JP2663114B2 - Lung function measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lung diffusion capacity (DLC).
More specifically, the present invention relates to a pulmonary function measuring device for measuring a pulmonary function such as O), and more particularly to a pulmonary function measuring device capable of washing or disinfecting a respiratory circuit mechanism in a range in which saliva, damp, etc. of a subject may splash. About.

[0002]

2. Description of the Related Art A pulmonary function measuring apparatus is a device in which a subject inhales and exhales a measurement gas to measure various pulmonary functions such as a lung diffusion capacity (DLCO). The device used an electromagnetic valve to switch the flow path of the respiratory gas during the measurement. In addition, this "lung diffusion ability" is the ability to take in CO gas from the alveoli into the lung capillaries, and if there is a lesion in the lung capillaries, this ability is reduced.
It is measured for the diagnosis of emphysema.

On the other hand, when a plurality of subjects are continuously measured,
Since the respiratory circuit mechanism of the device is contaminated by pathogens contained in saliva and sputum droplets in the breath and may infect other subjects, in order to prevent that infection, It is desirable that the breathing circuit of the device be easily cleaned and disinfected.

[0004]

However, since the above-mentioned conventional apparatus uses an electromagnetic valve for switching the flow path of the respiratory gas, saliva and the like in the expiration have been sprayed to the inside of the electromagnetic valve. For this reason, in order to completely prevent infection, it is necessary to disassemble, clean and assemble the solenoid valve, but this is practically impossible, and prevention of infection has been difficult.

Accordingly, the present invention has been made in view of the above circumstances, and it is possible to measure the lung diffusion ability, which is a basic lung function of a subject, and to cause saliva and the like in the exhaled breath to splash. It is an object of the present invention to provide a lung function measurement device capable of easily cleaning a certain range of respiratory circuit mechanisms.

[0006]

The means of the present invention for solving the above problems will be described.

According to a first aspect of the present invention, there is provided a lung function measuring apparatus for measuring a lung diffusing ability of a subject's respiratory function using a mixed gas containing a low concentration of carbon monoxide. A breathing circuit, and a ventilation pipe having one end detachably connected to the breathing circuit and the other end connected to the airway of the subject, and a flow rate or flow rate of the respiratory air flowing through the ventilation pipe. A mixed gas supply pipe detachably connected to the breathing circuit via a one-way valve; a sample bag detachably connected to an air intake provided in the breathing circuit; A respiratory circuit mechanism having detachable first opening / closing means for opening / closing a first ventilation port provided in the circuit and communicating with the atmosphere, and detachable second opening / closing means for opening / closing the air intake port is provided. It is characterized by the following.

According to a second aspect of the present invention, in the pulmonary function measuring apparatus, the breathing circuit mechanism has a second vent dedicated to exhalation communicating with the atmosphere through a one-way valve in the breathing circuit, and the second vent is provided. And a detachable third opening / closing means for opening / closing.

In the lung function measuring device according to a third aspect, the opening / closing means uses the mixed gas as a driving source.

[0010]

The operation of the present invention having the above configuration will be described.

According to the lung function measuring device of the first aspect,
When measuring the lung diffusing ability of the subject, for example, the first vent is opened, the air intake is closed, and quiet ventilation is performed. The mixed gas passes through the mixed gas supply pipe and is supplied to the airway of the subject via the one-way valve, the breathing circuit, and the ventilation pipe of the sensor. The first vent is opened, and the subject's first exhaled gas is exhausted from the first vent to the atmosphere by a predetermined amount. The first vent is closed and the air intake is opened, and the breath gas of the subject is collected in the sample bag. The first vent is opened and the air intake is closed, and the remaining exhaled gas of the subject is exhausted from the first vent to the atmosphere. The concentration data of the supplied gas mixture, the concentration data of the exhaled gas collected in the sample bag, and the detected value of the flow rate or flow rate of the respiratory gas flowing through the ventilation tube detected by the sensor are used to calculate the lung diffusion capacity of the subject. Is done.

In addition, a breathing circuit is formed in the block, and a first vent provided in the breathing circuit is opened and closed by detachable first opening / closing means, and a gas inlet provided in the breathing circuit is opened / closed by a second opening / closing means. Since the device is opened and closed by the means, it is not necessary to dispose an electromagnetic valve in a breathing circuit in which saliva or the like in exhaled air may splash. On the other hand, the range in which the saliva and the like may be splashed is around the breathing circuit formed in the block, the inside of the ventilation pipe of the sensor, the sample bag, the first opening / closing means, the second opening / closing means, and the breathing circuit. Therefore, from the breathing circuit, the sensor ventilation pipe, mixed gas supply pipe, sample bag,
By removing the first opening / closing means and the second opening / closing means, it is possible to easily perform cleaning or the like in the area.

[0013] According to the lung function measuring apparatus of the second aspect,
By opening the second vent before supplying the mixed gas to the airway of the subject, it is not necessary to open and close the vent in synchronization with the timing of intake of the mixed gas. Opening / closing control becomes easy.

According to a third aspect of the present invention, there is provided a lung function measuring apparatus.
By using the mixed gas as the driving source of the opening / closing means, the driving source of the opening / closing means can be omitted.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic diagram showing an embodiment of the lung function measuring apparatus according to the present invention.

As shown in FIG. 1, the lung function measuring apparatus of this embodiment has a block 1 made of, for example, aluminum, plastic, or the like.

On the surface of the block 1, a first ventilation port 1a communicating with the atmosphere, a valve storage port 1b provided at a position opposed to the first ventilation port 1a, a sensor mounting port 1c,
Standard gas supply port 1d, intake port 1e, and intake port 1e
A valve storage port 1f provided at a position opposed to the opening and a second ventilation port 1g communicating with the atmosphere are formed, and each of the openings 1a to 1g communicates with the inside of the block 1 to provide a path for breathing air. A breathing circuit 1h is formed.

Further, the present apparatus comprises a sensor 2 detachably connected to a sensor mounting port 1c of the block 1, and an air sampling port 1e.
A sample bag 3 which is detachably connected to a connector 3a to collect the breath (alveolar air) gas of the subject, a substrate 4 made of, for example, aluminum, plastic or the like, which holds the block 1 in a detachable manner, A standard gas supply source 5 for supplying a mixed gas (standard gas) containing carbon monoxide, a measurement system 6 for measuring lung diffusion capacity (DLCO),
Telescopic valves 12, 12 housed in the valve housings 1b, 1f,
A first air cylinder (first opening / closing means) 8a for opening and closing the first ventilation port 1a by expanding and contracting the expansion valve 12;
A second air cylinder (second opening / closing means) 8b that opens and closes the air intake port 1e by expanding and contracting the second air inlet 1e, and a third air valve that opens and closes the second ventilation port 1g by a valve 14 attached to the tip of a rod 8d.
, A one-way valve (incoming direction) 10a arranged in the standard gas supply port 1d, a one-way valve (outgoing direction) 10b arranged in the second ventilation port 1g, and control of the entire apparatus. And a control unit (see FIG. 2) 13 for controlling the operation. In addition, the one-way valve 10a may be disposed on a second auxiliary supply pipe 5c described later.

The sensor 2 includes a vent pipe 20 having one end detachably connected to the sensor mounting opening 1c of the block 1, a mouthpiece 21 detachably connected to the other end of the vent pipe 20, and a vent pipe. The laminar flow tube 22 includes a laminar flow tube 22 and a detection unit 23 attached to the ventilation tube 20 and configured to detect a pressure difference across the laminar flow tube 22. The differential pressure detected by the detection unit 23, that is, the detection signal of the flow rate of the respiratory air is sent to the control unit (see FIG. 2) 13 where the detection signal is integrated and the volume of the respiratory air is calculated.

The expansion / contraction valve 12 is made of, for example, rubber or the like, and has a bellows-like cylindrical portion 12a, a flange portion 12b formed on the open end side of the cylindrical portion 12a, and a bottom portion formed at the tip of the cylindrical portion 12a. 12c, and the cylindrical portion 12a is freely expandable and contractable in the axial direction.

The base 4 has a flange 12b of the telescopic valve 12.
A pair of holding openings 4a and 4c for holding the valve, a holding opening 4b for holding an end of a second auxiliary supply pipe 5c to be described later with a screw, and an opening for a moving space of the valve 14. 4d
And form. In addition, the substrate 4 holds the block 1 by a spring-fitted clamp (not shown). Thereby, the flange portion 12b and the seal 11 of the expansion valve 12 are pressed between the block 1 and the substrate 4,
Between the telescopic valve 12 and the valve storage ports 1b, 1f and the seal 11
And the supply port 1d prevents air from leaking.

The standard gas supply source 5 has a main supply pipe 5a.
And the first to fourth auxiliary supply pipes 5b, 5c, 5d, 5e are connected to the main supply pipe 5a. This first
A first port 7a is interposed in the auxiliary supply pipe 5b, and a first air cylinder 8a is connected to an end of the first port 7a. Also,
A second port 7b and a demand valve 9 are interposed in the second auxiliary supply pipe 5c, and a seal 11 is provided at an end thereof. A third port 7c is interposed in the third auxiliary supply pipe 5d, and a third air cylinder 8c is connected to an end of the third port 7c. Further, a fourth port 7d is connected to the fourth auxiliary supply pipe 5e.
, And the second air cylinder 8b is connected to the end.

The measuring system 6 has a pump 60 provided with an exhaust port 60a and a vent port 60b, and a suction pipe 61 is connected between the pump 60 and the block 1. Suction tube 6
1 includes a fifth port 7e, a first filter 62 for dehumidifying the sampled gas with silica gel, and a second filter for absorbing carbon dioxide (CO ₂ ) with soda lime from the sampled gas. 63, a He meter 64 for measuring the concentration of helium (He), and a CO meter 65 for measuring the concentration of carbon monoxide (CO). Also,
The main supply pipe 5a is connected to the fifth port 7e via a manual valve 7f. This manual valve 7f is
It is used when the concentration of the standard gas supplied by the standard gas supply source 5 is measured by the He meter 64 and the CO meter 65. The end of the suction pipe 61 on the block 1 side is detachably connected to the air intake port 1 e of the block 1.

The first to fifth ports 7a to 7e
Is constituted by a solenoid valve, and is opened and closed by a control unit (see FIG. 2) 13.

Under the control of a control unit (see FIG. 2), the first to third air cylinders 8a to 8c have a rod 8d protruding and retracting, and respectively have a first ventilation port 1a, an air intake port 1e, and a The second vent 1g is opened and closed. That is, when the first port 7a is turned on, the standard gas supply source 5
From the first air cylinder 8 through the main supply pipe 5a, the first port 7a and the first auxiliary supply pipe 5b.
a, the rod 8d of the first air cylinder 8a protrudes from the initial position, and the telescopic valve 12 extends to close the first vent 1a. Also, the fourth
Is turned on, the standard gas from the standard gas supply source 5 is supplied to the second air cylinder 8b through the main supply pipe 5a, the fourth port 7d, and the fourth auxiliary supply pipe 5e. The rod 8d of the second air cylinder 8b protrudes from the initial position, and the telescopic valve 12 extends so that the air intake port 1e
Is to be closed. When the third port 7c is turned on, the standard gas from the standard gas supply source 5 receives the main supply pipe 5a, the third port 7c, and the third auxiliary supply pipe 5d.
Is supplied to the third air cylinder 8c, and the rod 8d of the third air cylinder 8c projects from the initial position to close the second vent 1g by the valve 14.

The first, third and fourth ports 7a,
When 7c and 7d are turned off, the standard gas from the standard gas supply source 5 is not supplied to the first to third air cylinders 8a to 8c, the rod 8d automatically returns to the initial position, and the expansion valve 12 is returned to the original position. , The valve 14 is separated from the block 1, and the first and second vents 1a and 1g and the air intake 1e are opened.

FIG. 2 is a block diagram showing a control system of this embodiment.

This embodiment has a control unit 13 for controlling the entire apparatus. The control unit 13 includes the first to fifth ports 7a to 7e, the detection unit 23, the pump 60, and the He meter 64. And the CO meter 65 are connected to each other.

The control unit 13 controls the on / off control of the first to fifth ports 7a to 7e and the drive control of the pump 60, and outputs a detection signal from the detection unit 23,
He concentration measured value from e-meter 64 and CO meter 65
For example, based on the measured CO concentration, the lung diffusion capacity (DLCO) by the tidal breathing method is calculated. It should be noted that the lung diffusion ability may be obtained by a steady state method in which the carbon monoxide gas exchange is performed in a steady state.

Next, the operation of the present embodiment will be described with reference to FIGS. 1 and 3 to 6 and the flowchart of FIG. FIG. 1 is a view showing a state in which the first to third air cylinders 8a to 8c are not driven, FIGS. 3 and 6 are views showing a drive state of the second air cylinder 8b, and FIG. FIG. 5 shows a driving state of the second air cylinders 8a and 8b.
FIG. 5 is a diagram showing a driving state of first and third air cylinders 8a and 8c. The initial state is as shown in FIG.
The first port 7a is turned off and the first ventilation port 1a is in an open state. The third port 7c is turned off and the second ventilation port 1a is opened.
g is in an open state, the fourth port 7d is turned on, and the air intake port 1e is in a closed state.

First, the fifth port 7 e is turned on under the control of the control unit 13, and the sample bag 3 is turned on by the pump 60.
Suction the gas inside.

Next, the subject holds the mouthpiece 21 of the sensor 2 in his mouth and performs quiet ventilation (normal breathing) (S).
1). Inhalation and expiration of the subject in this quiet ventilation
As shown by the dashed line in FIG. 3, the first and second vents 1a,
Done through 1 g.

Next, the subject starts maximum calling. The exhalation at the maximum exhalation is performed through the first and second vents 1a and 1g as shown by the broken lines in FIG. When the operator operates a start switch (not shown) during the maximum call, the control unit 13 causes the first and second ports 7 to operate.
a, 7b are turned on. When the first port 7a is turned on, the standard gas from the standard gas supply source 5 passes through the main supply pipe 5a, the first port 7a, and the first auxiliary supply pipe 5b, as shown in FIG. The air is supplied to the first air cylinder 8a, the rod 8d of the first air cylinder 8a projects from the initial position, and the telescopic valve 12 extends to close the first ventilation port 1a. The exhalation at the maximum exhalation is performed through the second vent 1g as shown by the broken line in FIG.

Subsequently, the subject starts maximum inspiration. Since the second port 7b is turned on, when the subject performs the maximum inhalation operation, the demand valve 9 is opened in response to the operation, and the standard gas from the standard gas supply source 5 is turned on in FIG.
As shown by the broken line, the main supply pipe 5a, the second port 7
b, The second auxiliary supply pipe 5c, the demand valve 9, the one-way valve 10a and the ventilation pipe 20 of the sensor 2 are taken into the lungs of the subject (S2). At this time, the detecting unit 23
The differential pressure across the laminar flow tube 22 is detected, and a detection signal is sent to the control unit 13.

Next, after the subject holds his / her breath for 10 seconds (S3), the subject starts the maximum exhalation operation (S4, S5, S).
6). At the same time, the control unit 13 turns off the first port 7a. When the first port 7a is turned off, as shown in FIG. 3, the standard gas from the standard gas supply source 5 is not supplied to the first air cylinder 8a, and the rod 8d automatically returns to the initial position. Then, the telescopic valve 12 contracts to its original state, and the first vent 1a is opened. For example, 0.5 liter of the first exhaled gas of the subject is exhausted to the atmosphere through the first and second vents 1a and 1g (S4).

Next, as shown in FIG. 5, the control unit 13
The first port 7a is turned on to close the first vent 1a, and the third port 7c is turned on to activate the second vent 1a.
g is closed, the fourth port 7d is turned off, and the air intake port 1e is opened. The breath (1 liter) of the subject is taken into the sample bag 3 as shown by the broken line in FIG.
5).

Subsequently, the control unit 13 performs, as shown in FIG.
The first and third ports 7a and 7c are turned off again to open the first and second vents 1a and 1g, and the fourth port 7d is turned on to drive the second air cylinder 8b to collect air. Mouth 1e
Is closed to allow the remaining exhaled gas to flow through the first and second vents 1a,
Exhaust to the atmosphere through 1 g (S6). Note that the amount of gas discharged in step S4 and the amount of gas collected in step S5 are controlled by the control unit 13 based on a detection signal from the detection unit 23.

When the exhaled gas of the subject is collected in the sample bag 3 in this way, the control unit 13 controls each unit to obtain the expiratory lung diffusion capacity (DLCO) (S7).
That is, in the state of FIG. 6, the control unit 13 turns on the fifth port 7e to drive the pump 60, and the exhaled gas collected in the sample bag 3 passes through the suction pipe 61 to the fifth port 7e. , A first filter 62 and a second filter 63 to a He meter 64 and a CO meter 65. The He meter 64 measures the concentration of helium (He) in the collected breath gas, sends the measured value of the He concentration to the control unit 13, and the CO meter 65 sets the carbon monoxide ( The CO concentration is measured, and the measured CO concentration value is sent to the control unit 13. The control unit 13 includes a detection unit 23
On the basis of the detection signal from the sensor, the measured He concentration from the He meter 64, the measured CO concentration from the CO meter 65, and the previously measured respective He and CO concentrations of the supplied standard gas. The capability (DLCO) is obtained by calculation. The gas that has passed through the He meter 64 and the CO meter 65 passes through the inside of the pump 60 and is exhausted from the exhaust port 60a.

After the lung diffusion ability is determined in this way, the area where saliva or the like in the expired air may have been sprayed is washed or disinfected to prevent infection of the subject. The range includes the breathing circuit 1h formed in the block 1, the inside of the ventilation pipe 22 of the sensor 2, the inside and outside of the mouthpiece 21, the inside of the sample bag 3, the outside of the two telescopic valves 12, the one-way valves 10a, 10
b and the inside of the suction tube 61.

First, the clamp 1 is loosened to remove the block 1 and the expansion / contraction valve 12 from the substrate 4, the sensor 2 is pulled out from the sensor mounting port 1c, and the connector 3a is loosened to remove the air sampling port 1e.
, The one-way valves 10 a and 10 b and the suction pipe 61 are removed from the block 1.

Next, the breathing circuit 1h in the block 1, the removed sensor 2, the sample bag 3, the one-way valve 10a,
10b, telescopic valve 12, mouthpiece 21, and suction pipe 61
Are each cleaned or disinfected and then assembled again as shown in FIG.

As described above, according to the present embodiment, the following effects can be obtained.

(1) The lung diffusion ability, which is a basic lung function of a subject, can be measured.

(2) A breathing circuit 1h is formed in the block 1, the first ventilation port 1a is opened and closed by a first air cylinder 8b via an expansion valve 12, and the air intake port 1e is opened via an expansion valve 12. Since the second air cylinder 8b is opened and closed and the second ventilation port 1g is opened and closed by the third air cylinder 8c, an electromagnetic valve is provided in the breathing circuit 1h in which saliva or the like in exhaled air may splash. Need not be placed.

Therefore, the ventilation pipe 20, the sample bag 3, the expansion valve 12 and the like of the sensor 2 can be removed from the breathing circuit 1h to easily clean the breathing circuit mechanism in a range where saliva or the like may be splashed. Thus, it is possible to prevent infection of other subjects by pathogenic bacteria contained in saliva and sputum droplets in breath.

(3) The elongated first to third air cylinders 8a to 8c are arranged in parallel, and each of the air cylinders 8a to 8c
c and the first and second vents 1a, 1g,
Since the air intake port 1e is provided, the first to third air cylinders 8a to 8c can be arranged in a narrow space, and a respiratory circuit 1h with a small dead space can be formed. High measurements can be made.

Since the standard gas from the standard gas supply source 5 is also used as a drive source for the first to third air cylinders 8a to 8c, a drive source dedicated to each of the air cylinders 8a, 8b, 8c is omitted. can do.

Therefore, each of the air cylinders 8a, 8b, 8c
Drive parts (ports 7a, 7c, 7d, auxiliary supply pipe 5)
b, 5d, 5e, etc.) can also be arranged in an extremely space-saving manner, so that the entire respiratory circuit mechanism can be extremely compactly realized, and the apparatus can be downsized.

(4) Since the second vent 1g is provided in addition to the first vent 1a, by opening the second vent 1g after starting the maximum call, the maximum intake from the maximum call can be obtained. The opening and closing of the vents need not be performed in synchronization with the timing of, so that the opening and closing control of the vents becomes easy.

In this embodiment, the case where the lung diffusing ability is measured has been described. However, it is also possible to adopt a configuration in which N ₂ washing out and other items of the lung function are also measured. For example, when measuring N ₂ washout, first, the air intake port 1e is kept closed, and quiet ventilation with the atmosphere is performed. When the measurement is started, the first ventilation port 1a is closed, and the quiet ventilation is continued as it is. . O ₂ gas is inhaled from the gas supply port 1d during inhalation,
Expiration is discharged from the second vent 1g to the atmosphere through the one-way valve 10b. An N ₂ meter for detecting the concentration of N _{2 in} the gas taken in from the breathing circuit 1h of the block 1 is added,
Measurement data of N ₂ washout can be obtained from the measurement data of the flow rate or flow rate of the respiratory gas by the sensor 2 and the N ₂ concentration data in the exhalation.

In this embodiment, the sensor 2 for detecting the flow rate of the respiratory gas is used, but a sensor for directly detecting the flow rate of the respiratory gas flowing through the ventilation pipe may be used.

In this embodiment, the second vent 1g dedicated to exhalation is provided, but exhalation and inhalation may be performed only through the first vent 1 without providing the second vent. Second vent 1 without one-way valve 10b without providing vent 1
Expiration and inspiration may be performed only with g. Also,
The first vent 1a may be provided with a one-way valve for inhaling the atmosphere to be exclusively used for the inhalation. In this case, if it is necessary to call the atmosphere, it is necessary to open the second vent 1g. Alternatively, the first vent 1a may be dedicated to exhalation, and the second vent 1g may be dedicated to inhalation.

[0054]

According to the present invention described in detail above, the following effects can be obtained.

According to the first aspect of the present invention, the lung diffusion ability, which is a basic lung function of the subject, can be measured, and a respiratory circuit is formed in the block, and the first respiratory circuit is provided in the respiratory circuit. Is opened and closed by the first opening / closing means which can be attached and detached, and the air intake port provided in the breathing circuit is opened / closed by the second opening / closing means, so that saliva and the like during expiration may be splashed. There is no need to place an electromagnetic valve in the breathing circuit. For this reason, the ventilation pipe, mixed gas supply pipe, sample bag, first opening / closing means, and second opening / closing means of the sensor are removed from the breathing circuit to clean the breathing circuit mechanism in a range where saliva or the like may splash. It can be done easily.

According to the second aspect of the present invention, it is not necessary to open and close the vent in synchronization with the timing of the intake of the mixed gas, so that the opening and closing of the vent can be easily controlled.

According to the third aspect of the present invention, since the drive source of the opening / closing means can be omitted, the breathing circuit mechanism can be made compact, and the apparatus can be downsized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of the present embodiment.

FIG. 2 is a block diagram showing a control system according to the embodiment.

FIG. 3 is a diagram for explaining the operation of the present embodiment.

FIG. 4 is a diagram for explaining the operation of the present embodiment.

FIG. 5 is a diagram for explaining the operation of the present embodiment.

FIG. 6 is a diagram for explaining the operation of the present embodiment.

FIG. 7 is a flowchart showing the operation of the present embodiment.

[Explanation of symbols]

 1 block 1a first vent 1g second vent 1e air intake 1h breathing circuit 2 sensor 3 sample bag 5c second auxiliary supply pipe (mixed gas supply pipe) 8a first air cylinder (first open / close Means) 8b Second air cylinder (second opening / closing means) 8c Third air cylinder (third opening / closing means) 10a, 10b One-way valve 12 Telescopic valve 20 Ventilation pipe 23 Detector

Claims (3)

(57) [Claims] 1. A pulmonary function measuring apparatus for measuring a lung diffusing capacity of a respiratory function of a subject using a mixed gas containing a low concentration of carbon monoxide, wherein a respiratory circuit serving as a path of respiratory air is formed. A ventilator pipe having one end detachably connected to the breathing circuit and the other end connected to the airway of the subject, and a sensor for detecting a flow rate or a flow rate of the breathing air flowing through the breathing pipe; A gas mixture pipe removably connected to the air supply port via a one-way valve; a sample bag removably connected to a gas inlet provided in the breathing circuit; and a first gas communicating with the atmosphere provided in the breathing circuit. A lung function measurement device comprising: a respiratory circuit mechanism having detachable first opening / closing means for opening / closing a ventilation port of the apparatus, and detachable second opening / closing means for opening / closing the air intake port. 2. The breathing circuit mechanism according to claim 1, wherein the breathing circuit includes a second vent for exclusive use of exhalation communicating with the atmosphere through a one-way valve, and a detachable third vent for opening and closing the second vent. The lung function measuring device according to claim 1, further comprising an opening / closing means. 3. The lung function measuring apparatus according to claim 1, wherein the opening / closing means uses the mixed gas as a driving source.