Human body breathing heat metabolism detection device and method based on piston type air cylinder

Abstract

The invention discloses a human body breathing heat metabolism detection device and method based on a piston type air cylinder. The detection device comprises a flow detection module, a respiratory gas sampling module, a gas concentration analysis module, a control unit and a computer, wherein the flow detection module is used for two-way flow detection of respiratory gas; the breathing gas sampling module is used for sampling and collecting breathing gas, physically averaging and discharging the breathing gas at constant flow; the gas concentration analysis module is used for concentration detection and concentration calibration of oxygen and carbon dioxide in respiratory gas; the control unit is responsible for control and signal acquisition of motors, valves, sensors and the like in the device; the computer is responsible for data collection, calculation and analysis, man-machine interaction and result display. The detection method comprises the following steps: firstly, carrying out concentration calibration, then, carrying out a metabolism test on a subject based on a breathing mask or a breathing machine, and finally, calculating and obtaining a metabolism index according to the measured gas concentration and flow parameters. The method can be applied to two metabolism detection scenes of mechanical ventilation and spontaneous respiration, the test is reliable, and engineering realization is easy.

Description

Technical Field

[0001] The present invention relates to the field of human energy metabolism detection, and in particular to a human respiratory heat metabolism detection device and method based on a piston cylinder. Background Art

[0002] Human respiratory heat metabolism detection equipment plays an important role in medical applications such as nutritional support, prevention and diagnosis of metabolic diseases. For example, the metabolic test results of critically ill patients are an important basis for physicians to formulate nutritional support plans. The principle of indirect calorimetry is the "gold standard" for human metabolic detection. It is achieved by detecting the oxygen consumption and carbon dioxide production of the subjects. At present, the detection methods based on the principle of indirect calorimetry equipment mainly include: (1) Hood dilution method. The metabolic detection equipment using this method uses an air collection hood to mix and dilute the human respiratory gas with air and then draw it into the corresponding analysis unit to achieve flow and concentration detection, and complete the calculation of oxygen consumption and carbon dioxide production. This method has the advantages of high comfort, simple air path and good accuracy. However, due to the use of the air collection hood structure, it cannot be adapted to the ventilator pipeline, making it impossible to apply it to the metabolic detection scenario of mechanically ventilated subjects, and it is difficult to identify the real-time metabolic changes of the subjects.

[0003] (2) Mixing chamber method. The metabolic detection equipment using this method first collects human exhaled air based on a mixing chamber, physically averages it, and then dilutes it with air before exhaling it. Finally, the component concentrations of the gas in the mixing chamber, the diluted gas, and the inhaled gas are detected. Combined with the flow detection of the diluted exhaust gas, the oxygen consumption and carbon dioxide production are calculated. This method has high stability, high accuracy, and can be adapted to the application scenarios of subjects under spontaneous breathing and mechanical ventilation. In addition, although the design of the mixing chamber reduces the frequency response requirements of the concentration sensor, it increases the complexity of the gas path structure. The equipment is large and it is difficult to carry out disinfection and sterilization of medical equipment, making the risk of cross-infection between subjects difficult to control.

[0004] (3) Breath-by-breath method. The metabolic detection equipment using this method detects the flow rate in the respiratory pathway and detects the concentration using bypass sampling in the respiratory pathway, completing the flow rate and concentration signal detection of each breath of the subject, and realizing the calculation of oxygen consumption and carbon dioxide production. This method has the advantages of strong real-time performance and high adaptability to application scenarios. However, it has high requirements for the frequency response of the concentration sensor, and is highly dependent on the time alignment algorithm of the flow signal and the concentration signal. It is complex to implement and difficult to implement in engineering. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a human respiratory caloric metabolism detection device and method based on a piston cylinder, which is suitable for both mechanically ventilated and spontaneously breathing subjects, has a reliable air path structure, and has low requirements on the dynamic performance of the gas concentration sensor. It can realize highly safe and comfortable human energy metabolism detection.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme: A human respiratory heat metabolism detection device based on a piston cylinder is composed of a flow detection module, a respiratory sampling module, a gas concentration analysis module, a control unit and a computer. The flow detection module is used for bidirectional flow detection of the subject's respiratory gas; the respiratory sampling module is used for sampling, collecting, physically averaging and constant flow discharge of the subject's respiratory gas; the gas concentration analysis module is used for oxygen and carbon dioxide concentration detection and sensor concentration calibration in the subject's respiratory gas; the control unit is responsible for the control and signal acquisition of various motors, valves, sensors, etc. in the device; the computer is responsible for data collection, calculation and analysis, human-computer interaction and result display.

[0007] Preferably, the flow detection module is a detachable tubular structure consisting of a porous air block plate, a main differential pressure sensor, a sampling hole A, a sampling hole B, a pipeline and an air pipe. The porous air block plate is vertically installed in the center of the pipeline, and when the respiratory air flows through, air flow resistance is generated to form an air pressure difference; the sampling holes A and B are installed on both sides of the porous air block plate at equal intervals to provide an air flow path for sampling and analyzing the respiratory air flow and respiratory air concentration; the main differential pressure sensor connects the sampling holes A and B through the air pipe to detect the air pressure difference between the respiratory air in the pipeline and the two ends of the porous air block plate, and then calculates a two-way flow signal.

[0008] Preferably, the respiratory gas sampling module is composed of an air pressure difference detection unit and a piston cylinder sampling unit. The air pressure difference detection unit is used to detect the air pressure difference in the piston cylinder and in the pipeline of the flow detection module; the piston cylinder sampling unit is designed for the following purposes: first, to collect the subject's respiratory gas by extracting air in proportion; second, to physically average the concentrations of various gas components in the respiratory gas; and third, to discharge the collected subject's respiratory gas to the gas concentration analysis module at a constant flow.

[0009] Preferably, the air pressure difference detection unit is composed of a micro-differential pressure sensor, a fifth switch valve, a sixth switch valve, a seventh switch valve, an eighth switch valve and an air pipe. Sampling hole C and sampling hole D are the air inlet holes of the exhalation piston cylinder and the air inlet holes of the inhalation piston cylinder, respectively. The X end of the fifth switch valve is connected to the sampling hole A through the air pipe, the X end of the sixth switch valve is connected to the sampling hole D through the air pipe, the X end of the seventh switch valve is connected to the sampling hole B through the air pipe, and the X end of the eighth switch valve is connected to the sampling hole C through the air pipe. The X end of the micro-differential pressure sensor is connected to the Y end of the fifth switch valve and the Y end of the seventh switch valve through the air pipe, and the Y end of the micro-differential pressure sensor is connected to the Y end of the sixth switch valve and the Y end of the eighth switch valve through the air pipe.

[0010] Preferably, the piston cylinder sampling unit is composed of a first switch valve, a second switch valve, a third switch valve, a fourth switch valve, a first electric push rod, a second electric push rod, an inhalation piston cylinder, an exhalation piston cylinder, a pressure difference sensor and a trachea. The sampling hole A, the first switch valve, the exhalation piston cylinder sampling hole C, the exhalation piston cylinder outlet and the third switch valve inlet are connected in sequence through the trachea to form an exhalation phase sampling airflow path; the sampling hole B, the second switch valve, the inhalation piston cylinder sampling hole D, the inhalation piston cylinder outlet and the fourth switch valve inlet are connected in sequence through the trachea to form an inhalation phase sampling airflow path. One end of the pressure difference sensor is connected to the outlet of the third switch valve, the outlet of the fourth switch valve, the inlet end of the oxygen sensor and the outlet of the proportional valve through the trachea, and the other end of the pressure difference sensor is connected to the air. The first electric push rod and the second electric push rod are respectively connected to the piston rods of the exhalation and inhalation piston cylinders, which are used to drive and adjust the position of the piston rods to achieve sampling, extraction and exhaust of the subject's respiratory gas.

[0011] Preferably, when the subject is in the inhalation stage. First, the fifth and sixth switch valves in the air pressure difference detection unit are opened, and the seventh and eighth switch valves are closed. At this time, the micro-pressure difference sensor detects the air pressure difference between the sampling hole A and the sampling hole D; secondly, the second and third switch valves in the piston cylinder sampling unit are opened, and the first and fourth switch valves are closed. At this time, the inhalation piston cylinder is waiting to be evacuated, and the piston rod of the inhalation piston cylinder is at the top, and the exhalation piston cylinder is waiting to be exhausted, and the piston rod of the exhalation piston cylinder is at the bottom; then, after the inhalation stage begins, the second electric push rod pulls the piston rod of the inhalation piston cylinder, and the inhaled gas of the subject in the flow detection module is inhaled into the inhalation piston cylinder through the second switch valve. During this period, based on the ADRC negative feedback control algorithm, the air pressure difference between sampling hole A and sampling hole D is used as the observation signal to control the second electric push rod to pull the piston rod of the inhalation piston cylinder, so that the air pressure difference between sampling hole A and sampling hole D is 0, thereby realizing that the suction flow of the inhalation piston cylinder is proportional to the inhalation flow of the subject in the flow detection module, completing the proportional collection of the inhalation gas of the subject and the physical average of the gas component concentration based on the inhalation cylinder; finally, at the same time after the inhalation stage begins, the first electric push rod pushes the piston rod of the exhalation piston cylinder, and the exhaled gas of the subject in the exhalation piston cylinder is discharged to the gas concentration analysis module through the third switch valve. During this period, based on the PID negative feedback control algorithm, the air pressure at the inlet of the oxygen sensor detected by the pressure difference sensor is used as the observation signal, and the first electric push rod is controlled to adjust the pushing rate of the piston rod in the exhalation piston cylinder, so that the air pressure at the outlet of the third switch valve is constant until the gas in the exhalation piston cylinder is exhausted, so as to realize the constant pressure and constant flow to discharge the exhaled gas of the subject in the exhalation piston cylinder to the oxygen sensor in the gas concentration analysis module. When the subject is in the exhalation stage. First, the seventh and eighth switch valves in the air pressure difference detection unit are opened, and the fifth and sixth switch valves are closed. At this time, the micro-pressure difference sensor detects the air pressure difference between sampling hole B and sampling hole C; secondly, the first and fourth switch valves in the piston cylinder sampling unit are opened, and the second and third switch valves are closed. At this time, the exhalation piston cylinder is waiting to be evacuated, and the piston rod of the exhalation piston cylinder is at the top, and the inhalation piston cylinder is waiting to be exhausted, and the piston rod of the inhalation piston cylinder is at the bottom; then, after the exhalation stage begins, the first electric push rod pulls the piston rod of the exhalation piston cylinder, and the exhaled air of the subject in the flow detection module is inhaled into the exhalation piston cylinder through the first switch valve. During this period, based on the ADRC negative feedback control algorithm, the air pressure difference between the sampling hole B and the sampling hole C is used as the observation signal to control the first electric push rod to pull the piston rod of the exhalation piston cylinder, so that the air pressure difference between the sampling hole B and the sampling hole C is 0, thereby achieving the exhalation flow of the exhalation piston cylinder being proportional to the exhaled air flow of the subject in the flow detection module, completing the proportional extraction and collection of the exhaled air of the subject and the physical averaging of the gas component concentration based on the exhalation cylinder; finally, at the same time as the exhalation stage begins, the second electric push rod pushes the piston rod of the inhalation piston cylinder, and the inhaled air of the subject in the inhalation piston cylinder is discharged to the gas concentration analysis module through the fourth switch valve.During this period, based on the PID negative feedback control algorithm, the air pressure at the oxygen sensor inlet detected by the pressure difference sensor is used as the observation signal to control the second electric push rod to adjust the pushing rate of the piston rod in the inhalation piston cylinder, so that the air pressure at the outlet of the fourth switch valve is constant until the gas in the inhalation piston cylinder is exhausted, so as to discharge the inhaled gas of the subject in the inhalation piston cylinder to the oxygen sensor in the gas concentration analysis module at a constant pressure and flow. Among them, the inhalation and exhalation stages of the subject are detected and identified by the main pressure difference sensor in the flow detection module. In particular, during the first breathing stage of the subject, the exhaust gas of the exhalation piston cylinder is air.

[0012] Preferably, the gas concentration analysis module is composed of an oxygen sensor, a carbon dioxide sensor, a first high-pressure calibration gas source, a second high-pressure calibration gas source, a first pressure reducing valve, a second pressure reducing valve, a first pressure relief valve, a second pressure relief valve, a proportional valve and an air pipe. The first high-pressure calibration gas source, the first pressure reducing valve, the first pressure relief valve and the proportional valve are sequentially connected through the air pipe to form a first group of calibration gas flow paths, and the second high-pressure calibration gas source, the second pressure reducing valve, the second pressure relief valve and the proportional valve are sequentially connected through the air pipe to form a second group of calibration gas flow paths. The air outlet of the oxygen sensor is connected to the air inlet of the carbon dioxide sensor. The air outlet of the carbon dioxide sensor is connected to the air. The oxygen sensor and the carbon dioxide sensor are used to detect oxygen and carbon dioxide concentration signals in the sampled gas.

[0013] Preferably, when the oxygen sensor and the carbon dioxide sensor in the gas concentration analysis module are calibrated based on the concentration of the first group of calibration gas: first, the second high-pressure calibration gas source is closed, and the first high-pressure calibration gas source is opened, and the calibration gas is reduced in pressure by the first pressure reducing valve and then flows to the first pressure relief valve; then, the first pressure relief valve is opened, and the calibration gas is depressurized and flows to the air inlet of the proportional valve; finally, the proportional valve is opened, and the calibration gas is sent to the oxygen sensor and the carbon dioxide sensor through the proportional valve. During this period, the pressure difference sensor in the piston cylinder sampling unit detects the outlet pressure of the proportional valve as an observation signal, and the opening size of the proportional valve is controlled based on the PID negative feedback control algorithm to achieve a constant pressure at the outlet of the proportional valve, and the calibration gas of the first high-pressure calibration gas source is sent to the oxygen sensor at a constant pressure and flow. When the oxygen sensor and carbon dioxide sensor in the gas concentration analysis module are calibrated based on the concentration of the second set of calibration gas: first, close the first high-pressure calibration gas source, open the second high-pressure calibration gas source, and the calibration gas is reduced in pressure by the second pressure reducing valve to the second pressure relief valve; then, the second pressure relief valve is opened, and the calibration gas is depressurized to the proportional valve inlet; finally, the proportional valve is opened, and the calibration gas is sent to the oxygen sensor and the carbon dioxide sensor through the proportional valve. During this period, the differential pressure sensor in the piston cylinder sampling unit detects the outlet pressure of the proportional valve as an observation signal, and the opening size of the proportional valve is controlled based on the PID negative feedback control algorithm to achieve a constant pressure at the outlet of the proportional valve, and the calibration gas of the second high-pressure calibration gas source is sent to the oxygen sensor at a constant pressure and constant flow. When the subject is undergoing a metabolic test: close the proportional valve, the subject's respiratory gas is discharged from the respiratory gas sampling module to the oxygen sensor at a constant pressure and constant flow, and then discharged to the air after passing through the carbon dioxide sensor, so as to achieve the detection of the oxygen concentration and carbon dioxide concentration of the subject's respiratory gas.

[0014] The present invention also provides a method for detecting human respiratory heat metabolism based on a piston cylinder, based on the above detection device, comprising the following steps: Step 1: The operator performs gas concentration calibration of the oxygen sensor and carbon dioxide sensor.

[0015] First, when calibrating the first group of gases, open the first high-pressure calibration gas source, and the calibration gas is reduced in pressure by the first pressure reducing valve to the first pressure relief valve; then, the first pressure relief valve is opened, and the calibration gas passes through the proportional valve outlet to realize the first group of calibration gas flow path, ventilate and wait for the gas flow to stabilize, collect the average gas concentration over a period of time, and complete the oxygen sensor range point calibration and carbon dioxide sensor zero point calibration; secondly, when calibrating the second group of gases, open the second high-pressure calibration gas source, and the calibration gas is reduced in pressure by the second pressure reducing valve to the second pressure relief valve; then, the second pressure relief valve is opened, and the calibration gas passes through the proportional valve outlet to realize the second group of calibration gas flow path, ventilate and wait for the gas flow to stabilize, collect the average gas concentration over a period of time, and complete the oxygen sensor zero point calibration and carbon dioxide sensor range point calibration. Finally, close each high-pressure calibration gas source and valve to complete the gas concentration calibration of the oxygen sensor and carbon dioxide sensor.

[0016] Step 2: The subject completes user registration and login on the computer, makes preparations for the metabolic test, and starts the test.

[0017] When used in a spontaneously breathing subject, the subject wears a breathing mask, one end of the flow detection module is connected to the breathing mask, and the other end is connected to the air. When used in a mechanically ventilated subject, the subject is connected to the ventilator, and both ends of the flow detection module are installed in the ventilator patient circuit between the ventilator Y-shaped interface and the subject. The main pressure difference sensor in the flow detection module measures the pressure difference at both ends of the porous air block plate, thereby identifying the inhalation and exhalation stages of the subject and obtaining the bidirectional flow of the subject's breathing gas. When the subject starts to inhale, the inhalation piston cylinder is to be pumped, and the exhalation piston cylinder is to be exhausted. During inhalation, the inhalation piston cylinder pumps and collects the subject's inhaled air, and the exhalation piston cylinder discharges the collected last exhaled air of the subject through the third switch valve to the gas concentration analysis module at a constant pressure and flow. The oxygen sensor and the carbon dioxide sensor detect the average oxygen concentration and carbon dioxide concentration of the subject's last exhaled air. When the subject starts to exhale, the exhalation piston cylinder is to be pumped, and the inhalation piston cylinder is to be exhausted. During exhalation, the exhalation piston cylinder draws air to collect the subject's exhaled air, and the inhalation piston cylinder discharges the collected subject's last inhaled air through the fourth switch valve to the gas concentration analysis module at a constant pressure and flow. The oxygen sensor and the carbon dioxide sensor detect the average oxygen concentration and the average carbon dioxide concentration of the subject's last inhaled air.

[0018] Step 3: The computer calculates the metabolism-related indicators based on the data collected and uploaded by the control unit: oxygen uptake per minute, carbon dioxide production per minute. The formula derivation is expressed as follows: Exhaled air volume per breath: (1) (2) in, is the volume of exhaled air in a certain respiratory cycle (mL); is the time when exhalation starts in a breathing cycle (s); is the end time of exhalation in a breathing cycle (s); is the subject's respiratory flow rate (mL / s); is the time (s); is the gas standard state correction factor; is the ambient atmospheric pressure (kPa).

[0019] Oxygen uptake per minute ( ): (3) Carbon dioxide production per minute ( ): (4) in, is the time when inspiration starts in a breathing cycle (s); is the mean oxygen concentration of each breath exhaled by the subject (%); is the mean carbon dioxide concentration of each breath exhaled by the subject (%); is the mean oxygen concentration of each breath inhaled by the subject (%); is the mean carbon dioxide concentration of each breath inhaled by the subject (%); is the oxygen uptake per minute (mL / min); is the amount of carbon dioxide produced per minute (mL / min).

[0020] The respiratory quotient (RQ) can be calculated through the above-mentioned oxygen uptake per minute and carbon dioxide production per minute, and the resting metabolic rate (REE) can be calculated based on the Weir formula, thereby realizing a human respiratory heat metabolism detection based on a piston cylinder.

[0021] The beneficial effects achieved by the present invention are: 1. The present invention is based on the breathing sampling module of the piston cylinder sampling unit, which realizes the cyclic and proportional collection, physical buffering and constant pressure and constant flow gas component concentration analysis of the human body's inhaled and exhaled air, avoids the real-time human breath gas analysis at the millisecond level, does not require the dynamic performance of the oxygen sensor and the carbon dioxide sensor (i.e., the concentration sensor in the breath-by-breath method), and makes the human body metabolism detection and analysis easier to implement in engineering; 2. The present invention realizes constant pressure and constant flow control of the airflow in the process of analyzing the concentration of human respiratory gas components through the respiratory gas sampling module and the gas concentration analysis module, avoids the errors of the oxygen sensor and the carbon dioxide sensor caused by the fluctuation of the air pressure and the air flow, and improves the accuracy of human metabolism detection; 3. The present invention is based on a flow detection module, which can realize the detection of the flow and component concentration of human respiratory gas when the subject wears a mask or is connected to a ventilator, and supports two human metabolic test application scenarios: spontaneously breathing subjects and subjects under mechanical ventilation. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a human body respiratory heat metabolism detection device based on a piston cylinder of the present invention; Figure 2 It is a structural schematic diagram of a flow detection module device for metabolic testing of subjects under mechanical ventilation and spontaneous breathing; Figure 3 It is a schematic diagram of the structure of the piston cylinder device and its suction and exhaust; Figure 4The present invention is a flow chart of a method for detecting human respiratory heat metabolism based on a piston cylinder.

[0023] Among them, the accompanying drawings are marked as: 1-computer, 2-control unit, 3-porous air resistance plate, 4-main differential pressure sensor, 5-first switch valve, 6-second switch valve, 7-exhalation piston cylinder, 8-inhalation piston cylinder, 9-first electric push rod, 10-second electric push rod, 11-third switch valve, 12-fourth switch valve, 13-oxygen sensor, 14-carbon dioxide sensor, 15-proportional valve, 16-first pressure relief valve, 17-first pressure reducing valve, 18-first high-pressure calibration gas source, 19-differential pressure sensor, 20-second pressure relief valve, 21-second pressure reducing valve, 22-second high-pressure calibration gas source, 23-micro differential pressure sensor, 24-fifth switch valve, 25-sixth switch valve, 26-seventh switch valve, 27-eighth switch valve, 2.1-sampling hole A, 2.2-sampling hole B, 2.4 pipeline. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0025] like Figure 1 As shown, this embodiment provides a human respiratory heat metabolism detection device based on a piston cylinder, including a flow detection module, a respiratory gas sampling module, a gas concentration analysis module, a control unit 2 and a computer 1.

[0026] like Figure 2 As shown, the flow detection module is a detachable tubular structure composed of a porous air block plate 3, a main differential pressure sensor 4, a sampling hole A 2.1, a sampling hole B 2.2, a pipeline 2.4 of the flow detection module and an air pipe. The porous air block plate 3 is vertically and centrally installed inside the pipeline 2.4, and generates air flow resistance when the respiratory air flows through, forming an air pressure difference; the sampling holes A 2.1 and the sampling holes B 2.2 are installed on both sides of the porous air block plate 3 at equal intervals, providing an air flow path for the pressure analysis of the respiratory air flow and the sampling analysis of the respiratory air concentration; the main differential pressure sensor 4 is connected to the sampling holes A 2.1 and the sampling holes B 2.2 through the air pipe, which is used to obtain the air pressure difference between the respiratory air in the pipeline 2.4 and the two ends of the porous air block plate 3, and then calculate the two-way flow signal.

[0027] Specifically, when the device is used in a spontaneously breathing subject, the subject wears a breathing mask, one end of the flow detection module is connected to the breathing mask, and the other end is connected to air. When the device is used in a mechanically ventilated subject, the subject wears a ventilator, and both ends of the flow detection module are installed in the ventilator patient circuit between the ventilator Y-shaped interface and the subject.

[0028] The respiratory gas sampling module is composed of an air pressure difference detection unit and a piston cylinder sampling unit. The air pressure difference detection unit is used to detect the air pressure difference in the piston cylinder and the flow detection module pipeline; the piston cylinder sampling unit is designed for the following purposes: first, to collect the subject's respiratory gas by drawing air in equal proportion; second, to physically average the concentration of each gas component in the respiratory gas; third, to discharge the collected subject's respiratory gas to the gas concentration analysis module at a constant flow.

[0029] The air pressure difference detection unit is composed of a micro-differential pressure sensor 23, a fifth switch valve 24, a sixth switch valve 25, a seventh switch valve 26, an eighth switch valve 27 and an air pipe. The sampling hole C and the sampling hole D are the air inlet holes of the exhalation piston cylinder 7 and the air inlet holes of the inhalation piston cylinder 8, respectively. The X end of the fifth switch valve 24 is connected to the sampling hole A 2.1 through the air pipe, the X end of the sixth switch valve 25 is connected to the sampling hole D through the air pipe, the X end of the seventh switch valve 26 is connected to the sampling hole B 2.2 through the air pipe, and the X end of the eighth switch valve 27 is connected to the sampling hole C through the air pipe. The X end of the micro-differential pressure sensor 23 is connected to the Y end of the fifth switch valve 24 and the Y end of the seventh switch valve 26 through the air pipe, and the Y end of the micro-differential pressure sensor 23 is connected to the Y end of the sixth switch valve 25 and the Y end of the eighth switch valve 27 through the air pipe.

[0030] The piston cylinder sampling unit is composed of a first switch valve 5, a second switch valve 6, a third switch valve 11, a fourth switch valve 12, a first electric push rod 9, a second electric push rod 10, an inhalation piston cylinder 8, an exhalation piston cylinder 7, a differential pressure sensor 19 and an air pipe. The sampling hole A 2.1, the first switch valve 5, the sampling hole C of the exhalation piston cylinder 7, the air outlet of the exhalation piston cylinder 7 and the air inlet of the third switch valve 11 are connected in sequence through the air pipe to form an exhalation phase sampling airflow path; the sampling hole B 2.2, the second switch valve 6, the sampling hole D of the inhalation piston cylinder 8, the air outlet of the inhalation piston cylinder 8 and the air inlet of the fourth switch valve 12 are connected in sequence through the air pipe to form an inhalation phase sampling airflow path. One end of the differential pressure sensor 19 is connected to the air outlet of the third switch valve 11, the air outlet of the fourth switch valve 12, the air inlet end of the oxygen sensor 13 and the air outlet of the proportional valve 15 at the same time through the air pipe, and the other end of the differential pressure sensor 19 is connected to the air. The first electric push rod 9 and the second electric push rod 10 are respectively connected to the piston rods of the exhalation piston cylinder 7 and the inhalation piston cylinder 8, and are used to drive and adjust the positions of the piston rods to achieve sampling, extraction and exhaust of the subject's respiratory gas.

[0031] like Figure 1 and Figure 3As shown, when the subject is in the inhalation stage, first, the fifth switch valve 24 and the sixth switch valve 25 in the air pressure difference detection unit are opened, and the seventh switch valve 26 and the eighth switch valve 27 are closed. At this time, the micro-pressure difference sensor 23 detects the air pressure difference between the sampling hole A2.1 and the sampling hole D; then, the second switch valve 6 and the third switch valve 11 in the piston cylinder sampling unit are opened, and the first switch valve 5 and the fourth switch valve 12 are closed. At this time, the inhalation piston cylinder 8 is waiting to be evacuated, and the piston rod of the inhalation piston cylinder 8 is at the top, and the exhalation piston cylinder 7 is waiting to be exhausted, and the piston rod of the exhalation piston cylinder 7 is at the bottom; then, after the inhalation stage begins, the second electric push rod 10 pulls the piston rod of the inhalation piston cylinder 8, and the inhaled gas of the subject in the flow detection module is inhaled into the inhalation piston cylinder 8 through the second switch valve 6. During this period, based on the ADRC (auto-disturbance rejection control) algorithm, the air pressure difference between the sampling hole A2.1 and the sampling hole D is used as the observation signal to control the second electric push rod 10 to pull the piston rod of the suction piston cylinder 8, so that the air pressure difference between the sampling hole A2.1 and the sampling hole D is 0, thereby achieving the suction flow of the suction piston cylinder 8 being proportional to the inhaled air flow of the subject in the flow detection module, completing the proportional suction and collection of the subject's inhaled air and the physical averaging of the gas component concentration based on the inhalation cylinder; finally, at the same time as the start of the inhalation stage, the first electric push rod 9 pushes the piston rod of the exhalation piston cylinder 7, and the exhaled air of the subject in the exhalation piston cylinder 7 is discharged to the gas concentration analysis module through the third switch valve 11. During this period, based on the PID negative feedback control algorithm, the air pressure at the air inlet of the oxygen sensor 13 detected by the pressure difference sensor 19 is used as the observation signal to control the first electric push rod 9 to adjust the pushing rate of the piston rod in the exhalation piston cylinder 7, so that the air pressure at the air outlet of the third switch valve 11 is constant until the gas in the exhalation piston cylinder 7 is exhausted, thereby achieving constant pressure and constant flow to discharge the exhaled gas of the subject in the exhalation piston cylinder 7 to the oxygen sensor 13 in the gas concentration analysis module.

[0032] When the subject is in the exhalation stage, first, the seventh switch valve 26 and the eighth switch valve 27 in the air pressure difference detection unit are opened, and the fifth switch valve 24 and the sixth switch valve 25 are closed. At this time, the micro-pressure difference sensor 23 detects the air pressure difference between the sampling hole B 2.2 and the sampling hole C; secondly, the first switch valve 5 and the fourth switch valve 12 in the piston cylinder sampling unit are opened, and the second switch valve 6 and the third switch valve 11 are closed. At this time, the exhalation piston cylinder 7 is waiting to be evacuated, and the piston rod of the exhalation piston cylinder 7 is at the top, and the inhalation piston cylinder 8 is waiting to be exhausted, and the piston rod of the inhalation piston cylinder 8 is at the bottom; then, after the exhalation stage begins, the first electric push rod 9 pulls the piston rod of the exhalation piston cylinder 7, and the exhaled air of the subject in the flow detection module is inhaled into the exhalation piston cylinder through the first switch valve 5. During this period, based on the ADRC self-anti-disturbance control algorithm, the air pressure difference between the sampling hole B2.2 and the sampling hole C is used as the observation signal to control the first electric push rod 9 to pull the piston rod of the exhalation piston cylinder 7, so that the air pressure difference between the sampling hole B2.2 and the sampling hole C is 0, thereby achieving the exhalation flow of the exhalation piston cylinder 7 to be proportional to the exhaled air flow of the subject in the flow detection module, and completing the proportional extraction and collection of the exhaled air of the subject and the physical averaging of the gas component concentration based on the exhalation cylinder; finally, at the same time as the exhalation stage begins, the second electric push rod 10 pushes the piston rod of the inhalation piston cylinder 8, and the inhaled air of the subject in the inhalation piston cylinder 8 is discharged to the gas concentration analysis module through the fourth switch valve 12. During this period, based on the PID negative feedback control algorithm, the air pressure at the inlet of the oxygen sensor 13 detected by the pressure difference sensor 19 is used as the observation signal to control the second electric push rod 10 to adjust the pushing rate of the piston rod in the inhalation piston cylinder 8, so that the air pressure at the outlet of the fourth switch valve 12 is constant until the gas in the inhalation piston cylinder 8 is exhausted, so as to discharge the inhaled gas of the subject in the inhalation piston cylinder 8 to the oxygen sensor 13 in the gas concentration analysis module at a constant pressure and flow. Among them, the inhalation and exhalation stages of the subject are detected and identified by the main pressure difference sensor 4 in the flow detection module. In particular, in the first breathing stage of the subject, the exhaust gas of the exhalation piston cylinder is air.

[0033] The gas concentration analysis module is composed of an oxygen sensor 13, a carbon dioxide sensor 14, a first high-pressure calibration gas source 18, a second high-pressure calibration gas source 22, a first pressure reducing valve 17, a second pressure reducing valve 21, a first pressure relief valve 16, a second pressure relief valve 20, a proportional valve 15 and an air pipe. The first high-pressure calibration gas source 18, the first pressure reducing valve 17, the first pressure relief valve 16 and the proportional valve 15 are connected in sequence through the air pipe to form a first group of calibration gas flow paths, and the second high-pressure calibration gas source 22, the second pressure reducing valve 21, the second pressure relief valve 20 and the proportional valve 15 are connected in sequence through the air pipe to form a second group of calibration gas flow paths. The air outlet of the oxygen sensor 13 is connected to the air inlet of the carbon dioxide sensor 14. The air outlet of the carbon dioxide sensor 14 is connected to the air. The oxygen sensor 13 and the carbon dioxide sensor 14 are used to detect oxygen and carbon dioxide concentration signals in the sampled gas.

[0034] Specifically, when the oxygen sensor 13 and the carbon dioxide sensor 14 in the gas concentration analysis module are calibrated based on the concentration of the first set of calibration gas, first, the second high-pressure calibration gas source 22 is closed, and the first high-pressure calibration gas source 18 is opened, and the calibration gas is reduced in pressure by the first pressure reducing valve 17 and then flows to the first pressure relief valve 16; then, the first pressure relief valve 16 is opened, and the calibration gas is depressurized and flows to the air inlet of the proportional valve 15; finally, the proportional valve 15 is opened, and the calibration gas is sent to the oxygen sensor 13 and the carbon dioxide sensor 14 through the proportional valve 15. During this period, the pressure difference sensor 19 in the piston cylinder sampling unit detects the outlet pressure of the proportional valve 15 as an observation signal, and the opening size of the proportional valve 15 is controlled based on the PID negative feedback control algorithm to achieve a constant outlet pressure of the proportional valve 15, and the calibration gas of the first high-pressure calibration gas source 18 is sent to the oxygen sensor 13 at a constant pressure and flow.

[0035] When the oxygen sensor 13 and the carbon dioxide sensor 14 in the gas concentration analysis module are calibrated based on the concentration of the second set of calibration gas, first, the first high-pressure calibration gas source 18 is closed, and the second high-pressure calibration gas source 22 is opened, and the calibration gas is reduced in pressure by the second pressure reducing valve 21 and then flows to the second pressure relief valve 20; then, the second pressure relief valve 20 is opened, and the calibration gas is depressurized and flows to the air inlet of the proportional valve 15; finally, the proportional valve 15 is opened, and the calibration gas is sent to the oxygen sensor 13 and the carbon dioxide sensor 14 through the proportional valve 15. During this period, the differential pressure sensor 19 in the piston cylinder sampling unit detects the outlet pressure of the proportional valve 15 as an observation signal, and the opening size of the proportional valve 15 is controlled based on the PID negative feedback control algorithm to achieve a constant pressure at the outlet of the proportional valve 15, and the calibration gas of the second high-pressure calibration gas source 22 is sent to the oxygen sensor 13 at a constant pressure and flow. When the subject is undergoing metabolic testing: the proportional valve 15 is closed, and the subject's respiratory gas is discharged from the respiratory gas sampling module to the oxygen sensor 13 at a constant pressure and flow, and then discharged to the air after passing through the carbon dioxide sensor 14, thereby realizing the detection of the oxygen concentration and carbon dioxide concentration of the subject's respiratory gas.

[0036] like Figure 4 As shown, the present invention also provides a method for detecting human respiratory heat metabolism based on a piston cylinder, comprising the following steps: Step 1: The operator performs gas concentration calibration of the oxygen sensor 13 and the carbon dioxide sensor 14, including: First, when calibrating the first group of gases, open the first high-pressure calibration gas source 18, and the calibration gas is reduced in pressure by the first pressure reducing valve 17 to the first pressure relief valve 16; then, the first pressure relief valve 16 is opened, and the calibration gas is passed through the outlet of the proportional valve 15 to realize the first group of calibration gas flow path, ventilate and wait for the gas flow to stabilize, collect the average gas concentration over a period of time, and complete the range point calibration of the oxygen sensor 13 and the zero point calibration of the carbon dioxide sensor 14; then, when calibrating the second group of gases, open the second high-pressure calibration gas source 22, and the calibration gas is reduced in pressure by the second pressure reducing valve 21 to the second pressure relief valve 20; then, the second pressure relief valve 20 is opened, and the calibration gas is passed through the outlet of the proportional valve 15 to realize the second group of calibration gas flow path, ventilate and wait for the gas flow to stabilize, collect the average gas concentration over a period of time, and complete the zero point calibration of the oxygen sensor and the range point calibration of the carbon dioxide sensor. Finally, close each high-pressure calibration gas source and valve to end the gas concentration calibration of the oxygen sensor and the carbon dioxide sensor.

[0037] Step 2: The subject completes user registration and login on the computer, makes preparations for the metabolic test, and starts the test, including: When used in a subject with spontaneous breathing, the subject wears a breathing mask, one end of the flow detection module is connected to the breathing mask, and the other end is connected to the air. When used in a subject with mechanical ventilation, the subject wears a ventilator, and both ends of the flow detection module are installed in the ventilator patient circuit between the Y-shaped interface of the ventilator and the subject. The main pressure difference sensor 4 in the flow detection module measures the air pressure difference at both ends of the porous air block plate 3, thereby identifying the inhalation and exhalation stages of the subject and obtaining the bidirectional flow of the subject's breathing gas. When the subject starts to inhale, the inhalation piston cylinder 8 is to be pumped, and the exhalation piston cylinder 7 is to be exhausted. The last exhaled gas of the subject in the exhalation piston cylinder 7 is discharged to the gas concentration analysis module at constant pressure and constant flow through the third switch valve 11, and the oxygen sensor 13 and the carbon dioxide sensor 14 detect the average oxygen concentration and carbon dioxide concentration of the last exhaled gas of the subject. When the subject starts to exhale, the exhalation piston cylinder is to be pumped, and the inhalation piston cylinder is to be exhausted. The last inhaled gas inhaled by the subject in the inhalation piston cylinder is discharged to the gas concentration analysis module at constant pressure and flow through the fourth switch valve 12, and the oxygen sensor 13 and the carbon dioxide sensor 14 detect the average oxygen concentration and the average carbon dioxide concentration of the last inhaled gas of the subject.

[0038] Step 3: Computer 1 calculates metabolism-related indicators based on the data collected and uploaded by control unit 2: oxygen uptake per minute, carbon dioxide production per minute. The formula derivation is expressed as follows: Exhaled air volume per breath: (1) (2) in, is the volume of exhaled air in a respiratory cycle (in mL); is the time when exhalation starts in a breathing cycle (unit: s); is the end time of exhalation in a breathing cycle (unit: s); is the subject's respiratory flow rate (in mL / s); is the time (unit s); is the gas standard state correction factor; is the ambient atmospheric pressure (in kPa).

[0039] Oxygen uptake per minute for: (3) Carbon dioxide production per minute for: (4) in, is the time when inspiration starts in a breathing cycle (unit: s); is the mean oxygen concentration of each breath exhaled by the subject (%); is the mean carbon dioxide concentration of each breath exhaled by the subject (%); is the mean oxygen concentration of each breath inhaled by the subject (%); is the mean carbon dioxide concentration of each breath inhaled by the subject (%); is the oxygen uptake per minute (mL / min); It is the amount of carbon dioxide produced per minute (mL / min).

[0040] The respiratory quotient RQ can be calculated through the above-mentioned oxygen uptake per minute and carbon dioxide production per minute, and the resting metabolic rate REE can be calculated based on the Weir formula, thereby realizing a human respiratory heat metabolism detection based on a piston cylinder.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A human body breathing heat metabolism detection device based on a piston cylinder, characterized in that: It includes a flow detection module, a breathing gas sampling module, a gas concentration analysis module, a control unit and a computer; The flow detection module is used for bidirectional flow detection of the subject's respiratory gas; The respiratory gas sampling module is used for sampling, collecting, physically averaging and discharging the subject's respiratory gas at a constant flow rate; The gas concentration analysis module is used for oxygen and carbon dioxide concentration detection and concentration calibration in the subject's breath; The control unit is responsible for the control and signal collection of each motor, valve, and sensor; The computer is responsible for data collection, calculation and analysis, human-computer interaction and result display.

2. A human body breathing heat metabolism detection device based on a piston cylinder according to claim 1, characterized in that: The flow detection module is a detachable tubular structure consisting of a porous air block plate (3), a main pressure difference sensor (4), a sampling hole A (2.1), a sampling hole B (2.2), a pipeline (2.4) and an air pipe; the porous air block plate (3) is vertically and centrally mounted inside the pipeline (2.4); the sampling hole A (2.1) and the sampling hole B (2.2) are mounted on both sides of the porous air block plate (3) at equal intervals; the main pressure difference sensor (4) is connected to the sampling hole A (2.1) and the sampling hole B (2.2) via the air pipe; the main pressure difference sensor (4) is connected to the sampling hole A (2.1) and the sampling hole B (2.2) via the air pipe, and is used to obtain the pressure difference between the respiratory gas in the pipeline and the two ends of the porous air block plate (3); when the respiratory gas flows through the porous air block plate (3), a pressure difference is generated, and a bidirectional respiratory flow signal is obtained.

3. A human body breathing heat metabolism detection device based on a piston cylinder according to claim 1, characterized in that: The respiratory gas sampling module is composed of a pressure difference detection unit and a piston cylinder sampling unit; the pressure difference detection unit comprises a micro-pressure difference sensor (23), a fifth switch valve (24), a sixth switch valve (25), a seventh switch valve (26), an eighth switch valve (27) and an air pipe, and is used to detect the pressure difference in the piston cylinder and in the pipeline of the flow detection module; the piston cylinder sampling unit comprises a first switch valve (5), a second switch valve (6), a third switch valve (11), a fourth switch valve (12), a first electric push rod (9), a second electric push rod (10), an inhalation piston cylinder (8), an exhalation piston cylinder (7), a pressure difference sensor (19) and an air pipe, and is used to proportionally extract and collect the respiratory gas of the subject, and physically average and discharge it to the gas concentration analysis module at a constant flow.

4. A human body breathing heat metabolism detection device based on a piston cylinder according to claim 3, characterized in that: In the air pressure difference detection unit, the sampling hole C and the sampling hole D are respectively the air inlet hole of the exhalation piston cylinder (7) and the air inlet hole of the inhalation piston cylinder (8); the X end of the fifth switch valve (24) is connected to the sampling hole A through an air pipe, the X end of the sixth switch valve (25) is connected to the sampling hole D through an air pipe, the X end of the seventh switch valve (26) is connected to the sampling hole B through an air pipe, and the X end of the eighth switch valve (27) is connected to the sampling hole C through an air pipe; the X end of the micro-pressure difference sensor (23) is connected to the Y end of the fifth switch valve (24) and the Y end of the seventh switch valve (26) through an air pipe, and the Y end of the micro-pressure difference sensor (23) is connected to the Y end of the sixth switch valve (25) and the Y end of the eighth switch valve (27) through an air pipe.

5. The human body breathing heat metabolism detection device based on a piston cylinder according to claim 3 is characterized in that: The sampling hole A, the first switch valve (5), the sampling hole C of the exhalation piston cylinder (7), the air outlet of the exhalation piston cylinder (7) and the air inlet of the third switch valve (11) are connected in sequence through the air pipe to form an exhalation phase sampling air flow path; the sampling hole B, the second switch valve (6), the sampling hole D of the inhalation piston cylinder (8), the air outlet of the inhalation piston cylinder (8) and the air inlet of the fourth switch valve (12) are connected in sequence through the air pipe to form an inhalation phase sampling air flow path; one end of the differential pressure sensor (19) is connected to the air outlet of the third switch valve (11), the air outlet of the fourth switch valve (12), the air inlet end of the oxygen sensor (13) and the air outlet of the proportional valve (15) through the air pipe, and the other end of the differential pressure sensor (19) is connected to the air outlet of the third switch valve (11), the air outlet of the fourth switch valve (12), the air inlet end of the oxygen sensor (13) and the air outlet of the proportional valve (15) at the same time. The air is connected; the first electric push rod (9) and the second electric push rod (10) are respectively connected to the piston rods of the exhalation piston cylinder (7) and the inhalation piston cylinder (8), and are used to drive and adjust the positions of the piston rods to achieve sampling, extraction and exhaust of the subject's breath; in the inhalation stage, first, the fifth switch valve (24) and the sixth switch valve (25) of the air pressure difference detection unit are opened, and the seventh switch valve (26) and the eighth switch valve (27) are closed at the same time, and the air pressure difference between the sampling holes A (2.1) and D is detected by the micro-pressure difference sensor (23); then, in the piston cylinder sampling unit, the second switch valve (6) and the third switch valve (11) are opened, and the first switch valve (5) and the fourth switch valve (12) are closed.At this time, the inhalation piston cylinder (8) is ready to be evacuated, and the exhalation piston cylinder (7) is ready to be exhausted; after the inhalation stage begins, the second electric push rod (10) pulls the piston rod of the inhalation piston cylinder (8), and the inhaled gas of the subject enters the cylinder through the second switch valve (6); during this period, based on the ADRC negative feedback control algorithm, the air pressure difference between sampling holes A and D is used as an observation signal to control the second electric push rod (10) to pull the piston rod of the inhalation piston cylinder (8), so that the air pressure difference between sampling holes A (2.1) and sampling hole D is 0, thereby ensuring that the air extraction flow is proportional to the inhaled gas flow of the subject, and completing the physical average of the gas component concentration in the cylinder; finally, at the same time as the inhalation stage begins, the first electric push rod (9) pushes the exhalation piston cylinder (7), and the exhaled gas is discharged to the gas concentration analysis module through the third switch valve (11); during this period, based on the PID negative feedback control algorithm, the air pressure difference between the sampling holes A and D is used as an observation signal to control the second electric push rod (10) to pull the piston rod of the inhalation piston cylinder (8), so that the air pressure difference between the sampling holes A (2.1) and the sampling hole D is 0. A feedback control algorithm is used to adjust the pushing speed of the piston rod of the exhalation piston cylinder (7) to ensure that the air pressure at the exhaust port is constant until the gas is completely discharged to the gas concentration analysis module; in the exhalation phase, firstly, the seventh switch valve (26) and the eighth switch valve (27) of the air pressure difference detection unit are opened, and the fifth switch valve (24) and the sixth switch valve (25) are closed at the same time, and the air pressure difference between the sampling holes B and C is detected by the micro-pressure difference sensor (23); then, in the piston cylinder sampling unit, the first switch valve (5) and the fourth switch valve (12) are opened, and the second switch valve (6) and the third switch valve (11) are closed; at this time, the exhalation piston cylinder (7) is ready to be evacuated, and the inhalation piston cylinder (8) is ready to be exhausted; secondly, after the exhalation phase begins, the first electric push rod (9) pulls the piston rod of the exhalation piston cylinder (7), and the exhaled gas of the subject enters the cylinder through the first switch valve (5). During this period, based on the ADRC negative feedback control algorithm, the pressure difference between the sampling holes B (2.2) and C is used as an observation signal to control the first electric push rod (9) to pull the piston rod of the exhalation piston cylinder (7), so that the pressure difference between the sampling hole B (2.2) and the sampling hole C is 0, thereby ensuring that the suction flow rate is proportional to the exhaled gas flow rate of the subject and completing the physical average of the gas component concentration in the cylinder; finally, at the same time as the exhalation phase begins, the second electric push rod (10) pushes the inhalation piston cylinder (8), and the inhaled gas is discharged to the gas concentration analysis module through the fourth switch valve (12); during this period, based on the PID negative feedback control algorithm, the pushing rate of the piston rod of the inhalation piston cylinder (8) is adjusted to ensure that the gas pressure at the exhaust port is constant until the gas is completely discharged to the gas concentration analysis module; wherein, the inhalation and exhalation phases of the subject are detected and identified by the main pressure difference sensor (4) in the flow detection module; in the first breathing phase of the subject, the gas discharged from the exhalation piston cylinder (7) is air.

6. The human body breathing heat metabolism detection device based on a piston cylinder according to claim 1, characterized in that: The gas concentration analysis module is composed of an oxygen sensor (13), a carbon dioxide sensor (14), a first high-pressure calibration gas source (18), a second high-pressure calibration gas source (22), a first pressure reducing valve (17), a second pressure reducing valve (21), a first pressure relief valve (16), a second pressure relief valve (20), a proportional valve (20) and an air pipe; the first high-pressure calibration gas source (18), the first pressure reducing valve (17), the first pressure relief valve (16) and the proportional valve (15) are sequentially connected through the air pipe to form a first group of calibration gas flow paths, and the second high-pressure calibration gas source (22), the second pressure reducing valve (21), the second pressure relief valve (20) and the proportional valve (15) are sequentially connected through the air pipe to form a second group of calibration gas flow paths. The gas outlet of the oxygen sensor (13) is connected to the gas inlet of the carbon dioxide sensor (14); the gas outlet of the carbon dioxide sensor (14) is connected to the air; the oxygen sensor (13) and the carbon dioxide sensor (14) are used to detect oxygen and carbon dioxide concentration signals in the sampled gas.

7. The human body breathing heat metabolism detection device based on a piston cylinder according to claim 6, characterized in that: When calibrating the oxygen sensor (13) and the carbon dioxide sensor (14), the calibration gas is introduced through the first high-pressure calibration gas source (18) or the second high-pressure calibration gas source (22), passes through the pressure reducing valve and the pressure relief valve to reach the proportional valve (15), and during this process, the proportional valve (15) is adjusted based on the PID negative feedback control algorithm to ensure that the gas pressure at the gas outlet is constant; the calibration gas from the first high-pressure calibration gas source (18) or the second high-pressure calibration gas source (22) is delivered to the oxygen sensor (13) at a constant pressure and flow; when the subject is undergoing a metabolic test, the proportional valve (15) is closed, and the subject's respiratory gas is discharged from the respiratory gas sampling module at a constant pressure and flow to the oxygen sensor (13), and then discharged to the air after passing through the carbon dioxide sensor (14), thereby realizing the detection of the oxygen concentration and carbon dioxide concentration of the subject's respiratory gas.

8. A method for detecting human respiratory heat metabolism based on a piston cylinder, characterized in that: The steps include: Step 1: The operator performs gas concentration calibration of the oxygen sensor (13) and the carbon dioxide sensor (14); first, during the first group of gas calibration, the first high-pressure calibration gas source (18) is opened, and the calibration gas is decompressed through the first pressure reducing valve (17) and then flows to the first pressure relief valve (16); then, the first pressure relief valve (16) is opened, and the calibration gas flows through the gas outlet of the proportional valve (15), thereby realizing the first group of calibration gas flow passages, ventilating and waiting for the gas flow to stabilize, and collecting the average gas concentration over a period of time, thereby completing the range point calibration of the oxygen sensor (13). The second set of gas is calibrated by opening the second high-pressure calibration gas source (22), and the calibration gas is decompressed by the second pressure reducing valve (21) and then flows to the second pressure relief valve (20); then, the second pressure relief valve (20) is opened, and the calibration gas flows through the outlet of the proportional valve (15) to realize the second set of calibration gas flow passage, and after the gas flow is ventilated and stabilized, the average gas concentration over a period of time is collected to complete the zero point calibration of the oxygen sensor (13) and the range point calibration of the carbon dioxide sensor (14). Finally, each high-pressure calibration gas source and valve are closed to end the gas concentration calibration of the oxygen sensor (13) and the carbon dioxide sensor (14); Step 2: The subject completes user registration and login on the computer, makes preparations before the metabolic test, and starts the test; Step 3: The computer calculates metabolism-related indicators based on the data collected and uploaded by the control unit: oxygen uptake per minute and carbon dioxide production per minute.

9. A method for detecting human respiratory heat metabolism based on a piston cylinder according to claim 8, characterized in that: The second step comprises: when used on a spontaneously breathing subject, the subject wears a breathing mask, one end of the flow detection module is connected to the breathing mask, and the other end is connected to air; when used on a mechanically ventilated subject, the subject wears a ventilator, and both ends of the flow detection module are installed in the ventilator patient circuit between the ventilator Y-shaped interface and the subject; the main pressure difference sensor (4) in the flow detection module measures the pressure difference between the two ends of the porous air blocking plate (3), thereby identifying the inhalation and exhalation phases of the subject and obtaining the bidirectional flow of the subject's respiratory gas. When the subject starts to inhale, the inhalation piston cylinder (8) is ready to be evacuated, and the exhalation piston cylinder (7) is ready to be exhausted; the last exhaled air of the subject in the exhalation piston cylinder (7) is discharged to the gas concentration analysis module through the third switch valve (11) at a constant pressure and constant flow, and the oxygen sensor (13) and the carbon dioxide sensor (14) detect and obtain the average oxygen concentration and the average carbon dioxide concentration of the last exhaled air of the subject; when the subject starts to exhale, the exhalation piston cylinder (7) is ready to be evacuated, and the inhalation piston cylinder (8) is ready to be exhausted; the last inhaled air of the subject in the inhalation piston cylinder (8) is discharged to the gas concentration analysis module through the fourth switch valve (12) at a constant pressure and constant flow, and the oxygen sensor (13) and the carbon dioxide sensor (14) detect and obtain the average oxygen concentration and the average carbon dioxide concentration of the last inhaled air of the subject.

10. The method for detecting human respiratory heat metabolism based on a piston cylinder according to claim 8, characterized in that: The formula involved in step 3 is derived as follows: Exhaled air volume per breath: （1） （2） in, It is the volume of exhaled air in a certain breathing cycle, in mL; It is the time when exhalation starts in a breathing cycle, in seconds; It is the end time of exhalation in a breathing cycle, in seconds; is the subject's respiratory flow rate, in mL / s; is the time, in seconds; is the gas standard state correction factor; is the ambient atmospheric pressure, in kPa; Oxygen uptake per minute for: （3） Carbon dioxide production per minute for: （4） in, It is the time when inspiration starts in a breathing cycle, in seconds; The average oxygen concentration of each breath exhaled by the subject; The mean carbon dioxide concentration of each breath exhaled by the subject; The average oxygen concentration of each breath inhaled by the subject; is the average carbon dioxide concentration of each breath inhaled by the subject; is the oxygen uptake per minute, in mL / min; is the amount of carbon dioxide produced per minute, in mL / min; The respiratory quotient RQ can be calculated through the above-mentioned oxygen uptake per minute and carbon dioxide production per minute, and the resting metabolic rate REE can be calculated based on the Weir formula, thereby realizing a human respiratory heat metabolism detection based on a piston cylinder.

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