TWI904054B - Ventilation system with improved valving - Google Patents

Abstract

A respiratory ventilators system having an inlet configured to be connected to a pressurized air or gas source; an outlet configured to be connected to a patient interface; a valve in-line between the inlet and the outlet; and a control unit configured to control the valve for controlling flow of pressurized air or gas from the source to the patient, wherein the valve includes an air or gas reservoir or accumulator incorporated into the valve body.

Description

Ventilation system with improved valves

This disclosure is generally related to respiratory care systems, and more specifically, to mechanical ventilation systems or respiratory care systems, i.e., ventilators or respirators. This disclosure is particularly useful for providing respiratory support to human or animal patients whose breathing is impaired by disease, and will be described in conjunction with such uses. It can also be used to treat patients with sleep apnea or as a component of anesthesia systems.

The current COVID-19 pandemic has highlighted the need for mechanical ventilation systems in patients with impaired respiratory systems. Respiratory therapy devices can be used to supply clean, breathable gas (usually air, with or without supplemental oxygen) to a patient at therapeutic pressure at appropriate times during their respiratory cycle. Therapeutic pressure assistance can be implemented in a manner synchronized with the patient's breathing, allowing for greater pressure during the patient's normal inspiratory cycle and lower pressure during expiration. Therapeutic pressure assistance can also be implemented beyond the patient's normal inspiratory cycle.

A respiratory care system typically includes a gas or airflow generator or compressed gas or air source, an air filter, a nasal mask, an oral mask or full face mask, an air delivery tube connecting the airflow generator to the mask, various sensors, and a microprocessor-based controller. Alternatively, a tracheostomy tube can be used as the patient interface instead of a mask. The airflow generator may include a servo-controlled motor and an impeller forming a blower. In some cases, a brake can be applied to the blower motor to reduce the blower speed more quickly, thereby overcoming the inertia of the motor and impeller. Despite inertia, braking allows the blower to reach lower pressure conditions more quickly and promptly to synchronize with the patient's exhalation. In some cases, the airflow generator may also include a valve configured to discharge the generated air into the atmosphere as a means of altering the pressure delivered to the patient, as an alternative to motor speed control. Sensors, such as pressure transducers, measure motor speed, mass flow rate, and outlet pressure. Optionally, the device may include humidifier and/or heater elements in the path of the air delivery loop. The controller may include data storage capacity, with or without integrated data capture and display capabilities.

Respiratory care systems can be used to treat a wide range of conditions, such as respiratory insufficiency or failure caused by lung, neuromuscular, or musculoskeletal diseases and respiratory control disorders. They can also be used for conditions associated with sleep-disordered breathing (SDB) (including mild obstructive sleep apnea (OSA)), allergic upper airway obstruction, or early upper airway viral infections.

The current Covid-19 pandemic has stretched the supply of respiratory care systems. Hospitals are being forced to share respiratory care systems, meaning two patients are sharing a ventilator. Hospitals are also using modified devices known for obstructive sleep apnea as a poor alternative to known ventilators.

In addition, current ventilation systems are complex and expensive equipment that requires constant monitoring and adjustment and are prone to malfunction.

This disclosure provides a simple, low-cost ventilator that overcomes the aforementioned and other shortcomings of the current state of prior art ventilators.

More specifically, this disclosure provides a ventilator that offers significant advantages over current ventilators in terms of cost, size reduction, weight reduction, power reduction, noise reduction, and reliability. A key feature of the instantaneous ventilator of this disclosure is a unique air or gas flow valve incorporating an air or gas reservoir or accumulator. Incorporating the air or gas reservoir or accumulator into the valve simplifies system construction and cost while providing improved response time, thereby offering better patient support. Traditional ventilators employ proportional solenoid valves (PSOL valves) or turbine-based designs, where the core flow/pressure regulating components are high-cost, multi-part products (ordering prices ranging from $1,500 to $2,000). Furthermore, in practice, static friction on the guide post of the plunger in a traditional PSOL valve can reduce valve sensitivity, potentially leading to lag effects. To overcome these and other drawbacks of traditional ventilators, this disclosure presents a novel, low-cost air or gas valve with an integrated air or gas reservoir or accumulator incorporated within the valve, comprising essentially five main components and essentially one moving part.

In one embodiment, the ventilator system disclosed herein includes: an inlet configured to connect to a source of pressurized air or gas; an outlet configured to connect to a patient interface; an inline valve located between the inlet and the outlet; and a control unit configured to control a valve for controlling the flow of pressurized air or gas from the source to the patient, wherein the valve includes an air or gas reservoir or accumulator incorporated into the valve body.

In a preferred embodiment, the valve includes a valve gate controlled by a linear drive mechanism, preferably a servo mechanism, a mechanical screw drive, or a voice coil drive.

The patient interface can be selected from a combination of a free face mask, intubation tube, and tracheostomy tube, and the pressurized air or gas source can be selected from a combination of a free air tank, compressor, air pump, and pressurized air pipeline.

This disclosure also provides a method for assisting a patient in need of breathing, comprising: providing a ventilation system as described above; connecting the ventilation system to a pressurized air source and to a patient interface; activating an air or gas flow to the ventilation system to preload an air or gas reservoir or accumulator; and controlling the flow of gas through the ventilation system by opening and closing valves.

In another embodiment of this disclosure, the ventilation system includes a heater and/or a humidifier for regulating air or gas.

A valve can be opened and closed in response to a patient’s normal breathing cycle, or a valve can be opened and closed to introduce air or gas flow beyond the patient’s normal breathing cycle.

Patients can be human animals or non-human animals.

In the detailed description below, the terms "air" and "gas" and the terms "respirator" and "ventilator" are used interchangeably.

The respiratory therapy device disclosed herein provides supplemental air or oxygen to the patient at intermittent time intervals based on the patient's natural Cheyne-Stokes breathing cycle or based on a programmed breathing cycle.

Referring to Figures 1 and 2, the ventilation system 10 includes a ventilation controller 12 connected to a pressurized gas source 14. The pressurized gas source may be pressurized air or an air/oxygen cylinder, a compressor or air pump as shown, or a pressurized air line. The ventilation controller 12, described in detail below, allows pressurized gas to flow to the patient via a gas supply line at location 16, which is attached to a patient interface, such as a nasal mask or full face mask 18 worn by the patient 22. Alternatively, the patient interface 18 may include an intubation tube or tracheostomy tube. Completing the system is a carbon dioxide graph monitor 24 that senses and measures inhaled and/or exhaled airflow from the patient, and a command input and monitor 26. The carbon dioxide graph monitor 24 and the command input and monitor 26 are known and do not require further description for understanding this disclosure.

At the center of the breathing ventilation system 10 disclosed in the present invention is a gas or airflow control valve 28, which has an integrated gas or air reservoir or accumulator as described below.

Referring now to Figures 3 through 5, the gas or pneumatic flow control valve 28 includes a valve housing 40 containing the active element of the gas or pneumatic flow control valve 28. A gas supply inlet 42 is shown on the negative X-axis plane, while a gas source outlet 44 is on the positive X-axis plane. Furthermore, the housing 40 forms a gas reservoir or accumulator 46. The gas supply inlet 42 can interface with a standard hospital _O2 source or any gas source (e.g., a gas cylinder or compressor).

The valve gate 48, described below with reference to Figures 3 and 4, controls the source flow rate QSource(t) based on its position along the X-axis. The face on the negative Z-plane slides along the X-axis on the sliding surface 50 of the valve body. The distance δ between the valve gate face on the positive X-axis and the valve body sealing surface 52 determines the flow resistance by forming a resistance channel between the valve body sealing surface and the valve gate Y-Z face on the positive X-axis.

Referring specifically to Figures 5 and 7, the gas or flow control valve 28 includes a valve gate 48 configured to slide along the X-axis of a sliding surface 50 of the valve housing to set its position along the X-axis. The gas or flow control valve 28 also includes a linear actuator 54, such as a servo mechanism formed of an electrostrictive material such as PZT or PMN, a magnetostrictive material, or a voice coil actuator or other linear actuator structure of a mechanical screw actuator. Its length and the resulting gate position are controlled under closed-loop control based on the desired source flow rate Q _{_Source (t)} or flow source pressure P_{_Source (t)}. Valve gate 48 can also be driven under open circuit control.

The preload force in the negative X direction is applied to the valve gate 48 assembly by the spring assembly 56.

The retaining screw drives the valve gate 48 in the X direction, thereby setting the preload force of the spring assembly and the initial position of the valve gate 48 along the X axis.

Spring plunger 58 provides preload to valve gate 48 in the negative Z direction. The purpose is to maintain an airtight seal between valve gate 48 and valve body sliding surface 50.

The gasket 60 maintains an airtight seal between the X-Z surfaces of the valve housing and the valve gate 48.

Referring again to Figures 1 and 2, the ventilation controller 12 includes an air or gas inlet 30 connected to a gas or airflow control valve 28. The control valve 28 has an outlet connected to the port, which includes an inspiratory flow connection 34 and an expiratory flow port 36, which in turn connects to the expiratory flow valve 38. The expiratory flow valve 38 can vent to the atmosphere or be connected to a _CO2 scrubber and recirculated via the gas inlet 30. The system also includes an expiratory flow sensor or respiration sensor 41 and a connection to a sensor for triggering the valve 28; the expiratory flow sensor or respiration sensor 41 is used to sense the patient's breathing. The sensors may include air quality sensors, temperature sensors, sound sensors, _CO2 sensors, or motion or stress sensors used to detect chest movement in a patient.

The valve cover surrounds the X-Z planes of the valve body, one on the positive Y-axis and one on the negative Y-axis. These covers form an airtight seal between the valve body 40 and the atmosphere.

Referring again to Figures 4 through 6, the left side of Figure 4 shows the valve in the closed position, where δ = 0, and the valve resistance R_{_Valve} (0) is infinite. Figure 5 shows the valve assembly where the gate has moved a distance δ along the X-axis in the negative direction. Therefore, the valve resistance is no longer infinite, and the gas flows from the reservoir to the gas source outlet, as shown in the figure.

The valve flow resistance R _{_Valve} (δ) is calculated as follows: Source flow, Q _{_Source} (t), is controlled by Equation 3, where: Reservoir pressure, P _{_Reservoir}(t), outlet pressure, P_{_Outlet}(t), source flow rate, Q _{_Source} (t), valve height, H_{_Valve}, valve depth along the Y-axis, D_{_Valve}, valve gate distance from the valve body sealing surface, δ_A _Resistance (δ) = cross-sectional area of resistance channel (Equation 1) = D_{_Valve} / δ_{Gas dynamic viscosity}, η(mass/(distance-time)). R_{_Valve}(δ) = exhaust flow resistance through the resistance channel = (8η/π)H_{_Valve} / A_{_Resistance}(δ) (Equation ² ). Then, the source flow rate can be determined by the following relationship: Q _{_Source}(t) = (P_{_Reservoir} (t) - P_Source(t)). _Outlet (t)) / R _Valve (δ) Formula 3)

The gas storage area in the valve body is necessary because the average source flow rate Q _{_Source} (t) does not exceed the available supply flow rate Q _{_Supply} (t), but the peak flow rate of Q_{_Source}(t) exceeds the available supply flow rate. This difference is due to the gas stored in the storage tank.

The force and torque balance of a generalized valve gate is illustrated in Figure 6. The control formulas for force and torque balance are provided in Equations 4 to 12. P _Reservoir = Reservoir pressure θ = Valve gate angle W = Valve gate width H = Valve gate height H _Valve = H / Cosθ Equation 4) D _Valve = Valve gate depth _L1 , _L2 & _L3 = Spring distance c _Friction = Wedge friction coefficient Z _Actuator = Actuator distance from Z = 0 P _Reservoir = Reservoir gas pressure F _PressureX = Force from chamber pressure in the X direction = -P _Reservoir HD Equation 5) F _PressureZ = Force from chamber pressure in the Z direction = -P _Reservoir (WD + H tan θ D / 2) Equation 6) F _Plunger = Force from spring plunger in the Z direction P _Resistor (Z) = Pressure along the flow barrier wall ≈ P _Reservoir (Z/H) Equation 7) F _PResistor = Force exerted on the barrier wall by the pressure generated by the flow = (P _Reservoir /2) D _Valve H _Valve Equation 8) F _Spring = Force provided by the preloaded spring F _Actuator = Force provided by the positioning actuator Z Force balance F _Z = F _Plunger + F _{Pressure Z} + 3F _Spring Sin θ Equation 9) F _Friction = Friction in the X direction = F _Z c _Friction Equation 10) X Force balance (3F _Spring + F _PResistor )Cos θ = F _{Pressure X} + F _Actuator Equation 11) Torque balance about the Y axis F _Spring (L ₁ + L ₂ + L ₃ )Cos θ ² + F _PResistor ((2/3)H/Cos θ)Cos θ ² = F _{Pressure X} H/2 + F _Actuator Z _Actuator (Form 12)

Referring also to Figure 7, valve assembly 28 controls the flow of source gas by changing the flow resistance R _{_Valve} (δ). This is achieved by changing the length (Figure 5) ΔX of actuator 54, which in turn causes valve gate 48 to move δ along the X-axis in the corresponding gap between valve gate 48 and valve body sealing surface 52. The reservoir pressure P_{_Reservoir} (t) is monitored by pressure sensor 70 (Figure 1) and used to calculate the required ΔX command, which controls Q_{_Source} (t), as outlined in Equation 3.

Gas flows through a flow sensor in the pipeline at gas supply inlet 42 to measure the source flow _QSource (t), which is a function of time t. The gas source controller and sensor/user interface use this flow measurement to calculate the required ΔX command, which controls _QSource (t), as outlined in Equation 3.

Similar to conventional ventilators, the inlet air or flow may require humidification and/or heating. This is achieved via commands from the controller to the humidification and heating module 72, which is connected to a reservoir 46 that adds water vapor, thereby adding humidity to the airflow through heating and subsequent water evaporation, piezoelectric atomization of water, or other conventional methods of adding water to the airflow. The gas can also be heated by the module as it flows through it.

Gas flows through a relative humidity sensor, which measures the relative humidity of the gas, RH(t), which is a function of time t. The controller uses this measurement to generate the required RH command, RH _Command (t), which is also a function of time.

The temperature and pressure source module measures the gas temperature T(t). The controller and sensor/user interface use this temperature measurement to calculate the heating command T _Command (t) to the humidification and heating module to control the gas temperature.

The temperature and pressure source module can also measure the gas outlet pressure _POutlet (t). This pressure is used by the controller and sensor/user interface to calculate the required ΔX command, which controls _QSource (t), as outlined in Equation 3. The outlet of the temperature and pressure module is connected to a gas supply line that terminates in a pressurized nasal cannula or other patient breathing equipment, such as a mask, intubation tube, or endotracheal tube.

The gas source controller and sensor/user interface includes sensor interfaces required to control the gas source flow rate Q _Source (t), pressure P _Outlet (t), temperature T(t), and relative humidity RH(t). It generates actuator commands ΔX(t), temperature commands T _Command (t), and relative humidity commands RH _Command (t). It also interfaces with user command input devices and status monitors to receive user-defined command sets: gas source flow rate Q _Source (t), pressure P _Outlet (t), T(t), and RH(t). The gas source controller and sensor/user interface also provides sensor readings to user command input devices and status monitors.

The user command input device and status monitor allows users to generate commands for the following: gas source flow rate Q _{_Source} (t), pressure P_{_Outlet} (t), T(t), and RH(t). It also displays sensor readings. The device can be an I-Pad-type interface that communicates with the pressurized nasal respirator assembly via wired or wireless means.

The gas supply line can be a standard _O2 line. The gas supply line can also be insulated to minimize heat loss as the gas travels from the gas source to the pressurized nasal ventilator assembly. The gas supply line can also be integrated with an electric heating element to maintain the gas temperature, and can also be integrated with power and data cabling to power the pressurized nasal ventilator assembly and receive sensor data from it. Because the gas supply line has a known flow resistance R _{_GSL}, the pressure P_{_Source} (t) at the inlet of the pressurized nasal _ventilator can be calculated using the formula P_{_Source}(t) = P _{_Outlet}(t) - Q_{_Source} (t) R_{_GSL}.

Additional sensors can be provided for the control of gas source components. These include, but are not limited to, chamber pressure P_{_chamber (t}), chamber temperature T_{_AC} , chamber relative humidity _RH _AC, ET_CO ₂ and/or O_₂ measurements from the chambers of self-pressurized nasal ventilators, and impedance-based devices for monitoring respiratory rate and tidal volume via chest movement (e.g., the system).

Referring to Figure 8, the overall operation is as follows: Gas source 14 supplies pressurized gas to ventilation controller 12, which opens valve 28 to supply gas to patient 22 at the required frequency, flow rate, and pressure to support the patient's breathing. Because of the pressurized gas or air supply in the air or gas reservoir 46 connected to valve 28, the delivery of pressurized air or gas to patient 22 occurs substantially simultaneously with the opening of the valve. The air or gas reservoir 46 is refilled upon the patient's exhalation.

Compared to conventional ventilation devices, the ventilation system disclosed herein is a low-cost, relatively simple device that is robust, small in size and light in weight, and exceptionally quick in responding to patient needs.

Figures 9A through 9C show the flow and pressure waveforms for the patient during three rise times (pressure support).

10: Ventilation system; 12: Ventilation controller; 14: Pressurized gas source; 16: Gas supply line; 18: Nasal mask or full face mask; 22: Patient; 24: Carbon dioxide monitor; 26: Command input and monitor; 28: Valve; 30: Air or gas inlet port; 34: Inspiratory flow connection; 36: Expiratory flow port; 38: Expiratory flow valve; 40: Valve. 41: Expiratory flow sensor or respiration sensor; 42: Gas supply inlet; 44: Gas source outlet; 46: Gas reservoir or accumulator; 48: Valve gate; 50: Valve body sliding surface; 52: Valve body sealing surface; 54: Linear actuator; 56: Spring assembly; 58: Spring plunger; 60: Washer; 70: Pressure sensor; 72: Humidification and heating module.

Further features and advantages of this disclosure can be seen from the following description in conjunction with the accompanying drawings, wherein the same element symbols represent the same parts, and wherein...

Figure 1 is a schematic diagram of a ventilation system connected to a compact ventilation device for a patient, as shown in conjunction with this disclosure.

Figure 2 is a perspective view of a compact ventilation device manufactured according to this disclosure;

Figure 3 is a cross-sectional view of the functional elements of the valve component of a compact ventilation device according to a preferred embodiment of this disclosure;

Figures 4 and 5 are cross-sectional functional element diagrams of the valve components of the compact ventilation device according to this disclosure.

Figure 6 is a diagram showing the torque balance of the valve components in this thematic disclosure;

Figure 7 is an exploded view of the valve component according to this disclosure;

Figure 8 is a flowchart illustrating the operation of the compact ventilation device disclosed in this invention; and

Figures 9A to 9C are diagrams illustrating the triggering airflow according to this disclosure.

10: Breathing ventilation system 12: Ventilation controller

Claims (5)

A ventilator system includes: an inlet configured to be connected to a source of pressurized air or gas; an outlet configured to be connected to a patient interface; a valve connected in series between the inlet and the outlet; and a control unit configured to control the valve to control the flow of pressurized air or gas from the source to a patient, wherein the valve includes a sealable air or gas reservoir or accumulator incorporated into a body of the valve, and wherein the sealable air or gas reservoir or accumulator is configured to be independent. A certain amount of pressurized air or gas is stored in the pressurized air or gas source, wherein the sealable air or gas reservoir or accumulator is configured to deliver the stored certain amount of pressurized air or gas together with pressurized air or gas from the pressurized air or gas source to the patient when the valve is opened, thereby increasing a peak flow rate of the air or gas delivered to the patient, and wherein the sealable air or gas reservoir or accumulator is configured to be filled with a pressurized air or gas reservoir when the valve used to control the flow of pressurized air or gas delivered to the patient is closed. The breathing ventilation system as described in claim 1, wherein the valve includes a valve gate controlled by a linear drive mechanism, the linear drive mechanism including a mechanical screw drive or a voice coil drive. The respiratory ventilation system as described in claim 1, wherein the patient interface is selected from a combination of a mask, an intubation tube and a tracheostomy tube. The breathing ventilation system as described in claim 1, wherein the pressurized air or gas source is selected from the group consisting of an air tank, a compressor, an air pump and pressurized air lines. The breathing ventilation system as described in claim 1 further includes at least one of a heater and a humidifier for regulating the air or gas.