JPH0244531B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Industrial Application Field) The present invention relates to a respiratory metabolism measuring device for measuring the concentration of oxygen and carbon dioxide in the exhaled air of a living body, and particularly to the structure of a mixing chamber that diffuses the exhaled air. (Prior Art) It is an important element in medical diagnosis to measure respiratory metabolic function by measuring oxygen and carbon dioxide concentrations in exhaled breath of a living body, especially a human body. The respiratory metabolic measuring device for this purpose includes a flow meter that measures the expiratory flow rate, a mixing chamber that eliminates concentration differences in exhaled air and diffuses it uniformly, and an oxygen/carbon dioxide sensor that measures the oxygen and carbon dioxide concentrations in exhaled air. It is made up of As shown in FIG. 3, the conventional mixing chamber 1 is formed into a closed cylindrical shape with pipes 2 and 3 provided on both end faces.
One end of the pipe 2 on the inlet side of the mixing chamber 3 protruded into the mixing chamber 1, and a large number of holes 2a were formed on the outer periphery. Mixing chamber 1 like this
has the effect of completely diffusing the exhaled air remaining in the chamber 1 and the newly sent exhaled air, thereby eliminating the concentration difference between the exhaled air within the chamber 1. However, there are individual differences in expiratory volume, and there are particularly large differences between at rest and during exercise. On the other hand, since the internal volume of the conventional mixing chamber 1 is constant, for example, if the exhaled air volume is as small as 300 c.c., it will take a long time for it to be completely diffused; There was a problem that the time required for diffusion was short and there was a time lag. For this reason, when trying to measure exhaled breath concentration after completion of diffusion, there was a drawback that the time delay was inconsistent. In addition, when attempting to automatically calibrate a flowmeter, a bypass must be installed in the pipes before and after the flowmeter, and calibration must be performed via a separate flow path using a separate calibration device. Another problem was that calibration was troublesome. (Problems to be Solved by the Invention) The present invention has a problem in conventional respiratory metabolic measuring devices because the mixing chamber has a constant internal volume, so a time difference occurs in the diffusion of exhaled air within the chamber, and the diffusion time The purpose of the present invention is to provide a respiration metabolism measuring device that can diffuse exhaled air in a short time and easily calibrate the flowmeter, solving the problems that it may take a long time to calibrate the flowmeter and that it is troublesome to calibrate the flowmeter. shall be. [Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a flowmeter for measuring the expiratory flow rate of a living body, a mixing chamber for diffusing the exhaled air, and a mixing chamber for diffusing the exhaled air. A respiration metabolism measuring device having a sensor for measuring gas concentrations such as oxygen and carbon dioxide concentrations, comprising: a partition wall slidably provided in the mixing chamber in an airtight manner; a driving means for driving the partition wall; A control device is provided for setting the amount of drive of the drive means based on a signal from a flow meter. (Function) According to the above configuration, by applying a signal detected by the flow meter to the driving means, the partition wall can be moved to a position that matches the expiratory volume. As a result, the volume of the part of the mixing chamber partitioned by the partition wall is automatically set to a volume that matches the preset expiratory volume, so that the exhaled air within the mixing chamber is completely diffused in a short period of time. It will be done. Furthermore, if the interval between the detection means for detecting the moving ends of the partition wall is set in advance to correspond to a constant volume change within the mixing chamber, then
The flow meter can be easily calibrated by comparing the constant fluid volume obtained by moving the partition wall by this distance and the integrated value of the flow meter. (Example) Hereinafter, an example of the respiratory metabolism measuring device according to the present invention will be described with reference to the drawings. An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.
A mouthpiece 1, a flexible tube 2, a direction changer 3, a bypass switching valve 4, a heater with a thermistor 5, a differential pressure flowmeter 6, a bypass switching valve 7, and a mixing chamber 8 are included in the pipe on the inlet side of the exhaled air to be measured. , a flexible tube 9, a switching valve 10, and a pipe 11 are connected in this order. An oxygen/carbon dioxide sensor 13 is connected to the downstream side of this piping 11 via a fan and a cooler 12 with a thermistor, and further downstream thereof a pump 14 is provided. 15,1
6 are valves 17, 18 and flowmeter 19, respectively.
20 are cylinders of zero gas and span gas for calibration, which are connected to the inlet side of the cooler 12 via a switching valve 21. The mixing chamber 8 is connected to the bypass switching valve 7 by a pipe 22, and one end of the pipe 22 protruding into the chamber 8 has an enlarged diameter and a sealed end surface. And this enlarged diameter part 22
A large number of holes 22b are formed on the outer peripheral surface of a. There is a V-shaped seal rubber 2 on the inner peripheral surface of the chamber 8.
A partition wall 24 is airtightly and slidably provided through the chamber 3, and a pipe is airtightly and slidably attached to the outlet side end surface of the chamber 8 via a V-shaped seal rubber 25. One end of 26 is open and fixed. A rack 27 is fixed in parallel to the axial direction on the outer peripheral surface of the portion of the pipe 26 that protrudes from the chamber 8.
A pinion gear 29 driven by a motor 28 meshes with the pinion gear 29 . Further, limit switches 31 and 32 and a potentiometer 33 attached to the main body frame 30 are arranged at the lower part of the pipe 26. 34 is a control device, which includes a calculation circuit 35 that converts the expiratory flow rate signal sent from the flow meter 6 into an expiratory volume, that is, a ventilation volume; and this calculation circuit 35.
Comparison in which the expiratory volume signal output from the potentiometer 33 and the position signal of the septum 24 sent from the potentiometer 33 are received and compared, and the septum movement amount is set based on the expiratory volume-position curve set and stored in advance. circuit 3
6, and a drive circuit 37 that drives the motor in accordance with the command signal output from the comparison circuit 36. Next, the operation of this embodiment will be explained. The exhaled breath of the person to be measured is sent from any direction to the heater 5 via the mouthpiece 1, the flexible tube 2, and the direction changer 3, and is heated to an appropriate temperature to prevent dew condensation. At this time, the bypass switching valves 4 and 7 are set in the straight direction. Then, the expiratory flow rate (unit/
S) is measured and sent into the mixing chamber 8. Here, the exhaled air is ejected from the hole 22b formed in the enlarged diameter portion 22a, and the exhaled air remaining in the space between the inlet side end face of the chamber 8 and the partition wall 24 is combined with the newly introduced exhaled air. are mixed and completely diffused without any concentration difference. This diffused exhaled air passes through the pipe 26, valve 10, and piping 11 to the cooler 12.
After being cooled to an appropriate temperature, oxygen and
The concentration of oxygen and carbon dioxide in exhaled breath is measured by the carbon dioxide sensor 13 and released into the atmosphere by the pump 14. Here, the relationship between the internal capacity of the chamber 8 and the amount of exhaled air, which allows exhaled air to be efficiently diffused within the chamber 8 in a short period of time, is shown in Table 1 below, for example.

[Table] The internal volume between the inlet side end face of the chamber 8 and the partition wall 24 is detected by a potentiometer 33 via a pipe 26 fixed to the partition wall 24. If the relationship between this internal volume and the expiratory volume measured by the flowmeter 6 deviates from the relationship shown in Table 1, the comparison circuit 36 drives the motor 28 in a direction that brings this relationship into agreement. A command to do this is issued to the drive circuit 37, and the motor 28 rotates to move the pipe 26 in the axial direction via the pinion gear 29 and the rack 27 until the partition wall 24 reaches a position where it has an appropriate internal volume and then stops. That is, the mixing chamber 8 can always be maintained at an internal volume that matches the expiratory volume measured by the flowmeter 6. Therefore, the exhaled air within the chamber 8 can be completely diffused in a short time. Next, a method for calibrating the flow meter 6 will be explained. The interval between the limit switches 31 and 32 is set in advance at a position where the amount of change in internal volume due to movement of the partition wall 24 in the chamber 8 is a constant value. Then, the valve 10 is closed to send fluid such as exhaled air to the flow meter 6, and the partition wall 24 is moved to adjust the flow rate between when a dog (not shown) provided on the pipe 26 hits the limit switch 31 and until the limit switch 32 is hit. Calibration is performed by comparing the cumulative volume of fluid that has passed through the chamber 6 with the set amount of change in the internal volume of the chamber 8. According to the method of calibrating the flowmeter 6 according to this embodiment,
There is no need to create a bypass using the switching valves 4 and 7 and calibrate using a separate calibrator as in the prior art, and the mixing chamber 8 can be used to easily calibrate even during exhalation measurement. In this embodiment, a case has been described in which the flowmeter is a differential pressure type flowmeter, but it goes without saying that this flowmeter is not limited to a differential pressure type. Note that if means such as a pulse motor whose movement amount is accurately proportional to the input signal is used as the partition wall driving device, the potentiometer 33 as the position detecting means can be omitted. [Effects of the Invention] As described above, according to the present invention, the internal volume of the mixing chamber provided in the respiratory metabolism measuring device is changed in accordance with the amount of inhaled air, so that the diffusion of exhaled air within the chamber is reduced. This can be done in a short time, and the flowmeter can be easily calibrated.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the respiratory metabolism measuring device according to the present invention, FIG. 2 is a longitudinal sectional view showing the mixing chamber of FIG. 1, and FIG. 3 is a longitudinal sectional view showing the conventional mixing chamber. It is a front view. 6...Flowmeter, 8...Mixing chamber, 1
3... Sensor, 24... Partition wall, 28... Motor (driving means), 31, 32... Limit switch (moving end detection means), 33... Potentiometer (position detection means), 34... Control device.

Claims (1)

[Claims] 1. In a respiratory metabolic measuring device that includes a flowmeter that measures the exhaled air flow rate of a living body, a mixing chamber that diffuses the exhaled air, and a sensor that measures the gas concentration in the exhaled air, a sensor that airtightly slides into the mixing chamber. 1. A respiratory metabolism measuring device comprising: a partition wall that can be provided, a driving means for driving the partition wall, and a control device for setting a driving amount of the driving means based on a signal from the flow meter.