JPH0152017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a residual air amount measuring device during artificial respiration, which is capable of measuring the residual air amount of a subject during artificial respiration.

The amount of gas in the lungs held at the calm expiratory position is the maximum inspiratory volume that can be inhaled from the calm inspiratory position, and the amount of air remaining in the lungs after exhaling as much air as possible. Functional residual capacity (FRC), which is expressed as the sum of a certain residual capacity, is important in knowing the standard of human respiratory function.

For example, when a patient is anesthetized during surgery, the patient's organs relax, and muscle relaxation also occurs in the organs surrounding the lungs, such as the stomach and intestines. This causes the lungs themselves to relax, reducing the amount of gas in the lungs and reducing functional residual capacity (FRC). When the functional residual capacity (FRC) decreases, the gas exchange function of the lungs becomes insufficient, and oxygen is not sufficiently supplied to the body.

Therefore, during surgery under anesthesia, if the patient's functional residual capacity (FRC) decreases below a predetermined value, the pressure of the gas delivered into the patient's lungs is increased to increase the so-called peep pressure. It is necessary to force gas into the relaxed lung cells by applying Conventional devices cannot apply peep pressure to the subject's lungs while measuring functional residual capacity (FRC), and when used in conjunction with a ventilator, switching operations are required, making handling inconvenient. It was hot.

In view of the above-mentioned current situation, this invention measures the functional residual capacity (FRC) of a subject by easily switching from the state in which the artificial respirator is attached to the measurement state, and also measures the peep pressure during the measurement. The present invention provides a residual air amount measuring device that can apply a residual air amount.

In this invention, a balloon container is attached in communication with an inlet to which exhaled air from a respirator is given,
A balloon is accommodated in this balloon container. On the other hand, a connection port connected to the oral cavity of the subject is provided, and a switching valve is attached to switch between connection between the connection port and the inlet and connection between the connection port and the inside of the balloon.
A suction pipe and a discharge pipe are inserted into the balloon, and a thermal conductivity helium sensor is disposed within the flow path of the suction pipe and discharge pipe to measure the helium gas concentration within the balloon. Further, there is provided means for compensating for variations in the detected value of the helium sensor by changing the atmospheric pressure of the thermal conductivity helium sensor in response to the peep pressure applied to the exhaled air supplied to the connection port.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The apparatus for measuring residual air during artificial respiration according to the present invention will be described in detail below based on embodiments thereof, with reference to the drawings.

A connecting port 1 in which a balloon container 11 containing a balloon 14 is communicated with an inlet 12 through which exhaled air from the artificial respirator A is given, and connected to the oral cavity of the subject.
7 and the inlet 12, and a three-way switching valve 19 that switches between the connection between the connection port 17 and the balloon 14;
is provided.

That is, a balloon container 11 made of, for example, a synthetic resin material and having a substantially square cylindrical shape is provided, and a communication port 13 is formed in one end surface of the balloon container 11.
A pressurizing port 20 is formed on one side of the balloon container 11 . The volume of this balloon container 11 is approximately 2
is formed. A balloon 14 made of, for example, rubber and having a volume of 1.5 is disposed within the balloon container 11 so that its inside communicates with the communication port 13. The edge of the communication port 13 of the balloon container 11 is bent toward the balloon container 11, and the balloon 14
An opening 15 is attached around the bent portion of the communication port 13 by means not shown and fixed around the bent portion.

A flow tube 16 is connected to the communication port 13 of this balloon container 11.
is connected. An inlet 12 is provided near one end of this flow tube 16, and the end on the inlet 12 side is used to switch the exhaled air from the respirator A or the measurement gas in the balloon 14 to the oral cavity side of the subject. connection port 17
It is said that A switching valve 19 is installed to perform this switching using the inlet 12, the connecting port 17, and the flow tube 16 as respective flow paths. Connection port 17
The flow tube 16 is attached to the oral cavity of the subject.
It has a structure in which a mouthpiece 10 that connects the mouthpiece and the lungs of the subject can be connected. A metering cylinder 21 is attached to the other end of the flow tube 16, and a vacuum manometer 22 is connected to the flow tube 16 near the metering cylinder 21.

Between the vacuum manometer 22 and the communication port 13, the flow tube 16 is branched via a three-way switching valve 23, and a flow tube 24 is provided. The end of the flow tube 24 is connected to a measuring gas balloon 25, and a measuring gas inlet 26 is provided near this end. A cylinder 27 filled with a mixed measuring gas of 15% He and 85% O ₂ used for ventilation of the subject is connected to the measuring gas intake port 26 . valve 23
A three-way switching valve 28 is attached to the flow tube 24 between the gas intake port 26 and the measurement gas intake port 26, and a discharge port 29 is provided in the flow tube 24 at the position where the valve 28 is attached.

A thermal conductivity helium sensor is provided to measure the concentration of He gas within the balloon via an inlet tube and an outlet tube inserted into the balloon.

That is, an inlet pipe 30 and an outlet pipe 31 are provided in the balloon 14.
The ends of each are fixedly disposed by means not shown. The suction pipe 30, the end of which is located inside the balloon 14, is led out from the balloon 14 and connected to an analysis cell 33-1 of a helium analyzer 33 through a soda lime pipe 32 filled with soda lime. This helium analyzer 33 is disposed within a container 35, and this container 35 is communicated with the balloon container 11 through a connecting pipe 36. It is desirable to make the diameter of the soda lime pipe as large as possible to minimize the frequency of replacement. Soda lime pipe 3 of suction pipe 30
2 and the analysis cell 33-1 of the helium analyzer 33, a pump 34 for gas circulation is installed. The discharge pipe 31 is configured to directly connect the balloon 14 and the analysis cell 33-1 of the helium analyzer 33. The inner diameter of these suction pipes 30 and discharge pipes 31 is 0.5 to 1 mm in order to reduce the dead space and maintain a high gas flow velocity.
It is set to a certain degree.

As the helium sensor used in the helium analyzer 33, for example, a thermal conductivity helium sensor is used. As shown in Figure 4, this is a structure in which a platinum wire is heated to form one arm of the Wheatstone bridge, and the gas to be detected is flowed against it at a constant speed. Various gases have different specific heat conductivities, so by flowing the test gas, the temperature of the platinum wire changes and its resistance value changes. By detecting this change in resistance value at the Wheatstone Bridge,
It is possible to measure the concentration of He gas.

Means is provided for compensating for variations in the detected value of the helium sensor depending on the peep pressure applied to the exhaled air supplied to the connection port.

That is, the ventilator A is attached so that the pressurizing port 20 of the balloon container 11 communicates with the ventilator 18 of the ventilator A.
8 is also connected to the inlet 12 of the flow tube 16. Further, in this installed state, the ventilator 18 of the respirator A is connected to the container 35 in which the helium analyzer 33 is disposed through the connecting pipe 36, and the circulation path of the comparison cell 33-2 of the analyzer 33 is connected. A balloon 33-3 is provided in communication with the balloon 33-3. A gas circulation pump 34-4 is attached to this circulation path. Therefore, when the ventilator 18 is driven and the pressure inside the balloon container 11 changes, the pressure change is transmitted to the container 35 through the connecting pipe 36 and the pressure inside the balloon 33-3 also changes, so that the ventilator 18 is always driven. The He concentration will be measured by the helium analyzer 33 under the pressure conditions set by .

The operation of the residual air amount measuring device of the present invention having such a configuration will be explained in order below. First switching valve 19
By switching , the inlet 12 of the flow tube 16 and the respirator A are brought into communication. In this state, the mouthpiece 10 is attached to the oral cavity of the anesthetized subject, the switching valve 19 is switched, and the oral cavity of the subject is communicated with the respirator A via the connecting port 17. The ventilator 18 is actuated to forcibly feed breathing gas, which is a mixture of oxygen gas and air, into the lungs of the subject to perform artificial respiration.

By switching the valve 23, the flow pipe 16 and the measuring cylinder 21
The operation piece 37 of the metering cylinder 21 is pulled in a state in which the gases are in communication with each other, and the residual gas in the balloon 14 and the flow tube 16 is sucked into the metering cylinder 21. Next, the valve 28 is switched to communicate the flow tube 24 and the exhaust port 29, and the valve 23 is switched to communicate the metering cylinder 21 with the flow tube 24, so that the residual gas sucked into the metering cylinder 21 is discharged to the outside through the exhaust port 29. Exhaust. The valves 23 and 28 are switched as necessary to repeatedly evacuate the inside of the balloon 14. Vacuum manometer 22
After confirming that the degree of vacuum within the balloon 14 and flow tube 16 has reached a predetermined value, evacuation is stopped.

By switching the valve 23, the flow pipe 24 and the measuring cylinder 21
The measurement gas balloon 25 and the flow tube 24 are brought into communication by switching the valve 28. When the measurement gas in the measurement gas balloon 25 is insufficient, it is possible to take the required amount of measurement gas into the measurement gas balloon 25 from the cylinder 27 by operating a pot (not shown). Measuring cylinder 21
is operated to measure and suck a predetermined amount of gas for measurement into the measuring cylinder 21. Next, the valve 23 is switched to bring the flow pipe 16 and the metering cylinder 21 into communication, and the operation piece 37 of the metering cylinder 21 is pushed in to send the measured gas in the metering cylinder 21 into the balloon 14 . Measuring gas balloon 14
When the supply to the inside is completed, the valve 23 is switched to close the end of the flow pipe 16 on the valve 23 side.

In this state, the balloon 14, the suction pipe 30, the discharge pipe 31, and the flow pipe 16 form a closed space system, into which a predetermined amount of measurement gas is supplied. In this state, confirm that the indicated value of the He concentration on the He analyzer 33 is stable, and use the adjustment knob (not shown) to adjust this state to 100 on the scale of the He concentration indicator.
Set to . This state is schematically shown in Figure 2. If the volume of the balloon 14 is 1.5 and the dead space consisting of the flow pipe 16, suction pipe 30, discharge pipe 31, etc. is DS, then the amount of He in the system is is expressed by the following formula.

(1.5 + DS) × 100 ... (1) However, × 100 is the initial setting of He15 in balloon 14.
%, initial He analysis value of _O2 85% mixed gas, i.e.
15% He is set as 100 on the meter reading of the He analyzer 33.

Next, switch the switching valve 19 to connect the connecting port 17 and the flow pipe 1.
6 is brought into communication with the inside of the balloon 14 and the lungs of the subject via the mouthpiece 10. The subject continues to breathe using the measurement gas in the balloon 14. He contained in the measurement gas is not absorbed into the blood even if it reaches the alveoli of the subject, so it diffuses into the lungs L of the subject and reaches a constant concentration after a few minutes. When the He concentration reaches equilibrium, the state will be as shown in Figure 3, and the functional residual air amount will be corrected to FRC and ATPS (referring to the state of temperature, pressure, and water vapor saturation at the time of measurement with the measuring instrument system). If the coefficient is BTPS, the amount of CO ₂ adsorbed by soda lime is ΔVS, and the He concentration at equilibrium is x, the amount of He in the system is expressed by the following equation.

(1.5 + DS + FRC / BTPS - △VS) ×x ... (2) However, ×x is the indicated value of the indicator of the He analyzer 33, where the initial setting value of He (15%) is set as 100 on the meter indication.

Since the amount of He in the system expressed by equations (1) and (2) is equal, connect both equations with an equal sign and set 1.5+D・S=M (3)
The formula is obtained.

FRC=(100M/x-M+△VS)BTPS...(3) BTPS is a correction coefficient based on the difference between the temperature inside the subject's body and the temperature inside the balloon, and is corrected under the conditions of 37℃ and 1 atm. It is. After measuring He concentration, selector valve 1
9 to cut off the connection between the subject's oral cavity and the inside of the balloon 14, and connect the subject's oral cavity to the respirator A via the inlet 12. In this state, the subject returns to the state where the artificial respirator A is attached and artificial respiration is performed. Then, the valve 23 is switched to open the flow pipe 16.
is connected to the measuring cylinder 21. Measuring cylinder 2
The exhaust gas in the balloon 14 is sucked into the measuring cylinder 21 by pulling the operating piece 37 of No. 1, and the amount of gas is measured. The difference between the amount of measurement gas initially sent into the balloon 14 and the amount of gas measured by the measuring cylinder 21 after measuring the He concentration is the CO ₂ adsorbed by the soda lime.
The amount of is △VS. Since M is given by the volume of the measurement system and ΔVS is given by the measured value, FRC can be found from equation (3) when the He concentration is measured.
If the subject's expiratory reserve volume (ERV) is measured in advance using spirometry, the residual volume can be determined as functional residual capacity (FRC) - expiratory reserve volume (ERV).

In this invention, with peep pressure applied
Helium concentration can be measured. Application of this peep pressure is performed by driving the ventilator 18 of the respirator A. When the He concentration is being measured, the ventilator 18 is driven and the balloon container 11 is
At the same time, the same peep pressure P is applied to the container 35 of the helium analyzer 33, and as shown in FIG. 5, the volume of the balloon 14 is reduced by ΔV as shown in FIG. Assuming that the amount of CO ₂ adsorbed by soda lime is △V′S, the atmospheric pressure is P ₀ , and the He concentration with peep pressure P applied is x _p (%), the amount of He in the system is as follows. It is expressed by the formula.

(1.5+DS−△V+FRC/BTPS−△V′S)×x _p ……(4) In equation (4), △V=(1.5+DS)×P/P ₀ +P, △V′S= P ₀ /P Since ₀ +P×△VS, using this and connecting equations (1) and (4) with an equal sign, the following equation can be obtained.

FRC=(100/x _p M−M+P/P ₀ +P・M +P ₀ /P ₀ +P・△V′S) BTPS ……(5) In other words, He concentration X _p with peep pressure P applied
By measuring , the functional residual capacity (FRC) can be calculated from equation (5).

When the pressure inside the balloon container 11 increases by applying the peep pressure P, this pressure is supplied to the container 35 through the connecting pipe 36, so that the comparison cell 33-2
The internal pressure of balloon 33-3 also increases and helium analyzer 3
3 operates under increased pressure conditions. In other words, by reciprocating the ventilator 18, the balloon 14-
As pressure changes due to pressurization and depressurization in the lungs, the internal pressure of the analysis cell 33-1 fluctuates, but at the same time the internal pressure of the comparison cell 33-2 of the helium analyzer 33 changes as well.
It varies depending on the pressure of the ventilator 18 applied to 3-3. Therefore, fluctuations occurring in the detected value of the helium sensor 33 in response to the peep pressure P are always compensated for.

Although not explicitly shown in the embodiments, it is desirable for hygiene reasons to attach a sterilization filter to the mouthpiece 10 portion. Further, a part of the balloon container 11 can be made transparent so that the balloon 14 stored therein can be monitored from the outside. In addition, when the valve is operated manually, it may be structured so that it can be easily rotated, so that the switching state can be clearly understood by the sound and feel of switching manually.

As explained in detail above, according to the present invention, it is possible to measure the functional residual capacity (FRC) while applying peep pressure, and the variation in the detected value of the He sensor due to the application of peep pressure is always compensated for. It is possible to provide a device for measuring residual air during artificial respiration, which is capable of measuring the amount of residual air in a state of

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2 and 3 are diagrams showing the principle of measuring the residual air amount without applying peep pressure, and FIG.
FIG. 5 is a diagram showing the principle of the He concentration meter, and is a diagram showing the principle of measuring the amount of residual air when peep pressure is applied. 11: Balloon container, 12: Inflow port, 13: Communication port, 14: Balloon, 16: Flow pipe, 17: Connection port, 18: Ventilator, 19: Switching valve, 21:
Measuring cylinder, 23, 28: valve, 30: suction pipe,
31: Discharge pipe, 33: Helium analyzer, 33-
1: Analysis cell, 33-2: Comparison cell, 33-3:
Balloon, 35: Container, 36: Connecting pipe.

Claims (1)

[Scope of Claims] 1. A measurement device that measures the functional residual capacity of a subject by easily switching from a state in which a respirator A is attached to a measurement state, comprising: A balloon container 11 communicating with the inlet 12, and a first balloon 14 accommodated in the container 11.
a connection port 17 connected to the oral cavity of the subject; a switching valve 19 that switches between connection between the connection port 17 and the inlet 12 and connection between the connection port 17 and the inside of the first balloon 14; , a suction pipe 30 inserted into the first balloon 14
The helium gas in the first balloon 14 is supplied to the analysis cell 33-1 via the discharge pipe 31 and the thermal conductivity helium sensor 33 measures its concentration, and the circulation path of the comparison cell 33-2 of the helium sensor 33. a second balloon 33-3 communicating with the helium sensor 33 and a container 35 containing the second balloon 33-3; a container 35 communicating with the container 35 and the balloon container 11 and a ventilator of the respirator A; 18, and a peep pressure is applied within the container 35 and the balloon container 11 by the ventilator 18 of the artificial respirator A. Residual air measurement device.