An oxygen concentration control device

Abstract

The oxygen concentration control device comprises a Venturi device provided with an air inlet and an air outlet, the air inlet is divided into a driving air inlet and a driven air inlet, the air inlet is connected with an oxygen source and an air source, and the gas from the oxygen source and the air source is mixed into gas with a set flow rate and oxygen concentration; the air outlet is connected with a breathing valve through an air outlet channel; the oxygen source is connected with the Venturi device through a flow control channel and an oxygen supplement channel, the flow control channel is connected with the driving air inlet of the Venturi device, and the oxygen supplement channel is connected with the driven air inlet of the Venturi device after being combined with the air inlet channel of the air source; the air source is connected with the Venturi device through an air inlet channel, and the air inlet channel is connected with the driven air inlet of the Venturi device after being combined with the oxygen supplement channel of the oxygen source; and the oxygen concentration control device controls the oxygen concentration of the gas in the air outlet channel by adjusting the flow rate of the oxygen supplement channel.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ventilator ventilation control, in particular to an oxygen concentration control device. BACKGROUND

[0002] At present, medical ventilators are divided into therapeutic ventilators and emergency ventilators, and different control methods of output oxygen concentration are adopted: the therapeutic ventilator usually configures an air compressor or a turbine to adjust the output oxygen concentration; the emergency ventilator, in order to be convenient to carry, generally does not configure an air compressor or a turbine, but mainly uses an oxygen source and a Venturi device to generate air-oxygen mixed gas, and then adjusts the output oxygen concentration.

[0003] In the existing emergency ventilator, the adjustment of oxygen concentration is mainly performed by means of joint adjustment of an electromagnetic valve and a mechanical valve (adjustment of oxygen concentration mechanical valve by an operator). The aforementioned adjustment method of the prior art has two problems: on the one hand, it can only adjust the oxygen concentration in a small range; on the other hand, it cannot realize accurate control of the oxygen concentration, but can only control the oxygen concentration with a relatively rough accuracy (10% adjustment accuracy) of "60%, 70%, 80%". SUMMARY

[0004] In order to overcome the poor oxygen concentration adjustment accuracy caused by the joint adjustment of an electromagnetic valve and a mechanical valve in the existing emergency ventilator, the present application uses two electronic proportional valves to realize the ventilation control function of the ventilator (adjustment of output flow and oxygen concentration), and simultaneously uses two PID algorithms to perform closed-loop control on the two proportional valves, so as to realize large-range and high-precision control of the oxygen concentration on the basis of realizing the ventilation control function.

[0005] Specifically, the present application provides an oxygen concentration control device, which comprises:

[0006] (1) a Venturi device, which is provided with an air inlet and an air outlet, the "air inlet" is divided into a driving air inlet and a driven air inlet, the gas entering the driving air inlet will form a negative pressure in the interior of the Venturi device, which will cause a certain proportion of gas to be sucked into the Venturi device from the driven air inlet, wherein the "air inlet" is connected with an "oxygen source and an air source", and the gas from the oxygen source and the air source is mixed into gas with a set flow and oxygen concentration, and then is transported to a breathing valve through the air outlet via an air outlet passage; the air outlet is connected with the breathing valve via the air outlet passage;

[0007] (2) an oxygen source, which is connected with the Venturi device via a flow control passage and an oxygen supplement passage, wherein the "flow control passage" is connected with the driving air inlet of the Venturi device, and the "oxygen supplement passage" is connected with the driven air inlet of the Venturi device after being combined with an "air inlet passage" of an air source;

[0008] (3) an air source, which is connected to the Venturi device through an air inlet channel, wherein the air inlet channel is combined with the oxygen supplement channel of the oxygen source, and the combined channel is connected to the driven inlet of the Venturi device;

[0009] The oxygen concentration control device adjusts the flow rate of the oxygen supplement channel to adjust the composition of oxygen and air in the gas entering the Venturi device through the driven inlet, thereby controlling the oxygen concentration of the gas in the outlet channel.

[0010] More preferably, the flow control channel is provided with a first proportional valve, i.e., an air suction control proportional valve, which adjusts the flow rate of the gas entering the driven inlet of the Venturi device by adjusting the opening degree of the air suction control proportional valve, thereby adjusting the total flow rate of the outlet channel.

[0011] More preferably, the outlet channel is provided with a first flow sensor, i.e., an air suction flow sensor, which measures the actual value of the total flow rate.

[0012] More preferably, the first proportional valve is provided with a first PID feedback control loop, which adjusts the opening degree of the first proportional valve according to the error between the actual value of the total flow rate measured by the first flow sensor and the target value of the total flow rate set in advance, to reduce the error between the actual value of the total flow rate and the target value of the total flow rate, thereby achieving accurate control of the total flow rate.

[0013] More preferably, the oxygen supplement channel is provided with a second proportional valve, i.e., an oxygen supplement proportional valve, which adjusts the flow rate of the oxygen supplement channel, thereby adjusting the composition of oxygen and air in the gas entering the Venturi device through the driven inlet.

[0014] More preferably, the air inlet channel is provided with a second flow sensor, i.e., an air flow sensor, which measures the air flow rate value sucked by the Venturi device.

[0015] More preferably, the second proportional valve is provided with a second PID feedback control loop, which adjusts the opening degree of the second proportional valve according to the difference between the actual value of the total flow rate of the airway measured by the first flow sensor and the flow rate value of the air inlet passage measured by the second flow sensor, so that the difference between the actual value of the total flow rate of the airway and the flow rate value of the air inlet passage corresponds to the set oxygen concentration of the outlet passage, and the difference between the actual value of the total flow rate of the airway and the flow rate value of the air inlet passage is constant at the set total flow rate of the airway and oxygen concentration value, thereby achieving accurate control of the oxygen concentration of the outlet passage.

[0016]

[0017] In the formula, F VO is the flow rate value of the oxygen supplement passage, F VInsp is the flow rate value of the flow control passage, and the sum of the two is the difference between the actual value of the total flow rate of the airway and the flow rate value of the air inlet passage, F All is the actual value of the total flow rate of the airway, O xyCon is the set value of the oxygen concentration of the outlet passage.

[0018] More preferably, the oxygen concentration control device further comprises a pressure reducing valve, which is connected to the oxygen source and located upstream of the flow control passage and the oxygen supplement passage, and the high-pressure oxygen source enters the flow control passage and the oxygen supplement passage after being reduced to a set pressure by the pressure reducing valve.

[0019] The technical effect of the present application is that the minimum oxygen concentration of the existing emergency respirator is usually 40-45%, and the maximum oxygen concentration is 100%, compared with the prior art, the lower limit of the adjustable minimum oxygen concentration of the device can reach below 40% under the condition of good Venturi characteristics, realizing a larger oxygen concentration adjustment range. In addition, the present patent realizes the control of oxygen concentration through air-oxygen flow ratio closed loop, instead of the feedback of the chemical oxygen sensor commonly used in the prior art, and uses high-precision proportional valve instead of the mechanical valve commonly used in the prior art, so that the oxygen concentration control precision of the present application is higher than that of the prior art and the control response speed is faster. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1The schematic diagram of the device structure and control principle of the present application, wherein the pressure sensor, PEEP control valve and the oxygen concentration control device of the present application are irrelevant, and are listed only for the structural integrity of the breathing machine; the "inspiration control proportional valve" and "oxygen supplement proportional valve" in the figure are "first proportional valve" and "second proportional valve"; the "air flow sensor" and "inspiration flow sensor" in the figure are "second flow sensor" and "first flow sensor";

[0021] Figure 2 The schematic diagram of the inspiration control proportional valve of the present application to realize constant flow control;

[0022] Figure 3 The schematic diagram of the oxygen supplement proportional valve of the present application to realize oxygen concentration control. DETAILED DESCRIPTION

[0023] The control of the flow and oxygen concentration of the emergency breathing machine of the present application is mainly realized by the control of the inspiration control proportional valve and the oxygen supplement proportional valve, and the control principle is as shown in the figure. Figure 1

[0024] Among them, the breathing machine is connected with a high-pressure oxygen source of 0.25-0.6 Mpa, and then the pressure of the high-pressure source is reduced to a constant value by a pressure reducing valve, and then is given to the front end of the inspiration control proportional valve and the front end of the oxygen supplement proportional valve.

[0025] The process of flow control and oxygen concentration control of the present application is described as follows:

[0026] I. Flow control

[0027] Since the pressure at the front end of the inspiration control proportional valve is much larger than that at the rear end, the pressure difference between the front end and the rear end can be approximately a constant value, so that after the opening of the inspiration control proportional valve is fixed, the flow at the rear end of the inspiration control proportional valve is approximately constant.

[0028] At the same time, after the output flow F VInsp of the inspiration control proportional valve is fixed, a negative pressure will be formed in the Venturi device, and a certain proportional air F VInsp will be inhaled according to the size of the output flow F Air of the inspiration control proportional valve, F VInsp = αF VInsp , and F Air is mixed with F All to become the final airway flow F VInsp , wherein α is a proportional coefficient, and its value is related to the characteristics of the Venturi device and the size of F All , and is generally 5-7.

[0029] F Air = F VInsp +F VInsp ​+F Insp (1)

[0030] Therefore, it can be considered that the total flow F All and the flow F VInsp output by the inhalation control proportional valve are in a positive proportional relationship. Since the flow output by the proportional valve is positively correlated with the driving voltage of the proportional valve, the relationship curve between the total flow and the control voltage of the inhalation control proportional valve can be calibrated in advance. When the total flow needs to be controlled, the proportional valve control voltage corresponding to the target total flow can be obtained in advance through the proportional valve characteristic curve, as a feedforward value of the control quantity.

[0031] Further, in order to make the total flow F All control more accurate, the real-time value of the total flow is collected as feedback, and PID operation is performed with the target value of the total flow, and the operation result is used as the feedback control quantity of the inhalation proportional valve control voltage. The combination of feedforward and feedback control methods makes the inhalation port flow quickly and accurately reach the target value, which serves as the basis for the constant flow control mode of the breathing machine VCV, and the constant flow control principle is shown in Figure 2 .

[0032] II. Oxygen concentration control

[0033] When adjusting the opening of the oxygen supplement proportional valve, the proportion of oxygen volume in the inhalation Venturi device flow can be changed to achieve oxygen concentration control.

[0034] Assuming that the oxygen flow F VO2 output by the oxygen supplement proportional valve is F VInsp , then

[0035] αF VInsp =F VO2 +F Air (2)

[0036] The oxygen concentration is defined as the ratio of the total oxygen volume to the total gas volume in the gas, and the gas volume is the integral of the flow, so the oxygen concentration of the output gas can be calculated by calculating the ratio of the total pure oxygen flow F O2 to the total gas flow F All at the outlet of the Venturi device. The oxygen concentration value is

[0037]

[0038] When the oxygen supplement proportional valve is completely closed, F VO2 is 0, at which time the oxygen concentration is the lowest. According to formulas (2) and (3), the minimum oxygen concentration is

[0039]

[0040] In the case of normal flow (about > 6L / min), the α value of the Venturi device is about 5-7, i.e. the minimum oxygen concentration is 30-34%. But when the driving gas flow of the Venturi device is low, the inhaled air tends to 0, i.e. the α value tends to 0, which will lead to the increase of the minimum oxygen concentration, so the controllable range of the minimum oxygen concentration is 40%.

[0041] When the oxygen supplement proportional valve is fully opened, the pressure at the front end of the oxygen supplement proportional valve is much higher than the atmospheric pressure, so the pressure at the front and rear ends is greater than the atmospheric pressure, which makes the external gas brought in by the Venturi device almost all pure oxygen, and air cannot enter, i.e. formula (3) F Air tends to 0, at which time the oxygen concentration value tends to 100%.

[0042] That is, in the case of normal operation of the machine, the flow F VO of the oxygen supplement proportional valve can be adjusted by adjusting the opening of the oxygen supplement proportional valve, so that the oxygen concentration is controllable in the range of 40%-100%.

[0043] From formula (3), the relationship between the total flow of the air suction control proportional valve and the oxygen supplement proportional valve and the oxygen concentration is

[0044]

[0045] According to the above analysis, when the opening of the air suction control proportional valve remains unchanged, the values of F VInsp and F All remain unchanged. When the machine needs to adjust the oxygen concentration at this flow, the opening of the oxygen supplement proportional valve can be adjusted to change the proportion of oxygen flow in the external gas flow brought in by the Venturi device, at which time it will not affect the flow F VInsp and the total flow F All of the airway in the air suction control proportional valve. (When the opening of the air suction control proportional valve is constant, F VInsp is constant, and the flow αF VInsp inhaled into the Venturi device is also constant. When the oxygen supplement proportional valve is closed, αF VInsp is all air, and the oxygen concentration is the lowest at this time. When the oxygen concentration needs to be adjusted, the oxygen supplement proportional valve is opened to change the proportion of oxygen flow in the flow αF VInsp inhaled into the Venturi device, thereby reducing the proportion of air, so as to realize the control of the oxygen concentration. The oxygen supplement proportional valve exists independently of the air suction control proportional valve, so adjusting the oxygen supplement proportional valve only changes the proportion of oxygen and air inhaled by the Venturi, and does not affect F VInsp and F All . F VInsp and F All are only related to the opening of the air suction control proportional valve.

[0046] When the ventilator is in different operating modes, F VInsp The F value will change depending on the parameter settings of different modes (the ventilator includes different breathing modes, such as PCV, VCV, etc., and the F value will change under different parameter settings in different modes). VInsp The target values ​​are also different. Based on the given target output oxygen concentration, the target oxygen flow rate required by the two valves at the target oxygen concentration can be calculated by equation (4). The "target oxygen flow rate required by the two valves" and the "actual oxygen flow rate of the two valves" are used as the two input parameters of the PID controller of the oxygen supplement proportional valve. The PID output is the voltage or PWM of the oxygen supplement proportional valve, so that the target oxygen flow rate of equation (4) can be satisfied by adjusting the flow rate of the oxygen supplement proportional valve, thereby realizing the control of the target oxygen concentration. The oxygen concentration feedback control principle is as follows: Figure 3 As shown, the total flow feedback F All and airflow feedback F Air All of these can be collected through flow sensors.

[0047] The technical solutions provided by the present invention will be further illustrated below with reference to the embodiments.

[0048] like Figure 1 The diagram illustrates the gas path structure and simplified control principle block diagram of this novel emergency ventilator for achieving high-precision oxygen concentration control. The device mainly includes a pressure reducing valve for constant pressure, two high-precision electronic proportional valves for controlling airway flow and oxygen concentration respectively, two flow sensors for acquiring total airway flow and inhaled air flow respectively, a pressure sensor for acquiring airway pressure, and a PEEP control valve and a breathing valve for achieving PEEP control (the pressure sensor and PEEP control valve are unrelated to the oxygen concentration control of this invention and are listed only for the sake of structural completeness of the ventilator). The flow direction of the gas in the entire gas path and the location of the device are indicated by arrows.

[0049] like Figure 2 As shown, in Figure 1 Based on the device, accurate control of total airway flow is achieved through a feedforward and feedback mechanism using an inspiratory control proportional valve. The flow rate setpoint is the target flow rate given after the ventilator's breathing mode is set, and the flow rate feedback is... Figure 1 The real-time value of total airway flow collected by the mid-inspiratory flow sensor.

[0050] like Figure 3As shown, the method for further realizing the oxygen concentration control in the total flow control of the inhalation control proportional valve is described. The target value of the flow sum of the two proportional valves under the current total flow can be calculated through the set oxygen concentration target value, the feedback value of the flow sum of the two proportional valves can be obtained through the difference of the inhalation flow sensor and the air flow sensor, and the opening of the oxygen supplement proportional valve can be obtained through the PID closed loop algorithm on the basis.

[0051] From the above specific description of the present application, it can be seen that the oxygen concentration control device provided by the present application ingeniously realizes the basic flow control requirement of the emergency respirator and the oxygen concentration control requirement of a large range and high precision.

[0052] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application is described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. An oxygen concentration control device for emergency ventilator, comprising: (1) a Venturi device, provided with an inlet and an outlet, wherein the inlet is divided into a driving inlet and a driven inlet, and wherein the inlet is connected to an oxygen source and an air source, and the gas from the oxygen source and the air source is mixed into gas with a set flow rate and oxygen concentration, and then the gas is delivered to a breathing valve through the outlet and an outlet passage; the outlet is connected to the breathing valve through the outlet passage; (2) an oxygen source, connected to the Venturi device through a flow control passage and an oxygen supplement passage, wherein the flow control passage is connected to the driving inlet of the Venturi device, and the oxygen supplement passage is connected to the driven inlet of the Venturi device after being combined with an air inlet passage of an air source; (3) an air source, connected to the Venturi device through an air inlet passage, wherein the air inlet passage is connected to the driven inlet of the Venturi device after being combined with the oxygen supplement passage of the oxygen source; the oxygen concentration control device controls the oxygen concentration of the gas in the outlet passage by adjusting the flow rate of the oxygen supplement passage; the flow control passage is provided with a first proportional valve for adjusting the flow rate into the driving inlet of the Venturi device, thereby adjusting the total flow rate of the outlet passage; the outlet passage is provided with a first flow rate sensor; the first proportional valve is provided with a first PID feedback control loop, which adjusts the opening degree of the first proportional valve according to the error between the actual value of the total flow rate measured by the first flow rate sensor and the target value of the total flow rate set in advance; the oxygen supplement passage is provided with a second proportional valve; the air inlet passage is provided with a second flow rate sensor for measuring the air flow rate value sucked by the Venturi device; the second proportional valve is provided with a second PID feedback control loop, which adjusts the opening degree of the second proportional valve according to the difference between the actual value of the total flow rate measured by the first flow rate sensor and the air flow rate value measured by the second flow rate sensor, so that the difference between the actual value of the total flow rate and the air flow rate value corresponds to the set oxygen concentration of the outlet passage, and the oxygen concentration of the outlet passage is accurately controlled; the relationship between the difference between the actual value of the total flow rate and the air flow rate value and the set oxygen concentration of the outlet passage is:

2. The oxygen concentration control device for emergency ventilator according to claim 1, further comprising a pressure reducing valve. wherein F VO2 is the flow value of the oxygen make-up passage, F VInsp is the flow value of the flow control passage, the sum of which is the "difference between the actual value of the total flow of the airway and the flow value of the air intake passage", F All is the actual value of the total flow of the airway, O xyCon is the set value of the oxygen concentration of the outlet passage. the pressure reducing valve is connected to the oxygen source and located in the upstream gas path of the flow control passage and the oxygen supplement passage, and the high-pressure oxygen source is reduced to a set pressure through the pressure reducing valve before entering the flow control passage and the oxygen supplement passage. ​ ​

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