apnea component waveform (heartbeat) are generated is because of the following circumstances. The subject takes various breaths such as shallow breathing, deep breathing, slow breathing, fast breathing, regular breathing, and irregular breathing depending on the measurement environment and condition. In addition, the heartbeat and heart rate of the subject may vary greatly depending on the condition. The generally used waveform forming method is based on the premise that the waveform to be formed is almost the same waveform without being affected by the environment or the like. However, the frequency of the subject's respiration and heartbeat usually changes greatly depending on the environment and condition. As described above, in order to accurately obtain the cardiac output from the waveform whose frequency may change significantly, it is necessary to generate a filter suitable for each using the frequency of the waveform.

The above is the configuration of the cardiac output measuring device 100. Next, the operation of the cardiac output measuring device 100 will be described.

(Operation of cardiac output measuring device)
FIG. 3 is an operation flowchart for the cardiac output measuring device 100 of the present embodiment to calculate the cardiac output. The operation flowchart will be described with reference to FIGS. 4A to 4D. Note that FIG. 4A is a diagram showing a microwave waveform (respiratory component waveform + apnea component waveform) measured by the heart rate waveform measuring unit. FIG. 4B is a diagram provided by the frequency calculation unit for explaining a method of calculating the frequency of the respiratory component waveform. FIG. 4C is a diagram provided by the frequency calculation unit for explaining a method for calculating the frequency of the apnea component waveform. FIG. 4D is a diagram showing an example of a cardiac output waveform after molding (a waveform for obtaining a cardiac output) used by the cardiac output calculation unit to calculate the cardiac output.

When the measurement start switch 140 is pressed, the control unit 110 instructs the transmission unit 122 to output microwaves, the transmission unit 122 outputs microwaves from the transmission antenna 124, and the microwaves are output to the chest of the subject. (S100). The microwave transmitted through the chest of the subject is received by the receiving antenna 126 (S101), and the received microwave is amplified by the receiving unit 128 and input to the heart rate waveform measuring unit 112.

The heart rate waveform measuring unit 112 measures the waveform of the microwave in which the respiratory component waveform and the apnea component waveform are mixed as shown in FIG. 4A from the input microwave (S102). This is because the subject measures the heartbeat waveform while breathing.

The frequency calculation unit 115 calculates the frequency of the respiratory component waveform among the microwave waveforms as shown in FIG. 4A measured by the heart rate waveform measurement unit 112 (S103). The frequency of the respiratory component waveform is calculated from the number of inflection points of the respiratory component waveform that appear within a unit time. Specifically, the frequency is calculated as follows.

The frequency calculation unit 115 measures the amplitude intensity of the microwave waveform shown in FIG. 4A at regular time intervals. For example, as shown in FIG. 4B, the amplitudes x1, x2, x3, x4, x5, x6, x7, x8 ... Of the heartbeat waveform are measured for each time ta. In this measurement, the total elapsed time required until x1 = Xn, that is, n such that x1 = Xn is obtained, and the frequency f is calculated by converting it into a value per unit time. For example, in the case of FIG. 4B, the amplitude intensity of the respiratory waveform component is the same for x1 and x8, and the measurement time required from the start of measurement (x1) to the acquisition of the same amplitude intensity again (x8) is ta8-ta1 = 7 × ta. Therefore, the value obtained by converting 7 × ta per unit time is the frequency.

The measurement time interval ta for calculating the frequency of the respiratory waveform component is about 10 times one cycle of the respiratory waveform component because it adversely affects the measurement accuracy if it is too small or too large with respect to the frequency of the respiratory waveform component. It is preferable to set the time so that the cycle becomes. Further, the criterion for setting x1 = Xn, that is, the criterion for determining how close the amplitude intensities are to be regarded as the same amplitude intensity can be freely set.

As a method of obtaining the frequency of the respiratory component waveform, a general method of finding the unevenness and the inflection point of the graph may be used. For example, the amplitude intensity x1, x2, x3, x4, x5, x6, x7, x8 ... Of the heartbeat waveform is measured at every ta for a certain period of time, a curve passing through these measurement points is drawn, and the slope of the tangent line changes. , The time point at which the inflection point is reached (the time point at ta8 where x8 is measured in FIG. 4B) may be obtained from the positive, zero, and negative changes of the double differentiation of the approximate expression of the curve. The frequency can be obtained by converting the time required for observing this inflection point into a value per unit time.

The frequency calculation unit 115 stores the frequency of the respiratory component waveform calculated as described above in the storage unit 117 (S104).

Next, the frequency calculation unit 115 calculates the frequency of the apnea component waveform among the microwave waveforms as shown in FIG. 4A measured by the heart rate waveform measurement unit 112 (S105). The frequency of the apnea component waveform is obtained from the number of bending points of the apnea component waveform that appear within a unit time by the same method as when calculating the frequency of the respiratory waveform component. Specifically, it is performed as follows.

The frequency calculation unit 115 measures the amplitude of the microwave waveform shown in FIG. 4A at regular time intervals. For example, as shown in FIG. 4C, the amplitude intensities y1, y2, y3, ... ym, ..., Yn of the heartbeat waveform are measured every time tb. In this measurement, the sum of the elapsed times required until ym = yn is obtained, and the frequency f is calculated by converting it into a value per unit time. In the case of FIG. 4C, since the amplitude intensity of the respiratory waveform component is the same for y2 and y10, the value obtained by converting tb10-tb2 = 8 × tb per unit time is the frequency. It should be noted that the calculation may be performed by using a general method for obtaining the unevenness and the inflection point of the graph, as in the explanation when calculating the frequency of the respiratory waveform component.

The frequency calculation unit 115 stores the frequency of the apnea component waveform calculated as described above in the storage unit 117 (S106).

The cardiac output calculation unit 116 generated a filter matching the frequency of the respiratory component waveform using the frequency of the respiratory component waveform stored in the step of S104, and applied the generated filter to remove the respiratory component. Shape the waveform (S107). Next, the cardiac output calculation unit 116 generated a filter matching the frequency of the apnea component waveform (heartbeat) using the frequency of the apnea component waveform stored in the step of S106, and generated the filter. A waveform is formed by applying a filter to extract the heartbeat more (S108).

From the process of the step S102 to the process of the step S108, the microwave waveform of FIG. 4A is formed into a heartbeat waveform as shown in FIG. 4D. The cardiac output calculation unit 116 calculates the cardiac output of the subject's heart from the molded heartbeat waveform (waveform for obtaining the cardiac output) shown in FIG. 4D (S109). The control unit 110 causes the display unit 154 to display the calculated cardiac output (S110).

Further, the frequency of the respiratory component waveform is calculated from the microwave waveform as shown in FIG. 4A (S103), the frequency of the apnea component waveform is calculated (S105), and the waveform for obtaining the heart rate output is formed (S105). The series of steps (S103 to S108) up to S108) can also be performed as follows.

First, a wide bandpass filter or lowpass filter is applied to the microwave waveform as shown in FIG. 4A. By doing so, fine irregularities derived from the apnea component waveform are removed from the microwave waveform as shown in FIG. 4A, and a waveform composed of only the respiratory component waveform can be obtained. With respect to this waveform, the frequency of the respiratory component waveform is calculated by using a method of calculating the frequency of the waveform based on the number of times the voltage crosses a certain threshold value per unit time (S103).

The frequency calculation unit 115 stores the frequency of the respiratory component waveform calculated as described above in the storage unit 117 (S104). The cardiac output calculation unit 116 generated a filter matching the frequency of the respiratory component waveform using the frequency of the respiratory component waveform stored in the step of S104, and applied the generated filter to remove the respiratory component. Shape the waveform (S107).

Next, the frequency of the apnea component waveform is calculated by using the waveform obtained in step S107 excluding the respiratory component and using a method of calculating the frequency of the waveform by the number of times the voltage crosses a certain threshold per unit time. (S105). Then, the frequency calculation unit 115 stores the frequency of the apnea component waveform calculated in this way in the storage unit 117 (S106). The cardiac output calculation unit 116 uses the frequency of the apnea component waveform stored in the step of S106 to generate a filter that matches the frequency of the apnea component waveform, and the generated filter is obtained in S107. By applying to the waveform excluding the respiratory component, a waveform for obtaining the cardiac output, which is a more extracted heartbeat, is formed (S108).

As described above, the cardiac output measuring device 100 measures the cardiac output. In the above example, the cardiac output is displayed on the display unit 154, but the cardiac output may be stored in the storage unit 117 or transmitted to the external terminal 170 via the communication unit 118. good.

In addition to the cardiac output, the stroke amount calculated from one waveform amplitude intensity may be displayed. Furthermore, the frequency of the heartbeat may be displayed as the heart rate. Further, the body surface area may be calculated from the input information such as the height and weight of the subject, and the cardiac output may be divided by the body surface area to be displayed as a cardiac index.

In the calculation of the stroke volume, it may be calculated from one waveform amplitude intensity, but by calculating the cardiac output from the heart rate waveform having a plurality of amplitudes and dividing the value by the heart rate. It may be calculated.

Although the present invention is described as a device for measuring cardiac output in the specification, regarding the amount of blood pumped from the heart, not only the cardiac output but also the stroke amount once and the cardiac index are used. Etc., and since these indexes can be converted to each other, these are not particularly limited in the present invention.

As described above, according to the cardiac output measuring device of the present embodiment, the influence of the subject's respiration can be removed, so that the accurate measurement of the cardiac output can be performed even when the subject is breathing. it can.

According to the cardiac output measuring device of the present embodiment, good measurement accuracy can be expected in the measurement of cardiac output. Further, according to the cardiac output measuring device of the present embodiment, it is possible to continuously monitor the cardiac output of a patient who is in poor condition in an intensive care unit or the like.

The embodiment of the cardiac output measuring device of the present invention has been described above. However, the technical idea of the cardiac output measuring device of the present invention is not limited to the embodiments exemplified above. The technical idea of the present invention may be embodied in an embodiment other than the embodiments illustrated above. Further, in the present embodiment, an electromagnetic wave having a frequency of 0.4 GHz to 1.00 GHz is used. Although it is explained that microwaves are used, the definition of microwaves is not due to the difference in definitions such as the definition of an electromagnetic wave having a frequency of 300 MHz to 300 GHz and the definition of an electromagnetic wave having a frequency of 3 GHz to 30 GHz. Further, it is preferable to set the frequency at which the waveform for which the cardiac output is obtained is obtained most clearly, and electromagnetic waves such as short wave, ultra high frequency wave, and ultra high frequency wave may be used.

This application is based on a Japanese patent application (Japanese Patent Application No. 2019-178910) filed on September 30, 2019, and the disclosure contents are referenced and incorporated as a whole.

100 cardiac output measuring device,
110 control unit,
111 processor,
112 Heart rate waveform measuring unit,
115 Frequency calculation unit,
116 Cardiac output calculation unit,
117 Memory,
118 Communication Department,
122 transmitter,
124 transmitting antenna,
126 receiving antenna,
128 receiver,
140 Measurement start switch,
152 Notification unit,
154 display section,
160 input section,
170 External terminal.

Claims (9)

A measuring means for measuring the waveform of microwaves that have passed through a living body,
A calculation means for calculating a waveform for obtaining cardiac output by numerically analyzing the waveform of the microwave, and
A cardiac output measuring device. The measuring means is
The cardiac output according to claim 1, further comprising a heartbeat waveform measuring unit, wherein the heartbeat waveform measuring unit measures a heartbeat waveform including a respiratory component waveform and an aspirating component waveform from the microwave transmitted through the living body. Quantitative measuring device. The calculation means is
A frequency calculation unit that calculates the frequencies of the respiratory component waveform and the apnea component waveform included in the microwave waveform measured by the heart rate waveform measuring unit, and
A cardiac output calculation unit that calculates a waveform for obtaining the cardiac output using the frequencies of the respiratory component waveform and the apnea component waveform, and
The cardiac output measuring device according to claim 2. The frequency calculation unit
The frequency of the respiratory component waveform is calculated from the number of inflection points of the respiratory component waveform appearing within a unit time, and the apnea component waveform is calculated from the number of inflection points of the apnea component waveform appearing within the unit time. The heart rate measuring device according to claim 3, which calculates a frequency. The frequency calculation unit
The frequency of the respiratory component waveform is calculated by the number of times the voltage value of the microwave waveform crosses a certain threshold per unit time, and the frequency of the microwave waveform crosses a certain threshold per unit time. The heart rate output measuring device according to claim 3, which calculates the frequency of the aspirating component waveform. The cardiac output calculation unit
The third aspect of claim 3, wherein a filter matching the frequency of the respiratory component waveform and a filter matching the frequency of the apnea component waveform are generated, and the waveform for obtaining the cardiac output is calculated using the generated filter. Cardiac output measuring device. The frequency calculation unit
The frequency of the respiratory component waveform is calculated using a waveform obtained by applying a predetermined low-pass filter or band-pass filter to the microwave waveform, and the heart rate output calculation unit matches the respiratory component waveform. The invention according to any one of claims 3 to 5, wherein a filter is generated, and the frequency of the aspiratory component waveform is calculated using a waveform obtained by applying a filter that matches the respiratory component waveform to the microwave waveform. Heart rate measuring device. further,
It has a filter coefficient calculation formula for generating a filter and a storage unit for storing the filter.
The cardiac output calculation unit
The sixth or seven claim 6 or 7, wherein a filter matching the frequency of the respiratory component waveform and a filter matching the frequency of the apnea component waveform are generated from the respective filter coefficient calculation formulas and filters stored in the storage unit. Cardiac output measuring device. The cardiac output measuring device according to claim 8, wherein the filter is a digital filter such as a low-pass filter or a band-pass filter.

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