JPS6312259B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metabolic rate measuring device, and more particularly to a device for measuring the respiratory metabolic rate of humans and animals.

The primary function of the lungs of humans and animals is to appropriately exchange oxygen and carbon dioxide gas between the outside air and the blood during breathing, that is, to carry out respiratory metabolism. Metabolic rate (hereinafter referred to as metabolic rate)
A metabolic rate measuring device (hereinafter referred to as a metabolic rate meter) is used to measure. In other words, the metabolic rate meter can be said to be a device for measuring lung function. In recent years, the influence of lung function on the body has attracted attention.
Measuring metabolic rate has become important not only for diagnostic purposes but also for health management.

Metabolic rate is measured by measuring the concentration of oxygen gas and carbon dioxide in the exhaled breath of a subject. Conventionally, metabolic rate meters have been used to measure oxygen gas concentration using magnetic sensors. Oxygen meters using type or discharge type oxygen meters are known. In other words, a magnetic oxygen meter uses the fact that oxygen gas is a paramagnetic substance to create a magnetic wind with the oxygen gas, or to displace a dumbbell filled with non-magnetic gas by the flow of oxygen gas. The flow rate of the magnetic wind is related to the amount of displacement of the dumbbell and the concentration of oxygen gas. In addition, discharge-type oxygen meters utilize the fact that when a high-frequency voltage is applied to a mixed gas of oxygen gas and an auxiliary gas such as nitrogen gas, an ionic current flows with a magnitude related to the oxygen gas concentration in the mixed gas. It is something. However, conventional metabolic rate meters using such magnetic or discharge oximeters have drawbacks as described below. In other words, A. Because the response speed of an oximeter is slow, it is difficult to detect instantaneous changes in metabolic rate in response to various stimuli, such as changes in metabolic rate immediately after a meal or medication, or changes in metabolic rate during exercise. almost impossible to measure. For example, the response speed of an oximeter that uses magnetic wind is approximately 20 to 30 seconds.
The measured value remains at an average value within the above period.

B. Measurement accuracy is low. In other words, a metabolic rate meter is required to be able to accurately measure changes in oxygen gas concentration of about 0.5 to 1 (%), whereas a magnetic oxygen meter has a full scale of about 0 to 2 (%), and a discharge type oxygen meter has a full scale of about 0 to 2 (%). Since the total value is about 0 to 10 (%), the response speed is slow and the measurement accuracy is low.
In addition, magnetic or discharge type oxygen meters have poor stability (for example, the stability of discharge type oxygen meters is
(about ±2%/10 minutes for 10% full scale), which further reduces measurement accuracy.

C Difficult to measure and compare oxygen gas concentration with outside air.
In other words, since the measured value obtained by the above-mentioned magnetic type or discharge type oxygen meter is an absolute value,
When using the metabolic rate meter in a small room,
If the oxygen gas concentration in the outside air changes due to the amount of moisture in the atmosphere, it becomes unclear whether the fluctuation in the measured value represents the fluctuation in the oxygen gas concentration due to the subject's breathing.

An object of the present invention is to provide a metabolic rate meter that can solve the above-mentioned drawbacks of conventional metabolic rate meters and can measure the metabolic rate of a subject at any given time with high precision and stability.

To achieve the above object, the present invention is an apparatus for measuring the respiratory metabolic rate of a subject from the oxygen gas concentration and carbon dioxide concentration in the subject's exhalation,
The device includes (a) a hood with an opening on one side, (b) a main flow pipe with one end open to the atmosphere connected to the other end of the hood, and (c) In the vicinity of the hood, a reference gas introduction pipe is opened at one end, (d) a bypass pipe is connected to the main flow pipe at one end, and (e) a bypass pipe is connected to the other end of the pipe, (a) (b) a second measurement pipe whose one end is connected to a carbon dioxide gas meter is connected at its other end; (c) one end is connected to a carbon dioxide gas meter; A third measuring pipe connected to the oxygen meter is connected at the other end, and (f) the oxygen meter includes (a) a partition made of an oxygen ion conductive solid electrolyte, and (b) provided on each wall of the partition. (c) means for heating the partition wall to a desired temperature; (g) the other end of the reference gas introduction piping opens at one side of the partition wall of the oxygen meter; (h) One end of the third measuring pipe is open on the other side of the partition wall, and is characterized by a metabolic rate measuring device.

In the present invention, the subject refers to both humans and animals.

To explain one embodiment of the metabolic rate meter of the present invention, in FIG. 1, 1 is a hood made of transparent plastic material. The hood 1 is large enough to accommodate the head or chest area of a human subject,
It has an opening on one side, and a main flow pipe 4 having a diaphragm pump 2 and a mass flow controller 3 is connected to the other side. 5 is a bypass pipe having a diaphragm pump 6, and this bypass pipe 6 is connected to the main flow pipe 4 on the outlet side of the mass flow controller 3, and further includes an electronic dehumidifier 7,
It is connected to three measuring pipes 10, 11, and 12 via a dehumidifying tube 8 filled with silica gel, calcium chloride, etc., and a dust filter 9.

The measuring pipe 10 is opened to the atmosphere via a flow rate regulator 13. In addition, the measurement piping 11 includes a check valve 14, a flow rate regulator 15, and a carbon dioxide gas meter 1.
6 and is open to the atmosphere. This carbon dioxide gas meter 16 utilizes the fact that infrared rays are selectively absorbed by carbon dioxide gas and its intensity is attenuated. The check valve 14 also includes a gas introduction pipe 1 for adjusting the zero point of the carbon dioxide meter 16.
7 and a span adjustment gas introduction pipe 18 are connected. Measurement pipe 12 is check valve 1
9, it is opened to the atmosphere via a flow rate controller 20 and an oxygen meter 21. The check valve 19 also includes a gas introduction pipe 22 for span adjustment of the oxygen meter 21.
is connected.

The oxygen meter 21 is as shown in FIG. That is, the oxygen meter 21 is made of approximately 400
A cylindrical partition 21A made of a solid electrolyte that has oxygen ion conductivity at high temperatures of ℃ or higher, porous electrodes 21B, 21C made of platinum or the like formed on both the inner and outer walls of this partition 21A, and these electrodes 21B, 21.
The electric furnace 21D has an electromotive force meter 21E such as an indicator and a recorder connected between C and C, and an electric furnace 21D that heats the partition wall 21A to a temperature of about 400° C. or higher. This type of oxygen meter is called a solid electrolyte oxygen meter.
When gases having different oxygen partial pressures are brought into contact with the electrodes 21B and 21C, the electrodes 21B and 21C
In the meantime, an electromotive force is generated based on the so-called Nernst equation, which corresponds to the difference in oxygen partial pressure in both gases.
That is, E=RT/4FlnP ₂ /P ₁ where E: Electromotive force F: Faraday's constant R: Gas constant T: Absolute temperature of the partition P ₁ : Oxygen partial pressure in the gas on one side of the partition P ₂ : Partial pressure of the partition Oxygen partial pressure in the gas on the other side Therefore, if the absolute temperature T of the partition wall and the oxygen partial pressure P ₁ or P ₂ in the gas on one side or the other end of the partition wall are known, the above electromotive force can be By measuring the partial pressure of oxygen in the gas on the other side or on one side of the partition wall P ₂
Alternatively, P ₁ , that is, the oxygen gas concentration can be measured. In addition, in Figure 2, 2
1F is a temperature measuring element such as a thermocouple that detects the temperature of the partition wall 21A.

Referring again to FIG. 1, 23 is a reference gas introduction pipe whose one end is open near the hood 1;
This reference gas introduction pipe 23 passes through a diaphragm pump 24, an electronic dehumidifier 7, a dehumidifying cylinder 25 that is exactly the same as the above-mentioned dehumidifying cylinder 8 and dust filter 9, a dust filter 26, a flow rate regulator 27, and an oxygen meter 21.
It is connected to the. Note that 28 is a drain discharger connected to the electronic dehumidifier 7.

Now, to explain the function of the metabolic rate meter as described above, first, the carbon dioxide gas meter and oxygen meter are calibrated.

To calibrate the carbon dioxide meter, connect the check valve 1 to the carbon dioxide meter 16 from the zero point adjustment gas introduction pipe 17.
4, a specified amount of gas that does not contain carbon dioxide gas, such as pure nitrogen gas, is flowed while adjusting the flow rate with a flow rate regulator 15, and its zero point is adjusted. In exactly the same manner, a gas containing carbon dioxide at a constant concentration of about 0.5 to 1.0 (%) is introduced from the span adjustment gas introduction pipe 18, and is passed through a carbon dioxide meter to adjust the span.

To calibrate the oxygen meter, first start the electric furnace 21D,
The partition wall 21A is kept at a constant temperature of about 800°C. In this state, the diaphragm pumps 2 and 6 are operated, and the arrow A is placed inside the partition wall 21A of the oxygen meter 21.
A specified amount of outside air introduced from the opening of the hood 1 is caused to flow through the main flow pipe 4, the bypass pipe 5, and the measurement pipe 12 from the direction. At this time, the subject is not placed inside the hood 1. Meanwhile, the diaphragm pump 24 is operated, and the partition wall 21A of the oxygen meter 21 is
The zero point of the oxygen meter 21 is adjusted by flowing a specified amount of outside air near the hood 1 from the direction of arrow B to the outside of the hood 1 through the reference gas introduction pipe 23. Next, the operation of the diaphragm pump 24 is stopped, and a specified amount of oxygen containing a constant concentration of about 0.8% is introduced from the span adjustment gas introduction pipe 22 to the outside of the partition wall 21A of the oxygen meter 21 in the direction of arrow B. Flow the gas and adjust the span of the oxygen meter 21.

Next, to measure the metabolic rate, first, the diaphragm pump 24 is operated again. Then, the mass flow controller 3 adjusts the flow rate of outside air flowing through the main flow pipe 4. This flow rate must be such that the subject housed in the hood 1 does not inhale the exhaled air again, and it depends on the volume of the hood 1 and whether the subject is an adult or a child. This can be determined by taking into consideration whether the child is a child or an infant, but normally 3 to 65 (/min) is sufficient. For example, if the subject is an adult, a flow rate of about 50 to 60 (/min) is appropriate, and if the subject is a child, a flow rate of about 10 to 20 (/min) is appropriate.
For infants, a flow rate of about 4 to 5 (/min) is appropriate.

Most of the outside air flowing through the main flow pipe 4 is
It is released into the atmosphere from one end, but a part of it is taken out into the bypass pipe 5 by a diaphragm pump 6, and the moisture is removed by an electronic dehumidifier 7 set at a temperature of 2 to 3 (℃). Most of the moisture is removed, and almost all of the moisture is further removed by the dehumidifying cylinder 8, and then sent to the dust filter 9 for cleaning.
The flow rate of the outside air flowing inside this bypass flow path 5 is 1
(/minute) is sufficient.

The outside air that has passed through the dust filter 9 is sent to three measurement pipes 10, 11, and 12. Then, the carbon dioxide gas meter 1 is
6, and the flow rate of outside air introduced into the inside of the partition wall 21A of the oxygen meter 21 is 100, respectively.
(ml/min), and the remaining amount is adjusted so that the remaining amount is released into the atmosphere from one end of the measuring pipe 10.

On the other hand, the outside air in the vicinity of the hood 1 introduced into the reference gas introduction pipe 23 by the diaphragm pump 24 is collected by the electronic dehumidifier 7, the dehumidifying cylinder 25, and the dust in the same way as the outside air flowing through the bypass channel 5. It is introduced into the flow rate regulator 27 through the filter 26, and after being adjusted to a flow rate of about 100 (ml/min) by the flow rate regulator 27, it is introduced into the outside of the partition wall 21A of the oxygen meter 21 from the direction of arrow B. be done.

Now, while maintaining the above-mentioned state, the subject's head or the part up to the vicinity of the chest is accommodated in the hood 1. Then, the exhaled air of the subject passes through the main flow pipe 4 and the bypass pipe 5 to the carbon dioxide meter 16.
Then, it is introduced inside the partition wall 21A of the oxygen meter 21. Therefore, the carbon dioxide gas concentration in the exhaled breath can be measured by the carbon dioxide gas meter 16, and the oxygen gas concentration can be measured by the oxygen meter 21, and the metabolic rate of the subject can be determined. The metabolic rate is
It is usually expressed as the respiratory quotient (increase in carbon dioxide gas/amount of oxygen gas consumed), and this value is for a normal adult.
It is about 0.6.

In the above embodiment, the carbon dioxide meter and oxygen meter include
A device that calculates the respiratory quotient and automatically outputs the metabolic rate may be connected.

In addition, in the above embodiment, the flow rate of exhaled air or outside air on each side of the partition wall of the oximeter is 100 (ml/min).
However, this value may be changed as appropriate depending on the size of the partition wall. In other words, if the flow rate is too small, gas diffusion and mixing will occur, reducing measurement accuracy.
On the other hand, if it is too large, heat transfer will be large and a large-capacity electric furnace will be required, which is uneconomical. Also,
In order to further reduce measurement errors, it is preferable to equalize the flow rates on each side of the partition wall. Furthermore, the direction of flow of exhaled air or outside air on each side of the partition wall may be the same.

Furthermore, the size of the hood may be such that it can accommodate the entire animal, particularly in cases where the metabolic rate of the small animal is to be measured.

As explained above, the metabolic rate meter of the present invention uses a solid electrolyte oxygen meter with high response speed and measurement accuracy to measure the oxygen gas concentration in the exhaled breath of the subject. It is possible to extremely accurately measure the state of change in metabolic rate in response to various stimuli, such as the state of change in metabolic rate during exercise and the state of change in metabolic rate during exercise. In addition, since the measurement is performed in comparison with the oxygen gas concentration in the outside air, it is possible to detect fluctuations in the oxygen gas concentration in the outside air due to factors such as when the metabolic rate meter is used in a small room or due to the amount of moisture in the atmosphere. It does not affect the measured values, and it has never happened that it becomes unclear whether the fluctuations in the measured values represent fluctuations in the oxygen gas concentration caused by the subject's breathing. These effects can be further improved by the following.

In other words, when people stand around the hood, the atmospheric composition near the hood changes slightly due to absorption, and the subject inhales the changed atmosphere. Since the reference gas introduction pipe is opened nearby, air with almost the same composition as that actually inhaled by the test subject can be introduced to the oxygen meter as a reference gas, preventing measurement errors due to changes in the composition of the air. can do. In particular, when the subject is a person who consumes a small amount of oxygen gas, such as an infant, the influence of changes in the composition of the atmosphere becomes large; however, in the present invention, there is almost no such concern.

Further, the present invention provides a main flow pipe whose one end is open to the atmosphere, connects a bypass pipe to the main flow pipe, further connects three measurement pipes to the bypass pipe, and connects a first pipe to the main flow pipe. The first pipe is opened to the atmosphere, and the second pipe is connected to a carbon dioxide gas meter.
Since an oxygen meter is connected to the third pipe, the flow rate in the main flow pipe is maintained at a high flow rate that prevents the subject from inhaling his or her own exhaled air again, and the exhaled air in the main flow pipe is The bypass piping prevents delays in response speed, but allows the flow to be guided to the measurement piping at a level that does not significantly increase piping resistance.Furthermore, the first piping allows for the measurement of carbon dioxide and oxygen meters. Since the flow rate of exhaled air flowing into the device can be reduced to the most suitable flow rate, not only the response speed and measurement accuracy are improved, but also the capacity of the dehumidifier can be reduced, making the device compact and low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing one embodiment of the metabolic rate meter of the present invention, and FIG. 2 is a schematic longitudinal sectional view showing one embodiment of the solid electrolyte oxygen meter. 1: Hood, 2, 6, 24: Diaphragm pump, 3: Mass flow controller, 4: Main flow piping, 5: Bypass piping, 7: Electronic dehumidifier, 8,
25: Dehumidification tube, 9, 26: Dust filter, 1
0, 11, 12: Measurement piping, 13, 15, 2
0, 27: Flow rate regulator, 14, 19: Check valve, 16: Carbon dioxide meter, 17: Gas introduction piping for zero point adjustment, 18, 22: Gas introduction piping for span adjustment, 21: Oxygen meter, 21A: Partition wall, 21B, 21
C: electrode, 21D: electric furnace, 21E: electromotive force meter,
21F: Temperature measuring element, 23: Reference gas introduction pipe, 2
8: Drain discharger.

Claims (1)

[Scope of Claims] 1. A device for measuring the respiratory metabolic rate of a test subject from the oxygen gas concentration and carbon dioxide gas concentration in the breath of the test subject, the device comprising: (a) an opening on one side; (b) On the other side of the hood, a main flow pipe with one end open to the atmosphere is connected at the other end; (c) In the vicinity of the hood, there is a pipe for introducing a reference gas. (d) a bypass pipe is connected to the main flow pipe at one end; (e) a bypass pipe is connected to the other end of the bypass pipe; (a) a pipe having one end open to the atmosphere; (b) a second measuring pipe whose one end is connected to a carbon dioxide meter is connected at its other end; (c) a third measuring pipe whose one end is connected to an oxygen meter; (f) the oxygen meter comprises: (a) a partition wall made of an oxygen ion conductive solid electrolyte; (b) an electrode provided on each wall surface of the partition wall; (c) a means for heating the partition wall to a desired temperature; ) The metabolic rate measuring device, wherein the one end of the third measuring pipe is open on the other side of the partition wall.