JPH0558336B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ventilation/blood flow ratio distribution measuring device for measuring the lung function of a subject.

[Conventional technology]

Although humans are not the only subjects to be tested, it is important to measure lung function, especially in patients with lung disease, to obtain the ventilation/perfusion ratio distribution, which is essentially related to the gas exchange function of the lungs. In other words, many lung diseases are accompanied by the progression of unevenness in the ventilation/blood flow ratio distribution.
Measurement of blood flow ratio distribution provides extremely meaningful information for evaluation of lung function and clinical diagnosis of lung diseases.

Vol. 36, No. 5, published in October 1988 of "Mass Spectrometry", the journal of the Mass Spectrometry Society
No. 5, CCtober 1988), as introduced on page 204 of the inventor's paper, conventional ventilation and
It is stated that many studies have been conducted and several methods have been proposed regarding the measurement of blood flow ratio distribution.

Among them, the most representative one is Lenfant.
Okubo's _N2 washout method with pure _O2 , with Wagner
One example is the washing-out method using six types of inert gases by West et al. The former is based on time-series data of _N2 exhaled volume and _O2 arterial blood partial pressure measured during N2 washout due to pure _O2 respiration, and the distribution of lung volume, lung ventilation, and pulmonary blood flow is calculated as a function of the alveolar washout time constant _. This is a method to determine the ventilation/blood flow ratio distribution in the form of their correlation.The latter is a method that determines the ventilation/blood flow ratio distribution from the arterial blood, venous blood, and alveolar partial pressure when washing out six types of inert gases with different solubility. This is a method that directly analyzes the ventilation/blood flow ratio distribution in the lungs. However, as pointed out in some literature, the former has significant physiological changes in the ventilation/blood flow ratio distribution and problems with resolution when breathing pure O ₂ , and the latter has problems with resolution. There are still problems to be solved before each can be applied clinically, such as the uniqueness of the mathematical solution and considerable operational complexity. Moreover, these methods are open and invasive methods that involve the simultaneous collection of arterial blood or mixed arterial and venous blood.

On the other hand, many studies have been conducted on the measurement of pulmonary blood flow and ventilation/blood flow ratio using inert gas. The frequency response of Zwart et al.
response) is one of them. This method is
Based on the human body's anesthetic gas uptake dynamics model proposed by Mapleson, by breathing halothane gas whose concentration changes sinusoidally above a certain frequency, the effects of recirculation are eliminated, and ventilation and This is a method of measuring blood flow ratio.
Brovko, Wiberg et al. and Akman and Roy et al. further developed several algorithms to develop this method into a long-term on-line measurement of pulmonary blood flow. However, these methods measure only the overall ventilation/perfusion ratio or pulmonary blood flow, and are not methods for measuring the ventilation/perfusion ratio distribution itself.

[Problem to be solved by the invention]

The conventional methods for measuring ventilation/blood flow ratio distribution described above do not cause significant physiological changes in the subject during measurement, are invasive as they require blood sampling, and are difficult to measure due to frequency response. also simply overall
This method has the disadvantage that it can only measure the ventilation/blood flow ratio or pulmonary blood flow, but cannot measure the ventilation/blood flow ratio distribution itself.

[Purpose of the invention]

In view of the above drawbacks, the present inventor developed a multiple compartment model (multiple compartment model).
compartment model), multiple
compartment transfer function (multiple compartment
We have devised a new method (hereinafter referred to as MCTF method) for measuring ventilation/blood flow ratio distribution by incorporating the concept of transfer functon (hereinafter referred to as MCTF). In other words, a lung transfer function is obtained from a multiple compartment model of the lungs that is segmented by differences in inert gas washout time constants, and a group of equations is derived from the frequency characteristics of this transfer function. While a subject inhales halothane gas whose concentration changes sinusoidally, the frequency of the sine wave is varied to continuously measure changes in the halothane concentration in the inhaled and exhaled air. Through this measurement, the frequency response of the lungs is determined, the above equations are solved, and the ventilation/blood flow ratio distribution is calculated. Based on this fact, an object of the present invention is to provide a ventilation/blood flow ratio distribution measuring device that can efficiently and accurately measure ventilation/blood flow ratio distribution without the drawbacks pointed out in conventional methods. shall be.

[Means to solve the problem]

The ventilation/blood flow ratio distribution measuring device of the present invention calculates a transfer function between exhalation and inhalation of changes in index gas concentration in a model of the subject's lungs that is fractionated based on differences in inert gas washout time constants, Ventilation of the subject's lungs
This is a ventilation/blood flow ratio distribution measurement device that measures the blood flow ratio distribution, and the ventilation/blood flow ratio distribution measuring device changes according to a sinusoidal signal given to the breathing air conduit that guides the subject's inhalation and exhalation, and the concentration of an indicator gas contained in the air. an inspiratory air generation means for generating inspiratory air; when the subject is inhaling, the inspiratory air is supplied to the subject through a respiratory conduit; and when the subject is exhaling, exhaled air from the respiratory conduit is supplied to the subject through an exhaust device; a flow rate detection means for detecting the flow rate of gas flowing through the respiratory air conduit, an analyzer for detecting the composition ratio between gas components contained in the gas in the respiratory air conduit, and an inspiratory air generation means. and a data processing device that calculates the ventilation/blood flow ratio distribution of the subject from the detection results of the flow rate detection means and the analysis device.

Furthermore, the ventilation/blood flow ratio distribution measuring device of the present invention includes:
In a model of the subject's lungs that is fractionated based on the difference in inert gas washout time constant, the transfer function between expiration and inspiration of the change in the index gas concentration is determined, and the ventilation/blood flow ratio distribution in the subject's lungs is determined. It is a ventilation/blood flow ratio distribution measuring device, which includes a flow controller that takes in air compressed by a compressor and flows out a flow rate corresponding to the applied control signal, and a flow controller that takes in air compressed by a compressor and flows out the air at a flow rate corresponding to the applied control signal, and a flow controller that takes in air that has been compressed by a compressor and flows out the air at a flow rate corresponding to the applied control signal. A reservoir containing a test liquid that is a source of an inert test indicator gas that, when dissolved in arterial blood, distributes more to the tissues than to the blood, and an air flow exiting the flow controller. An inlet pipe leading into the test liquid in the storage tank, a main gas pipe, and a gas flow mainly composed of air taken in from one upstream end of the main gas pipe to the other downstream end. A gas flow generator is used to conduct a gas flow, and an air flow introduced into the storage tank by an inlet pipe leads to a gas discharged from the storage tank containing the vapor of the test liquid as an indicator gas. a gas supply conduit connected at one end to the main gas conduit for introducing the gas flow from the main gas conduit; and a respiratory conduit connected at one end to the respiratory tract of the subject. An air conduit, an exhaust conduit whose one end is connected to an exhaust device, and the other ends of each of a gas supply conduit, a breathing air conduit, and an exhaust conduit are connected, and when the subject inhales, the gas in the gas supply conduit is transferred to the breathing air conduit. a valve mechanism for exhausting the gas in the respiratory conduit through the exhaust conduit when the subject exhales; a flow rate detection means for detecting the flow rate of gas flowing in the respiratory conduit; An analyzer detects the composition ratio between gas components contained in the gas, and a sine wave signal is applied as a control signal to the flow controller, thereby determining the amount of gas contained in the gas flow in the main gas conduit in response to the applied control signal. While changing the concentration of the indicator gas in a sinusoidal manner,
It has a data processing device that calculates the ventilation/blood flow ratio distribution of the subject from the detection results of the flow rate detection means and the analysis device. Preferably, the control signal applied to the flow controller by the data processing device is composed of a superimposed signal series whose frequency changes over time, and each superimposed signal making up the series is composed of a plurality of sine wave signals having different frequencies. Composed of superimposed images.

[Effect]

First, to describe the principle of the present invention, in a single compartment model of the lung, when breathing inert gas, the gas dynamics of inhalation, expiration, intrapulmonary and internal circulation, including recirculation, are coupled as follows according to the law of conservation of mass. It can be expressed as a linear differential equation.

(λ _b・V _b +λ _L・V _L +V _A )・P〓 _A (t)=V _A・[P _I (t)
−P _A (t)〕+ _M 〓 ^j=1 λ _b・Q〓 _j [P _j (t)−P _A (t)] ……(1a) (λ _b・V _bj +λ _j・V _j )・P〓 _j (t) = λ _b・Q〓 _j・[P _A (t)−P _j (t)] ……(1b) Here, P _A (t), P _I (t), P _j (t ): alveolar partial pressure of inert gas, inspiratory partial pressure, partial pressure in body tissue compartment j λ _b ,
λ _L , λ _j : Blood solubility of inert gas, lung tissue solubility, solubility of body tissue compartment j Q〓 _j : Blood flow of body tissue compartment j Σ ^M _j=1 Q〓 _j : Sum of blood flow of each tissue compartment , pulmonary blood flow Q〓 V〓 equal to _{c A} : Lung ventilation V _A , V _L , V _b : Alveolar capacity, lung tissue volume, pulmonary blood volume V _j : Volume of body tissue compartment j V _bj : Body tissue compartment Since Equation (1) is linear, the lung frequency transfer function G is determined by the Fourier transform P _A (jω) and P _I (jω) of P _A (t) and P _I (t). (jω)=P _A (jω)/P _I (jω) is obtained. If we take halothane, which has a large tissue-to-blood partition function, as an inert gas, change the gas concentration in a sinusoidal manner, and change the sinusoidal period to 5.
If taken within minutes, the effect of recirculation can be almost ignored. Therefore, single compartment
The model transfer function G _S (jω) is expressed by the following equation.

G _S (jω) = P _A (jω) / P _I (jω) = (1 + λ _b・Q〓 _c /V〓 _A −jωτ _L ) / [(1 + λ _b・Q〓 _c /V〓 _A ) ² +ω ² τ _L ² ] ...(2) Here, ω: Each frequency of the inhaled gas concentration sine wave τ _L : Alveolar ventilation time constant, which is expressed by the following equation.

τ _L = (λ _b・V _b + λ _L・V _L + V _A )/V〓 _A …(3) If we replace C _A = λ _b・V _b + λ _L・V _L + V _A , the formula becomes
(2) is equivalent to the transfer function of the electric circuit shown in Figure 4a.

Next, we will consider extension to the multiple compartment model. lungs with multiple different time constants
The following physiological assumptions are required to represent the multiple compartment model.

(1) Each compartment has a parallel relationship with each other and is independent.

(2) The index inert gas alveolar partial pressure in each compartment is equal to the pulmonary capillary blood partial pressure.

(3) The ventilation/blood flow ratio distribution remains unchanged during the measurement.

(4) The amount of lung tissue in each compartment is applicable.
It is proportional to the lung volume of the compartment.

From the above assumptions, the single
The compartment model is shown in Figure 7b.
Can be extended to compartment model.
In this model, it is assumed that the lung is composed of N compartments each having a sinusoidal amplitude P _Ai of alveolar partial pressure, a blood flow Q〓 _Ci , a ventilation V〓 _Ai , and a time constant τ _Li .

From equation (2), each
The Fourier transform ratio P _Ai /P I (jω) of the index gas partial pressure P Ai (t) in the compartment and the intake gas partial pressure P _I (t) is _{P Ai / P I (} jω) = (1+λ _b・Q 〓 _Ci /V〓 _Ai −jωτ _Li ) / [(1+λ _b ·Q〓 _Ci /V〓 _Ai ) ² +ω ² τ _Li ² ] i=1, 2, ~, N (4). Furthermore, from the parallel relationship of each compartment, P _A = Σ ^N _i=1 P _Ai・V〓 _Ai ／V〓 _A = Σ ^N _i=1 P _Ai・v〓 _Ai (5) Here, V〓 _A is the lung This is the amount of ventilation throughout the cell. Also
v〓 _Ai is the ventilation distribution and satisfies the following formula.

Σ ^N _i=1 v〓 _Ai = 1 From equations (4) and (5), the transfer function G _n (jω) of the multiple compartment model is G _n (jω) = P _A /P _I (jω) = Σ ^N _{i =1} {v〓 _Ai (1+λ _b・Q〓 _Ci /V〓 _Ai −jωτ _Li ) / [(1+λ _b・Q〓 _Ci /V〓 _Ai ) ² +ω ₂ τ _Li ² ]}. Furthermore, for the frequencies ω _K of N types of sine waves, the real part R _e [P _A /P _I (jω)] of G _n (jω) is expressed by the following simultaneous equations.

R _e [P _A /P _I (jω _K )] =Σ ^N _i=1 {v〓 _Ai (1−λ _b・Q〓 _Ci /V〓 _Ai ) / [(1+λ _b・Q〓Ci/V〓 _Ai ) ² +ω _k ² τ _Li ² ]} k = 1, 2, ~, N (7) If the ventilation distribution v〓 _Ai corresponding to the ventilation time constant τ _Li is known, by solving the simultaneous equations (7) Then, the ventilation and ventilation of N compartments each have a time constant τ _Li .
The blood flow ratio V〓 _Ai /Q〓 _Ci can be calculated. Furthermore, if the lung volume distribution v _i blood flow distribution q〓 _i corresponding to the time constant τ _Li is known, the lung volume can be calculated as a function of the ventilation/blood flow ratio distribution from the relationship of V〓 _Ai /Q〓 _Ci , v _i . Distribution v (V〓 _A /Q〓 _C ), blood flow distribution q
(V〓 _A /Q〓 _C ), that is, the ventilation/blood flow ratio distribution can be determined.

Ventilation distribution v〓 _Ai corresponding to time constant τ _Li , lung volume distribution v _i
According to Nakamura, Takishima et al., He
It can be determined using the washout method. Blood flow distribution q〓 _i is
Calculate from v〓 _Ai and V〓 _Ai /Q〓 _Ci and overall V〓 _A.
In addition, when inhaling halothane gas whose concentration changes sinusoidally, R _e [P _A /P _I (jω _k )] is calculated by Fourier transform from the time series data of the inhalation concentration of the continuously measured exhaled halothane gas. can do.

According to equation (3), the time constant τ _L of alveolar ventilation depends on the solubility of the gas in the lung tissue. He lung tissue, blood solubility is negligible, whereas halothane lung tissue,
Blood solubility is quite large, same as assumption (4)
The time constant τ _Li ^* for He of the compartment and
The time constant τ _Li for halothane has the following relationship.

τ _Li = τ _Li ^* + (λ _L・v _i・V _L )/V〓 _Ai + (λ _b・V _bi )/V〓 _Ai = τ _Li ^* + (λ _L・v _i・V _L )/V 〓 _Ai (8) ((λ _b・V _bi )/V〓 _Ai ≪τ _Li ^* + (λ _L・v _i・V _L )/V〓 _Ai ) Here, λ _b and λ _L are related to halothane. be. In addition, the lung tissue volume V _L can be determined in advance by the C ₂ H ₂ rebreathing method. In the present invention based on the above principle, the data processing device controls the flow controller and calculates the concentration of the index gas contained in the air flow. The air flow is changed in a sinusoidal manner, and the gas components of the subject's breath corresponding to the air flow are analyzed by an analyzer to determine the ventilation/blood flow ratio distribution.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the ventilation/blood flow ratio distribution measuring device of the present invention, and FIG. 2 shows the control signals applied to the flow controller 20 of the embodiment of FIG. FIG. 3 is a time chart for explaining the relationship with changes in the concentration of halothane. FIG. 3 is a time chart showing the control signal applied to the flow controller 20 in the embodiment of FIG. 1.

Constantly pressurized air from compressor 22 is supplied into the water in tank 32 and to flow controller 20 when valves 21 and 33 are open, respectively. The flow controller 20 changes the flow rate of air supplied to the compressor 22 via the valve 21 in accordance with the sinusoidal variation of the applied control voltage V, and sends out the air as an air flow V. The air stream V is led into the halothane liquid in the tank 23 by an inlet pipe P ₁ and is led into the main gas conduit 25 via an outlet pipe P ₂ containing halothane vapor as an indicator gas.
Air is taken in from one end of the main gas conduit 25, and the indicator gas from the outlet pipe _P2 is mixed into the taken air at the connection point _J1 at a constant flow rate of 20/min.
The gas flow A ₁ is sucked into the exhaust pump 29 provided at the other end of the main gas conduit 25 and discharged to the outside. The gas supply conduit _P3 and the exhaust conduit _P4 are each connected to the breathing conduit _P5 , and a one-way valve constituting the one-way valve device 27 is disposed at each connection point. Mouthpiece 2 is attached to the tip of breathing conduit P ₅ .
8 is installed. During this time, from the connection point J ₂ a portion of the gas flow A ₁ is supplied to the gas supply conduit P ₃ when the valve 34 is closed and the valve 26 is open.
During inspiration, this gas is introduced into the breathing conduit P ₅ by the action of the one-way valve device 27 and is inhaled by the subject. During expiration, by the action of the one-way valve device 27, the exhaled gas is discharged into the exhaust conduit P ₄ , joins the gas flow A ₁ at the connection point J ₃ and is discharged via the exhaust pump 29. The bag 30 stores air containing water vapor from the tank 32 and helium gas (hereinafter referred to as He gas) from the gas cylinder 31, and the valve 34 is opened.
When the valve 26 is closed, in order to supply the stored mixed gas to the gas supply conduit _P3 and perform He mixing,
Introduce He into the subject's lungs. Respiratory flow meter 13
detects the gas flow flowing into the exhaust conduit _P4 . Mass spectrometer 12 detects the composition ratio between gaseous components within respiratory conduit _P5 . The A/D converter 11 performs A/D conversion on the detection result of the pneumotachograph 13 and the detection result of the mass spectrometer 12, respectively, and outputs them as pneumoflow data and mass spectrometry data. After reading the preset program and data from the floppy disk 16, the microcomputer 10 sequentially outputs a sine wave signal of a set frequency, and appears in the respiratory conduit _P5 in accordance with the output sine wave signal. The ventilation/blood flow ratio distribution is calculated from the respiratory flow rate data and mass spectrometry data related to the concentration of the indicator gas. The calculation results are stored on the floppy disk 16 and displayed on the CRT 15.

Next, the control signal V will be explained with reference to FIGS. 2 and 3.

The microcomputer 10 outputs a sinusoidal control voltage V via the D/A converter 14 to control the flow controller 20. The flow controller 20 outputs an air flow V〓. The Halothane concentration F contained in the gas flow A ₁ of the main gas conduit 25 changes sinusoidally in a manner similar to the control voltage V.
In other words, the change in the halothane concentration F linearly follows the change in the sinusoidal control voltage V. here
The purpose of changing the halothane concentration in a sinusoidal manner is to minimize the effects of recirculation.

In this example, the halothane gas concentration must include 16 types of frequency components in order to determine the ventilation/blood flow ratios of 16 compartments. Therefore, as shown in Figure 3, while combining signals of two types of frequencies, 26
The D/A converter 14 outputs 16 types of signals with a period of 18 seconds to 5 minutes per minute. As a result, the measurement time was reduced to 2/3 compared to outputting one type at a time.

Next, the operation of the embodiment shown in FIG. 1 will be explained.

(1) Close valves 21, 26, and 34, and close valve 33.
Open air from tank 32, gas cylinder 3
1 to helium and oxygen from the gas cylinder 35 to the bag 30, helium He8% to 10
%, oxygen O ₂ 21%, carbon dioxide CO ₂ approximately 0.05%, and the remainder nitrogen N ₂ , and then valves 33 and 35 are closed. Next, valve 34
The bag 30 is opened to allow the subject to breathe the mixed gas stored in the bag 30 through the conduit _P3 . The mass spectrometer measures the concentration of helium through a gas introduction probe. The measurement results are input to the microcomputer 10 through the A/D converter 11 and monitored by the CRT 15.

(2) At the point when the gas in the subject's lungs and the mixed gas in the bag reach equilibrium, that is, the helium concentration in exhaled air becomes equal to the helium concentration in the bag, close the valve 34 and open the valve 26. Make it. The gas not containing helium in the main gas conduit 25 is J ₂ ,
Subject inhales through P ₃ , P ₅ , P ₅ , P ₄ ,
_Helium washout (He
washout) until the helium in the subject's lungs is completely washed out. During this time, the helium and carbon dioxide concentrations measured by the mass spectrometer and the expiratory flow rate measured by the pneumotachograph 13 are inputted at high speed to the microcomputer 10 via the A/D converter 11 and stored on the floppy disk 16. .

(3) Open the valve 21 and D/A converter 14
Flow controller 2 based on control signal V from
Output air flow V from 0 and valve 2
6 is opened and a gas flow A _I containing halothane gas having a sinusoidal concentration is supplied to the gas supply conduit P ₃ ;
Have the subject breathe. During this time, mass spectrometer 1
The halothane and carbon dioxide concentrations measured in step 2 and the expiratory flow rate measured by the pneumotachograph 13 are inputted at high speed to the microcomputer 10 via the A/D converter 11 and stored on the floppy disk 16.

(2) and (3) are performed virtually simultaneously, but they can also be performed independently.

Next, the process of analyzing the data obtained by the above measurements, that is, the off-line processing by the microcomputer 10 will be explained.

(A) Depending on the helium concentration during helium flushing in step (2) above and the expiratory flow rate, the following type 1
Solving the Fredholm integral equation, the displacement distribution v(τ ^* _L )
seek.

V _He (t)/V _He (t ₀ ) =∫ ^∞ ₀ v (τ ^* _L ) exp (−t/τ ^* _L ) d (τ ^* _L ) where V _He (to) and V _He (t) are the total amount of helium flushed out and the amount of helium in the lungs at time t, respectively, and are obtained by calculating the amount of helium excreted with each breath. The amount of helium discharged for each breath is determined by integrating the respiratory flow rate of each breath and the helium concentration difference between inspiration and exhalation over the expiration time (taking into account the time difference between the respiratory flow rate signal and the gas concentration signal).

The ventilation volume distribution function v _A (τ ^* _L ) is calculated using the following formula.

v〓 _A (τ ^* _L ) = [V _He (to) / F _He (to)] ・ v (τ ^* _L ) / τ ^* _L / _V〓 AHere, F _He (to) is the lung value immediately before the start of washout. This is the internal helium concentration. Note that V〓 _A is the overall alveolar ventilation, which is calculated using the following formula.

V〓 _A = RR・V _C02 /F _Ecp2 Here, RR and F _Ecp2 are determined from the respiration rate, end-expiratory carbon dioxide concentration, expiratory flow rate, and carbon dioxide data, respectively. V _cp2 is the amount of carbon dioxide produced once, and is determined by integrating the product of the exhaled carbon dioxide concentration and expiratory flow rate over the expiratory time.

To explain using the example of the measurement results of v _L (τ ^* _L ) and v〓 _A (τ ^* ) shown in Fig. 5, which will be described later, v _L (τ ^* _L ) and v〓 _A (τ ^* )
is discretized, the range of the horizontal axis τ ^* of v _L (τ ^* _L and v〓 _A (τ ^* ) is divided into n (N = 16 in this example) compartments, and the center point τ of each division is ^* Let _i be the time constant of this compartment. Correspondingly, let the cumulative values of v and v〓 _A in each division v _i and v〓 _Ai be the lung volume distribution and ventilation distribution of this compartment.

(B) First, the halothane concentration at the end of expiration is determined from the halothane concentration and expiratory flow rate data obtained in step (3) above.
Detect FA(t) and end-expiratory halothane concentration Fi(t). The point in time when the expiratory flow rate changes from positive to zero is defined as the end of expiration, and the point in time when the expiratory flow rate changes from zero to positive is defined as the end of expiration.

Next, F _A (t) and F _I (t) are fractionated on the time axis using the method shown in Figure 3, and each is subjected to Fourier transform using FFT to calculate R _e [P _A
(jω)/P _I (jω)] Find _k .

In addition, the time constant τ _i for halothane is determined from the time constant τ ^* _i for helium in each compartment using equation (8).

Using τ _i , R _e [P _A (jω)/P _I (jω)] _k , ω _k and the already obtained v〓 _Ai , solve the following equation (Equation (7)) and calculate V〓 of each compartment. Obtain _Ai /Q _Ci .

R _e [P _A (jω) / P _I (jω)] _k = _N 〓 ^j=1 {v〓 _Ai (1+λ _b・Q〓 _Ci /V〓 _Ai ) / [(1+λ _b・Q〓 _Ci /V〓 _Ai )＋ω _k ² τ _Li ² 〕｝……
(7) k=1, 2, 3,...N Finally, calculate the blood flow distribution q〓 _i in each compartment using the following equation.

q〓 _i = Q〓 _Ci / _N 〓 ⁱ⁼¹ Q〓 _Ci where Q〓 _Ci = V〓 _A・v〓 _Ai・Q〓 _Ci )/V〓 _AiHowever , as mentioned above, V _A is the carbon dioxide Calculate based on measurement results.

(C) Using the method illustrated in Figure 8 a, b, and c for the case of three compartments, calculate the lung volume distribution v _i (Figure 8 a) and ventilation/blood flow ratio V〓 _Ai / of each compartment.
From Q〓 _Ci (Fig. 8b), the relationship between v and V〓 _A /Q〓 _c (Fig. 8
Figure c) is found. Furthermore, using the same method, we calculated the blood flow distribution q〓 _i and ventilation/blood flow ratio V〓 _Ai /Q〓 _Ci of each compartment.
Find the relationship between q〓 and V〓 _A /Q〓 _C from. By this,
Ventilation/blood flow ratio distribution v~ _V〓A / _Q〓C , q〓~ _V〓A / _Q〓C are finally determined.

All of the above offline analyzes are performed on a microcomputer.

An example in which the ventilation/blood flow ratio distribution measuring device of this embodiment is applied to diagnosis of an actual subject will be described.

4 healthy subjects N ₁ , N ₂ , N ₃ , N ₄ , emphysema patient
The ventilation/blood flow ratio distribution was measured for two patients X ₁ and X ₂ , one patient Y with pulmonary fibrosis, and one patient Z with pulmonary embolism.

Figure 5 shows the Re of these subjects N ₁ , N ₂ , ~, Z.
(P _A /P _I )-ω curves are shown together.
As mentioned earlier, this curve corresponds to the sinusoidal shape of the inhaled air.
It represents the frequency characteristics of the lungs with respect to halothane gas concentration. For healthy subjects N ₁ , N ₂ , N ₃ , N ₄ , Re
The (P _A /P _I )-ω curves show almost the same tendency. The slopes of the curves for emphysema patients X ₁ and X ₂ and pulmonary fibrosis patient Y are relatively flat, but the slope of the curve for pulmonary embolism patient Z is significantly large.

FIG. 6 relates to subjects N ₁ , N ₂ , . . . , Z. v _A −
τ, v-τ curves are shown. The lung volume distribution v of a healthy person is symmetrically distributed with a time constant of about 30 seconds to 1 minute. Pulmonary embolism showed a similar v distribution. There are cases in which the v distribution of emphysema and pulmonary fibrosis has lost its symmetry, and it is generally scattered in areas with large time constants, and there is a large deviation between the peaks of the v _A distribution and the v distribution.

FIG. 7 shows ventilation/blood flow distribution curves v-V _A /Q _C and q-V _A /Q _C for subjects N ₁ , N ₂ , ~, Z. These two types of distribution in healthy subjects are concentrated around the ventilation/perfusion ratio of 0.8, and exhibit a roughly log-normal distribution shape. On the other hand, the distribution of emphysema and pulmonary fibrosis is highly dispersive, with a bias toward the side with a small ventilation/perfusion ratio. Regarding pulmonary embolism, the two distribution patterns were generally broader than in healthy subjects, and tended to be biased towards the side with a large ventilation/perfusion ratio.

〔Effect of the invention〕

As explained above, the present invention generates and outputs a mixed air in which the concentration of an index gas changes sinusoidally at multiple frequencies as time progresses, gives the generated mixed air to a subject, and then inhales the air during exhalation. By analyzing the components, the following effects can be obtained.

1. Can supply mixed air that does not cause physiological changes to the subject.

2 Test time can be shortened by combining multiple frequencies.

3 A pneumotachograph, a mass spectrometer, and a preprogrammed data processing device automatically perform ventilation and
Blood flow ratio distribution can be measured and calculated.

4. The test can be performed noninvasively.

5. The measurement operation is simpler than the conventional ventilation/blood flow ratio distribution measurement method.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the ventilation/blood flow ratio distribution measuring device of the present invention, and FIG. 2 shows the control signals applied to the flow controller 20 of the embodiment of FIG. 3 is a time chart showing the control signal applied to the flow controller 20 in the embodiment of FIG. 1, and FIG. 4 is a time chart for explaining the relationship with the concentration change of halothane. _A / P _I ) - ω curve, Fig. 5 is a graph showing v _A - τ, v - τ curve, Fig. 6 is a ventilation/blood flow ratio distribution curve v - V〓 _A /Q〓 _c ,
Graphs showing q〓−V〓 _A /Q〓 _c , Figure 7 a, b are equivalent circuits showing the single compartment model and multiple compartment model of the lung, respectively, Figure 8 a, b, c are the respective Compartment lung volume distribution V _i and the following blood flow ratio V〓 _Ai /Q〓 _ci and v
This is an example of a method for finding the relationship V〓 _A /Q〓 _c . 10...Microcomputer, 11...A/
D converter, 12... Mass spectrometer, 13...
Respiratory flowmeter, 14...D/A converter, 15...
...CRT, 16...Flotspy disc, 20...
...Flow controller, 21, 26, 33, 34
... Valve, 22 ... Compressor, 23,2
4, 32...Tank, 25...Main gas conduit, 27
... One-way valve device, 28 ... Mouthpiece, 29 ...
...exhaust pump, 30...bag, 31,35...gas cylinder.

Claims (1)

[Claims] 1. In a model of the subject's lungs that is segmented based on the difference in the washout time constant of an inert gas, a transfer function between exhalation and inspiration of a change in the concentration of an index gas is determined, and the ventilation of the subject's lungs is determined.・It is a ventilation/blood flow ratio distribution measurement device that measures the blood flow ratio distribution, and includes a respiratory air conduit that guides the subject's inhalation and exhalation, and a sine wave signal that gives the concentration of an index gas contained in the air. an inspiratory air generating means for generating inspiratory air by changing the amount of air; when the subject is inhaling, the inspiratory air is supplied to the subject through a respiratory conduit; and when the subject is exhaling, exhaled air from the respiratory conduit is supplied to the subject through an exhaust device; a flow rate detection means for detecting the flow rate of gas flowing through the respiratory air conduit; an analyzer for detecting the composition ratio between gas components contained in the gas in the respiratory air conduit; and an inspiratory air generator. Ventilation/blood flow ratio distribution measurement characterized by having a data processing device that applies a sine wave signal to the means and calculates the ventilation/blood flow ratio distribution of the subject from the detection results of the flow rate detection means and the analyzer. Device. 2. In a model of the subject's lungs separated by differences in inert gas washout time constants, the transfer function between expiration and inspiration of the change in the index gas concentration was determined, and the ventilation/blood flow ratio distribution in the subject's lungs was calculated. The desired ventilation/blood flow ratio distribution measurement device includes a flow controller that takes in air compressed by a compressor and flows out at a flow rate corresponding to an applied control signal, and a flow controller that takes in air compressed by a compressor and flows out at a flow rate corresponding to an applied control signal, and inhaled,
A reservoir contains a test liquid that is a source of an inert test indicator gas that, when dissolved in arterial blood, distributes more to tissues than to the blood; and a reservoir contains the air flow exiting the flow controller. an inlet pipe leading into a test liquid, a main gas pipe, and a gas flow mainly composed of air introduced from one upstream end of the main gas pipe to the other downstream end, flowing through the main pipe. a gas flow generator and an air flow introduced into the reservoir by the inlet pipe to direct the gas containing the vapor of the test liquid as an indicator gas from the reservoir to the main gas conduit upstream of the main gas conduit; a gas supply conduit connected at one end to the main gas conduit for introducing the gas flow from the main gas conduit; and a respiratory air conduit connected at one end to the respiratory tract of the subject. and an exhaust conduit whose one end is connected to the exhaust device, and the other ends of each of the gas supply conduit, breathing air conduit, and exhaust air conduit are connected, and when the subject inhales, the gas in the gas supply conduit is passed through the breathing air conduit. a valve mechanism for exhausting gas in the respiratory conduit through an exhaust conduit when the subject exhales; a flow rate detection means for detecting the flow rate of gas flowing in the respiratory conduit; an analyzer that detects the composition ratio between gas components contained; and an analyzer that applies a sinusoidal signal as a control signal to a flow controller to detect an indicator gas contained in a gas flow in a main gas conduit in response to the applied control signal. A ventilation/blood flow ratio distribution characterized in that the ventilation/blood flow ratio distribution is characterized by having a data processing device that changes the concentration of the fluid in a sinusoidal manner and calculates the ventilation/blood flow ratio distribution of the subject from the detection results of the flow rate detection means and the analyzer. measuring device. 3. The control signal that the data processing device applies to the flow controller is composed of a superimposed signal sequence whose frequency changes over time, and each superimposed signal making up the sequence is a plurality of sine wave signals having different frequencies superimposed. 3. The ventilation/blood flow ratio distribution measuring device according to claim 2.