A medical breathing machine double-level pressure conversion control algorithm

Abstract

The present application relates to a kind of medical breathing machine bi-level pressure conversion control algorithm, comprising the following steps: the flow value of breathing machine outlet end is obtained by the differential pressure of breathing machine outlet end, and then the moment of patient's spontaneous breathing is obtained;Exhalation trigger moment starts, when the difference between the current mask end pressure collected and the set EPAP pressure value is greater than the set error, then the next step is executed;Current mask pressure is greater than the set EPAP pressure value, determine the value of brake interval variable i, execute PWM pulse width modulation type brake mode to make fan run;Enter to exhalation pressure stable stage, that is, closed loop control fan speed is used.The difference between actual mask pressure and exhalation pressure set value and exhalation pressure set value are combined to judge the value of PWM pulse width modulation type brake brake interval variable, so that the pressure can quickly and stably drop when the pressure is converted from inspiration phase to expiration phase.

Description

Technical Field

[0001] This invention belongs to the field of automatic pressure and flow control devices for medical ventilators, specifically a dual-level pressure conversion control algorithm for medical ventilators. Background Technology

[0002] With the development of technology, non-invasive ventilators can now operate in multiple modes and with multiple parameters. Among them, bilevel breathing mode is the most commonly used breathing mode in clinical practice.

[0003] When using bilevel respiratory mode, the device detects the expiratory transition point, and the ventilator quickly transitions from the inspiratory phase to the expiratory phase, with the pressure changing from the set inspiratory pressure to the set expiratory pressure. This rapid pressure release is problematic. Some manufacturers focus on the rapid pressure drop from high to low pressure, neglecting the need for a stable pressure decrease. An overly rapid pressure drop can cause lung discomfort, and prolonged use can lead to respiratory fatigue, hindering recovery. A stable pressure drop protects lung elasticity and achieves therapeutic goals.

[0004] Currently, most manufacturers focus on the speed of pressure switching between inhalation and exhalation, so there is still room for adjustment in controlling the stable pressure drop. Therefore, this invention will solve the problem of stable pressure drop during the transition from inhalation to exhalation in a ventilator. Summary of the Invention

[0005] The purpose of this invention is to provide a dual-level pressure switching control algorithm for medical ventilators to overcome the technical defects mentioned above, such as unstable pressure drop during the transition from inhalation to exhalation in a ventilator.

[0006] The technical solution adopted by this invention to achieve the above objectives is: a dual-level pressure conversion control algorithm for a medical ventilator, comprising the following steps:

[0007] S1) The ventilator outlet flow rate is obtained by acquiring the differential pressure at the ventilator outlet, and then the patient's spontaneous breathing time is obtained.

[0008] S2) When the exhalation trigger begins (i.e., the transition from inhalation to exhalation), if the difference between the current mask pressure and the set EPAP pressure value is greater than the set error, then step S3) is executed.

[0009] S3) When the current mask pressure is greater than the set EPAP pressure value, determine the value of the brake interval variable i and execute the PWM pulse width modulation braking mode to make the fan run.

[0010] S4) Enter the expiratory pressure stabilization stage, that is, the fan speed is controlled in a closed loop according to the set EPAP pressure value.

[0011] Obtaining the flow value at the outlet end of the ventilator from the differential pressure at the outlet end of the ventilator, and further obtaining the moment of the patient's spontaneous breathing, includes the following steps:

[0012] Obtaining the flow rate parameter of the patient based on the flow value at the outlet end of the ventilator;

[0013] Obtaining the inspiration trigger moment and the expiration trigger moment based on the flow rate parameter of the patient.

[0014] The flow rate parameter of the patient includes at least one of the total leakage volume of the patient, the leakage volume at the patient end, and the flow at the patient end.

[0015] In step S2), when the difference between the currently collected mask end pressure and the set EPAP pressure value is less than or equal to the set error, step S4) is executed.

[0016] In step S3), when the current mask pressure is less than or equal to the set EPAP pressure value, step S4) is executed.

[0017] In step S3), determining the value of the brake interval variable i is specifically as follows:

[0018] If the current mask pressure - the set EPAP pressure value <= 1 cmH2O, then i = 0,

[0019] If the current mask pressure - the set EPAP pressure value > k cmH2O, then i = k; i = 1, 2,

[0020] If the current mask pressure - the set EPAP pressure value > k cmH2O, and (the set IPAP pressure value - the set EPAP pressure value) < H cmH2O; then i = H; i = 3,..., N, N = 9; H is a set value.

[0021] In step S3), executing the PWM pulse width modulation braking method includes the following steps:

[0022] Recording the timer timing value when the current brake interval variable i does not change, and judging whether the timing value is greater than or equal to the difference between the maximum brake time threshold and the brake interval variable i;

[0023] If it is less, output a control electrical signal in PWM mode, and make the fan work through the drive fan drive circuit;

[0024] Otherwise, output a low-level signal to brake the fan.

[0025] A dual-level pressure conversion control system for a medical ventilator includes:

[0026] A flow acquisition module, configured to obtain the flow value at the outlet end of the ventilator from the differential pressure at the outlet end of the ventilator, and further obtain the moment of the patient's spontaneous breathing;

[0027] The pressure conversion module is used to start from the moment of exhalation when the inhalation is converted to exhalation. When the difference between the current mask pressure and the set EPAP pressure value is greater than the set error, the value of the braking interval variable i is determined and the PWM pulse width modulation braking mode is executed to make the fan run.

[0028] The expiratory pressure stabilization control module is used to enter the expiratory pressure stabilization stage, that is, to use closed-loop control of the fan speed according to the set EPAP pressure value.

[0029] A bi-level pressure switching control device for a medical ventilator includes a memory and a processor; the memory is used to store a computer program; the processor is used to implement a bi-level pressure switching control algorithm for a medical ventilator when the computer program is executed.

[0030] A computer-readable storage medium storing a computer program that, when executed by a processor, implements a dual-level pressure conversion control algorithm for a medical ventilator.

[0031] This invention relates to an air-oxygen mixing device for a medical ventilator, comprising a first housing, a second housing, and a fan assembly. The first housing contains an upper guide channel and an upper cavity, while the second housing contains a lower guide channel and a lower cavity. The first and second housings are sealed together, and the upper and lower guide channels are correspondingly connected to form a bent air-oxygen mixing inlet channel. The first housing has an oxygen inlet communicating with the upper guide channel, and the second housing has an air inlet communicating with the lower guide channel. The upper and lower cavities are correspondingly connected to form a receiving cavity, and the fan assembly is disposed within the receiving cavity. The receiving cavity has a cavity inlet communicating with the air-oxygen mixing inlet channel, and the output end of the air-oxygen mixing inlet channel is equipped with a flow detection element. The cavity inlet is equipped with an oxygen concentration sensor. The receiving cavity has a cavity outlet, and the second housing has a housing outlet communicating with the housing outlet.

[0032] The fan assembly includes a fan, a third housing, and a fourth housing, wherein the third housing and the fourth housing are sealed together to form a fan compartment, and the fan compartment is located in the receiving cavity. The fan is located in the fan compartment. The third housing is provided with a fan compartment air inlet that communicates with the inside of the receiving cavity. The fan is provided with a fan inlet and a fan outlet, and the fan outlet extends out of the fan compartment and connects to the cavity outlet.

[0033] The fan is mounted on a fan support, and the fan support has a fan support leg on its lower side. The fourth housing has a fan support fixing column that cooperates with the fan support leg.

[0034] The flow detection element includes an air resistance assembly and a differential pressure sensor. The air resistance assembly includes an air resistance grid and a first connecting port and a second connecting port disposed on the air resistance grid. The output end of the air-oxygen mixing inlet channel is provided with an air resistance slot. The air resistance grid is installed on the air resistance slot, and the first connecting port and the second connecting port are respectively disposed on both sides of the air resistance slot. The differential pressure sensor is disposed on the first housing, and the differential pressure sensor is provided with a first pressure detection port and a second pressure detection port, wherein the first pressure detection port is connected to the first connecting port, and the second pressure detection port is connected to the second connecting port.

[0035] The cavity has an air inlet with an oxygen concentration sensor slot for mounting the oxygen concentration sensor. The second housing has an air outlet, and both the cavity outlet and the housing outlet communicate with this outlet. The first housing has a first oxygen inlet and a second oxygen inlet. A housing seal is provided between the first and second housings. The cavity outlet and the housing outlet are integrally formed with the housing seal.

[0036] The present invention has the following beneficial effects and advantages:

[0037] 1. The value of the PWM pulse width modulation braking interval variable is determined by the difference between the actual mask pressure and the expiratory pressure setting value, so that the pressure can drop quickly and stably when the breathing phase changes from the inspiratory phase to the expiratory phase.

[0038] 2. Since the airflow directly blown out by the fan is not stable, the present invention ensures that the gas blown out from the fan chamber outlet (i.e., the air outlet 18 of the housing in the air-oxygen mixing device used in this embodiment) is a smooth airflow; and based on this, a method for automatically adjusting the PWM pulse width frequency and automatically adjusting the PWM duty cycle is designed to brake and control the fan when the pressure drops, which can more freely adjust the stability of the pressure drop so that the degree of pressure drop can meet the patient's comfort level. Attached Figure Description

[0039] Figure 1 The method flow of the present invention Figure 1 ;

[0040] Figure 2 This is a comparison diagram of the pressure rise waveform of the present invention;

[0041] Figure 3 This is a schematic diagram of the overall structure of the air-oxygen mixing device used in this embodiment;

[0042] Figure 4 This is an exploded view of the air-oxygen mixing device used in this embodiment;

[0043] Figure 5 This is a cross-sectional view of the air-oxygen mixing device used in this embodiment;

[0044] Figure 6 for Figure 4 A schematic diagram of the first shell structure in the middle;

[0045] Figure 7 for Figure 4 A schematic diagram of the second shell structure in the diagram;

[0046] Figure 8 for Figure 4 Schematic diagram of the differential pressure sensor in the diagram;

[0047] Figure 9 for Figure 4 A schematic diagram of the air resistance component structure in the middle;

[0048] Figure 10 for Figure 4 A schematic diagram of the housing seal structure;

[0049] Figure 11 for Figure 4 A schematic diagram of the structure of the fan and fan support in the middle;

[0050] Figure 12 for Figure 4 A schematic diagram of the fourth shell structure in the diagram;

[0051] The components are as follows: 1. Differential pressure sensor; 2. First housing; 3. Oxygen concentration sensor; 4. Housing seal; 5. Fan compartment air inlet; 6. Third housing; 7. Fan; 8. Fan support; 9. Fourth housing; 10. Second housing; 11. Sealing cover; 12. Air inlet; 13. Lower guide channel; 14. Air resistance assembly; 15. Second oxygen inlet; 16. Upper guide channel; 17. First oxygen inlet; 18. Housing outlet; 9. Gas resistance slot; 20. Oxygen concentration sensor slot; 21. Fixing column; 22. First pressure detection port; 23. Second pressure detection port; 24. Gas resistance grid; 25. First connecting port; 26. Second connecting port; 27. Cavity outlet; 28. Outlet port of outlet chamber; 29. ​​Outlet chamber; 30. Fan support leg; 31. Fan inlet; 32. Fan outlet; 33. Fan support fixing column; 34. Upper cavity; 35. Lower cavity. Detailed Implementation

[0052] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0053] like Figure 1As shown, this invention uses PWM pulse width modulation to reduce the ventilator pressure from the higher set IPAP pressure value during inspiration to the set EPAP pressure value during expiration. When the fan is working, it is at a high level of the PWM signal, and when the fan brakes, it is at a low level of the PWM signal. Furthermore, the fan speed is inconsistent during operation, so it is necessary to adaptively adjust the PWM pulse width and frequency.

[0054] This invention includes the following steps:

[0055] Step 1: Data Collection

[0056] S101: Fits the relationship between the digital voltage output and the mask end pressure into a function, which is used to calculate the required voltage when the pressure signal is known during the feedback control process, and uses the digital voltage output as the control output to obtain the real-time mask end pressure that can stably follow the set pressure value.

[0057] S102: Set ventilator control parameter data, including pressure rise time and (IPAP, EPAP) pressure setpoint.

[0058] S103: Collect the differential pressure at the ventilator outlet using a differential pressure sensor (fitted to the actual flow rate of the flow sensor, the flow rate value at this moment can be obtained from the known differential pressure) to collect the ventilator outlet flow rate; collect the ventilator outlet pressure and the pressure value at the patient's mask end using a pressure sensor.

[0059] Step Two:

[0060] S201: Based on the obtained flow rate value, the patient's total air leakage, patient-side air leakage, patient-side flow rate and other parameter values ​​can be calculated. These parameters are then used as inputs for common respiratory triggering algorithms such as flow rate difference method, graphical method and volume method to analyze the patient's spontaneous breathing time, monitor the inspiratory and expiratory markers, and be ready to trigger the pressure at any time. When the expiratory marker is triggered, the pressure is converted into expiratory pressure.

[0061] The analysis revealed that the patient's spontaneous breathing time could be obtained through one of the following methods:

[0062] Based on the patient's flow velocity parameters, a flow velocity difference curve is obtained using the flow velocity difference method, and then the inspiratory and expiratory trigger times are determined; based on the patient's flow velocity parameters, a graphical flow velocity reference curve is obtained using the graphical method, and then the inspiratory and expiratory trigger times are determined; based on the patient's flow velocity parameters, an integral curve of the patient's flow velocity is obtained using the volumetric method, and then the inspiratory and expiratory trigger times are determined.

[0063] S202: Expiratory parameter initialization.

[0064] If the difference between the current patient mask pressure and the set EPAP pressure value is greater than 1 cmH2O, proceed to the next step and implement PWM pulse width modulation braking mode to make the fan run according to the PWM signal to reduce the pressure; otherwise, proceed to S205.

[0065] S203: Determine whether the current mask pressure is less than or equal to the set EPAP pressure value;

[0066] If the value is greater than or equal to 1 cmH2O, the brake variable i is determined by judging whether the difference between the current mask pressure and the set EPAP pressure value is greater than or equal to 1 cmH2O. The value of i varies between 0 and 9, and the PWM pulse width and frequency are automatically adjusted accordingly. Otherwise, step S205 is executed.

[0067] Specifically, the value of the braking variable i is determined as follows:

[0068]

[0069] S204: Determine whether the timer value recorded in step S203 for the current braking variable i (used to calculate the time during which the braking variable does not change during the ventilator pressure decrease) is less than or equal to the difference between the set value 10 and the braking interval variable i. If it is less, output the DA value corresponding to the actual pressure and send it to the ventilator's fan drive circuit to make the fan work; otherwise, brake the fan. Here, variable i is used to determine the PWM pulse width (high-level hold time) and frequency.

[0070] The fan braking mode operates at a low level of PWM, while the fan operation operates at a high level of PWM. The PWM pulse width and frequency are determined by this method. Furthermore, the duty cycle of the PWM is different for each cycle, so the PWM frequency is also adaptively adjusted during the pressure drop. In other words, the PWM duty cycle is controlled by calculating the single-digit number of the time during which the braking variable i does not change during the ventilator pressure drop and the relationship between the number 10 and the difference between the braking variable.

[0071] S205: Entering the expiratory pressure stabilization stage, the fan speed is controlled by PID to ensure that the pressure at the patient's mask end meets the set EPAP pressure; return to step S101.

[0072] In the existing technology, the pressure drop is too slow during the adjustment phase. During the transition between IPAP and EPAP pressures, the actual pressure is higher than the set EPAP pressure, so the pressure waveform will form a slope. Furthermore, the pressure drop waveform is inconsistent when changing to different lung models. Sometimes the pressure waveform has a slope, but sometimes the pressure will drop below the set pressure value in a short period of time, forming a depression on the pressure waveform.

[0073] The PWM pulse width modulation braking algorithm of this invention solves the problems of pressure waveform dips or slopes that sometimes occur when changing the lung model during the pressure drop process; it reduces the pressure drop time and makes the pressure drop process more stable and smooth.

[0074] Theoretically, within the achievable pressure and flow range, the input voltage and actual pressure of a ventilator's fan should have a linear relationship. However, due to resistance in the real environment, the relationship between the input voltage and actual pressure of most fans is a non-linear, quadratic, monotonically increasing function. Furthermore, different ventilators have different internal structures, leading to varying resistance in the fan's environment. Additionally, different ventilator manufacturers use fans with different pressure ranges and different motor drive chips, resulting in variations in fan response time and the time to reach a stable pressure. This inherent characteristic of ventilators—the varying pressure response time—leads to different characteristics during the transition from inspiratory to expiratory phases. Some ventilators may not require additional pressure control during pressure rise; simple PID control can achieve a stable inspiratory pressure setpoint. Similarly, during pressure drop, due to the fluid dynamics-compliant design, simple PID control can also ensure a stable and rapid transition from inspiratory to expiratory pressure. Therefore, different approaches are needed for different characteristics.

[0075] Since the airflow directly blown out by the fan is unstable, the internal structure of the ventilator used in this embodiment (medical ventilator air-oxygen mixing device) increases the path of the gas in the fan chamber (i.e., the air-oxygen mixing inlet channel), so that the gas blown out from the fan chamber outlet (i.e., the air outlet 18 of the housing in the air-oxygen mixing device used in this embodiment) is a smooth airflow; and on this basis, an automatic adjustment method for PWM pulse width frequency and automatic adjustment method for PWM duty cycle is designed to brake and control the fan when the pressure drops, which can more freely adjust the stability of the pressure drop so that the pressure drop can meet the patient's comfort level.

[0076] Therefore, the internal structure of the ventilator designed for the ventilator used in this embodiment, along with the selected fan, motor, motor drive chip, and other components, and the pressure and flow characteristics exhibited by the ventilator used in this embodiment, are such that the applied-for technology can make the pressure stable and drop rapidly.

[0077] from Figure 2It can be seen that the pressure drop time without using PWM (Pulse Width Modulation) braking method is 2.266-1.584 = 0.682s and 1.846-1.782 = 0.064s. Figure 2 The initial decline in upward pressure was too rapid, but the subsequent adjustment was too slow. Figure 2 The pressure drop was too rapid, which is inconsistent with respiratory mechanics; the pressure drop time using the PWM pulse width modulation braking method was 2.664 - 2.53 = 0.134 s, meaning that through... Figure 2 The comparison demonstrates that, under the same ventilator settings, the IPAP pressure transition to the EPAP pressure setting maintains both a stable and relatively rapid pressure drop, consistent with the pressure drop curve that provides comfort for the patient.

[0078] This implementation can be used in the following medical ventilator air-oxygen mixing devices:

[0079] like Figures 3-12 As shown, the air-oxygen mixing device of the medical ventilator includes a first housing 2, a second housing 10, and a fan assembly, wherein... Figure 4 As shown, the first housing 2 has an upper guide channel 16 and an upper cavity 34, and the second housing 10 has a lower guide channel 13 and a lower cavity 35. The first housing 2 and the second housing 10 are sealed together, and the upper guide channel 16 and the lower guide channel 13 are correspondingly connected to form a bent air-oxygen mixing inlet channel. The first housing 2 has an oxygen inlet communicating with the upper guide channel 16, and the second housing 10 has an air inlet 12 communicating with the lower guide channel 13. The upper cavity 34 and the lower cavity 35 are correspondingly connected to form a receiving cavity, and the fan assembly is disposed in the receiving cavity. Figure 6 As shown, the accommodating cavity has a cavity air inlet communicating with the air-oxygen mixing air inlet channel, and the output end of the air-oxygen mixing air inlet channel is equipped with a flow detection element. The cavity air inlet is equipped with an oxygen concentration sensor 3, such as... Figure 10As shown, the accommodating cavity is provided with a cavity outlet 27, and the second housing 10 is provided with a housing outlet 18, and the cavity outlet 27 and the housing outlet 18 are connected. When the device is working, oxygen enters the upper guide channel 16 through the oxygen inlet, and air enters the lower guide channel 13 through the air inlet 12. Oxygen and air are mixed in the air-oxygen mixing inlet channel formed by the combination of the upper guide channel 16 and the lower guide channel 13. Since the air-oxygen mixing inlet channel is bent, the air-oxygen mixing stroke can be greatly extended, ensuring that air and oxygen are fully mixed and improving the mixing uniformity of air and oxygen. In addition, when the mixed gas is output from the air-oxygen mixing inlet channel, the gas flow rate is detected and calculated by the flow detection element. When it enters the accommodating cavity, the oxygen concentration is detected by the oxygen concentration sensor 3 to achieve precise control of oxygen concentration. Then the mixed gas enters the fan assembly and is discharged from the cavity outlet 27 of the accommodating cavity by the action of the fan assembly, and finally output from the housing outlet 18 on the second housing 10.

[0080] like Figure 4 and Figures 11-12 As shown, in this embodiment, the fan assembly includes a fan 7, a third housing 6, and a fourth housing 9, wherein the third housing 6 and the fourth housing 9 are sealed together to form a fan compartment, the fan compartment is disposed in the receiving cavity, and the fan 7 is disposed in the fan compartment, as shown. Figure 4 As shown, the third housing 6 is provided with a fan compartment air inlet 5 that communicates with the accommodating cavity, as... Figure 11 As shown, the fan 7 is provided with a fan inlet 31 and a fan outlet 32, and as... Figure 5 As shown, the fan outlet 32 ​​extends out of the fan compartment and connects to the cavity outlet 27. The mixed gas enters through the cavity inlet of the accommodating cavity, then enters the fan compartment through the fan compartment inlet 5, and enters the fan 7 through the fan inlet 31, and finally exits through the fan outlet 32.

[0081] like Figure 11 As shown, the fan 7 is mounted on a fan support 8, and the fan support 8 has fan support legs 30 on its lower side, as... Figure 12 As shown, the fourth housing 9 is provided with a fan support fixing post 33 that cooperates with the fan support leg 30. In this embodiment, the fan support 8 is made of elastic silicone material, which can play a shock absorption role for the fan 7. Additionally, as shown... Figure 6 As shown, the first housing 2 and the second housing 10 are provided with fixing columns 21 for assisting in fixing the wind turbine compartment.

[0082] like Figure 4 and Figures 8-9 As shown, in this embodiment, the flow detection element includes a gas resistance assembly 14 and a differential pressure sensor 1, wherein... Figure 9As shown, the air resistance assembly 14 includes an air resistance grid 24 and a first connecting port 25 and a second connecting port 26 disposed on the air resistance grid 24, as follows: Figure 6 As shown, the output end of the air-oxygen mixing intake channel is provided with an air resistance slot 19, and the air resistance mesh 24 is fixed by being snapped into the air resistance slot 19. Furthermore, the first connecting port 25 and the second connecting port 26 are respectively located on both sides of the air resistance slot 19. Figure 3 As shown, the differential pressure sensor 1 is mounted on the first housing 2, and as... Figure 8 As shown, the differential pressure sensor 1 is provided with a first pressure detection port 22 and a second pressure detection port 23. The first pressure detection port 22 is connected to the first connecting port 25, and the second pressure detection port 23 is connected to the second connecting port 26. When the mixed gas passes through the gas resistance component 14, a pressure difference is formed on both sides of the gas resistance grid 24. The first pressure detection port 22 in the differential pressure sensor 1 detects the gas pressure before flowing through the gas resistance component 14, and the second pressure detection port 23 detects the gas pressure after flowing through the gas resistance component 14. The control system calculates the mixed gas flow rate based on the pressure difference on both sides and adjusts the oxygen and air input according to the flow rate and oxygen concentration. The gas resistance grid 24 and the differential pressure sensor 1 are both technologies known in the art and are commercially available products. In this embodiment, the minimum cross-sectional area of ​​the gas resistance grid 24 is greater than or equal to 5 mm2, the number of grids is greater than or equal to 18, and the ventilation area is greater than or equal to 150 mm2. In addition, calculating the gas flow rate based on the pressure difference is also a technology known in the art.

[0083] like Figure 6 As shown, the cavity inlet is provided with an oxygen concentration sensor slot 20 for installing the oxygen concentration sensor 3. The oxygen concentration sensor 3 is a technology known in the art and is a commercially available product.

[0084] like Figure 7 As shown, in this embodiment, the second housing 10 is provided with an air outlet 29 having an air inlet 28, and the air outlet 27 of the accommodating cavity is connected to the air inlet 28 of the air outlet, and the air outlet 29 is connected to the air outlet 18 of the housing. Figures 4-5 As shown, the second housing 10 has a sealing cover 11 on its lower side for sealing the air outlet chamber 29.

[0085] like Figure 4 As shown, in this embodiment, the first housing 2 is provided with a first oxygen inlet 17 and a second oxygen inlet 15, and both the first oxygen inlet 17 and the second oxygen inlet 15 are connected to the upper guide channel 16. The second oxygen inlet 15 is a spare oxygen inlet.

[0086] like Figure 4As shown, in this embodiment, a housing seal 4 is provided between the first housing 2 and the second housing 10 to achieve a seal, such as... Figure 10 As shown, the shape of the housing seal 4 matches the shape of the first housing 2 and the second housing 10, as well as the internal air-oxygen mixing inlet channel, accommodating cavity, and other structures. In this embodiment, the housing seal 4 adopts an H-type sealing ring, and the cavity outlet 27 and the housing outlet 18 are integrally set with the housing seal 4 to ensure the sealing effect.

[0087] The working principle of this device is as follows:

[0088] When this device is working, oxygen enters the upper guide channel 16 through the oxygen inlet on the first housing 2, and air enters the lower guide channel 13 through the air inlet 12 on the second housing 10. Oxygen and air are mixed in the air-oxygen mixing intake channel formed by the combination of the upper guide channel 16 and the lower guide channel 13. Since the air-oxygen mixing intake channel is bent, the air-oxygen mixing stroke can be greatly extended, ensuring that air and oxygen are fully mixed and improving the mixing uniformity of air and oxygen. In addition, when the mixed gas is output from the air-oxygen mixing intake channel, the gas flow rate is detected and calculated by the flow detection element. When it enters the accommodating cavity, the oxygen concentration is detected by the oxygen concentration sensor 3 to achieve precise control of oxygen concentration. Then the mixed gas enters the fan assembly and is discharged from the cavity outlet 27 of the accommodating cavity by the action of the fan assembly. Finally, it is output from the housing outlet 18 on the second housing 10.

Claims

1. A bi-level pressure conversion control system for a medical ventilator, comprising a bi-level pressure conversion control algorithm for a medical ventilator, characterized in that, It includes the following steps: S1) Obtain the flow value at the ventilator outlet end through the differential pressure at the ventilator outlet end, and then obtain the patient's spontaneous breathing moment; S2) Starting from the moment when inhalation turns to exhalation, that is, the exhalation trigger moment, when the difference between the currently collected mask end pressure and the set EPAP pressure value is greater than the set error, then execute step S3); S3) When the current mask pressure is greater than the set EPAP pressure value, determine the value of the brake interval variable i, and execute the PWM pulse width modulation braking method to make the fan operate; S4) Enter the exhalation pressure stabilization stage, that is, adopt closed-loop control of the fan speed according to the set EPAP pressure value; In step S3), the determination of the value of the brake interval variable i is specifically as follows: Current mask pressure - Set EPAP pressure value <= 1 cmH2O, then i = 0, Current mask pressure - Set EPAP pressure value > k cmH2O, then i = k; i = 1, 2, Current mask pressure - Set EPAP pressure value > k cmH2O, and (Set IPAP pressure value - Set EPAP pressure value) < H cmH2O; then i = H; i = 3,..., N, N = 9; H is a set value; In step S3), the execution of the PWM pulse width modulation braking method includes the following steps: Record the timer timing value when the current brake interval variable i does not change, and judge whether the timing value is greater than or equal to the difference between the maximum brake time threshold and the brake interval variable i; If it is less, output a control electrical signal in the PWM manner, and make the fan work through the driving fan drive circuit; Otherwise, output a low-level signal to brake the fan.

2. A medical ventilator bi-level pressure conversion control system according to claim 1, comprising a medical ventilator bi-level pressure conversion control algorithm, characterized in that, The obtaining of the flow value at the ventilator outlet end through the differential pressure at the ventilator outlet end, and then obtaining the patient's spontaneous breathing moment includes the following steps: Obtain the patient's flow rate parameter according to the flow value at the ventilator outlet end; Obtain the inhalation trigger moment and the exhalation trigger moment according to the patient's flow rate parameter.

3. A bi-level pressure conversion control system for a medical ventilator according to claim 2, comprising a bi-level pressure conversion control algorithm for a medical ventilator, characterized in that, The patient's flow rate parameter includes at least one of the patient's total leakage volume, the patient end leakage volume, and the patient end flow rate.

4. A bi-level pressure conversion control system for a medical ventilator according to claim 1, comprising a bi-level pressure conversion control algorithm for a medical ventilator, characterized in that, In step S2), when the difference between the currently collected mask end pressure and the set EPAP pressure value is less than or equal to the set error, execute step S4).

5. A bi-level pressure conversion control system for a medical ventilator according to claim 1, comprising a bi-level pressure conversion control algorithm for a medical ventilator, characterized in that, In step S3), when the current mask pressure is less than or equal to the set EPAP pressure value, execute step S4).

6. The dual-level pressure conversion control system for a medical ventilator according to claim 1, characterized in that, It includes: A flow acquisition module for obtaining the flow value at the ventilator outlet end through the differential pressure at the ventilator outlet end, and then obtaining the patient's spontaneous breathing moment; A pressure conversion module for starting from the moment when inhalation turns to exhalation, that is, the exhalation trigger moment, when the difference between the currently collected mask end pressure and the set EPAP pressure value is greater than the set error, then when the current mask pressure is greater than the set EPAP pressure value, determine the value of the brake interval variable i, and execute the PWM pulse width modulation braking method to make the fan operate; An exhalation stability control module for entering the exhalation pressure stabilization stage, that is, adopting closed-loop control of the fan speed according to the set EPAP pressure value.

7. A dual-level pressure conversion control device for a medical ventilator, characterized in that, It includes a memory and a processor; the memory is used to store a computer program; the processor is used, when executing the computer program, to apply to a medical ventilator bi-level pressure conversion control system as described in any one of claims 1-5, including a medical ventilator bi-level pressure conversion control algorithm.

8. A computer-readable storage medium, characterized in that, The storage medium stores a computer program, which, when executed by a processor, is applied to a medical ventilator bi-level pressure conversion control system as described in any one of claims 1-5, including a medical ventilator bi-level pressure conversion control algorithm.

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