Human body respiratory heat metabolism detection device and method based on piston type air cylinderTechnical Field
The invention relates to the field of human body energy metabolism detection, in particular to a human body respiratory heat metabolism detection device and method based on a piston type air cylinder.
Background
The human respiratory heat metabolism detection device plays an important role in medical application aspects such as nutrition support, metabolic disease prevention and diagnosis. For example, metabolic testing of critically ill patients is an important basis for physicians to formulate nutritional support programs. The principle of indirect calorimetry is the "gold standard" of human metabolism detection, which is achieved by detecting the oxygen consumption and carbon dioxide production of a subject. At present, the detection method based on indirect heat measurement principle equipment mainly comprises the following steps:
(1) Head cap dilution method. The metabolism detection equipment applying the method mixes and dilutes the human breathing gas and air through the gas collecting hood and then pumps the diluted human breathing gas and air into corresponding analysis units to realize flow and concentration detection and complete calculation of oxygen consumption and carbon dioxide production. The method has the advantages of high comfort level, simple air path and good accuracy. However, due to the application of the gas collecting hood structure, the gas collecting hood structure cannot be matched with a pipeline of a breathing machine, so that the gas collecting hood structure cannot be applied to a metabolism detection scene of a mechanical ventilation subject, and the real-time metabolic change of the subject is difficult to identify.
(2) A hybrid cavity process. The metabolism detection equipment using the method collects the exhaled air of the human body based on the mixing cavity, physically averages the exhaled air, and then dilutes the exhaled air with air and discharges the exhaled air, and finally detects the component concentrations of the gas in the mixing cavity, the diluted gas and the inhaled gas, and combines the flow detection of the diluted discharged gas to realize the calculation of the oxygen consumption and the carbon dioxide production. The method has the application scene of high stability and high accuracy and can be suitable for the subjects under spontaneous breathing and mechanical ventilation. In addition, the design of the mixing cavity reduces the frequency response requirement of the concentration sensor, but increases the complexity of the gas path structure, has larger equipment volume and is difficult to carry out disinfection and sterilization of medical equipment, so that the risk of cross infection among subjects is not easy to control.
(3) The method is carried out by taking the mouth-qi. The metabolic detection equipment applying the method detects the flow rate on the respiratory path and detects the concentration on the respiratory path by using a bypass air extraction sampling mode, so that the flow rate and concentration signal detection of each mouth gas of a subject is completed, and the calculation of the oxygen consumption and the carbon dioxide production is realized. The method has the advantages of strong real-time performance and high adaptation degree of application scenes. However, the method has high requirements on the frequency response of the concentration sensor, is highly dependent on a time alignment algorithm of the flow signal and the concentration signal, is complex to realize, and is not easy to realize engineering.
Disclosure of Invention
In order to solve the technical problems, the invention provides a human body respiratory heat metabolism detection device and method based on a piston cylinder, which are suitable for two application scenes of mechanical ventilation and spontaneous breathing of a subject, have reliable gas path structure and low requirements on the dynamic performance of a gas concentration sensor, and can realize high-safety and high-comfort human body energy metabolism detection.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a human body respiratory heat metabolism detection device based on a piston type air cylinder comprises a flow detection module, a respiratory 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 breathing gas of the subject, the breathing gas sampling module is used for sampling and collecting the breathing gas of the subject, physically averaging and constant-current discharging, the gas concentration analysis module is used for detecting the concentration of oxygen and carbon dioxide in the breathing gas of the subject and calibrating the concentration of a sensor, the control unit is responsible for controlling and collecting signals of motors, valves, sensors and the like in the device, and the computer is responsible for data collection, calculation and analysis, human-computer interaction and result display.
Preferably, the flow detection module is a detachable tubular structure consisting of a porous air resistance plate, a main differential pressure sensor, a sampling hole A, a sampling hole B, a pipeline and an air pipe. The main pressure difference sensor is connected with the sampling hole A and the sampling hole B through air pipes and is used for detecting the air pressure difference of the breathing air in the pipeline at two ends of the porous air resistance plate, and further calculating to obtain a bidirectional flow signal.
The breath sampling module is preferably composed of a breath pressure difference detection unit and a piston cylinder sampling unit, wherein the breath pressure difference detection unit is used for detecting the breath pressure difference in a piston cylinder and in a pipeline of the flow detection module, the piston cylinder sampling unit is designed for uniformly pumping and collecting breath of a subject, and is used for physically averaging the concentration of each gas component in the breath, and the breath pressure of the collected subject is discharged to the gas concentration analysis module in a constant flow mode.
Preferably, the air pressure difference detection unit is composed of a micro pressure difference sensor, a fifth switch valve, a sixth switch valve, a seventh switch valve, an eighth switch valve and an air pipe. The sampling hole C and the sampling hole D are respectively an air inlet hole of the air exhaling piston cylinder and an air inlet hole of the air inhaling piston cylinder. The X end of the fifth switch valve is connected with the sampling hole A through an air pipe, the X end of the sixth switch valve is connected with the sampling hole D through an air pipe, the X end of the seventh switch valve is connected with the sampling hole B through an air pipe, and the X end of the eighth switch valve is connected with the sampling hole C through an air pipe. The X end of the micro-pressure difference sensor is connected with the Y end of the fifth switch valve and the Y end of the seventh switch valve through air pipes, and the Y end of the micro-pressure difference sensor is connected with the Y end of the sixth switch valve and the Y end of the eighth switch valve through air pipes.
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 differential pressure sensor and an air pipe. The sampling hole A, the first switch valve, the sampling hole C of the expiration piston cylinder, the air outlet hole of the expiration piston cylinder and the air inlet of the third switch valve are sequentially connected through an air pipe to form an expiration phase sampling airflow passage, and the sampling hole B, the second switch valve, the sampling hole D of the inspiration piston cylinder, the air outlet hole of the inspiration piston cylinder and the air inlet of the fourth switch valve are sequentially connected through the air pipe to form an inspiration phase sampling airflow passage. One end of the differential pressure sensor is simultaneously connected with the air outlet of the third switch valve, the air outlet of the fourth switch valve, the air inlet end of the oxygen sensor and the air outlet of the proportional valve through an air pipe, and the other end of the differential pressure sensor is connected with air. The first electric push rod and the second electric push rod are respectively connected with piston rods of the expiration piston cylinder and the inspiration piston cylinder and are used for driving and adjusting the positions of the piston rods so as to sample, exhaust and exhaust the breath of the subject.
Preferably, the subject is in the inspiration phase. First, fifth and sixth switching valves in the differential air pressure detecting unit are opened, and seventh and eighth switching valves are closed. And secondly, the second switch valve and the third switch valve in the piston cylinder sampling unit are opened, and the first switch valve and the fourth switch valve are closed. Then, after the inspiration phase begins, the second electric push rod pulls the piston rod of the inspiration piston cylinder, and the suction gas of the subject in the flow detection module is sucked into the inspiration piston cylinder through the second switch valve. During the period, based on an ADRC negative feedback control algorithm, the air pressure difference between the sampling hole A and the sampling hole D is used as an observation signal, and the second electric push rod is controlled to pull the piston rod of the air suction piston cylinder, so that the air pressure difference between the sampling hole A and the sampling hole D is 0, the air suction flow of the air suction piston cylinder is equal to the air suction flow of a subject in the flow detection module, and the air suction collection of the subject in equal proportion and the physical average of the concentration of the gas components based on the air suction cylinder are completed; finally, after the inspiration phase begins, the first electric push rod pushes a piston rod of an expiration piston cylinder, and expiration gas of a subject in the expiration piston cylinder is discharged to the gas concentration analysis module through a third switch valve. During the period, based on a PID negative feedback control algorithm, the air pressure of the air inlet of the oxygen sensor detected by the differential pressure sensor is used as an observation signal, the first electric push rod is controlled to adjust the pushing speed of the piston rod in the expiratory piston cylinder, so that the air pressure of the air outlet of the third switch valve is constant until the air in the expiratory piston cylinder is exhausted, and the constant pressure and constant flow are realized to exhaust the exhaled air of the subject in the expiratory piston cylinder to the oxygen sensor in the air concentration analysis module. The subject is in the expiratory phase. First, the seventh and eighth switching valves in the differential air pressure detecting unit are opened, and the fifth and sixth switching valves are closed. And secondly, the first switch valve and the fourth switch valve in the piston cylinder sampling unit are opened, and the second switch valve and the third switch valve are closed. at the moment, the expiratory piston cylinder is to be pumped, the expiratory piston cylinder piston rod is positioned at the topmost end, the inspiratory piston cylinder is to be exhausted, the inspiratory piston cylinder piston rod is positioned at the bottommost end, and then, after the expiration stage begins, the first electric push rod pulls the expiratory piston cylinder piston rod, and the exhaled air of the subject in the flow detection module is inhaled into the expiratory piston cylinder through the first switch valve. during the period, based on an ADRC negative feedback control algorithm, the air pressure difference between the sampling hole B and the sampling hole C is used as an observation signal, and the first electric push rod is controlled 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, the air extraction flow of the exhalation piston cylinder is equal to the air flow of the subject in the flow detection module, and the air extraction collection of the subject in equal proportion and the physical average of the concentration of the gas components based on the exhalation cylinder are completed; finally, after the expiration stage begins, the second electric push rod pushes the piston rod of the inspiration piston cylinder, and the inspiration gas of the subject in the inspiration piston cylinder is discharged to the gas concentration analysis module through the fourth switch valve. during the period, based on a PID negative feedback control algorithm, the air pressure of the air inlet of the oxygen sensor detected by the differential pressure sensor is used as an observation signal, the second electric push rod is controlled to adjust the pushing speed of the piston rod in the air suction piston cylinder, so that the air pressure of the air outlet of the fourth switch valve is constant until the air in the air suction piston cylinder is exhausted, and the constant pressure and constant flow are realized to exhaust the sucked air of a subject in the air suction piston cylinder to the oxygen sensor in the air concentration analysis module. Wherein the inhalation and exhalation phases of the subject are identified by detection by a primary differential pressure sensor in the flow detection module. In particular, during the first respiratory phase of the subject, the exhalation piston cylinder exhausts air.
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 proportional valve and a gas pipe. The first high-pressure calibration air source, the first pressure reducing valve and the proportional valve are sequentially connected through the air pipe to form a first group of calibration air flow passages, and the second high-pressure calibration air source, the second pressure reducing valve and the proportional valve are sequentially connected through the air pipe to form a second group of calibration air flow passages. The air outlet end of the oxygen sensor is connected with the air inlet end of the carbon dioxide sensor. The air outlet end of the carbon dioxide sensor is connected to the air. The oxygen sensor and the carbon dioxide sensor are used for detecting oxygen and carbon dioxide concentration signals in the sampling gas.
When the concentration of the oxygen sensor and the carbon dioxide sensor in the gas concentration analysis module is calibrated based on a first group of calibration gas, the second high-pressure calibration gas source is closed, the first high-pressure calibration gas source is opened, the calibration gas is decompressed through the first decompression valve and then reaches the first decompression valve, then the first decompression valve is opened, the calibration gas is decompressed and then reaches 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 the period, the pressure difference sensor in the piston cylinder sampling unit detects the air outlet pressure of the air outlet of the proportional valve as an observation signal, and controls the opening size of the proportional valve based on a PID negative feedback control algorithm to realize the constant air pressure of the air outlet of the proportional valve, and the constant pressure flow of the calibration air of the first high-pressure calibration air source is transmitted to the oxygen sensor. When the concentration of the oxygen sensor and the carbon dioxide sensor in the gas concentration analysis module is calibrated based on a second group of calibration gas, the first high-pressure calibration gas source is closed, the second high-pressure calibration gas source is opened, the calibration gas is decompressed through the second decompression valve and then reaches the second decompression valve, then the second decompression valve is opened, the calibration gas is decompressed and then reaches 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 the period, the pressure difference sensor in the piston cylinder sampling unit detects the air outlet pressure of the air outlet of the proportional valve as an observation signal, the opening size of the proportional valve is controlled based on a PID negative feedback control algorithm, the air pressure of the air outlet of the proportional valve is constant, and the constant pressure flow of the calibration air of the second high-pressure calibration air source is sent to the oxygen sensor. When the subject performs metabolic test, the proportional valve is closed, the breathing gas of the subject is discharged to the oxygen sensor by the breathing gas sampling module at constant pressure and constant flow, and is discharged to the air after passing through the carbon dioxide sensor, so that the oxygen concentration and the carbon dioxide concentration of the breathing gas of the subject are detected.
The invention also provides a human respiratory heat metabolism detection method based on the piston type air cylinder, which is based on the detection device and comprises the following steps:
step one, the operator carries out gas concentration calibration of the oxygen sensor and the carbon dioxide sensor.
Firstly, a first group of gas calibration is performed, a first high-pressure calibration gas source is opened, the calibration gas is depressurized through a first depressurization valve and then reaches a first depressurization valve, then the first depressurization valve is opened, the calibration gas passes through a gas outlet of a proportional valve, a first group of calibration gas flow passages are realized, the gas is ventilated and after the gas flow is stable, the gas concentration average value in a period of time is collected, the oxygen sensor range point calibration and the carbon dioxide sensor zero point calibration are completed, secondly, a second group of gas calibration is performed, a second high-pressure calibration gas source is opened, the calibration gas is depressurized through a second depressurization valve and then reaches a second depressurization valve, then the second depressurization valve is opened, the calibration gas passes through a gas outlet of the proportional valve, the second group of calibration gas flow passages are realized, the gas concentration average value in a period of time is collected after the gas flow is ventilated and the gas flow is stable, and the oxygen sensor zero point calibration and the carbon dioxide sensor range point calibration are completed. And finally, closing each high-pressure calibration air source and valve to finish the gas concentration calibration of the oxygen sensor and the carbon dioxide sensor.
And step two, the subject finishes user registration and login on a computer, prepares for metabolic testing and starts testing.
When the autonomous respiration subject applies, the subject wears the breathing mask, one end of the flow detection module is connected with the breathing mask, and the other end of the flow detection module is connected with air. When the mechanical ventilation subject is applied, the subject is connected with a breathing machine, and two ends of the flow detection module are arranged in a patient pipeline of the breathing machine between the Y-shaped interface of the breathing machine and the subject. And a main differential pressure sensor in the flow detection module measures the differential pressure of the two ends of the porous air resistance plate, so that the inspiration and expiration phases of the subject are identified, and the bidirectional flow of the inspiration of the subject is obtained. When the inhalation of the subject starts, the inhalation piston cylinder is to be evacuated, and the exhalation piston cylinder is to be evacuated. During inspiration, the inspiration piston cylinder is used for exhausting and collecting the inhaled gas of the subject, the expiration piston cylinder is used for exhausting the last exhaled gas of the collected subject to the gas concentration analysis module through the third switch valve under constant pressure and constant flow, and the oxygen concentration average value and the carbon dioxide concentration average value of the last exhaled gas of the subject are obtained through detection of the oxygen sensor and the carbon dioxide sensor. When the expiration of the subject begins, the expiration piston cylinder is to be exhausted, and the inspiration piston cylinder is to be exhausted. During expiration, the expiration piston cylinder is used for exhausting and collecting expiration gas of the subject, the inspiration piston cylinder is used for exhausting the collected last inspiration gas of the subject to the gas concentration analysis module through the fourth switch valve under constant pressure and constant flow, and the oxygen concentration average value and the carbon dioxide concentration average value of the last inspiration gas of the subject are obtained through detection of the oxygen sensor and the carbon dioxide sensor.
And thirdly, calculating metabolic related indexes, namely oxygen uptake per minute and carbon dioxide production per minute by a computer according to the data acquired and uploaded by the control unit. The expression derived from the formula is as follows:
volume of exhaled breath per breath:
(1)
(2)
Wherein,Is the volume (mL) of expired air during a certain respiratory cycle; is the expiration start time(s) in a certain respiratory cycle; Is the end of expiration time(s) in a certain respiratory cycle; Is the subject respiratory flow (mL/s); Time(s); Is a gas standard state correction coefficient; Is ambient atmospheric pressure (kPa).
Oxygen uptake per minute):
(3)
Carbon dioxide production per minute):
(4)
Wherein,Is the inspiration starting time(s) in a certain respiratory cycle; mean (%) of oxygen concentration for each exhaled breath of the subject; Mean (%) of carbon dioxide concentration for each exhaled breath of the subject; mean value (%) of oxygen concentration for each inhalation of the subject; Mean (%) of carbon dioxide concentration for each inhalation of the subject; oxygen uptake per minute (mL/min); Carbon dioxide production per minute (mL/min).
The Respiratory Quotient (RQ) can be calculated through the oxygen uptake per minute and the carbon dioxide production per minute, and the resting metabolic Rate (REE) can be calculated based on a Weir formula, so that the human respiratory heat metabolism detection based on the piston type air cylinder is realized.
The beneficial effects obtained by the invention are as follows:
1. The breath sampling module based on the piston cylinder sampling unit realizes the equal proportion collection, physical buffering and constant pressure and constant flow gas component concentration analysis of the inhaled gas and the exhaled gas of a human body in a circulating way respectively, avoids hundred-millisecond real-time human breath analysis, does not require the dynamic performance of an oxygen sensor and a carbon dioxide sensor (namely, a concentration sensor in an oral gas-making method), and ensures that the human metabolism detection analysis is easier to realize in engineering;
2. According to the invention, through the respiratory gas sampling module and the gas concentration analysis module, constant pressure and constant flow control of the gas flow in the concentration analysis process of the respiratory gas components of the human body is realized, errors of an oxygen sensor and a carbon dioxide sensor caused by fluctuation of the gas pressure and the gas flow are avoided, and the accuracy of human body metabolism detection is improved;
3. the invention is based on the flow detection module, can realize the detection of the flow and the component concentration of human body breathing gas when a subject wears a mask or is connected with a breathing machine, and supports the application scenes of two human body metabolism tests of the subject with spontaneous breathing and the subject with mechanical ventilation.
Drawings
FIG. 1 is a schematic diagram of a device for detecting human respiratory heat metabolism based on a piston cylinder;
FIG. 2 is a schematic diagram of the structure of a subject metabolic test flow detection module arrangement under mechanical ventilation and spontaneous breathing;
FIG. 3 is a schematic illustration of the structure of a piston cylinder device and its extraction and exhaust;
fig. 4 is a flowchart of a method for detecting human respiratory heat metabolism based on a piston cylinder according to the present invention.
The device comprises a 1-computer, a 2-control unit, a 3-porous air resistance plate, a 4-main pressure difference sensor, a 5-first switch valve, a 6-second switch valve, a 7-expiration piston cylinder, an 8-inspiration piston cylinder, a 9-first electric push rod, a 10-second electric push rod, a 11-third switch valve, a 12-fourth switch valve, a 13-oxygen sensor, a 14-carbon dioxide sensor, a 15-proportional valve, a 16-first pressure relief valve, a 17-first pressure relief valve, a 18-first high-pressure calibration air source, a 19-pressure difference sensor, a 20-second pressure relief valve, a 21-second pressure relief valve, a 22-second high-pressure calibration air source, a 23-micro pressure difference sensor, a 24-fifth switch valve, a 25-sixth switch valve, a 26-seventh switch valve, a 27-eighth switch valve, a 2.1-sampling hole A, a 2.2-sampling hole B and a 2.4 pipeline.
Detailed Description
For the purposes, technical solutions and advantages of the present invention, embodiments of the present invention will be further described below with reference to the accompanying drawings.
As shown in fig. 1, the embodiment provides a human respiratory heat metabolism detection device based on a piston cylinder, which comprises a flow detection module, a respiratory gas sampling module, a gas concentration analysis module, a control unit 2 and a computer 1.
As shown in fig. 2, the flow detection module is a detachable tubular structure composed of a porous air resistance plate 3, a main differential pressure sensor 4, a sampling hole a 2.1, a sampling hole B2.2, a pipeline 2.4 of the flow detection module and an air pipe. The porous air resistance plate 3 is vertically and centrally arranged in the pipeline 2.4, air flow resistance is generated when breathing air flows to form air pressure difference, the sampling holes A2.1 and the sampling holes B2.2 are arranged on two equidistant sides of the porous air resistance plate 3 to provide an air flow passage for breath air flow pressure measurement analysis and breath air concentration sampling analysis, the main pressure difference sensor 4 is connected with the sampling holes A2.1 and the sampling holes B2.2 through air pipes and is used for acquiring the air pressure difference between the breathing air in the pipeline 2.4 and the two ends of the porous air resistance plate 3, and further calculating to obtain bidirectional flow signals.
Specifically, when the spontaneous breathing subject applies, the subject wears the breathing mask, and one end of the flow detection module is connected with the breathing mask, and the other end of the flow detection module is connected with air. When the mechanical ventilation subject is applied, the subject wears the breathing machine, and two ends of the flow detection module are arranged in a breathing machine patient pipeline between the Y-shaped interface of the breathing machine and the subject.
The respiratory gas sampling module consists of a pressure difference detection unit and a piston cylinder sampling unit, wherein the pressure difference detection unit is used for detecting the pressure difference in a piston cylinder and in a pipeline of the flow detection module, the piston cylinder sampling unit is designed for uniformly pumping and collecting respiratory gas of a subject, and is used for physically averaging the concentration of each gas component in respiratory gas, and the respiratory gas of the collected subject is discharged to the gas concentration analysis module in a constant flow mode.
The air pressure difference detection unit consists of 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. The sampling holes C and 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 with the sampling hole A2.1 through an air pipe, the X end of the sixth switch valve 25 is connected with the sampling hole D through an air pipe, the X end of the seventh switch valve 26 is connected with the sampling hole B2.2 through an air pipe, and the X end of the eighth switch valve 27 is connected with the sampling hole C through an air pipe. The X end of the micro pressure difference sensor 23 is connected with the Y end of the fifth switch valve 24 and the Y end of the seventh switch valve 26 through air pipes, and the Y end of the micro pressure difference sensor 23 is connected with the Y end of the sixth switch valve 25 and the Y end of the eighth switch valve 27 through air pipes.
The piston cylinder sampling unit consists 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 inspiration piston cylinder 8, an expiration piston cylinder 7, a pressure difference sensor 19 and an air pipe. The sampling hole A2.1, the first switch valve 5, the sampling hole C of the expiration piston cylinder 7, the air outlet of the expiration piston cylinder 7 and the air inlet of the third switch valve 11 are sequentially connected through an air pipe to form an expiration phase sampling airflow passage, and the sampling hole B2.2, the second switch valve 6, the sampling hole D of the inspiration piston cylinder 8, the air outlet of the inspiration piston cylinder 8 and the air inlet of the fourth switch valve 12 are sequentially connected through the air pipe to form an inspiration phase sampling airflow passage. One end of the differential pressure sensor 19 is connected with 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 air pipes, and the other end of the differential pressure sensor 19 is connected with air. The first electric push rod 9 and the second electric push rod 10 are respectively connected with piston rods of the expiration piston cylinder 7 and the inspiration piston cylinder 8 and are used for driving and adjusting the positions of the piston rods so as to realize sampling, air extraction and air exhaust of the breathing gas of the subject.
As shown in fig. 1 and 3, in the inspiration phase of the subject, first, the fifth and sixth switching valves 24 and 25 in the differential air pressure detecting unit are opened, and the seventh and eighth switching valves 26 and 27 are closed. At this time, the micro pressure difference sensor 23 detects the air pressure difference between the sampling holes a2.1 and D, and then the second and third switching valves 6 and 11 in the piston cylinder sampling unit are opened and the first and fourth switching valves 5 and 12 are closed. At this time, the air suction piston cylinder 8 is to be pumped, the piston rod of the air suction piston cylinder 8 is at the topmost end, the air discharge piston cylinder 7 is to be discharged, the piston rod of the air discharge piston cylinder 7 is at the bottommost end, and then, after the air suction stage is started, the second electric push rod 10 pulls the piston rod of the air suction piston cylinder 8, and the suction air of the subject in the flow detection module is sucked into the air suction piston cylinder 8 through the second switch valve 6. The method is characterized in that an ADRC (automatic disturbance rejection control) algorithm is used as an observation signal based on the air pressure difference between a sampling hole A2.1 and a sampling hole D, a second electric push rod 10 is controlled to pull the piston rod of an air suction piston cylinder 8, the air pressure difference between the sampling hole A2.1 and the sampling hole D is 0, the air suction flow of the air suction piston cylinder 8 is equal to the air suction flow of a subject in a flow detection module, the air suction of the subject is collected in an equal proportion, the air component concentration of the air based on the air suction cylinder is physically averaged, and finally, the first electric push rod 9 pushes the piston rod of an air suction piston cylinder 7 when the air suction stage starts, and the air suction of the subject in the air suction piston cylinder 7 is discharged to a gas concentration analysis module through a third switch valve 11. During the period, based on a PID negative feedback control algorithm, the air pressure at the air inlet of the oxygen sensor 13 detected by the differential pressure sensor 19 is used as an observation signal, the first electric push rod 9 is controlled to adjust the pushing speed of a piston rod in the expiratory piston cylinder 7, so that the air pressure at the air outlet of the third switch valve 11 is constant until the air in the expiratory piston cylinder 7 is exhausted, and the constant pressure and constant flow are realized to exhaust the exhaled air of a subject in the expiratory piston cylinder 7 to the oxygen sensor 13 in the air concentration analysis module.
During the expiration phase, first, the seventh and eighth switching valves 26 and 27 in the differential air pressure detecting unit are opened, and the fifth and sixth switching valves 24 and 25 are closed. At this time, the micro pressure difference sensor 23 detects the air pressure difference between the sampling holes B2.2 and C, and secondly, the first switching valve 5 and the fourth switching valve 12 in the piston cylinder sampling unit are opened, and the second switching valve 6 and the third switching valve 11 are closed. At the moment, the expiratory piston cylinder 7 is to be pumped, the piston rod of the expiratory piston cylinder 7 is at the topmost end, the inspiratory piston cylinder 8 is to be exhausted, the piston rod of the inspiratory piston cylinder 8 is at the bottommost end, then, after the expiration stage begins, the first electric push rod 9 pulls the piston rod of the expiratory piston cylinder 7, and the exhaled air of the subject in the flow detection module is inhaled into the expiratory piston cylinder through the first switch valve 5. The method is characterized in that an ADRC active disturbance rejection control algorithm is used for taking the air pressure difference of a sampling hole B2.2 and a sampling hole C as an observation signal, a first electric push rod 9 is controlled to pull a piston rod of an exhalation piston cylinder 7, the air pressure difference of the sampling hole B2.2 and the sampling hole C is 0, the air extraction flow of the exhalation piston cylinder 7 is equal to the air flow of a subject in a flow detection module, the air extraction collection of the subject is completed in an equal proportion, the physical average of the concentration of gas components based on the exhalation cylinder is achieved, and finally, after the expiration stage is started, a second electric push rod 10 pushes the piston rod of the inhalation piston cylinder 8, and the air inhaled by the subject in the inhalation piston cylinder 8 is discharged to a gas concentration analysis module through a fourth switching valve 12. During the period, based on a PID negative feedback control algorithm, the air pressure of the air inlet of the oxygen sensor 13 detected by the differential pressure sensor 19 is used as an observation signal, the second electric push rod 10 is controlled to adjust the pushing speed of a piston rod in the air suction piston cylinder 8, so that the air pressure of the air outlet of the fourth switch valve 12 is constant until the air in the air suction piston cylinder 8 is exhausted, and the constant pressure and constant flow are realized to exhaust the sucked air of a subject in the air suction piston cylinder 8 to the oxygen sensor 13 in the air concentration analysis module. Wherein the inhalation and exhalation phases of the subject are identified by detection by the primary differential pressure sensor 4 in the flow detection module. In particular, during the first respiratory phase of the subject, the exhalation piston cylinder exhausts air.
The gas concentration analysis module consists 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 reducing valve 16, a second pressure reducing valve 20, a proportional valve 15 and a gas pipe. The first high-pressure calibration air source 18, the first pressure reducing valve 17, the first pressure reducing valve 16 and the proportional valve 15 are sequentially connected through an air pipe to form a first group of calibration air flow passages, and the second high-pressure calibration air source 22, the second pressure reducing valve 21, the second pressure reducing valve 20 and the proportional valve 15 are sequentially connected through the air pipe to form a second group of calibration air flow passages. The air outlet end of the oxygen sensor 13 is connected with the air inlet end of the carbon dioxide sensor 14. The air outlet end 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.
Specifically, when the oxygen sensor 13 and the carbon dioxide sensor 14 in the gas concentration analysis module are calibrated based on the first group of calibration gas concentration, firstly, the second high-pressure calibration gas source 22 is closed, the first high-pressure calibration gas source 18 is opened, the calibration gas is decompressed by the first decompression valve 17 and then reaches the first decompression valve 16, then the first decompression valve 16 is opened, the calibration gas is decompressed and then reaches 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 the period, the pressure difference sensor 19 in the piston cylinder sampling unit detects the air outlet pressure of the air outlet of the proportional valve 15 as an observation signal, and controls the opening size of the proportional valve 15 based on a PID negative feedback control algorithm to realize the constant air outlet pressure of the proportional valve 15, and the constant pressure constant flow of the calibration air of the first high-pressure calibration air source 18 is sent to the oxygen sensor 13.
When the oxygen sensor 13 and the carbon dioxide sensor 14 in the gas concentration analysis module are subjected to concentration calibration based on a second group of calibration gas, the first high-pressure calibration gas source 18 is closed, the second high-pressure calibration gas source 22 is opened, the calibration gas is decompressed by the second decompression valve 21 and then reaches the second decompression valve 20, then the second decompression valve 20 is opened, the calibration gas is decompressed and then reaches 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 the period, the pressure difference sensor 19 in the piston cylinder sampling unit detects the air outlet pressure of the air outlet of the proportional valve 15 as an observation signal, and controls the opening size of the proportional valve 15 based on a PID negative feedback control algorithm to realize the constant air outlet pressure of the proportional valve 15, and the constant pressure constant flow of the calibration air of the second high-pressure calibration air source 22 is sent to the oxygen sensor 13. When the subject performs metabolic test, the proportional valve 15 is closed, the breathing gas of the subject is discharged to the oxygen sensor 13 by the breathing gas sampling module at constant pressure and constant flow, and is discharged to the air after passing through the carbon dioxide sensor 14, so that the oxygen concentration and the carbon dioxide concentration of the breathing gas of the subject are detected.
As shown in fig. 4, the invention further provides a human respiratory heat metabolism detection method based on the piston cylinder, which comprises the following steps:
Step one, an operator performs gas concentration calibration of the oxygen sensor 13 and the carbon dioxide sensor 14, and the method comprises the following steps:
The method comprises the steps of firstly, opening a first high-pressure calibration air source 18 during first group air calibration, decompressing the calibration air through a first decompression valve 17 and then enabling the calibration air to reach a first decompression valve 16, then opening the first decompression valve 16, enabling the calibration air to pass through an air outlet of a proportional valve 15, achieving a first group of calibration air flow paths, ventilating, collecting an average value of air concentration in a period of time after air flow is stable, completing the calibration of a measuring range point of an oxygen sensor 13 and the calibration of a zero point of a carbon dioxide sensor 14, then opening a second high-pressure calibration air source 22 during second group air calibration, decompressing the calibration air through a second decompression valve 21 and then enabling the calibration air to reach a second decompression valve 20, opening the second decompression valve 20, enabling the calibration air to pass through an air outlet of the proportional valve 15, enabling the second group of calibration air flow paths, ventilating, collecting the average value of air concentration in a period of time after air flow is stable, and completing the calibration of the measuring range point of the oxygen sensor and the carbon dioxide sensor. And finally, closing each high-pressure calibration gas source and valve to finish the gas concentration calibration of the oxygen sensor and the carbon dioxide sensor.
Step two, the subject completes user registration and login on the computer, prepares before metabolic testing, starts testing, and comprises the following steps:
When the autonomous respiration subject applies, the subject wears the breathing mask, one end of the flow detection module is connected with the breathing mask, and the other end of the flow detection module is connected with air. When the mechanical ventilation subject is applied, the subject wears the breathing machine, and two ends of the flow detection module are arranged in a breathing machine patient pipeline between the Y-shaped interface of the breathing machine and the subject. The main differential pressure sensor 4 in the flow detection module measures the differential pressure of the air at the two ends of the porous air resistance plate 3, so as to identify the inspiration and expiration phases of the subject and obtain the bidirectional flow of the inspiration air of the subject. At the beginning of inhalation of the subject, the inhalation piston cylinder 8 is to be evacuated and the exhalation piston cylinder 7 is to be evacuated. The last expired gas of the subject in the expired piston cylinder 7 is exhausted to the gas concentration analysis module through the third switch valve 11 in a constant-pressure and constant-flow mode, and the oxygen sensor 13 and the carbon dioxide sensor 14 detect to obtain the average value of the oxygen concentration and the average value of the carbon dioxide concentration of the last expired gas of the subject. When the expiration of the subject begins, the expiration piston cylinder is to be exhausted, and the inspiration piston cylinder is to be exhausted. The last inhaled gas of the subject in the inhalation piston cylinder is discharged to the gas concentration analysis module through the fourth switch valve 12 in a constant-pressure and constant-current mode, and the oxygen concentration average value and the carbon dioxide concentration average value of the last inhaled gas of the subject are obtained through detection of the oxygen sensor 13 and the carbon dioxide sensor 14.
And thirdly, calculating metabolic related indexes, namely oxygen uptake per minute and carbon dioxide production per minute by the computer 1 according to the data acquired and uploaded by the control unit 2. The expression derived from the formula is as follows:
volume of exhaled breath per breath:
(1)
(2)
Wherein,Is the volume of expired air (in mL) during a certain respiratory cycle; Is the expiration start time (unit s) in a certain respiratory cycle; is the end of expiration time (in s) in a certain respiratory cycle; Is the subject respiratory flow (units mL/s); Time (units s); Is a gas standard state correction coefficient; Is ambient atmospheric pressure (in kPa).
Oxygen uptake per minuteThe method comprises the following steps:
(3)
carbon dioxide production per minuteThe method comprises the following steps:
(4)
Wherein,The inspiration starting time (unit s) in a certain respiratory cycle; mean (%) of oxygen concentration for each exhaled breath of the subject; Mean (%) of carbon dioxide concentration for each exhaled breath of the subject; mean value (%) of oxygen concentration for each inhalation of the subject; Mean (%) of carbon dioxide concentration for each inhalation of the subject; Oxygen uptake per minute (unit mL/min); carbon dioxide production per minute (unit mL/min).
The respiratory quotient RQ can be calculated through the oxygen uptake per minute and the carbon dioxide production per minute, and the resting metabolic rate REE can be calculated based on a Weir formula, so that the human respiratory heat metabolism detection based on the piston type air cylinder is realized.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.