CN108175412B - Head cover type indirect energy testing method and device - Google Patents
Head cover type indirect energy testing method and device Download PDFInfo
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- CN108175412B CN108175412B CN201711384501.4A CN201711384501A CN108175412B CN 108175412 B CN108175412 B CN 108175412B CN 201711384501 A CN201711384501 A CN 201711384501A CN 108175412 B CN108175412 B CN 108175412B
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- A—HUMAN NECESSITIES
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- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/08—Detecting, measuring or recording devices for evaluating the respiratory organs
- A61B5/083—Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
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Abstract
The invention discloses a head-mask type indirect energy testing method and a head-mask type indirect energy testing device, which can be used for simply and accurately measuring the energy metabolism rate of a human body. According to the invention, the negative pressure hood is used for collecting and analyzing the gas exhaled by the human body, so that the correction of errors of a mask and a physiological dead space is not required to be considered when the energy metabolism rate is calculated, the delay correction between the flow rate and the concentration is not required to be considered, the complexity of analysis and calculation of test data is simplified, and the measurement precision is improved; the concentration dilution ratio is reduced by designing the structure of the negative pressure hood and a corresponding self-adaptive air extraction speed adjustment algorithm; meanwhile, a pressure relief device is adopted to balance the pressure difference between the calibration gas and the measurement gas, so that the accuracy of the measurement result is improved. The invention can be used for measuring the resting energy consumption of the human body and has the advantages of comfort, safety and high measurement precision.
Description
Technical Field
The invention relates to the field of gas sample acquisition and analysis, in particular to a head cover type indirect energy testing method and device.
Background
The gas metabolism analyzer calculates the energy consumption of human body by testing the oxygen consumption and the carbon dioxide generation in a certain time, and the composition of three nutrients (carbohydrate, fat and protein) in the energy consumption, and is used for nutrition metabolism evaluation. In addition, the device can be matched with load equipment such as a treadmill, a power vehicle and the like to test oxygen uptake and carbon dioxide discharge of a human body under different exercise loads, and is used for evaluating the cardiopulmonary endurance test of the human body and noninvasive diagnosis of cardiopulmonary circulatory system diseases. Therefore, the gas metabolism test has important application value in the fields of nutrition diet guidance, disease diagnosis and rehabilitation.
Early gas metabolism tests were relatively simple and generally used the douglas air bag method. All exhaled air is collected into the air bags during the test process, and dozens of air bags are required during the whole test process. After the test is finished, the volume of the exhaled air is measured, and then the concentrations of oxygen and carbon dioxide in the air bag are analyzed by using a chemical analysis method, so that the whole process is slow and tedious. Because the Douglas air bag method can not do the real-time analysis of data, equipment is huge simultaneously, and the ventilation pipeline is closed, and expiratory resistance is very big. Compared with the Douglas air bag method, the micro mixing chamber method has the greatest advantage that the micro mixing chamber can be used for measuring in an open breathing mode, but is influenced by sampling errors and breathing dead space, and the accuracy of the micro mixing chamber still needs to be improved.
The hood type indirect energy testing method is an open type energy metabolism testing method, and compared with a closed type energy metabolism test, a test subject can freely breathe ambient air in the testing process without pipeline resistance, so that the testing process is more comfortable and more humanized; the hood type energy metabolism test sampling negative pressure hood collects the exhaled gas of a human body, nitrogen balance analysis calculation is utilized, error correction of related ventilation dead cavities is not needed, in addition, the flow rate of the exhaled gas of the human body changes in real time, the air exhaust speed of the hood is constant, analysis of gas concentration in the hood does not need to be related to the flow rate, namely, the flow rate does not need to be corrected, the reflection delay of a concentration sensor is not needed, and therefore the measurement result is more accurate and reliable.
Disclosure of Invention
The invention aims to provide a novel head cover type indirect energy testing method and a novel head cover type indirect energy testing device, so that the comfort level and the safety of a tester in the testing process are improved. The more accurate measurement of the exhaled gas of the human body is realized.
In order to achieve the purpose, the invention adopts the scheme that:
a hood type indirect energy testing device is characterized in that a gas collecting and mixing part consisting of a hood, a flow sensor, a damper and a first air pump realizes the collection and mixing of mixed gas consisting of human body exhaled gas and air, wherein the first air pump, the damper, the flow sensor and a hood air exhaust opening are sequentially connected through an air pipe; the gas concentration analysis part consisting of the first gas cylinder, the second gas cylinder, the four-way valve, the oxygen sensor, the carbon dioxide sensor and the second air pump realizes the gas concentration analysis, wherein the B end of the four-way valve is connected with an air pipe between the damper and the flow sensor and used for extracting gas in the air pipe, the A end of the four-way valve is communicated with ambient air, the gas extraction device is used for extracting environmental gas, high-concentration calibration gas in a first gas cylinder is connected to an overflow interface through a guide pipe sequentially through a first two-stage pressure reducing valve and a first electromagnetic valve, low-concentration calibration gas in a second gas cylinder is connected to one end of the overflow interface through a guide pipe sequentially through a second two-stage pressure reducing valve and a second electromagnetic valve, the other end of an overflow outlet is connected to the D end of a four-way valve through a pressure stabilizing valve, the four-way valve can selectively open any one passage A-C, B-C, D-C, a second air pump is connected with a buffer device, and meanwhile gas at the C end of; the control unit is responsible for controlling the pump and the valve in the detection device and collecting and uploading data; the man-machine interaction equipment is used for data processing, analysis and display.
Wherein, collect human expired air through the transparent hood of a part opening, this face guard is through containing one and being used for sealed soft surrounding edge, an air inlet and an extraction opening, and when the test was bled, the inside negative pressure that forms of hood, form the convection current between air inlet and the gas outlet, with people expired air suction fan pipeline in.
When the oxygen sensor and the carbon dioxide sensor are calibrated, high-pressure calibration gas in the gas cylinder is firstly released in pressure through the overflow interface, and then the calibration gas is pumped into the oxygen sensor and the carbon dioxide sensor through the second air pump to calibrate the concentration.
A hood type indirect energy testing method comprises the steps that when testing is started, the concentration of carbon dioxide in a hood is analyzed to adaptively adjust the air suction speed of a first air suction pump, the speed of the first air suction pump is divided into a plurality of gears, the air suction speed gear of the first air suction pump is preset according to weight at the beginning, then the minimum value and the maximum value of the concentration of the carbon dioxide in the hood in a respiratory cycle are analyzed every 50 seconds, the minimum value and the maximum value are compared with a preset threshold value, the gear of a fan is adjusted, and when the threshold value condition is met, the gear of the air suction speed is kept constant.
A head-mask indirect energy testing method comprises the following steps:
the method comprises the following steps: before a subject tests, a valve in the D-C direction of the four-way valve is opened, valves in other directions of the four-way valve are closed, the high-concentration part of the sensor is calibrated firstly, valves of a first gas cylinder and a first two-stage pressure reducing valve are opened, wherein the first gas cylinder is a high-concentration gas cylinder, a second air pump pumps gas at a constant speed, the calibration gas in the first gas cylinder enters an oxygen sensor and a carbon dioxide sensor through an overflow interface, one part of the calibration gas enters the oxygen sensor and the carbon dioxide sensor through a pressure stabilizing valve to calibrate the oxygen sensor and the carbon dioxide sensor, the other part of the calibration gas is discharged into the air, after a period of time, the calibration of the high-concentration part of the oxygen sensor and the high-concentration part of the carbon dioxide sensor is finished, a first electromagnetic valve is closed, the calibration of the low-concentration part of the sensor is carried out next, the valves, the calibrated gas in the second gas cylinder passes through the overflow interface, one part of the calibrated gas enters the oxygen sensor and the carbon dioxide sensor through the pressure stabilizing valve to calibrate the oxygen sensor and the carbon dioxide sensor, the other part of the calibrated gas is discharged into the air, after a period of time, the calibration of the low-concentration parts of the oxygen sensor and the carbon dioxide sensor is finished, and the second electromagnetic valve is closed;
step two: opening valves in the A-C direction of the four-way valve, closing valves in other directions of the four-way valve, pumping air in a test environment to an oxygen sensor and a carbon dioxide sensor by a second air pump at a constant speed, and measuring the average oxygen concentration and the average carbon dioxide concentration in the air within a period of time by the oxygen sensor and the carbon dioxide sensor;
step three: the method comprises the following steps that a subject registers information on a man-machine interaction device, after registration is completed, a tester helps the subject to take a head cover and informs the subject of attention in the measurement process, and the subject is allowed to rest for about half an hour so as to enter a resting state;
step four: opening the valves in the B-C direction of the four-way valve, closing the valves in the other directions of the four-way valve, clicking a start button, starting air extraction by a measuring start fan according to the budget speed, forming negative pressure in the head cover, sucking the environmental gas sucked into the head cover and the metabolic gas exhaled by the human body into an air extraction pipeline together, at the moment, the air extraction speed of the fan can be adjusted in a self-adaptive way every 50 seconds according to the concentration of the carbon dioxide, when the set carbon dioxide concentration requirement is met, the first air pump pumps gas at a constant gear speed, the pumped mixed gas enters a flow sensor, the flow sensor measures the flow of the mixed gas, a control unit collects gas flow data through the flow sensor, the second air pump samples the gas in the pipeline at a constant speed, a part of the sampled mixed gas enters a gas concentration analysis part, and the gas concentration analysis part acquires real-time concentration data of the gas in the pipeline;
step five: the human-computer interaction equipment calculates the oxygen intake and carbon dioxide discharge amount in a period of time according to the uploaded data collected by the control unit, and the calculation process is as follows:
volume of mixed gas discharged from head cover:
nitrogen concentration in the mixed gas discharged from the head cap: fEN2＝1-FECO2–FEO2
Nitrogen concentration in ambient air: fIN2＝1-FICO2–FIO2
Volume of air drawn into the hood: vin＝Vout×FEN2/FIN2
Oxygen uptake: vO2＝Vin×FEO2-Vout×FIO2
Carbon dioxide emission: vCO2＝Vout×FICO2-Vin×FECO2
Wherein: v (t) is the instantaneous flow rate of the mixed gas in the pumping pipeline; t is t1Is the time point at which sampling begins; t is t2The time point of the end of sampling; fECO2The average carbon dioxide concentration in the mixed gas discharged out of the hood; fEO2Is the average oxygen concentration in the mixed gas exiting the hood; fIO2Is the average oxygen concentration in the air being drawn; fICO2Is the average carbon dioxide concentration in the air drawn.
The invention has the following beneficial effects:
1. according to the head-mask indirect energy testing method, a test subject does not need to wear a mask in the testing process, exhaled air cannot leak, meanwhile, related dead space correction of the mask is not needed, and fresh air can be freely breathed in the testing process, so that the head-mask indirect energy metabolism testing method is simple, convenient and accurate.
2. The head cover type indirect energy testing method provided by the invention has the advantages that the speed of the fan is adjusted every 50 seconds when the testing is started, when the concentration of carbon dioxide reaches the preset concentration range, the gear of the air suction speed is not changed, namely the air suction speed of the fan is kept constant in the subsequent testing process, so that the flow speed and the concentration are not required to be aligned when the oxygen intake of a human body and the emission of the carbon dioxide are calculated, namely the delay time between the flow speed and the concentration analysis is not required to be corrected, and the calculation process is simple and accurate.
3. Through the shape and the gas exit position of design hood, at the measurement in-process of bleeding, make the air get into from people's head top air inlet, after mixing with human exhalation gas, inhaled nose below exhaust tube 16, the air current that forms of bleeding is the same with people exhalation air current direction, has improved the efficiency of bleeding, reduces the dilution proportion of gas concentration, finally improves the precision of concentration analysis.
4. When the sensor is calibrated, the positive pressure of the calibration gas in the gas tank is released by using the pressure overflow interface, and the pressure in the calibration time is kept equal to the pressure in the oxygen sensor 10 and the pressure in the carbon dioxide sensor 11 during testing through the pressure adjustment, so that the error caused by pressure compensation in the traditional testing process is eliminated, and the accuracy of gas concentration measurement is improved.
5. Before testing, the air exhaust speed of the first air exhaust pump 14 is determined by analyzing the concentration of carbon dioxide in the hood 18, so that the first air exhaust pump 14 can completely exhaust and analyze the gas exhaled by a subject at the minimum air exhaust speed, on one hand, the phenomenon that the carbon dioxide in the hood 18 is accumulated for multiple times due to too small air exhaust speed to cause carbon dioxide overflow and influence the accuracy of a measurement result is prevented, and simultaneously, the phenomenon that the discomfort is caused by too high carbon dioxide inhaled by a human body is prevented; on the one hand, under the condition that the accuracy of the sensor is limited, the phenomenon that the concentration of oxygen and carbon dioxide detected by the sensor is too low and the concentration detection accuracy is influenced because the air exhaust speed is too high and the exhaled gas of the human body is excessively diluted by air is prevented.
Drawings
FIG. 1 is a schematic structural diagram of a head-mounted indirect energy testing apparatus according to the present invention.
FIG. 2 is a flow chart of the operation of a head-mounted indirect energy testing apparatus according to the present invention.
Fig. 3 is a schematic diagram of the overflow interface structure of the present invention.
FIG. 4 is a schematic view of the structure of the hood for collecting body gases according to the present invention.
Fig. 5 is a graph showing the variation of carbon dioxide concentration in the exhaled air of a human body in the present invention.
FIG. 6 is a flow chart of the adaptive wind speed regulation method of the first air pump 14 in the invention.
In the figure: 1. a first gas cylinder; 2. a second gas cylinder; 3. a first two-stage pressure reducing valve; 4. a second two-stage pressure reducing valve; 5. a first solenoid valve; 6. a second solenoid valve; 7. an overflow interface; 8. a pressure maintaining valve; 9. a four-way valve; 10. an oxygen sensor; 11. a carbon dioxide sensor; 12. a buffer device; 13. a second air pump; 14. a first air pump; 15. a damper; 16. an air extraction pipeline; 17. a flow sensor; 18. a head cover.
Detailed Description
A headgear-style indirect energy testing apparatus according to an embodiment of the present invention is shown in fig. 1, and includes: the device comprises a first gas cylinder 1, a second gas cylinder 2, a first double-stage pressure reducing valve 3, a second double-stage pressure reducing valve 4, a first electromagnetic valve 5, a second electromagnetic valve 6, an overflow interface 7, a pressure stabilizing valve 8, a four-way valve 9, an oxygen sensor 10, a carbon dioxide sensor 11, a buffer device 12, a second air pump 13, a first air pump 14, a damper 15, an air pumping pipeline 16, a flow sensor 17 and a hood 18.
A hood type indirect energy measuring test device is characterized in that a gas collecting and mixing part consisting of a hood 18, a flow sensor 17, a damper 15 and a first air pump 14 realizes the collection and mixing of mixed gas consisting of human body exhaled gas and air, wherein the first air pump 14, the damper 15, the flow sensor 17 and a hood 18 air pumping opening are sequentially connected through an air pipe, the first air pump 14 pumps the human body exhaled gas in the hood through a passage and finally exhausts the gas to the air, the damper 15 is used for stabilizing air flow, and the flow sensor 17 is used for measuring the air exhaust flow speed; the gas concentration analysis part consisting of a first gas cylinder 1, a second gas cylinder 2, a four-way valve 9, an oxygen sensor 10, a carbon dioxide sensor 11 and a second air pump 13 realizes gas concentration analysis, wherein the B end of the four-way valve 9 is connected with a gas pipe between a damper 15 and a flow sensor 17 and is used for extracting gas in the gas pipe, the A end of the four-way valve 9 is communicated with ambient air and is used for extracting ambient gas, high-concentration calibration gas of the first gas cylinder 1 is connected to an overflow interface 7 through a guide pipe sequentially by a first two-stage pressure reducing valve 3 and a first electromagnetic valve 5, low-concentration calibration gas of the second gas cylinder 2 is connected to one end of the overflow interface 7 through a guide pipe sequentially by a second two-stage pressure reducing valve 4 and a second electromagnetic valve 6, the other end of the overflow outlet is connected to the D end of the four-way valve 9 through a pressure stabilizing valve, the second air pump 13 is connected with the buffer device 12, and simultaneously extracts the gas at the C end of the four-way valve 9 through the oxygen sensor 10 and the carbon dioxide sensor 11; the control unit is responsible for controlling the pump and the valve in the detection device and collecting and uploading data; the man-machine interaction equipment is used for data processing, analysis and display.
The working process of the hood-type human body exhaled air collecting device is shown in figure 2 and specifically comprises the following steps:
the method comprises the following steps: as shown in FIG. 1, the D-C directional valve of the four-way valve 9 is opened before the test of the subject, and the remaining directional valves of the four-way valve 9 are closed. The calibration of the high concentration part of the sensor is firstly carried out. The valves of the first gas cylinder 1 containing the high concentration calibration gas and the first two-stage pressure reducing valve 3 are opened. The second suction pump 13 pumps the gas at a constant speed. The calibration gas in the first gas cylinder 1 passes through the overflow connector 7, one part of the calibration gas enters the oxygen sensor 10 and the carbon dioxide sensor 11 through the pressure stabilizing valve, the oxygen sensor 10 and the carbon dioxide sensor 11 are calibrated, and the other part of the calibration gas is discharged into the air. After a certain time, the calibration of the high concentration portions of the oxygen sensor 10 and the carbon dioxide sensor 11 is finished, and the first electromagnetic valve 5 is closed. The calibration of the low concentration portion of the sensor is performed next. The valves of the second gas cylinder 2 containing the low-concentration calibration gas and the second two-stage pressure reducing valve 4 are opened. The second suction pump 13 pumps the gas at a constant speed. And the calibration gas in the second gas cylinder 2 passes through the overflow connector 7, one part of the calibration gas enters the oxygen sensor 10 and the carbon dioxide sensor 11 through the pressure stabilizing valve to calibrate the oxygen sensor 10 and the carbon dioxide sensor 11, and the other part of the calibration gas is discharged into the air. After a certain period of time, the calibration of the low concentration parts of the oxygen sensor 10 and the carbon dioxide sensor 11 is finished, and the second electromagnetic valve 6 is closed.
Step two: the valves in the directions of the four-way valve 9A-C are opened, and the valves in the other directions of the four-way valve 9 are closed. The second air pump 13 pumps air in the test environment to the oxygen sensor 10 and the carbon dioxide sensor 11 at a constant speed, and the oxygen sensor 10 and the carbon dioxide sensor 11 measure an average oxygen concentration and an average carbon dioxide concentration in the air over a period of time.
Step three: the subject registers information on the human-computer interaction device. After registration is complete, the test person assists the subject in carrying the hood 18 and advises the subject of the precautions taken during the measurement. The subject was allowed to rest for about half an hour to enter a resting state.
Step four: the valves in the B-C direction of the four-way valve 9 are opened, and the valves in the other directions of the four-way valve 9 are closed. When the start button is clicked, the measurement start fan starts to exhaust according to the budget speed, negative pressure is formed in the head cover 18, and the environment gas sucked into the head cover and the metabolic gas exhaled by the human body are sucked into the air exhaust pipeline 16 together. At this time, the air extraction speed of the fan is adaptively adjusted every 50 seconds according to the carbon dioxide concentration, and when the set carbon dioxide concentration requirement is met, the first air extraction pump 14 extracts air at a constant gear speed. The extracted mixed gas enters the flow sensor 17, and the flow sensor 17 measures the flow rate of the mixed gas. The control unit collects gas flow data via a flow sensor 17. The second pump 13 samples the gas in line 16 at a constant rate. A part of the mixed gas after sampling enters a gas concentration analysis part, and the gas concentration analysis part acquires real-time concentration data of the gas in the pipeline.
Step five: the human-computer interaction equipment calculates the oxygen intake and carbon dioxide discharge amount in a period of time according to the uploaded data collected by the control unit, and the calculation process is as follows:
volume of mixed gas discharged from head cover:
nitrogen concentration in the mixed gas discharged from the head cap: fEN2＝1-FECO2-FEO2
Nitrogen concentration in ambient air: fIN2＝1-FICO2-FIO2
Volume of air drawn into the hood: vin＝Vout×FEN2/FIN2
Oxygen uptake: vO2＝Vin×FEO2-Vout×FIO2
Carbon dioxide emission: vCO2＝Vout×FICO2-Vin×FECO2。
Wherein: v (t) is the instantaneous flow rate of the mixed gas in the pumping line 16; t is t1Is the time point at which sampling begins; t is t2The time point of the end of sampling; fECO2The average carbon dioxide concentration in the mixed gas discharged out of the hood; fEO2Is the average oxygen concentration in the mixed gas exiting the hood; fIO2Is the average oxygen concentration in the air being drawn; fICO2Is the average carbon dioxide concentration in the air drawn.
And the man-machine interaction equipment displays the measurement result.
In the first step: the oxygen sensor 10 used in the device is an electrochemical sensor, and the carbon dioxide sensor 11 is an infrared sensor, which belong to rapid analysis sensors. The reaction is very sensitive, typically to flow rate, pressure, temperature, and even to gas components. Because the second air pump 13 collects gas from the air extraction pipeline 16 during testing, the gas pressure in the pipeline is approximate to atmospheric pressure, in order to ensure that the pressure of the collected gas during calibration is equal to the pressure of the collected gas during testing, during calibration, the gas cylinder is firstly opened to reduce the gas pressure through the two-stage pressure reducing valve, and the calibrated gas passes through the overflow interface 7, as shown in fig. 3. The air pressure is further reduced to be approximate to atmospheric pressure, so that the pressure of the collected air during calibration is equal to that of the collected air during testing and is approximately equal to the atmospheric pressure. The length of an overflow pipeline connecting the overflow valve 7 and the air is more than 20cm, and the quantity of the calibration gas flowing into the overflow valve 7 is ensured to be larger than that of the gas pumped out of the overflow valve 7, the flow rate of the calibration gas exhausted into the air from the overflow pipeline is more than 250ML per minute, so that the air is prevented from diffusing into the calibration gas. The gas is extracted by the negative pressure generated by the second air extracting pump 13 in the gas calibration and gas measurement processes. Therefore, errors caused by pressure compensation in the traditional test process are eliminated, and the accuracy of gas concentration measurement is improved.
The invention relates to a hood type human body exhaled air collecting device, which is characterized in that a hood used by the device is as shown in figure 4, the volume of the hood is respectively about 10L, 20L and 35L according to the three types of large volume, medium volume and small volume inside the hood, the volume of the hood is respectively used for testing subjects with weights of 10kg to 20kg, 20kg to 40kg and more than 40kg, an air suction opening is positioned below a nasal air outlet during testing, the air suction amount of a fan is generally multiple times of the air amount exhaled by a human body, therefore, negative pressure can be formed in the hood, the open part around a neck is covered by a soft material in a wrapping mode, most of air flows in from an air inlet positioned at the top of the head of the human body, air convection is formed, and the aim of quickly pumping the human body. The hood 18 is generally made of transparent acrylic material, so that on one hand, the state of a testee can be observed, the safety of the test process is provided, and on the other hand, the testee does not feel oppressed and boring, and the hood is more humanized.
The invention relates to a hood type human body exhaled air collecting device, which adopts a fan speed self-adaptive control algorithm in the fourth step as follows:
as shown in fig. 5, the change of the carbon dioxide concentration in the exhaled air of the human body is shown, and the real-time concentration obtained by the carbon dioxide sensor 11 is the gas concentration in the pipeline 16, which is the result of the mixture of the exhaled air concentration of the human body and the inhaled air. The gas concentration in the pipeline changes with the pumping speed, and the conditions are as follows: the faster the air extraction speed, the larger the flow rate of air entering the hood, and the smaller the maximum concentration of carbon dioxide in the mixed gas after the air is mixed with the respiratory gas of the human body, and meanwhile, the smaller the change range of the concentration value of the carbon dioxide, namely the peak value of the concentration. Conversely, the lower the extraction rate, the lower the air flow rate into the hood, and the greater the maximum concentration of carbon dioxide in the mixed gas and the peak-to-peak concentration signal.
The gas concentration condition in the hood has certain influence on the comfort level, the measurement accuracy and the like of a person to be tested in the metabolism measurement. On one hand, if the carbon dioxide concentration in the hood is higher (more than 1 percent), the carbon dioxide concentration in blood is increased, the higher carbon dioxide concentration in blood stimulates the chemical receptors in the center and periphery of the human body, so that the respiratory center is stimulated, the respiratory effort is increased, namely, the breathing is deepened and accelerated, the comfort of a tested person is reduced, and the energy consumption is increased. In addition, the carbon dioxide concentration in the hood is higher, and the carbon dioxide concentration difference between the inside of the hood and the environment is increased, which puts higher requirements on the sealing performance of the contact part of the hood and a human body. On the other hand, if the air extraction speed is too high, the peak value of the carbon dioxide concentration signal in the hood is low (for example, less than 0.5%), the signal-to-noise ratio of the concentration signal is reduced, and the measurement accuracy is reduced.
According to the above analysis, in order to coordinate the comfort and accuracy of the metabolic test, the pumping speed needs to be dynamically adjusted to control the carbon dioxide concentration within a certain range, and the control targets are as follows:
(1) the peak value of the average carbon dioxide concentration is less than or equal to 1 percent;
(2) the peak value of the average carbon dioxide concentration signal is more than or equal to 0.5 percent
The fan speed range is 0-60L per minute, wherein the speed of increasing a gear is increased by 5L per minute, when a test is started, the initial speed setting of the fan is calculated according to weight information input by a human body, the general weight is 10L per minute under 10kg, 20L per minute under 10 kg-20 kg, 35L per minute above 20kg, after the fan speed is set, the fan speed judgment flow is started, firstly, after the flow rate is waited for 30 seconds and the like and the carbon dioxide concentration is stable, the average carbon dioxide concentration peak value and the average carbon dioxide concentration signal peak value in the following 20 seconds are acquired, then, the average carbon dioxide concentration peak value is judged to be more than 1%, if the average carbon dioxide concentration peak value is more than 1%, the first gear fan speed is increased, the fan speed judgment flow is restarted, if the average carbon dioxide concentration signal peak value is not more than 1%, whether the average carbon dioxide concentration, and re-entering the fan speed judgment process, wherein the carbon dioxide concentration variation range is within the control target range and the constant air extraction speed is kept and is not adjusted until the test is finished, and the result is shown in fig. 6 if the carbon dioxide concentration variation range is not less than 0.5%.
Claims (1)
1. A hood type indirect energy testing method utilizes a hood type indirect energy testing device, and the device is composed of a hood (18), a flow sensor (17), a damper (15) and a first air pump (14), wherein a gas collecting and mixing part is used for collecting and mixing mixed gas formed by exhaled gas of a human body and air, the first air pump (14), the damper (15), the flow sensor (17) and an air sucking opening of the hood (18) are sequentially connected through an air pipe to form a first passage, the first air pump (14) is used for sucking the exhaled gas of the human body in the hood through the first passage and finally exhausting the exhaled gas to the air, the damper (15) is used for stabilizing air flow, and the flow sensor (17) is used for measuring air sucking flow speed; the gas concentration analysis part consisting of a first gas cylinder (1), a second gas cylinder (2), a four-way valve (9), an oxygen sensor (10), a carbon dioxide sensor (11) and a second air pump (13) realizes gas concentration analysis, wherein the B end of the four-way valve (9) is connected with a gas pipe between a damper (15) and a flow sensor (17) and is used for extracting gas in the gas pipe, the A end of the four-way valve (9) is communicated with ambient air and is used for extracting ambient gas, high-concentration calibration gas in the first gas cylinder (1) is connected to an overflow interface (7) through a guide pipe sequentially via a first two-stage pressure reducing valve (3) and a first electromagnetic valve (5), low-concentration calibration gas in the second gas cylinder (2) is connected to one end of the overflow interface (7) through a guide pipe sequentially via a second two-stage pressure reducing valve (4) and a second electromagnetic valve (6), and the other end of an overflow, the four-way valve (9) can selectively open any one of the passages A-C, B-C, D-C, the second air pump (13) is connected with the buffer device (12), and meanwhile, the gas at the C end of the four-way valve (9) is extracted through the oxygen sensor (10) and the carbon dioxide sensor (11); the control unit is responsible for controlling the pump and the valve in the detection device and collecting and uploading data; the human-computer interaction equipment is used for data processing, analysis and display;
the method comprises the following steps that gas exhaled by a human body is collected through a transparent hood (18) with a part opened, the hood comprises a soft surrounding edge used for sealing, an air inlet and an air exhaust opening, negative pressure is formed inside the hood when air exhaust is tested, convection is formed between the air inlet and the air outlet, and the gas exhaled by the human body is pumped into a fan pipeline (16);
when the oxygen sensor (10) and the carbon dioxide sensor (11) are calibrated, firstly, high-pressure calibration gas in a gas cylinder is subjected to pressure release through an overflow interface, and then the calibration gas is pumped into the oxygen sensor (10) and the carbon dioxide sensor (11) through a second air pump (13) to carry out concentration calibration; the method is characterized in that:
the head-mask indirect energy testing method comprises the following steps: when the test is started, analyzing the concentration of carbon dioxide in the hood to adaptively adjust the air extraction speed of the first air extraction pump (14), dividing the speed of the first air extraction pump (14) into a plurality of gears, presetting the air extraction speed gear of the first air extraction pump (14) according to the weight at the beginning, analyzing the minimum value and the maximum value of the concentration of the carbon dioxide in the hood (18) in a respiratory cycle every 50 seconds, comparing the minimum value and the maximum value with a preset threshold value, adjusting the gear of a fan, and keeping the air extraction speed gear constant after the threshold value condition is met;
the method comprises the following specific steps:
the method comprises the following steps: before a test subject tests, a valve in the D-C direction of a four-way valve (9) is opened, valves in other directions of the four-way valve (9) are closed, firstly, the high-concentration part of a sensor is calibrated, valves of a first gas cylinder (1) and a first two-stage pressure reducing valve (3) are opened, wherein the first gas cylinder (1) is a high-concentration gas cylinder, a second air pump (13) pumps gas at a constant speed, the calibrated gas in the first gas cylinder (1) passes through an overflow interface (7), one part of the gas enters an oxygen sensor (10) and a carbon dioxide sensor (11) through a pressure stabilizing valve, the oxygen sensor (10) and the carbon dioxide sensor (11) are calibrated, the other part of the gas is discharged into the air, after a period of time, the calibration of the high-concentration parts of the oxygen sensor (10) and the carbon dioxide sensor (11) is finished, a first electromagnetic valve (5) is closed, opening valves of a second gas cylinder (2) and a second two-stage pressure reducing valve (4), wherein the second gas cylinder (2) is a low-concentration gas cylinder, a second air pump (13) pumps gas at a constant speed, a part of the calibrated gas in the second gas cylinder (2) enters an oxygen sensor (10) and a carbon dioxide sensor (11) through a pressure stabilizing valve through an overflow interface (7), the oxygen sensor (10) and the carbon dioxide sensor (11) are calibrated, the other part of the calibrated gas is discharged into the air, after a period of time, the low-concentration part of the oxygen sensor (10) and the carbon dioxide sensor (11) is calibrated, and closing a second electromagnetic valve (6);
step two: opening valves in the A-C direction of the four-way valve (9), closing valves in other directions of the four-way valve (9), pumping air in a test environment to an oxygen sensor (10) and a carbon dioxide sensor (11) by a second air pump (13) at a constant speed, and measuring the average oxygen concentration and the average carbon dioxide concentration in the air within a period of time by the oxygen sensor (10) and the carbon dioxide sensor (11);
step three: the testee registers information on the man-machine interaction equipment, after the registration is completed, the testee is helped to take the head cover (18) and inform the testee of the attention matters in the measuring process, and the testee is allowed to rest for about half an hour so as to enter a resting state;
step four: opening a valve in the B-C direction of a four-way valve (9), closing valves in other directions of the four-way valve (9), clicking a start button, starting air extraction by a measurement start fan according to a budget speed, forming negative pressure in a hood (18), sucking ambient gas sucked into the hood and metabolic gas exhaled by a human body into an air extraction pipeline (16) together, wherein the air extraction speed of the fan can be adjusted in a self-adaptive manner at intervals of 50 seconds according to carbon dioxide concentration, when a set carbon dioxide concentration requirement is met, a first air extraction pump (14) extracts gas at a constant gear speed, the extracted mixed gas enters a flow sensor (17), the flow sensor (17) measures the flow of the mixed gas, a control unit acquires gas flow data through the flow sensor (17), a second air extraction pump (13) samples the gas in the pipeline (16) at a constant speed, and a part of the sampled mixed gas enters a gas concentration analysis part, the gas concentration analysis part acquires real-time concentration data of gas in the pipeline;
step five: the human-computer interaction equipment calculates the oxygen intake and carbon dioxide discharge amount in a period of time according to the uploaded data collected by the control unit, and the calculation process is as follows:
volume of mixed gas discharged from head cover:
nitrogen concentration in the mixed gas discharged from the head cap: fEN2＝1-FECO2–FEO2
Nitrogen concentration in ambient air: fIN2＝1-FICO2–FIO2
Volume of air drawn into the hood: vin＝Vout×FEN2/FIN2
Oxygen uptake: vO2＝Vin×FEO2-Vout×FIO2
Carbon dioxide emission: vCO2＝Vout×FICO2-Vin×FECO2
Wherein: v (t) is the instantaneous flow rate of the mixed gas in the pumping pipeline (16); t is t1Is the time point at which sampling begins; t is t2The time point of the end of sampling; fECO2The average carbon dioxide concentration in the mixed gas discharged out of the hood; fEO2Is the average oxygen concentration in the mixed gas exiting the hood; fIO2Is the average oxygen concentration in the air being drawn; fICO2Is the average carbon dioxide concentration in the air being drawn;
in order to coordinate the comfort and accuracy of the metabolic test, the air pumping speed needs to be dynamically adjusted to control the concentration of carbon dioxide within a certain range, and the control targets are as follows:
(1) the peak value of the average carbon dioxide concentration is less than or equal to 1 percent;
(2) the peak value of the average carbon dioxide concentration signal is more than or equal to 0.5 percent
The fan speed range is 0-60L per minute, wherein the speed of increasing a gear is increased by 5L per minute, when a test is started, the initial speed setting of the fan is calculated according to weight information input by a human body, the general weight is 10L per minute under 10kg, 20L per minute under 10 kg-20 kg, 35L per minute above 20kg, after the fan speed is set, the fan speed judgment flow is started, firstly, after the flow rate is waited for 30 seconds and the like and the carbon dioxide concentration is stable, the average carbon dioxide concentration peak value and the average carbon dioxide concentration signal peak value in the following 20 seconds are acquired, then, the average carbon dioxide concentration peak value is judged to be more than 1%, if the average carbon dioxide concentration peak value is more than 1%, the first gear fan speed is increased, the fan speed judgment flow is restarted, if the average carbon dioxide concentration signal peak value is not more than 1%, whether the average carbon dioxide concentration, and re-entering the fan speed judgment flow, wherein the carbon dioxide concentration change range is within the control target range if the carbon dioxide concentration change range is not less than 0.5%, keeping the constant air extraction speed, and not adjusting until the test is finished.
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