Lung ventilation function detection system and method based on Venturi tube

Abstract

The invention discloses a venturi tube-based lung ventilation function detection system and method. The venturi tube-based lung ventilation function detection system comprises a venturi sampling device, a gas analyzing and processing device and a standard gas conveying device, the Venturi sampling device is used for generating to-be-tested gas of a subject after the standard gas conveying device provides test gas by establishing a gas passage based on a Venturi tube and a mixing chamber; the gas analyzing and processing device is used for analyzing and processing the received gas to be tested and the standard gas conveyed by the standard gas conveying device and then generating a lung ventilation function detection result. On the basis of the venturi tube and the mixing chamber, constant-proportion collection and physical buffering are carried out on exhaled air of a human body respectively, hundred milliseconds of real-time human body breathing air analysis is avoided, meanwhile, non-dispersive infrared gas sensor errors caused by air pressure and air flow fluctuation are avoided, and the lung ventilation function detection precision is improved.

Description

Technical Field

[0001] The present invention relates to the field of lung function testing, and in particular to a venturi tube-based lung ventilation function testing system and method. Background Art

[0002] Existing classic pulmonary ventilation function testing equipment usually uses an electrochemical sensor as the core to build a gas analyzer, and is equipped with a test gas path and a gas collection bag for the pulmonary ventilation test method. However, some existing pulmonary ventilation capacity testing equipment, especially those that use a constant speed pump to extract the sampled gas and perform real-time concentration analysis, often place extremely high demands on the dynamic response performance of the gas concentration sensor. For example, the response time usually needs to be less than 150 milliseconds. This not only leads to high costs and limited selection of core sensors, but also when the subject's exhaled flow rate changes greatly, the instantaneous fluctuations in the sensor readings may introduce significant measurement noise. In addition, such equipment also faces challenges in stably controlling the flow and pressure of the sampled gas entering the analysis chamber. In particular, when it is necessary to accurately obtain information on gas components at different stages of exhalation, even small fluctuations in flow or pressure may affect the accuracy of concentration measurements.

[0003] At present, the detection of lung ventilation capacity mainly relies on fast-responding gas sensors. Patent document CN113854997B discloses a lung diffusion function test device and method based on the one-breath method. The device extracts the exhaled gas of the test subject into a non-dispersive infrared sensor at a constant speed to achieve real-time concentration detection of the exhaled gas of the human body, thereby extracting lung diffusion test indicators. Although the device and method can achieve rapid detection of lung diffusion capacity and avoid cross-infection, it still has limitations: the method has extremely 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 popularity 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 intrapulmonary air pressure during breath-holding. Patent document CN113854997B discloses a lung diffusion function test device and method based on the one-breath method, and patent document CN202111271625.8 discloses a lung diffusion function detection system. Neither of these involves the detection of the above-mentioned physiological behaviors. If the tester does not strictly follow the standard to complete the test, the final lung ventilation test indicator will be seriously deviated. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a pulmonary ventilation function detection system and method based on a Venturi tube, which is designed as a human pulmonary ventilation capacity detection system and method with a reliable air path structure, high measurement accuracy, and low requirements on the dynamic performance of the gas concentration sensor, and can achieve high-safety and high-comfort pulmonary ventilation function detection.

[0006] In order to achieve the above object, the present invention provides the following solutions:

[0007] In a first aspect, the present invention proposes a pulmonary ventilation capacity detection system based on a Venturi tube, the detection system comprising: a Venturi sampling device, a gas analysis and processing device, and a standard gas delivery device;

[0008] The venturi sampling device generates the test gas of the subject by establishing a gas passage based on a venturi tube and a mixing chamber and after the standard gas delivery device provides the test gas;

[0009] The gas analysis and processing device analyzes and processes the received gas to be tested and the standard gas delivered by the standard gas delivery device to generate a lung ventilation capacity test result;

[0010] Wherein, the venturi tube and the mixing chamber are both provided with port a, port b, port c and port d, and the gas passage includes a main airflow passage formed by connecting port a and port d of the venturi tube, and an auxiliary airflow passage formed by connecting port b of the venturi tube to port a and port b of the mixing chamber to port c of the venturi tube in sequence; port c and port d of the mixing chamber are respectively connected to a gas analysis and processing device.

[0011] Furthermore, the venturi tube includes a gradually contracting inlet section, a throat with a diameter smaller than the diameter of the main airflow path, and a gradually expanding outlet section. When the respiratory airflow passes through port a and port d of the venturi tube, an air pressure difference is formed between port b and port c of the venturi tube, so that the exhaled airflow in the venturi tube enters the mixing chamber at a flow rate proportional to the exhaled airflow of ports a and b of the venturi tube, and after being mixed and averaged, is discharged through port b of the mixing chamber to port c of the venturi tube, thereby realizing proportional sampling of the exhaled airflow.

[0012] Furthermore, the Venturi sampling device also includes a mouthpiece, a first air pressure sensor, an ultrasonic flow sensor, a first switch valve, a second switch valve and an air pipe connected to the external air, wherein the mouthpiece is connected to the ultrasonic flow sensor, the a port of the Venturi tube to the d port of the Venturi tube in sequence, and then connected to one end of the first switch valve and the second switch valve respectively, the other end of the first switch valve is connected to the air pipe, the other end of the second switch valve is connected to the standard air delivery device, and the first air pressure sensor is connected between the mouthpiece and the ultrasonic flow sensor.

[0013] Furthermore, 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, an air resistor and an air pump connected in sequence, wherein a second air pressure sensor is connected between the non-dispersive infrared gas sensor and the buffer tank, the output end of the air pump is connected to the c port of the mixing chamber, and the third solenoid valve is connected to the d port of the mixing chamber.

[0014] Furthermore, 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, wherein 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.

[0015] Furthermore, 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 balancing device is connected between the first pressure reducing valve and the first solenoid valve, and is connected to the second switch valve through the intake gas pressure balancing device, wherein the first solenoid valve and the second solenoid valve each include a gas inlet port c, a gas outlet port a, and a port b for discharging gas into the air; the a ports of the first solenoid valve and the second solenoid valve are connected to the c port of the third solenoid valve. Furthermore, the non-dispersive infrared gas sensor is used to calibrate the gas concentration, including a first group of gas concentration calibration and a second group of gas concentration calibration. When performing the first group of gas concentration calibration, a passage between port a of the first solenoid valve and port c of the third solenoid valve is established, the second high-pressure calibration gas source is closed, and the first high-pressure calibration gas source is opened. The standard gas passes through the first pressure reducing valve and the first solenoid valve in sequence to the non-dispersive infrared gas sensor. After ventilation and collection of the average gas concentration over a period of time, the range point calibration of the non-dispersive infrared gas sensor is completed; when performing the second group of gas concentration calibration, the second solenoid valve and the third solenoid valve are enabled, a passage between port a of the second solenoid valve and port c of the third solenoid valve is established, the first high-pressure calibration gas source is closed, and the second high-pressure calibration gas source is opened. The standard gas passes through the second pressure reducing valve and the second solenoid valve in sequence to the non-dispersive infrared gas sensor. After ventilation and collection of the average gas concentration over a period of time, the zero point calibration of the non-dispersive infrared gas sensor is completed.

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

[0017] In a second aspect, the present invention provides a detection method for the venturi tube-based lung ventilation capacity detection system according to the first aspect, the detection method comprising the following steps:

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

[0019] Step S102. After completing the gas concentration calibration and flow rate volume calibration, the subject is started to perform a pulmonary ventilation function test. The subject wears the mouthpiece correctly, opens the first switch valve, closes the second switch valve, and breathes normally into the air through the mouthpiece until three to four tidal breaths into the air are completed and exhaled to the residual lung 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 volume through the inhalation gas pressure equalization device through the mouthpiece; all valves and the first high-pressure calibration gas source are closed, and the subject holds his breath for 8 to 10 seconds; then, the first switch valve is opened, and the subject exhales the gas into the air to the residual lung volume. During this period, the exhaled gas flows from the b port of the venturi tube to the a port of the mixing chamber in a specific ratio and undergoes physical averaging in the mixing chamber. Finally, under the action of the vacuum pump, the exhaled gas in the mixing chamber passes through the d port 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 air resistance, and the vacuum pump in sequence, and finally flows back 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. The non-dispersive infrared gas sensor detects the concentrations of methane and carbon monoxide in the exhaled gas. This completes the entire test process.

[0020] Step S103: Calculate the lung ventilation capacity test result of this test based on the acquired test data.

[0021] Furthermore, the lung ventilation capacity test results calculated in step S103 include the alveolar volume V A and carbon monoxide diffusing capacity D LCO , specifically:

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

[0023]

[0024] in,

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

[0026]

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

[0028] Furthermore, when testing in step S102, it also includes establishing a dynamic judgment process based on a sampling window to achieve adaptive determination of the intra-alveolar F ACO and F ACH4 The dynamic determination process of the sampling window includes a dynamic start timing and a dynamic end timing of the sampling window; wherein the dynamic start timing includes when the cumulative exhaled gas volume is greater than or equal to the set initial cumulative exhaled volume lower limit, and then when it is determined whether the real-time exhaled flow rate stability index is lower than a preset stability threshold, if so, then the sampling window is opened;

[0029] Dynamic termination timing includes terminating the sampling window if the real-time expiratory flow rate is lower than the preset minimum effective expiratory flow rate threshold; or, the real-time expiratory flow rate stability index exceeds the preset stability threshold again; or, the accumulated exhaled gas volume exceeds the preset upper limit value.

[0030] The beneficial effects achieved by the present invention are:

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

[0032] (2) The present invention realizes constant pressure and constant current control during the analysis of human exhaled gas components and standard gas concentration through a gas analysis and processing device, thereby avoiding the error of non-dispersive infrared gas sensors caused by fluctuations in air pressure and air volume, and improving the accuracy of lung ventilation function detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of the lung ventilation capacity detection system based on the Venturi tube of the present invention.

[0034] Figure 2 It is a flow chart of the method for detecting lung ventilation capacity based on a Venturi tube of the present invention.

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

[0036] The present application is described in further detail below in conjunction with the accompanying drawings. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0037] like Figure 1 As shown, the present invention proposes a pulmonary ventilation capacity detection system based on a Venturi tube, comprising a Venturi sampling device, a gas analysis and processing device, and a standard gas delivery device. The Venturi sampling device generates the test gas of the subject by establishing a gas passage based on the Venturi tube and the mixing chamber, and after the standard gas delivery device provides the test gas, the gas analysis and processing device analyzes and processes the received test gas and the standard gas delivered by the standard gas delivery device, and generates the pulmonary ventilation capacity detection result, wherein the Venturi sampling device samples the exhaled gas component concentration, the gas analysis and processing device is responsible for obtaining the gas component concentration of the test gas and performing analysis and processing, and the standard gas delivery device has the following functions: (1) providing inhaled test gas during pulmonary ventilation testing, i.e., reducing pressure, regulating air pressure, and supplying output of the high-pressure standard gas in the high-pressure gas source group; (2) providing the gas analysis and processing device with the standard gas required for concentration calibration, i.e., reducing pressure, releasing pressure, and supplying output of the high-pressure standard gas in the high-pressure gas source group.

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

[0039] Secondly, the mixing chamber 5 in this embodiment is also one of the key components of the gas processing link. Its main function is to effectively physically buffer and homogenize 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 and desired buffering effect of the downstream gas analysis and processing device. In this embodiment, its effective volume V is preferably 50mL. The mixing chamber 5 is essentially constructed as 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 sampled gas over time. Its filtering characteristics are mainly determined by the volume V of the mixing chamber 5 and the actual sampling flow rate Q_sample entering the downstream gas analysis and processing device. The significant technical effect brought about by this is that the mixing chamber 5 can effectively attenuate and average the instantaneous high-frequency fluctuations in the sampled gas concentration caused by factors such as uneven mixing of alveolar gas and dead space gas during the respiratory cycle or changes in exhaled flow rate. After processing by the mixing chamber 5, the gas concentration changes transmitted to the non-dispersive infrared gas sensor 11 of the gas analysis and processing device for analysis will become relatively gentle and stable. This characteristic greatly reduces the requirements for the dynamic response speed of the non-dispersive infrared gas sensor 11. Compared to directly analyzing rapidly changing sampled gas (typically requiring a sensor response time of less than 150ms), this embodiment allows the use of NDIR sensors with relatively slow response times (e.g., 500ms or even longer), lower costs, or improved stability. Alternatively, under equivalent sensor conditions, it can obtain a concentration measurement signal with lower noise and a higher signal-to-noise ratio. Ultimately, a high-quality, easy-to-process concentration curve that better represents the average exhaled gas composition is output, providing the basis for subsequent accurate calculation of the carbon monoxide diffusing capacity (DLCO) and related physiological parameters.

[0040] In this embodiment, the Venturi sampling device also includes 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 tube connected to the external air. The mouthpiece 1 is sequentially connected to the ultrasonic flow sensor 3, the port a of the Venturi tube 4, and the port d of the Venturi tube 4. It is then connected to 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 to the air tube to form a complete breathing pathway. The other end of the second on-off valve 7 is connected to the standard air delivery device. The first air pressure sensor 2 is connected between the mouthpiece 1 and the ultrasonic flow sensor 3.

[0041] Ultrasonic flow sensor 3 detects bidirectional respiratory airflow. Then, when the subject inhales test gas to the total lung volume, first valve 6 closes and second valve 7 opens. The subject inhales pressure-regulated test gas provided by the standard gas delivery device, which then flows through second valve 7, Venturi tube 4, ultrasonic flow sensor 3, and mouthpiece 1. During this period, ultrasonic flow sensor 3 detects the inhaled test gas flow rate. Next, when the subject holds their breath for 8 to 10 seconds, first valve 6 and second valve 7 close, and the subject maintains breath-holding for this period. Simultaneously, first air pressure sensor 2 detects the air pressure at mouthpiece 1, i.e., the air pressure within the lungs during breath-holding. This air pressure data is used to assess the subject's breath-holding success. Finally, when the subject exhales to the residual lung volume, first valve 6 opens and second valve 7 closes, allowing the subject's exhaled air to flow through mouthpiece 1, ultrasonic flow sensor 3, Venturi tube 4, and first valve 6, returning to the atmosphere. During this period, ultrasonic flow sensor 3 detects the exhaled air flow rate. At the same time, in the contraction section of the Venturi tube 4, the increased exhaled airflow velocity causes the air pressure at the contraction to decrease, thereby generating an adsorption effect. When the cross-sectional areas of the four ports a, b, c, and d of the Venturi tube 4 are set, proportional extraction of the sampled gas can be achieved. Specifically, when exhaled air flows through ports a and d of the Venturi tube 4, a pressure difference is formed between ports b and c of the Venturi tube 4. The exhaled air in the Venturi tube 4 enters the mixing chamber 5 at a flow rate proportional to the exhaled air flow from ports a and b. After being mixed evenly, it is discharged through port b of the mixing chamber 5 and then to port c of the Venturi tube, achieving proportional sampling of the exhaled air.

[0042] In this embodiment, the gas analysis and processing device includes a third solenoid valve 8, a gas flow controller 9, a micro-flow sensor 10, a non-dispersive infrared gas sensor (NDIR) 11, a buffer tank 12, an air resistor 13 and an air pump 14 connected in sequence, wherein a second air pressure sensor 15 is connected between the NDIR sensor 11 and the buffer tank 12, and the output end of the air pump 14 is connected to the c port of the mixing chamber 5, wherein the third solenoid valve 8 is a two-position three-way type, including 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 solenoid valve 8 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.

[0043] It should be noted that the system of this embodiment also includes an external or internal host 23 or control device 24 to analyze and process the acquired data. This external component is not protected by this system and is sufficient only to implement the corresponding functions. Therefore, it will not be described in detail. The host or control device monitors the pressure signal collected by the first air pressure sensor 2, which effectively reflects the pressure at the subject's mouth and even in the lungs. As described above, during the test, within a very short period of time (the first 200 milliseconds) after the subject begins the breath-holding state, the system first determines a stable pressure reference value (P_ref). Subsequently, throughout the entire breath-holding period, the system compares the currently monitored pressure value (P_t) with this reference value P_ref in real time. In this embodiment, a narrowband pressure fluctuation threshold (ΔP_threshold) is preset, which is set to ±0.15 kPa. If at any time during the breath-holding period, the absolute difference between the monitored pressure value P_t and the pressure reference value P_ref (|P_t-P_ref|) exceeds the preset threshold ΔP_threshold, the system determines that there may be a problem with the quality of the breath-holding operation. Such supra-threshold pressure fluctuations usually indicate that the subject has failed to strictly maintain a breath-holding state, and that situations such as mouthpiece leakage, swallowing movements, involuntary physiological movements (Valsalva or Mueller movements) may have occurred. These physiological behaviors will interfere with the stable state of gas distribution and partial pressure in the lungs, thereby significantly affecting the accuracy of indicators such as the carbon monoxide diffusion capacity (DLCO) calculated subsequently. Based on the monitored pressure fluctuations, 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 23 and issue a warning signal to remind the operator to pay attention or guide the subject to make adjustments.

[0044] According to the principles of fluid dynamics (Bernoulli's law), when the exhaled air flow reaches the throat through the contraction section of the venturi tube (4), the flow rate increases, resulting in the static pressure in the throat area being significantly lower than the pressure at its upstream port a. 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 air flow path into the auxiliary air flow path (port b to port c) through the port b opened laterally in the throat or near-throat area. The key is to accurately 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 port b) so that a stable and predictable proportional relationship is formed between the sampled air flow Q_sample extracted from the port b and the total exhaled air flow Q_main flowing through the port ad of the main air path, i.e., Q_sample = k*Q_main. This proportional coefficient k is determined in this design based on the geometric dimensions and is 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 thus achieved has the following significant advantages over traditional active pump sampling: First, it has a simple structure and does not require an additional sampling pump or complex flow control unit to directly extract the main gas path gas, reducing the complexity of the system and potential failure points; second, the sampling ratio is guaranteed by a fixed physical structure, with high stability and is not easily affected by power supply fluctuations or pump performance drift; third, the sampling process responds to changes in the main gas path flow in real time, and can more realistically reflect the gas composition ratio during different exhalations; fourth, it has less interference with the flow field of the main gas path and is more in line with the physiological breathing state.

[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; an intake gas pressure equalizing device 22 is connected between the first pressure reducing valve 17 and the first solenoid valve 18, and is connected to the second switch valve 7 through the intake gas pressure equalizing device 22, wherein the first solenoid valve 18 and the second solenoid valve 21 each include a gas inlet port c, a gas outlet port a, and a port b 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, and 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 tee pipe joint, the air inlet of the intake gas pressure equalizing device 22 is connected to the air outlet of the first pressure reducing valve 17, and the air outlet of the intake gas pressure equalizing device 22 is connected to the air 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 a mixed gas of 3000 ppm methane, 3000 ppm carbon monoxide, and 21% oxygen; the second high-pressure calibration gas source is composed of 100% nitrogen.

[0047] In this embodiment, the NDIR sensor 11 is used to calibrate the gas concentration, including the calibration of the first group of gas concentrations and the calibration of the second group of gas concentrations. When performing the calibration of the first group of gas concentrations, a passage is established between the a port of the first solenoid valve 18 and the c port of the third solenoid 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 solenoid valve 18 in turn to the non-dispersive infrared gas sensor 11, and the gas concentration average over a period of time is ventilated and collected to complete the range point calibration of the non-dispersive infrared gas sensor 11; wherein, the standard gas is discharged into the air through the b port of the first solenoid valve 18 through the air pipe tee, thereby realizing the pressure relief regulation and supply of the first group of standard gases during the sensor concentration calibration. During the second set of gas concentration calibration, the second solenoid valve 21 and the third solenoid valve 8 are enabled, establishing a passage between port a of the second solenoid valve 21 and port c of the third solenoid 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 solenoid valve 21 to the non-dispersive infrared gas sensor 11. The gas is ventilated and the average gas concentration over a period of time is collected, completing the zero point calibration of the non-dispersive infrared gas sensor 11. Finally, the high-pressure calibration gas sources and valves are closed to complete the gas concentration calibration of the NDIR sensor 11. The standard gas is discharged into the air through the tracheal tee and port b of the second solenoid valve 21, achieving pressure relief and supply of the second set of standard gas for sensor concentration calibration. When the test gas is inhaled to the total lung capacity, the first solenoid valve 18 and the second solenoid valve 21 are first 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 system. During this period, the inhaled gas pressure equalization device 22 is responsible for adjusting the pressure and flow of the test gas to suit the subject's breathing needs, achieving pressure regulation and supply of the test gas during the pulmonary ventilation function test. In this embodiment, the first high-pressure calibration gas source 16 consists of a mixture of 3000 ppm methane, 3000 ppm carbon monoxide, and 21% oxygen; the second high-pressure calibration gas source 19 consists of 100% nitrogen.

[0048] According to the purpose of the present invention, the present invention also proposes a detection method of a lung ventilation capacity detection system based on a Venturi tube, such as Figure 2 As shown, the specific steps include:

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

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

[0051] When calibrating the concentration of the first set of standard gases, a passage is established between port a of the first solenoid valve 18 and port c of the third solenoid 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 solenoid valve 18 in sequence to the non-dispersive infrared gas sensor 11. After ventilation and collecting the average gas concentration over a period of time, the range point calibration of the non-dispersive infrared gas sensor 11 is completed; wherein, the standard gas is discharged into the air through the port b of the first solenoid valve 18 through the air pipe tee, thereby realizing the pressure relief regulation and supply of the first set of standard gases during sensor concentration calibration. During the second set of gas concentration calibration, the second solenoid valve 21 and the third solenoid valve 8 are enabled, establishing a passage between port a of the second solenoid valve 21 and port c of the third solenoid 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 solenoid valve 21 to the non-dispersive infrared gas sensor 11. After ventilation and collecting the average gas concentration over a period of time, 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 to complete the gas concentration calibration of the NDIR sensor 11.

[0052] When calibrating the flow rate of the ultrasonic flow sensor 3, first disconnect the mouthpiece 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 3 seconds, click on the flow rate calibration in the software, wait for 3 seconds, slowly exhaust the gas in the barrel (complete the pushing action within 3s-8s, and do not pause in the middle, otherwise the calibration will be repeated), and wait for it to end automatically. Finally, after the flow calibration is completed, volume verification is required. Implement the following steps in sequence: pull the 3L calibration barrel to the maximum position, wait for 3 seconds, click on the volume measurement in the software, wait for 3 seconds, slowly exhaust the gas in the barrel, and wait for the test to complete. Repeat the volume verification steps for the flow calibration of the ultrasonic flow sensor 3 twice.

[0053] Step S102. After completing the gas concentration calibration and flow rate volume calibration, the subject is started to perform a lung ventilation function test. The subject wears the mouthpiece 1 correctly, the first switch valve 6 is opened, the second switch valve 7 is closed, and normal air breathing is performed through the mouthpiece 1 until three to four tidal breaths are completed and the air is exhaled to the residual lung volume; then, the first switch valve 6 is closed, the second switch valve 7 is opened, and the subject inhales the test gas to the total lung volume through the mouthpiece 1 through the inhalation gas pressure equalization device 22; all valves and the first high-pressure calibration gas source 16 are closed, and the subject maintains a breath-holding state for 8 to 10 seconds; then, the first switch valve 6 is opened, and the subject exhales the gas to the residual lung volume; during this period During this period, the exhaled gas flows from the b port of the venturi tube 4 to the a port of the mixing chamber 5 in a specific proportion and is physically averaged in the mixing chamber 5; finally, under the action of the suction pump 14, the exhaled gas in the mixing chamber 5 passes through the d port of the mixing chamber 5, the third solenoid valve 8, the gas flow controller 9, the micro flow sensor 10, the non-dispersive infrared gas sensor 11, the buffer tank 12, the air resistance 13 and the suction pump 14 in sequence, and finally flows back to the c port of the mixing chamber 5, and is discharged to the c port of the venturi tube 4 through the b port of the mixing chamber 5; wherein, the non-dispersive infrared gas sensor 11 detects the concentrations of methane and carbon monoxide in the exhaled gas, completing the entire test process.

[0054] In this embodiment, when a subject needs to undergo a test, he or she needs to complete user registration and login on the host 23 and make preparations for the pulmonary ventilation function test before starting the test.

[0055] Step S103: Calculate the lung ventilation capacity test result of this test based on the acquired test data.

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

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

[0058]

[0059] Among them, V A is the alveolar volume (mL), V E is the volume of exhaled air during the exhalation phase (mL), V ee is the residual volume (mL), V D is the dead space volume (mL), F ACO is the concentration of carbon monoxide in the alveoli (%), F ICO is the concentration of carbon monoxide in the inhaled test gas (%), FACH4 is the concentration of methane in the alveoli (%), F ICH4 is the concentration of methane in the inhaled test gas (%), t BH is the breath holding time (s), D LCO is the carbon monoxide diffusion capacity of the lung (mmol / min / kPa), P B is the ambient atmospheric pressure (760 mmHg), P H2O It is the partial pressure of water vapor in the alveoli (47 mmHg).

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

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

[0062] Among them, V Dequip is the dead space volume of the equipment (mL), V Danat is the dead space volume of the human body (mL), and w is the weight of the subject (kg).

[0063] Combined with the average concentration of methane 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 is the average concentration of methane at the end of tidal exhalation (%), t0 is the time of inhalation of test gas, t f is the end time of the test, Tr(t) is the real-time concentration of methane in the main air flow path of the Venturi sampling gas system (%), Q e (t) is the real-time airflow rate of the main airflow path of the Venturi sampling air path system.

[0066] Given that the average concentration of methane at the end of tidal expiration varies only slightly, it is considered a constant value. In the main airflow path of the Venturi sampling system, the average concentration of methane at the end of tidal expiration can be expressed as:

[0067]

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

[0069] Assuming that exhaled gas is an incompressible fluid and that the gases in mixing chamber 5 are fully mixed, based on the physical properties of the Venturi tube 4, a constant proportion of gas in the main airflow path of the Venturi sampling gas system will flow into the mixing chamber 5 through the auxiliary pipeline of the Venturi tube 4. The equation for the methane molecular weight of exhaled gas in the mixing chamber 5 is:

[0070]

[0071] Among them, 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 proportional coefficient.

[0072] In calculating 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 and avoid interference caused by early dead space gas mixing and terminal exhalation instability, the present invention particularly adopts an optimization strategy for dynamically adjusting the sampling window of the analysis module based on real-time expiratory flow rate.

[0073] The specific implementation method is as follows:

[0074] (1) Setting the initial sampling volume threshold: The host 23 first sets an initial cumulative exhaled volume lower limit (V_start_threshold) for starting to consider collecting alveolar gas. This threshold is slightly larger than the previously calculated physiological dead space volume VD 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 at high frequency using the ultrasonic flow sensor 3. Simultaneously, the stability index of the current expiratory flow rate is continuously calculated within a short sliding window of 200 milliseconds, and the standard deviation (σ_Qe) and coefficient of variation (CV_Qe = σ_Qe / mean(Qe)) of the flow rate signal within this window are calculated.

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

[0077] Condition 1 (volume condition): cumulative exhaled volume VE(t) ≥ V_start_threshold.

[0078] Condition 2 (Flow Stability): After condition 1 is met, the real-time calculated expiratory flow stability index (CV_Qe) is lower than the preset stability threshold (CV_threshold), set at 10%. This indicates that the subject has entered a relatively stable and uniform exhalation phase.

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

[0080] Condition 1 (low flow): The real-time exhalation flow rate Qe(t) is lower than the preset minimum effective flow rate threshold (Qe_min_threshold), set to Qe_min_threshold = 0.2 L / s. This usually indicates that exhalation is nearing its natural end or the effort level has significantly decreased.

[0081] Condition 2 (flow instability condition): The real-time calculated exhalation flow stability index (CV_Qe) exceeds the preset stability threshold (CV_threshold) again, indicating that exhalation becomes irregular or fluctuates.

[0082] Condition three (volume upper limit condition): the cumulative expired volume VE(t) reaches a preset upper limit (90% of the total expired volume) to avoid including the last 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 is that it can adaptively determine the optimal alveolar gas sampling interval based on the actual and dynamic exhalation pattern of individual subjects, intelligently exclude the influence of early mixed gas and terminal unstable gas, thereby significantly improving the calculated F ACO and F ACH4 The representation of the true alveolar gas composition ultimately improves the accuracy of the carbon monoxide diffusing capacity (DLCO) calculation and the comparability of test results between different individuals.

[0084] The carbon monoxide concentration in the alveoli to be measured is F ACO and the alveolar methane concentration F ACH4 The measurement method and the average concentration of methane at the end of tidal exhalation T ree The measurement methods are the same, the difference is the start and end time points t1 and t2 are different. The specific t1 and t2 corresponding to each test quantity are shown in the following table.

[0085]

[0086] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0087] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0088] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A pulmonary ventilation function detection system based on a Venturi tube, 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 of the subject by establishing a gas passage based on a venturi tube and a mixing chamber and after the standard gas delivery device provides the test gas; The gas analysis and processing device analyzes and processes the received gas to be tested and the standard gas delivered by the standard gas delivery device to generate a lung ventilation function test result; Wherein, the venturi tube and the mixing chamber are both provided with port a, port b, port c and port d, and the gas passage includes a main airflow passage formed by connecting port a and port d of the venturi tube, and an auxiliary airflow passage formed by connecting port b of the venturi tube to port a and port b of the mixing chamber to port c of the venturi tube in sequence; port c and port d of the mixing chamber are respectively connected to a gas analysis and processing device.

2. The venturi tube-based pulmonary ventilation function detection system according to claim 1, characterized in that: The venturi tube includes a gradually converging inlet section, a throat section with a diameter smaller than the diameter of the main airflow path, and a gradually expanding outlet section. When the respiratory airflow passes through ports a and d of the venturi tube, an air pressure difference is formed between ports b and c of the venturi tube, causing the exhaled airflow in the venturi tube to enter the mixing chamber at a flow rate proportional to the exhaled airflow of ports a and b of the venturi tube. After being mixed and averaged, it is discharged through port b of the mixing chamber to port c of the venturi tube, thereby realizing proportional sampling of the exhaled airflow.

3. The venturi tube-based lung ventilation function detection system according to claim 1, characterized in that: The Venturi sampling device also includes a mouthpiece, a first air pressure sensor, an ultrasonic flow sensor, a first switch valve, a second switch valve and an air pipe connected to external air, wherein the mouthpiece is connected to the ultrasonic flow sensor, the a port of the Venturi tube to the d port of the Venturi tube in sequence, and then connected to one end of the first switch valve and the second switch valve respectively, the other end of the first switch valve is connected to the air pipe, the other end of the second switch valve is connected to the standard air delivery device, and the first air pressure sensor is connected between the mouthpiece and the ultrasonic flow sensor.

4. The venturi tube-based pulmonary ventilation function detection system according to claim 3, characterized in that: 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, an air resistor and an air pump connected in sequence, wherein a second air pressure sensor is connected between the non-dispersive infrared gas sensor and the buffer tank, the output end of the air pump is connected to the c port of the mixing chamber, and the third solenoid valve is connected to the d port of the mixing chamber.

5. The venturi tube-based lung ventilation function detection system according to claim 4, 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, wherein 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.

6. The venturi tube-based lung ventilation function detection system according to claim 4, characterized in that: 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 equalizing device is connected between the first pressure reducing valve and the first solenoid valve, and is connected to the second switch valve through the intake gas pressure equalizing device, wherein the first solenoid valve and the second solenoid valve each include a gas inlet port c, a gas outlet port a, and a port b for discharging gas into the air; the a ports of the first solenoid valve and the second solenoid valve are connected to the c port of the third solenoid valve.

7. The venturi tube-based lung ventilation function detection system according to claim 6, characterized in that: The non-dispersive infrared gas sensor is used to calibrate the gas concentration, including a first group of gas concentration calibration and a second group of gas concentration calibration. When performing the first group of gas concentration calibration, a passage between port a of the first solenoid valve and port c of the third solenoid valve is established, the second high-pressure calibration gas source is closed, and the first high-pressure calibration gas source is opened. The standard gas passes through the first pressure reducing valve and the first solenoid valve in sequence to the non-dispersive infrared gas sensor. After ventilation and collection of the average gas concentration over a period of time, the range point calibration of the non-dispersive infrared gas sensor is completed; when performing the second group of gas concentration calibration, the second solenoid valve and the third solenoid valve are enabled, a passage between port a of the second solenoid valve and port c of the third solenoid valve is established, the first high-pressure calibration gas source is closed, and the second high-pressure calibration gas source is opened. The standard gas passes through the second pressure reducing valve and the second solenoid valve in sequence to the non-dispersive infrared gas sensor. After ventilation and collection of the average gas concentration over a period of time, the zero point calibration of the non-dispersive infrared gas sensor is completed; When performing the first set of gas concentration calibration, the standard gas is discharged into the air through the b port of the first solenoid valve, and when performing the second set of gas concentration calibration, the standard gas is discharged into the air through the b port of the second solenoid valve.

8. The detection method of the pulmonary ventilation function detection system based on a Venturi tube according to any one of claims 1 to 7, characterized in that: The detection method comprises the following steps: Step S101. The operator debugs the Venturi tube-based lung ventilation function detection system and performs gas concentration calibration based on the non-dispersive infrared gas sensor and flow rate and volume calibration of the ultrasonic flow sensor; Step S102. After completing gas concentration and flow rate volume calibrations, the subject begins a pulmonary ventilation function test. The subject wears the mouthpiece correctly and breathes normally into air through the mouthpiece, with the first on-off valve open and the second on-off valve closed, until three to four tidal breaths into air are completed and exhaled to the residual lung volume. Next, the first on-off valve is closed and the second on-off valve is opened. The subject inhales the test gas through the mouthpiece through the inhalation gas pressure equalization device to the total lung volume. 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 on-off valve is opened, and the subject exhales into the air to the residual lung 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 undergoes physical averaging 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 solenoid valve, the gas flow controller, the micro-flow sensor, the non-dispersive infrared gas sensor, the buffer tank, the air resistance, and the suction pump, and finally flows back to the c port of the mixing chamber and is discharged through the b port of the mixing chamber to the c port of the venturi tube. The non-dispersive infrared gas sensor detects the concentrations of methane and carbon monoxide in the exhaled gas, completing the entire testing process. Step S103: Calculate the pulmonary ventilation function test result of this test based on the acquired test data.

9. The method for detecting lung ventilation function based on a Venturi tube according to claim 8, characterized in that: The lung ventilation function test results calculated in step S103 include the alveolar volume V A and carbon monoxide diffusing capacity D LCO , specifically: V A =V E +V ee -V D in, V D =V Danat +V Dequip =2.2×w+V Dequip In the above formula, V A is the alveolar volume, V E is the volume of exhaled air during the exhalation phase, V ee is the residual volume of the lungs, V D is the dead space volume, F ACO is the concentration of carbon monoxide in the alveoli, F ICO is the concentration of carbon monoxide in the inhaled test gas, F ACH4 is the concentration of methane in the alveoli, F ICH4 is the concentration of methane in the inhaled test gas, t BH is the breath holding time, D LCO is the diffusing capacity of the lung for carbon monoxide, P B is the ambient atmospheric pressure, P H2O is the partial pressure of water vapor in the alveoli, V Dequip is the dead space volume of the equipment, V Danat is the dead space volume of the human body, w is the weight of the subject, T ree is the average concentration of methane at the end of tidal exhalation, t0 is the time of inhaling the test gas, t f is the end time of the test, Tr(t) is the real-time concentration of methane in the main air flow path, Q e (t) is the real-time airflow rate of the main airflow path, T ree-avg is the constant value of the average methane concentration at the end of tidal expiration, t1 and t2 are the test periods at the end of tidal expiration, and t ree (t) is the real-time methane gas concentration in the mixing chamber, V is the volume of the mixing chamber, and k is the proportional coefficient.

10. The method for detecting lung ventilation function based on a Venturi tube according to claim 9, characterized in that: When testing in step S102, it also includes establishing a dynamic judgment process based on the sampling window to achieve adaptive determination of the alveolar F ACO and F ACH4 The dynamic determination process of the sampling window includes the dynamic start timing and dynamic termination timing of the sampling window; The dynamic start timing includes when the cumulative exhaled gas volume is greater than or equal to the set initial cumulative exhaled volume lower limit, and then when it is determined whether the real-time exhaled flow rate stability index is lower than a preset stability threshold, if so, the sampling window is opened; Dynamic termination timing includes terminating the sampling window if the real-time expiratory flow rate is lower than the preset minimum effective expiratory flow rate threshold; or, the real-time expiratory flow rate stability index exceeds the preset stability threshold again; or, the accumulated exhaled gas volume exceeds the preset upper limit value.

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