Venturi-based lung gas exchange function detection system and method

Abstract

The application discloses a kind of lung gas exchange function detection system and method based on Venturi tube, including Venturi sampling device, gas analysis processing device, standard gas conveying device;The Venturi sampling device passes through the gas passage based on Venturi tube and mixing chamber is established, and after the standard gas conveying device provides test gas, the test gas of subject to be tested is generated;The gas analysis processing device is analyzed and handled after the standard gas of the test gas received and the standard gas conveying device is transported, and generates lung gas exchange function detection result.The present application is based on Venturi tube and mixing chamber, realizes respectively to the constant proportion collection and physical buffer of human exhaled gas, avoids hundred millisecond level real-time human respiratory gas analysis, simultaneously, avoids the error of non-dispersive infrared gas sensor caused by air pressure and air flow fluctuation, improves the precision of lung gas exchange function detection.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lung function detection, in particular to a lung ventilation function detection system and method based on a Venturi tube. BACKGROUND

[0002] The existing classical lung ventilation function detection equipment usually constructs a gas analyzer with an electrochemical sensor as the core, and cooperates with the test gas circuit and gas collection bag of the lung ventilation test method. However, some existing lung ventilation capacity detection equipment, especially those technical solutions that use constant speed pumps to extract sampling gas and perform real-time concentration analysis, often have very high requirements for the dynamic response performance of the gas concentration sensor, such as a response time usually less than 150 milliseconds, which not only leads to high cost and limited selection of the core sensor, but also when the subject's exhalation flow rate changes greatly, the instantaneous fluctuations of the sensor readings may introduce significant measurement noise. In addition, such equipment also faces challenges in stable control of the sampling gas flow and pressure entering the analysis cavity, especially when accurate information of gas components at different stages of exhalation is required, small fluctuations in flow or pressure may affect the accuracy of concentration measurement.

[0003] Currently, lung ventilation capacity detection mainly relies on fast-response gas sensors. Patent document CN113854997B discloses a lung diffusion function examination device and method based on one-breath method. The device extracts the lung diffusion test index by extracting the subject's exhaled gas at a constant speed into a non-dispersive infrared sensor to realize real-time concentration detection of human exhaled gas. Although the device and method can realize fast detection of lung diffusion capacity and can avoid cross-infection, it still has limitations: the method has very high requirements for the response time of the gas sensor, which needs to be less than 150 milliseconds, which greatly increases the cost of the gas sensor and is not easy to implement in engineering, thereby limiting the popularization of lung ventilation capacity detection in China.

[0004] In addition, some physiological behaviors can affect the accuracy of lung ventilation test indicators, such as changes in lung pressure during the breath-holding phase. The lung diffusion function examination device and method based on one-breath method disclosed in patent document CN113854997B and the detection system for lung diffusion function disclosed in patent document CN202111271625.8 do not involve detection of the above physiological behaviors. If the subject does not strictly complete the test according to the standard, the final lung ventilation test indicator will have a serious deviation. SUMMARY

[0005] To solve the above technical problems, the present application provides a lung ventilation function detection system and method based on a Venturi tube, which is designed as a human lung ventilation capacity detection system and method with reliable air path structure, high measurement accuracy and low requirement for dynamic performance of a gas concentration sensor, and can realize high safety and high comfort lung ventilation function detection.

[0006] To achieve the above object, the present application provides the following scheme:

[0007] In the first aspect, the present application provides a lung ventilation capacity detection system based on a Venturi tube, which comprises a Venturi sampling device, a gas analysis processing device and a standard gas delivery device.

[0008] The Venturi sampling device establishes a gas path based on a Venturi tube and a mixing chamber, and generates test gas of a subject after the standard gas delivery device provides test gas.

[0009] The gas analysis processing device generates a lung ventilation capacity detection result after analyzing and processing the received test gas and the standard gas delivered by the standard gas delivery device.

[0010] The Venturi tube and the mixing chamber are each provided with a port a, a port b, a port c and a port d, the gas path comprises a main gas flow path formed by the port a and the port d of the Venturi tube, and an auxiliary gas flow path formed by the port b of the Venturi tube connected to the port a, the port b of the mixing chamber and the port c of the Venturi tube in sequence, and the port c and the port d of the mixing chamber are connected to the gas analysis processing device.

[0011] Further, the Venturi tube comprises a gradually converging inlet section, a throat section with a diameter smaller than that of the main gas flow path, and a gradually diverging outlet section, when the respiratory gas flow passes through the port a and the port d of the Venturi tube, a pressure difference is formed between the port b and the port c of the Venturi tube, so that the exhaled gas flow in the Venturi tube enters the mixing chamber at a flow rate proportional to the exhaled gas flow rate of the port a and the port b of the Venturi tube, and is discharged to the port c of the Venturi tube through the port b of the mixing chamber after mixing and averaging, to realize proportional sampling of the exhaled gas flow.

[0012] Further, the Venturi sampling device further comprises a mouthpiece, a first air pressure sensor, an ultrasonic flow sensor, a first on-off valve, a second on-off valve and an air tube connected with air, wherein the mouthpiece is connected with the ultrasonic flow sensor, the a port of the Venturi tube to the d port of the Venturi tube in sequence, and then connected with one end of the first on-off valve and the second on-off valve respectively, the other end of the first on-off valve is connected with the air tube, the other end of the second on-off valve is connected with the standard gas delivery device, and the first air pressure sensor is connected between the mouthpiece and the ultrasonic flow sensor.

[0013] Further, the gas analysis processing device comprises a third electromagnetic valve, a gas flow controller, a micro flow sensor, a non-dispersive infrared gas sensor, a buffer tank, a gas resistance and a gas suction pump connected in sequence, wherein the non-dispersive infrared gas sensor is connected with the second air pressure sensor between the buffer tank, the output end of the gas suction pump is connected with the c port of the mixing chamber, and the third electromagnetic valve is connected with the d port of the mixing chamber.

[0014] Further, the third electromagnetic valve is a two-position three-way type, comprising a common port a port, a normally open port b port and a normally closed port c port, wherein the c port of the third electromagnetic valve is connected with the standard gas delivery device, and the b port of the third electromagnetic valve is connected with the d port of the mixing chamber.

[0015] Further, the standard gas delivery device comprises a first high-pressure standard gas source, a first pressure-reducing valve and a first solenoid valve connected in sequence; and a second high-pressure standard gas source, a second pressure-reducing valve and a second solenoid valve connected in sequence; the first pressure-reducing valve and the first solenoid valve are connected with an inhalation gas pressure equalization device, and are connected to the second switch valve through the inhalation gas pressure equalization device, wherein the first solenoid valve and the second solenoid valve each comprise a gas inlet port c port, a gas outlet port a port, and a port b port for discharging gas into the air; the a port of the first solenoid valve and the a port of the second solenoid valve are connected to the c port of the third solenoid valve. Further, the non-dispersive infrared gas sensor is used for calibrating gas concentration, including first group gas concentration calibration and second group gas concentration calibration, when the first group gas concentration calibration is performed, the a port of the first solenoid valve and the c port of the third solenoid valve are connected, the second high-pressure standard gas source is closed, the first high-pressure standard gas source is opened, the standard gas passes through the first pressure-reducing valve, the first solenoid valve and the non-dispersive infrared gas sensor in sequence, the average value of the gas concentration in the ventilation and collection period is obtained, and the range point calibration of the non-dispersive infrared gas sensor is completed; when the second group gas concentration calibration is performed, the second solenoid valve and the third solenoid valve are enabled, the a port of the second solenoid valve and the c port of the third solenoid valve are connected, the first high-pressure standard gas source is closed, the second high-pressure standard gas source is opened, the standard gas passes through the second pressure-reducing valve, the second solenoid valve and the non-dispersive infrared gas sensor in sequence, the average value of the gas concentration in the ventilation and collection period is obtained, and the zero point calibration of the non-dispersive infrared gas sensor is completed.

[0016] Wherein, when the first group gas concentration calibration is performed, the standard gas is discharged into the air through the b port of the first solenoid valve, and when the second group gas concentration calibration is performed, the standard gas is discharged into the air through the b port of the second solenoid valve.

[0017] In a second aspect, the present application provides a detection method based on the Venturi tube-based lung gas exchange capacity detection system of the first aspect, the detection method comprising the following steps:

[0018] Step S101. The operator debugs the Venturi tube-based lung gas exchange capacity detection system, and performs gas concentration calibration based on the non-dispersive infrared gas sensor and flow rate volume calibration of the ultrasonic flow sensor;

[0019] Step S102. After completing the gas concentration calibration and flow rate volume calibration, start the pulmonary ventilation function test on the subject, the subject correctly wears the mouthpiece, the first switch valve is opened, the second switch valve is closed, and normal air breathing is performed through the mouthpiece until three to four tidal breaths of air are completed and exhaled to the lung residual volume; then, the first switch valve is closed, the second switch valve is opened, and the subject inhales the test gas to the total lung capacity through the mouthpiece and the inhalation gas pressure equalization device; all valves and the first high-pressure calibration gas source are closed, and the subject maintains a breath-holding state for 8-10 seconds; then, the first switch valve is opened, and the subject exhales the gas to the lung residual volume; during this period, the exhaled gas flows from the b port of the Venturi tube to the a port of the mixing chamber at a specific ratio, and is physically averaged in the mixing chamber; finally, under the action of the suction pump, the exhaled gas in the mixing chamber passes through the d port of the mixing chamber, the third electromagnetic valve, the gas flow controller, the micro-flow sensor, the non-dispersive infrared gas sensor, the buffer tank, the gas resistance, and the suction pump in turn, and finally returns to the c port of the mixing chamber and is discharged to the c port of the Venturi tube through the b port of the mixing chamber; wherein the non-dispersive infrared gas sensor detects the concentrations of methane and carbon monoxide in the exhaled gas; complete the entire test process;

[0020] Step S103. Calculate the pulmonary ventilation capacity detection result of this test according to the obtained detection data.

[0021] Further, the pulmonary ventilation capacity detection result of this test calculated in step S103 includes the alveolar volume V A and the carbon monoxide lung diffusion capacity D LCO , specifically:

[0022] V A = V E + V ee - V D

[0023]

[0024] wherein,

[0025] V D = V Danat + V Dequip = 2.2 x w + V Dequip

[0026]

[0027] In the above formula, V A is the alveolar volume, V E is the volume of exhaled gas during the exhalation phase, V ee is the lung residual volume, V D is the dead space volume, and F ACOF is the concentration of carbon monoxide in the alveoli, ICO F is the concentration of carbon monoxide in the inhaled test gas, ACH4 F is the concentration of methane in the alveoli, ICH4 F is the concentration of methane in the inhaled test gas, BH D is the breath-holding time, LCO P is the carbon monoxide lung diffusion capacity, B P is the ambient atmospheric pressure, H2O V is the alveolar water vapor partial pressure, Dequip V is the equipment dead space volume, Danat V is the human dead space volume, w is the weight of the subject, and T is the test time, ree t0 is the inhaled test gas time, t is the average concentration of end-tidal methane, f Tr(t) is the real-time concentration of methane in the main airflow path, e Q(t) is the real-time airflow rate of the main airflow path, ree-avg t1 and t2 are the end-tidal test periods, t is the constant value of the average concentration of end-tidal methane, ree V is the volume of the mixing chamber, and k is the proportional coefficient.

[0028] Further, during the test in step S102, a dynamic judgment process based on a sampling window is established to achieve adaptive determination of F ACO and the use interval of F ACH4 , the dynamic judgment process of the sampling window includes a dynamic opening time and a dynamic termination time of the sampling window; wherein the dynamic opening time includes when the cumulative exhaled gas volume is greater than or equal to the set initial cumulative exhaled volume lower limit, and then determining whether the real-time exhalation flow rate stability index is lower than the preset stability threshold value, if yes, the sampling window is opened;

[0029] The dynamic termination time includes if the real-time exhalation flow rate is lower than the preset minimum effective exhalation flow rate threshold value; or, the real-time exhalation flow rate stability index exceeds the preset stability threshold value again; or, the cumulative exhaled gas volume exceeds the preset upper limit value, then the sampling window is terminated.

[0030] The beneficial effects obtained by the present application are:

[0031] (1) The present application is based on a Venturi tube and a mixing chamber, which realizes constant proportional collection and physical buffering of human exhaled gas respectively, avoids real-time human respiratory gas analysis at the level of hundreds of milliseconds, reduces the dynamic performance requirements of non-dispersive infrared gas sensors, and makes it easier to implement lung gas exchange function detection and analysis in engineering;

[0032] (2) The application realizes constant pressure and constant flow control in the analysis process of the components of human exhaled air and standard gas concentration through the gas analysis processing device, avoids the error of the non-dispersive infrared gas sensor caused by gas pressure and gas flow fluctuation, and improves the accuracy of lung gas exchange function detection. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural schematic diagram of the lung gas exchange capacity detection system based on the Venturi tube of the application.

[0034] Figure 2 is a flow schematic diagram of the lung gas exchange capacity detection method based on the Venturi tube of the application.

[0035] Among them, the reference signs are: 1-bite, 2-first air pressure sensor, 3-ultrasonic flow sensor, 4-Venturi tube, 5-mixing chamber, 6-first on-off valve, 7-second on-off valve, 8-third electromagnetic valve, 9-gas flow controller, 10-micro flow sensor, 11-NDIR sensor, 12-buffer tank, 13-gas resistance, 14-pump, 15-second air pressure sensor, 16-first high-pressure calibration gas source, 17-first pressure reducing valve, 18-first electromagnetic valve, 19-second high-pressure calibration gas source, 20-second pressure reducing valve, 21-second electromagnetic valve, 22-inhalation air pressure equalizing device, 23-host computer, 24-control module. DETAILED DESCRIPTION

[0036] The following further describes the application in conjunction with the drawings, and it is necessary to point out here that the following detailed description is only used to further illustrate the application and cannot be understood as limiting the protection scope of the application, and those skilled in the art can make some non-essential improvements and adjustments to the application according to the above application content.

[0037] As Figure 1 shown, the application provides a lung gas exchange capacity detection system based on a Venturi tube, which comprises a Venturi sampling device, a gas analysis processing device and a standard gas delivery device. The Venturi sampling device generates the test gas of the subject by establishing a gas path based on the Venturi tube and the mixing chamber and providing the test gas after the standard gas delivery device provides the test gas; the gas analysis processing device generates the lung gas exchange capacity detection result after analyzing and processing the received test gas and the standard gas delivered by the standard gas delivery device, wherein the Venturi sampling device samples the concentration of the exhaled air components, the gas analysis processing device is responsible for obtaining and analyzing the gas component concentration of the test gas, and the standard gas delivery device functions include: (1) providing the inhalation test gas during lung gas exchange test, i.e. high-pressure standard gas pressure reduction, pressure adjustment and supply output in the high-pressure gas source group; (2) providing the standard gas required for the concentration calibration of the gas analysis processing device, i.e. high-pressure standard gas pressure reduction, pressure relief and supply output in the high-pressure gas source group.

[0038] As Figure 1 shown, the Venturi sampling device first sets a Venturi tube 4 and a mixing chamber 5 with special geometric structure, which realizes accurate proportional sampling of gas. First, the Venturi tube 4 and the mixing chamber 5 are provided with a port a, a port b, a port c and a port d. The port a and the port d of the Venturi tube 4 are communicated to form a main gas flow path. The port b of the Venturi tube 4 is connected to the port a, the port b of the mixing chamber 5 in sequence and then to the port c of the Venturi tube 4 to form an auxiliary gas flow path. As Figure 1 shown, the Venturi tube 4 of the embodiment further includes a gradually converging inlet section, a throat portion with a diameter smaller than that of the main gas flow path, and a gradually diverging outlet section. The diameter of the throat portion of the Venturi tube 4 and the diameters of the port a and the port d are set in an optimized ratio, which is 0.45 in the embodiment, to ensure that a stable and sufficiently significant pressure drop can be generated within the normal physiological expiratory flow range (0.2 L / s to 8 L / s) of the subject.

[0039] Secondly, the mixing chamber 5 in the embodiment is also one of the key components of the gas processing link, which mainly functions to effectively physically buffer and homogenize the concentration of the exhaled gas obtained by proportional sampling. The mixing chamber 5 has a preset internal volume V, which is set according to the sampling requirements of the downstream gas analysis processing device and the desired buffering effect. In the embodiment, the effective volume V of the mixing chamber 5 is preferably 50 mL. The mixing chamber 5 essentially constitutes a physical low-pass filter, which is used to smooth the signal of the rapid fluctuation of the concentration of each component (such as CO, CH4) in the sampling gas over time. The filtering characteristics are mainly determined by the volume V of the mixing chamber 5 and the actual sampling flow rate Q_sample of the downstream gas analysis processing device. The significant technical effect brought by this is that the mixing chamber 5 can effectively attenuate and average the instantaneous high-frequency fluctuations of the sampling gas concentration caused by factors such as uneven mixing of alveolar gas and dead space gas in the respiratory cycle or expiratory flow rate changes. After being processed by the mixing chamber 5, the concentration change of the gas delivered to the non-dispersive infrared gas sensor 11 of the gas analysis processing device for analysis will become relatively smooth and stable. This characteristic greatly reduces the requirement for the dynamic response speed of the non-dispersive infrared gas sensor 11. Compared with directly analyzing the rapidly changing sampling gas (which usually requires a sensor response time of less than 150 ms), the embodiment allows the use of NDIR sensors with relatively slower response times (for example, up to 500 ms or even longer), lower costs or better stability, or under the same sensor conditions, obtains a concentration measurement signal with lower noise and higher signal-to-noise ratio. Finally, a high-quality, easy-to-process, and more representative concentration curve of the average components of exhaled gas is output, which provides a basis for subsequent accurate calculation of carbon monoxide lung diffusion capacity DLCO and related physiological parameters.

[0040] In the embodiment, the Venturi sampling device further comprises a mouthpiece 1, a first air pressure sensor 2, an ultrasonic flow sensor 3, a first on-off valve 6, a second on-off valve 7 and an air pipe connected with air. The mouthpiece 1 is connected with the ultrasonic flow sensor 3, the a port of the Venturi tube 4 to the d port of the Venturi tube 4 in sequence, and then connected with one end of the first on-off valve 6 and the second on-off valve 7 respectively. The other end of the first on-off valve 6 is connected with the air pipe to air, forming a complete breathing path. The other end of the second on-off valve 7 is connected to the standard gas delivery device, and the first air pressure sensor 2 is connected between the mouthpiece 1 and the ultrasonic flow sensor 3.

[0041] The ultrasonic flow sensor 3 detects the bidirectional respiratory gas flow. When the total amount of inhaled test gas reaches the lung, the first on-off valve 6 is closed and the second on-off valve 7 is opened. The subject inhales the pressure-regulated test gas provided by the standard gas delivery device, which passes through the second on-off valve 7, the Venturi tube 4, the ultrasonic flow sensor 3 and the mouthpiece 1 in sequence. During this period, the ultrasonic flow sensor 3 obtains the inhaled flow of the test gas. Then, when the subject holds his breath for 8-10 seconds, the first on-off valve 6 and the second on-off valve 7 are closed, and the subject maintains the breath-holding state during this period. At the same time, the first air pressure sensor 2 detects the air pressure at the mouthpiece 1, i.e. the air pressure in the lung when holding breath. The completion of the breath-holding task of the subject is evaluated by the air pressure data. Finally, when the total amount of exhaled gas reaches the lung residual gas position, the first on-off valve 6 is opened and the second on-off valve 7 is closed. The exhaled gas passes through the mouthpiece 1, the ultrasonic flow sensor 3, the Venturi tube 4 and the first on-off valve 6 in sequence and returns to the air. During this period, the ultrasonic flow sensor 3 obtains the exhaled gas flow. At the same time, in the contraction section of the Venturi tube 4, the increase of the exhaled gas flow velocity causes the decrease of the air pressure at the contraction section, thereby generating the adsorption effect. When the cross-sectional areas of the four ports a, b, c and d of the Venturi tube 4 are set, proportional sampling of the sampled gas can be achieved. Specifically, when the exhaled gas flows through the a port and the d port of the Venturi tube 4, the air pressure difference between the b port and the c port of the Venturi tube 4 is formed, and the exhaled gas in the Venturi tube 4 enters the mixing chamber 5 in a proportion to the flow rate of the exhaled gas at the a port and the b port. After mixing, the exhaled gas is discharged from the b port of the mixing chamber 5 to the c port of the Venturi tube, achieving proportional sampling of the exhaled gas.

[0042] In the embodiment, the gas analysis processing device comprises a third electromagnetic valve 8, a gas flow controller 9, a micro flow sensor 10, a non-dispersive infrared gas sensor (NDIR) 11, a buffer tank 12, a gas resistance 13 and a gas suction pump 14 connected in sequence, wherein the NDIR sensor 11 is connected with the second gas pressure sensor 15 and the buffer tank 12, and the output end of the gas suction pump 14 is connected with the c port of the mixing chamber 5, wherein the third electromagnetic valve 8 is a two-position three-way type, comprising a common port a port, a normally open port b port and a normally closed port c port, wherein the c port of the third electromagnetic valve 8 is connected with the standard gas delivery device, and the b port of the third electromagnetic valve is connected with the d port of the mixing chamber.

[0043] It should be noted that the system of the embodiment further comprises a host computer 23 or a control device 24 externally connected or internally provided to realize analysis and processing of the acquired relevant data. The externally connected part does not constitute the protected content of the system and only needs to realize the corresponding function, so it is not described in detail. The host computer or the control device realizes monitoring of the pressure signal that can effectively reflect the pressure in the mouth and even the lung of the subject, which is collected by the first gas pressure sensor 2. As described above, in the test process, in the very short time (the first 200 milliseconds) when the subject starts to hold breath, the system first determines a stable pressure reference value (P_ref). Subsequently, during the entire breath-holding duration, the system compares the current monitored pressure value (P_t) with the reference value P_ref in real time. In the embodiment, a narrow pressure fluctuation threshold (ΔP_threshold) is preset, which is set to ±0.15 kPa. If the absolute difference |P_t-P_ref| between the monitored pressure value P_t and the pressure reference value P_ref at any time during breath-holding exceeds the preset threshold ΔP_threshold, the system determines that the quality of this breath-holding operation may be problematic. Such an over-threshold pressure fluctuation usually indicates that the subject fails to strictly maintain the breath-holding state, and may have situations such as mouthpiece air leakage, swallowing action, involuntary physiological action (Valsalva or Mueller action) and the like. These physiological behaviors will interfere with the stability of the gas distribution and partial pressure in the lung, and then significantly affect the accuracy of the indicators such as carbon monoxide lung diffusion capacity (DLCO) calculated subsequently. According to the monitored pressure fluctuation, the system is further configured to perform corresponding feedback or processing actions to improve the test quality control level. The system can display the pressure fluctuation curve in real time on the user interface of the host computer 23 and issue a warning signal to remind the operator to pay attention or guide the subject to adjust.

[0044] According to the principle of fluid dynamics (Bernoulli's law), when the exhaled air flows through the converging section of the Venturi tube (4) to the throat, the flow rate increases, resulting in a significant drop in static pressure at the throat region compared to the pressure at the upstream a-port. The present invention utilizes this negative pressure effect to passively and in real-time draw a portion of the exhaled air flow from the main flow path into the auxiliary flow path (b-port to c-port) through the b-port opened laterally at the throat or near-throat region. The key is to precisely control the geometric parameters of the Venturi tube (4), including the area ratio of the throat to the main channel, the position and aperture of the b-port, so that the sampling air flow Q_sample extracted from the b-port forms a stable and predictable proportional relationship with the total exhaled air flow Q_main flowing through the main gas path a-d-port, i.e. Q_sample = k * Q_main. The proportionality coefficient k is determined according to the geometric dimensions in this design, k = 0.03 (i.e. sampling 3% of the main air flow), and has good linearity and stability within the preset working flow range.

[0045] The passive proportional sampling mechanism achieved has the following significant advantages over traditional active pump sampling: first, the structure is simple, without the need for additional sampling pumps or complex flow control units to directly extract the main gas path gas, reducing the complexity and potential failure points of the system; second, the sampling ratio is guaranteed by fixed physical structure, with high stability and less susceptible to power fluctuations or pump performance drift; third, the sampling process responds in real time to changes in the main gas path flow, providing a more accurate reflection of the gas composition ratio at different exhalation times; fourth, the flow field disturbance to the main gas path is small, more in line with physiological breathing conditions.

[0046] In this embodiment, the standard gas delivery device includes a first high-pressure calibration gas source 16, a first pressure reducing valve 17, and a first solenoid valve 18 connected in sequence; and a second high-pressure calibration gas source 19, a second pressure reducing valve 20, and a second solenoid valve 21 connected in sequence; the first pressure reducing valve 17 and the first solenoid valve 18 are connected by an inhalation gas pressure equalization device 22 and connected to the second switch valve 7 through the inhalation gas pressure equalization device 22, wherein the first solenoid valve 18 and the second solenoid valve 21 each include a gas inlet port c-port, a gas outlet port a-port, and a port b-port for discharging gas into the air; the a-ports of the first solenoid valve 18 and the second solenoid valve 21 are connected to the c-port of the third solenoid valve, the b-port of the first solenoid valve 18 is connected to the b-port of the second solenoid valve and the air through a gas tube tee, the gas inlet of the inhalation gas pressure equalization device 22 is connected to the gas outlet of the first pressure reducing valve 17, and the gas outlet of the inhalation gas pressure equalization device 22 is connected to the gas inlet of the second switch valve 7 in the Venturi sampling device. In this embodiment, the first high-pressure calibration gas source is composed of 3000 ppm methane, 3000 ppm carbon monoxide, and a mixed gas containing 21% oxygen; the second high-pressure calibration gas source is composed of 100% nitrogen.

[0047] In the present embodiment, the NDIR sensor 11 is used for gas concentration calibration, including a first set of gas concentration calibration and a second set of gas concentration calibration. When the first set of gas concentration calibration is performed, the a port of the first electromagnetic valve 18 is connected to the c port of the third electromagnetic valve 8, the second high-pressure calibration gas source 19 is closed, and the first high-pressure calibration gas source 16 is opened. The standard gas passes through the first pressure reducing valve 17 and the first electromagnetic valve 18 to the non-dispersive infrared gas sensor 11 in sequence. The average gas concentration is collected for a period of time, and the range point calibration of the non-dispersive infrared gas sensor 11 is completed. The standard gas is discharged to the air through the b port of the first electromagnetic valve 18 via a gas pipe tee, thereby achieving pressure relief adjustment and supply of the first set of standard gas during sensor concentration calibration. When the second set of gas concentration calibration is performed, the second electromagnetic valve 21 and the third electromagnetic valve 8 are enabled, the a port of the second electromagnetic valve 21 is connected to the c port of the third electromagnetic valve 8, the first high-pressure calibration gas source 16 is closed, and the second high-pressure calibration gas source 19 is opened. The standard gas passes through the second pressure reducing valve 20 and the second electromagnetic valve 21 to the non-dispersive infrared gas sensor 11 in sequence. The average gas concentration is collected for a period of time, and the zero point calibration of the non-dispersive infrared gas sensor 11 is completed. Finally, the high-pressure calibration gas sources and valves are closed, and the gas concentration calibration of the NDIR sensor 11 is completed. The standard gas is discharged to the air through the b port of the second electromagnetic valve 21 via a gas pipe tee, thereby achieving pressure relief adjustment and supply of the second set of standard gas during sensor concentration calibration. When the total lung capacity is inhaled, first, the first electromagnetic valve 18 and the second electromagnetic valve 21 are disabled. Then, the second high-pressure calibration gas source 19 is closed, and the first high-pressure calibration gas source 16 is opened. The standard gas passes through the first pressure reducing valve 17 and the inhalation gas pressure equalization device 22 to the Venturi sampling gas path system in sequence. During this period, the inhalation gas pressure equalization device 22 is responsible for adjusting the pressure and flow of the test gas to adapt to the breathing needs of the subject, thereby achieving pressure adjustment and supply of the test gas during lung gas exchange function testing. In the present embodiment, the first high-pressure calibration gas source 16 is composed of 3000 ppm methane, 3000 ppm carbon monoxide, and a mixed gas containing 21% oxygen; and the second high-pressure calibration gas source 19 is composed of 100% nitrogen.

[0048] According to the purpose of the present application, the present application further provides a detection method of a Venturi tube-based lung gas exchange capacity detection system, as shown in Figure 2 The detection method specifically includes the following steps:

[0049] Step S101. The operator debugs the Venturi tube-based lung gas exchange capacity detection system and performs gas concentration calibration based on the non-dispersive infrared gas sensor and flow volume calibration of the ultrasonic flow sensor.

[0050] In this embodiment, the operator carries out NDIR sensor 11 gas concentration calibration and ultrasonic flow sensor 3 flow rate volume calibration. Specifically includes:

[0051] When calibrating the first set of standard gas concentration, the a port of the first solenoid valve 18 is connected to the c port of the third solenoid valve 8, the second high-pressure calibration gas source 19 is closed, the first high-pressure calibration gas source 16 is opened, the standard gas passes through the first pressure reducing valve 17, the first solenoid valve 18 to the non-dispersive infrared gas sensor 11, and the average gas concentration is collected for a period of time, and the range point calibration of the non-dispersive infrared gas sensor 11 is completed. The standard gas is discharged to the air through the first solenoid valve 18 b port through the gas tube three-way, realizing the pressure relief adjustment and supply of the first set of standard gas during sensor concentration calibration. When calibrating the second set of gas concentration, the second solenoid valve 21 and the third solenoid valve 8 are enabled, the a port of the second solenoid valve 21 is connected to the c port of the third solenoid valve 8, the first high-pressure calibration gas source 16 is closed, the second high-pressure calibration gas source 19 is opened, the standard gas passes through the second pressure reducing valve 20, the second solenoid valve 21 to the non-dispersive infrared gas sensor 11, and the average gas concentration is collected for a period of time, and the zero point calibration of the non-dispersive infrared gas sensor 11 is completed. Finally, close each high-pressure calibration gas source and valve, and complete the gas concentration calibration of the NDIR sensor 11.

[0052] When calibrating the flow of the ultrasonic flow sensor 3, first disconnect the bite mouth 1 from the ultrasonic flow sensor 3, and connect the 3L calibration barrel to the ultrasonic flow sensor 3. Then, pull the 3L calibration barrel to the bottom, wait for 3s, click the flow rate calibration in the software, wait for 3s, slowly exhaust the gas in the barrel (3s-8s to complete the pushing action, do not pause in between, otherwise re-calibrate), and wait for automatic completion. Finally, the volume verification is required after the flow calibration is completed. Implement in turn: pull the 3 calibration barrel to the maximum, wait for 3s, click the volume measurement in the software, wait for 3s, slowly exhaust the gas in the barrel, and wait for the test to complete. Repeat the volume verification step of the ultrasonic flow sensor 3 flow calibration twice.

[0053] Step S102. After completing the gas concentration calibration and flow rate / volume calibration, the lung gas exchange function test is started on the subject. The subject correctly wears mouthpiece 1, the first switch valve 6 is opened, and the second switch valve 7 is closed. The subject breathes normally through mouthpiece 1 until three to four tidal breaths are completed and the lung residual volume is reached. Then, the first switch valve 6 is closed and the second switch valve 7 is opened. The subject inhales test gas to the lung total volume through mouthpiece 1 via the inhalation pressure equalization device 22. All valves and the first high-pressure calibration gas source 16 are closed, and the subject holds their breath for 8 to 10 seconds. Subsequently, the first switch valve 6 is opened, and the subject exhales gas to the lung residual volume. During this period... During the process, exhaled gas flows from port b of venturi tube 4 to port a of mixing chamber 5 in a specific ratio and undergoes physical averaging within mixing chamber 5. Finally, under the action of pump 14, the exhaled gas in mixing chamber 5 passes sequentially through port d of mixing chamber 5, third solenoid valve 8, gas flow controller 9, microflow sensor 10, non-dispersive infrared gas sensor 11, buffer tank 12, gas resistance 13, and pump 14, ultimately flowing back to port c of mixing chamber 5 and being discharged through port b of mixing chamber 5 to port c of venturi tube 4. The non-dispersive infrared gas sensor 11 detects the concentrations of methane and carbon monoxide in the exhaled gas, thus completing the entire test process.

[0054] In this embodiment, when a subject needs to undergo testing, they need to complete user registration and login on the host 23, and prepare for the lung gas exchange function test before starting the test.

[0055] Step S103. Calculate the lung ventilation capacity test result based on the obtained test data.

[0056] In this embodiment, the host 23 calculates lung gas exchange-related indicators—carbon monoxide pulmonary diffusion capacity and alveolar volume—based on data collected and uploaded by the control unit. The formula derivation is expressed as follows:

[0057] V A =V E +V ee -V D

[0058]

[0059] Among them, V A V represents alveolar volume (mL). E V is the volume (mL) of air exhaled during the exhalation phase. ee It is residual lung capacity (mL), V D F represents the dead space volume (mL). ACO The concentration of carbon monoxide in the alveoli (%), F ICO F represents the concentration (%) of carbon monoxide in the inhaled test gas.ACH4 F represents the concentration (%) of methane in the alveoli. ICH4 The concentration (%) of methane in the inhaled test gas, t BH D is the breath-holding time (s). LCO P represents the pulmonary diffusion capacity of carbon monoxide (mmol / min / kPa). B At ambient atmospheric pressure (760 mmHg), P H2O This is the partial pressure of water vapor in the alveoli (47 mmHg).

[0060] Dead space volume comprises two parts: the dead space volume of the human body and the dead space volume of equipment. The dead space volume of equipment can be directly measured, while the dead space volume of the human body is estimated using a formula:

[0061] V D =V Danat +V Dequip =2.2×w+V Dequip

[0062] Among them, V Dequip V represents the dead space volume (mL) of the device. Danat denoted as dead space volume (mL), and w as the subject's weight (kg).

[0063] Combining the average methane concentration at the end of tidal exhalation, test time, real-time methane concentration, and real-time airflow rate, V ee The formula derivation is expressed as follows:

[0064]

[0065] Among them, T ree The mean concentration (%) of methane at the end of tidal exhalation, t0 is the time of inhalation of the test gas, t f At the end of the test, Tr(t) represents the real-time concentration (%) of methane in the main gas flow path of the Venturi sampling gas path system, and Q represents the time when the test ends. e (t) represents the real-time airflow rate of the main airflow path of the Venturi sampling gas path system.

[0066] Given the small variation in the average methane concentration at the end of tidal breath, it is considered a constant. The average methane concentration at the end of tidal breath in the main gas flow path of the Venturi sampling system can be expressed as:

[0067]

[0068] Among them, T ree-avg t1 and t2 are constant values ​​(%) of the average methane concentration at the end of tidal breath, and t1 and t2 are the test periods at the end of tidal breath.

[0069] Assuming the exhaled gas as incompressible fluid, and the gas in the mixing chamber 5 is fully mixed. Based on the physical characteristics of the Venturi tube 4, a constant proportion of gas in the main gas flow path of the Venturi sampling gas path system will flow into the mixing chamber 5 through the auxiliary pipeline of the Venturi tube 4, then the equation of the exhaled methane molecular weight in the mixing chamber 5 is:

[0070]

[0071] Where, t ree (t) is the real-time methane gas concentration in the mixing chamber 5 (%), V is the volume of the mixing chamber 5 (mL), and k is the proportionality coefficient.

[0072] In the calculation of the key alveolar carbon monoxide concentration (F ACO ) and alveolar methane concentration (F ACH4 ), in order to ensure that the analyzed gas sample can more accurately represent the subject's mid-expiratory, stable alveolar gas, avoid the interference of early dead space gas mixing and late expiratory instability, the present application particularly adopts an optimization strategy based on real-time expiratory flow rate dynamic adjustment of the analysis module sampling window.

[0073] The specific implementation method is as follows:

[0074] (1) Set the initial sampling volume threshold: the host 23 first sets an initial cumulative exhaled volume threshold (V_start_threshold) for starting to collect alveolar gas, which is slightly larger than the physiological dead space volume VD calculated previously, and is set to V_start_threshold=VD+0.1L, to ensure that the flushing of the dead space gas has been basically completed.

[0075] (2) Real-time monitoring of expiratory flow rate stability: during the subject's exhalation, the system monitors the instantaneous expiratory flow rate Qe(t) in real time and high frequency through the ultrasonic flow sensor 3. At the same time, the stability index of the current expiratory flow rate is calculated continuously in a short time sliding window with a length of 200 milliseconds, and the standard deviation (σ_Qe) and coefficient of variation (CV_Qe=σ_Qe / mean(Qe)) of the flow rate signal in the window are calculated.

[0076] (3) Dynamically determine the starting time of the sampling window: only when the following two conditions are met at the same time, the system determines that the alveolar gas sampling window starts (t_sample_start):

[0077] Condition one (volume condition): cumulative exhaled volume VE(t)≥V_start_threshold.

[0078] Condition two (flow rate stability condition): After condition one is met, the real-time calculated expiratory flow rate stability index (CV_Qe) is lower than the pre-set stability threshold (CV_threshold), which is set as CV_threshold = 10%. This indicates that the subject has entered a relatively stable and uniform expiratory phase.

[0079] (4) Dynamic determination of sampling window termination timing: The end of the alveolar gas sampling window (t_sample_end) is determined when any of the following conditions is first triggered:

[0080] Condition one (flow rate too low condition): The real-time expiratory flow rate Qe(t) is lower than the pre-set minimum effective flow rate threshold (Qe_min_threshold), which is set as Qe_min_threshold = 0.2 L / s. This usually indicates that the expiration is close to natural end or the effort level is significantly reduced.

[0081] Condition two (flow rate instability condition): The real-time calculated expiratory flow rate stability index (CV_Qe) again exceeds the pre-set stability threshold (CV_threshold), indicating that the expiration becomes irregular or fluctuates.

[0082] Condition three (volume upper limit condition): The cumulative exhaled volume VE(t) reaches a pre-set upper limit (90% of the total exhaled volume) to avoid including the end residual gas.

[0083] This method of dynamically adjusting the sampling window based on real-time flow rate replaces the traditional fixed volume interval (e.g. 0.8L to 1.0L) sampling or averaging method. Its core advantage lies in the ability to adaptively determine the optimal alveolar gas sampling interval according to the actual and dynamic expiratory pattern of individual subjects, intelligently excluding the influence of early mixed gas and late unstable gas, thereby significantly improving the accuracy of the calculated F ACO and F ACH4 The representative of the true alveolar gas composition ultimately improves the accuracy of the carbon monoxide lung diffusion capacity (DLCO) calculation and the comparability of test results between different individuals.

[0084] The measured concentration of carbon monoxide in the alveoli F ACO and the concentration of methane in the alveoli F ACH4 The measurement method of the average concentration of methane at the end of tidal expiration T ree is the same as the measurement method of the average concentration of methane at the end of tidal expiration T ree , with the difference being the starting and ending time points t1 and t2, which are shown in the following table for each test quantity.

[0085]

[0086] In the present application, unless specifically defined and limited otherwise, the terms "mounting", "connected", "connecting", "fixed", and the like should be understood broadly, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0087] In the present application, unless specifically defined and limited otherwise, the first feature is "on" or "under" the second feature. The first and second features can be in direct contact or indirectly contact through an intermediate medium. Moreover, the first feature can be directly above or obliquely above the second feature, or only indicate that the horizontal height of the first feature is higher than that of the second feature. The first feature can be directly below or obliquely below the second feature, or only indicate that the horizontal height of the first feature is less than that of the second feature.

[0088] The above-described embodiments only express several embodiments of the present application, which are described in detail and specifically, but should not be understood as a limitation on the scope of the present application. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of protection of the present application.

Claims

1. A pulmonary gas exchange function detection system based on Venturi tubes, characterized in that, The detection system includes: a Venturi sampling device, a gas analysis and processing device, and a standard gas delivery device; The Venturi sampling device generates the test gas for the subject by establishing a gas passage based on a Venturi tube and a mixing chamber, after the test gas is provided by the standard gas delivery device. The gas analysis and processing device analyzes and processes the received test gas and the standard gas delivered by the standard gas delivery device to generate lung gas exchange function test results. The Venturi tube and the mixing chamber are each provided with port a, port b, port c, and port d. The gas passage includes a main gas flow passage formed by connecting ports a and d of the Venturi tube, and an auxiliary gas flow passage formed by sequentially connecting port b of the Venturi tube to ports a and b of the mixing chamber and then to port c of the Venturi tube. Ports c and d of the mixing chamber are respectively connected to a gas analysis and processing device. The Venturi sampling device also includes a mouthpiece, a first pressure sensor, an ultrasonic flow sensor, a first switching valve, a second switching valve, and an air tube for external air supply. The mouthpiece is connected in sequence to the ultrasonic flow sensor, port a of the Venturi tube, and port d of the Venturi tube, and then to one end of the first and second switching valves respectively. The other end of the first switching valve is connected to the air tube, and the other end of the second switching valve is connected to the standard air delivery device. The first pressure sensor is connected between the mouthpiece and the ultrasonic flow sensor. The gas analysis and processing device includes a third solenoid valve, a gas flow controller, a micro-flow sensor, a non-dispersive infrared gas sensor, a buffer tank, a gas resistance, and a vacuum pump connected in sequence. A second pressure sensor is connected between the non-dispersive infrared gas sensor and the buffer tank. The output end of the vacuum pump is connected to port c of the mixing chamber, and the third solenoid valve is connected to port d of the mixing chamber. The standard gas delivery device includes a first high-pressure calibration gas source, a first pressure reducing valve, and a first solenoid valve connected in sequence; and a second high-pressure calibration gas source, a second pressure reducing valve, and a second solenoid valve connected in sequence; an intake gas pressure equalization device is connected between the first pressure reducing valve and the first solenoid valve, and is connected to the second switching valve through the intake gas pressure equalization device; wherein the first solenoid valve and the second solenoid valve each include a gas inlet port (c port), a gas outlet port (a port), and a port (b port) for discharging gas into the air; the a port of the first solenoid valve and the second solenoid valve are connected to the c port of the third solenoid valve. The non-dispersive infrared gas sensor is used to calibrate gas concentration, including a first set of gas concentration calibrations and a second set of gas concentration calibrations.

2. The pulmonary gas exchange function detection system based on Venturi tubes according to claim 1, characterized in that, The Venturi tube includes a gradually narrowing inlet section, a throat with a diameter smaller than that of the main airflow passage, and a gradually expanding outlet section. When the breathing airflow passes through ports a and d of the Venturi tube, a pressure difference is formed between ports b and c of the Venturi tube. This causes the exhaled airflow in the Venturi tube to enter the mixing chamber at a flow rate proportional to the exhaled airflow at ports a and b of the Venturi tube. After being mixed and averaged, the airflow is discharged through port b of the mixing chamber to port c of the Venturi tube, thus achieving proportional sampling of the exhaled airflow.

3. The pulmonary gas exchange function detection system based on Venturi tubes according to claim 2, characterized in that, The third solenoid valve is a two-position three-way type, including a common port a, a normally open port b, and a normally closed port c. The c port of the third solenoid valve is connected to the standard gas delivery device, and the b port of the third solenoid valve is connected to the d port of the mixing chamber.

4. The pulmonary gas exchange function detection system based on Venturi tubes according to claim 3, characterized in that, When calibrating the first set of gas concentrations, a path is established between port a of the first solenoid valve and port c of the third solenoid valve. The second high-pressure calibration gas source is closed, and the first high-pressure calibration gas source is opened. The standard gas passes sequentially through the first pressure reducing valve and the first solenoid valve to the non-dispersive infrared gas sensor. The average gas concentration is collected over a period of time to complete the range calibration of the non-dispersive infrared gas sensor. When calibrating the second set of gas concentrations, the second and third solenoid valves are enabled, a path is established between port a of the second solenoid valve and port c of the third solenoid valve, the first high-pressure calibration gas source is closed, and the second high-pressure calibration gas source is opened. The standard gas passes sequentially through the second pressure reducing valve and the second solenoid valve to the non-dispersive infrared gas sensor. The average gas concentration is collected over a period of time to complete the zero-point calibration of the non-dispersive infrared gas sensor. During the calibration of the first set of gas concentrations, the standard gas is discharged into the air through port b of the first solenoid valve. During the calibration of the second set of gas concentrations, the standard gas is discharged into the air through port b of the second solenoid valve.

5. The detection method of the pulmonary gas exchange function detection system based on Venturi tubes as described in any one of claims 1-4, characterized in that, The detection method includes the following steps: Step S101. The operator debugs the venturi-based lung gas exchange function detection system and performs gas concentration calibration based on a non-dispersive infrared gas sensor and flow rate / volume calibration based on an ultrasonic flow sensor. Step S102. After completing the gas concentration calibration and flow rate / volume calibration, the lung gas exchange function test is started on the subject. The subject wears the mouthpiece correctly and breathes normally into the air through the mouthpiece. The first switch valve is opened and the second switch valve is closed until three to four tidal breaths are completed and the lung residual volume is reached. Then, the first switch valve is closed and the second switch valve is opened. The subject inhales test gas into the total lung volume through the mouthpiece and the inhaled air pressure equalization device. All valves and the first high-pressure calibration gas source are closed, and the subject holds his breath for 8 to 10 seconds. Subsequently, the first switch valve opens, and the subject exhales air to the residual lung capacity. During this period, the exhaled air flows from port b of the Venturi tube to port a of the mixing chamber in a specific ratio, and undergoes physical averaging within the mixing chamber. Finally, under the action of the suction pump, the exhaled air in the mixing chamber passes sequentially through port d of the mixing chamber, the third solenoid valve, the gas flow controller, the micro-flow sensor, the non-dispersive infrared gas sensor, the buffer tank, the gas resistance, and the suction pump, ultimately flowing back to port c of the mixing chamber and being discharged from port b of the mixing chamber to port c of the Venturi tube. The non-dispersive infrared gas sensor detects the concentrations of methane and carbon monoxide in the exhaled air, completing the entire test process. Step S103. Calculate the lung gas exchange function test results based on the obtained test data.

6. The method for detecting pulmonary gas exchange function based on Venturi tubes according to claim 5, characterized in that, In step S103, the lung ventilation function test results for this test are calculated, including alveolar volume. and carbon monoxide pulmonary diffusion capacity Specifically: ; In the above formula, This represents the volume of the alveoli. It refers to the volume of air exhaled during the exhalation phase. It is the residual lung capacity. dead space volume This refers to the concentration of carbon monoxide in the alveoli. The concentration of carbon monoxide in the inhaled test gas. This represents the concentration of methane in the alveoli. To determine the concentration of methane in the inhaled test gas, For breath-holding time, Carbon monoxide pulmonary diffusion capacity, Atmospheric pressure. It is the partial pressure of water vapor in the alveoli. The dead space volume of the equipment. The volume of dead space in the human body. For the subject's weight, The average concentration of methane at the end of tidal exhalation. The time when the test gas is inhaled. The end time of the test. The real-time concentration of methane in the main gas flow path. The real-time airflow rate of the main airflow path. This represents a constant value for the average methane concentration at the end of tidal exhalation. and The end-tidal breath test period. V represents the real-time methane gas concentration in the mixing chamber, V is the volume of the mixing chamber, and k is the proportionality coefficient.

7. The method for detecting pulmonary gas exchange function based on Venturi tubes according to claim 6, characterized in that, During the test in step S102, the method also includes establishing a dynamic judgment process based on a sampling window to adaptively determine the alveolar contents. and The sampling window's dynamic judgment process includes the dynamic opening and dynamic termination timing of the sampling window within the sampling window's range. The dynamic activation timing includes, when the cumulative exhaled gas volume is greater than or equal to the set initial cumulative exhaled volume lower limit, and when it is determined whether the real-time exhaled flow rate stability index is lower than the preset stability threshold, if so, the sampling window is activated. The dynamic termination timing includes when the real-time expiratory flow rate is lower than the preset minimum effective expiratory flow rate threshold; or when the real-time expiratory flow rate stability index exceeds the preset stability threshold again; or when the cumulative exhaled gas volume exceeds the preset upper limit value, then the sampling window will be terminated.

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