JPH0630917A - Pigment dilution curve measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain an apparatus which achieves measurement of a pigment dilution curve in a non-invasion manner and accurately by determining first and second variables from a changing rate of extinction after light with first and second wavelengths transmits through tissue. CONSTITUTION:Light generated with a light source apparatus 1 transmits through at tissue 102 and converted into an electric signal with a photosensor 21 to be amplified with an amplifier 22. An output signal of the amplifier is sorted into signals corresponding to light with wavelengths lambda1 and lambda2 with a multiplexer 31 to calculate changes A1 and A2 in extinction with a changes detection circuits 36 and 37 and DELTAA1/DELTAA2=PHI0 is calculated with extinction changing rate calculator 4. {X=X0} is determined to satisfy PHI0={C1+f1(X)/{C2+ f2(X)} with respect to the ratio PHI0 with an independent variable calculator 6 and a correction item calculator 7 and f1 (X0) and f2 (X0) are calculated based on the results. When a pigment is injected into blood of a person to be inspected, a changeover switch 5 is changed over to the position of a relative density calculator 8 for pigments in blood and the Cd' is calculated to satisfy PHI0={f10(Cd')+f1(X0)}/{f20(Cd')+f2-(X0)}.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring a so-called dye dilution curve of a blood dye concentration at one point in the circulatory system when a dye is injected into the circulatory system.

The dye dilution curve is very effective for diagnosing the circulatory system and is used for measuring cardiac output, circulating blood volume, hepatic foreign body excretion ability, shunt, regurgitation in heart valves, and the like.

[0003]

2. Description of the Related Art Initially, the measurement of a dye dilution curve was carried out by continuously sucking blood and letting it pass through a cuvette, and measuring the blood transmitted light. This is invasive and consumes blood, which is disadvantageous in that it is particularly invasive when the amount of blood in the body is small. After that, several devices were devised and put into practical use as a device for non-invasively measuring the dye dilution curve, such as a device for continuous measurement of transmitted light from the earlobe.

[0004]

[Problems to be Solved by the Invention]. However, conventional devices of this type have not been fully utilized clinically due to the drawbacks such as troublesome operation and poor accuracy.
The present invention has been made in view of this situation, and an object thereof is to provide an apparatus for noninvasively and accurately measuring a dye dilution curve.

[0005]

The structure of claim 1 is the first
And light generating means for generating light of each of the second wavelengths, and light detecting means for receiving the light generated from the light generating means through the living tissue and converting the transmitted light into an electric signal.
From the change in the transmitted light of the first and second wavelengths detected by the light detecting means, the change in the extinction degree of the living tissue ΔA ₁ ,
A change detecting means for detecting a .DELTA.A _2, a change ratio calculating means for calculating a ratio of .DELTA.A ₁ and .DELTA.A ₂ of this change detecting means detects [Phi, when [Phi this change ratio calculating means has calculated is given, [Phi = {C ₁ + f ₁ (X)} / {C ₂ + f ₂ (X)}
The first calculation of X = X ₀ that satisfies (C ₁ , C ₂ : constants, f ₁ (X), f ₂ (X): a function having X as an independent variable)
Variable calculation means, function value calculation means for calculating and storing the values of f ₁ (X ₀ ), f ₂ (X ₀ ) based on X ₀ calculated by the first variable calculation means, respectively. When Φ calculated by the change ratio calculating means is given, Φ = {f ₁₀ (Cd
′) + F ₁ (X ₀ )} / {f ₂₀ (Cd ′) + f ₂ (X
₀ )} (f ₁₀ (Cd ′), f ₂₀ (Cd ′): a function having Cd ′ as an independent variable, f ₁ (X ₀ ), f ₂ (X ₀ ): the function calculated by the function value calculating means A second variable calculating means for calculating Cd ′ satisfying a value) and switching of Φ calculated by the change ratio calculating means to the first variable calculating means or the second variable calculating means. And a switching means for performing.

According to a second aspect of the present invention, in addition to the above configuration, a hemoglobin concentration storage means for storing the hemoglobin concentration Hb, Cd 'calculated by the second variable calculation means, and Hb stored by the hemoglobin concentration storage means. Cd '
A dye concentration calculating means for calculating Hb to obtain the dye concentration Cd is added.

According to the structure of claim 3, in the structure of claim 1, the first variable calculating means is f ₂ (X) = K · f ₁ (X)
The feature is that calculation is performed using the relationship of (K: constant).

[0008]

According to the first aspect of the invention, the switching means first applies the Φ calculated by the change ratio calculating means to the first variable calculating means. Next, the operator inserts the living tissue to be measured into the gap between the light generating means and the light detecting means. The light detecting means receives the light from the light generating means which has passed through the living tissue and converts it into an electric signal. The change detection means changes the extinction degree of the transmitted light of the first and second wavelengths ΔA ₁ ,
Detect ΔA ₂ . The change ratio calculation means uses the ΔA ₁ and ΔA
Calculate the ratio Φ of ₂ . The first variable calculation means uses Φ calculated by the change ratio calculation means, and Φ = {C ₁ + f ₁ (X)} /
X = X ₀ that satisfies {C ₂ + f ₂ (X)} is calculated.
The function value calculation means calculates and stores the values of f ₁ (X ₀ ) and f ₂ (X ₀ ) based on X ₀ calculated by the first variable calculation means.

Next, the Φ calculated by the change ratio calculating means is applied to the second variable calculating means by the switching means. The light detecting means, the change detecting means and the change ratio calculating means perform the same operation as described above, and the change ratio calculating means calculates Φ. This Φ is given to the second variable calculation means. The second variable calculation means uses this Φ and f ₁ (X
₀ ), f ₂ (X ₀ ), Φ = {f ₁₀ (Cd ′)
+ F ₁ (X ₀ )} / {f ₂₀ (Cd ′) + f ₂ (X ₀ )}
Cd ′ satisfying the above condition is calculated.

In the structure of the second aspect, the operation until the calculation of Cd 'is the same as the above-mentioned operation, but in this structure, the dye concentration calculating means further uses this Cd' and Hb stored in the hemoglobin concentration storing means. Cd'.Hb is calculated to obtain the dye concentration Cd.

In the above two operations, the switching means is Φ
Is applied to the second variable calculation means immediately before or at the same time as the injection of the dye into the living body.
Alternatively, it is preferable that it is at the latest just before the dye reaches the measurement site.

In the structure of claim 3, in the above operation, the first variable calculating means calculates f ₀ (f ₂ (X)) when calculating X _0.
= K · f ₁ (X) is used.

[0013]

Embodiment First, the principle of this embodiment will be described.

Regarding the dimming of blood, Shaster (Sch
From theoretical studies and experiments based on the theory of Uster), it is known that if the incident light is an appropriate scattered light and the incident window diameter and the transmission window diameter are appropriate, the following equation holds.

Zb = ΔAb / ΔDb = {(Eh Hb + Ed Cd) (Eh Hb + Ed Cd + FHb)} ^1/2 = {(Eh + Ed Cd / Hb) (Eh + Ed Cd / Hb + F)} ^1/2 · Hb (1) Zb: Extinction degree per unit thickness of blood. We will call it the dimming rate. ΔAb: Variation in blood extinction degree. ΔDb: Variation in blood thickness. Eh: extinction coefficient of hemoglobin. Ed: absorption coefficient of dye. Cd: Blood dye concentration. Hb: blood hemoglobin concentration. F: Blood scattering coefficient. Regardless of the wavelength of light.

The pulsation component of the extinction degree of the living tissue is not only due to the pulsation of blood but also due to the pulsation of the thickness of tissues other than blood (referred to as pure tissue). It becomes like a formula.

Zt = ΔAt / ΔDt = {(Eh + Ed Cd / Hb) (Eh + Ed Cd / Hb + F)} ^1/2 · Hb + Zx (2) Zt: Extinction degree per unit thickness of living tissue. ΔAt: Pulsation amount of extinction of living tissue. ΔDt: Pulsation of the thickness of living tissue. Zx: Includes dimming due to pulsation of the thickness of pure tissue,
Correction term (unknown).

The measurement is performed at two wavelengths λ ₁ and λ ₂ . As an example of the dye, ICG (indocyanine-gr
een). The absorption of ICG is λ ₁ = 80
It is maximum at 5 nm and zero at λ ₂ = 890 nm. Light wavelengths are indicated by suffixes 1 and 2.

The ratio Φ of the pulsation of the extinction degree when the light transmitted through the living tissue is measured at two wavelengths is given by the following equation.

Φ = ΔA ₁ / ΔA ₂ = [{(Eh ₁ + Ed ₁ Cd / Hb) (Eh ₁ + Ed ₁ Cd / Hb + F)} ^1/2 + Ex ₁ ] / {Eh ₂ (Eh ₂ + F) + Ex ₂ } (3) Ex ₁ = Zx ₁ / Hb, Ex ₂ = Zx ₂ / Hb; this is also called a correction term. Where ΔA ₁ = log I _{1t2 −log} I _1t1 (4) ΔA ₂ = log I _{2t2 −log} I _2t1 (5) I _1t1 : Intensity of light of wavelength λ ₁ at time t ₁ I _{1t 2} : Wavelength at time t ₂ . lambda ₁ of the light intensity I _2t1: time t ₁ at the wavelength lambda ₂ of the light intensity I _2t2: a [Phi before strength dye injection wavelength lambda ₂ of light at time t ₂ and [Phi _0. Φ is as follows. Φ ₀ = ΔA ₁ / ΔA ₂ = [{Eh ₁ (Eh ₁ + F)} ^1/2 + Ex ₁ ] / [{Eh ₂ (Eh ₂ + F)} ^1/2 + Ex ₂ ] (6) where Φ ₀ Is the measured value, Eh ₁ , Eh ₂ , F are known numbers,
Ex ₁ and Ex ₂ are unknowns. Let Ex ₂ = KEx ₁ . For convenience, do the following: All are known values. Eb ₁ = {Eh ₁ (Eh ₁ + F)} ^1/2 , Eb ₂ = {Eh ₂ · (Eh ₂ + F)} ^1/2 Therefore, Φ ₀ = (Eb ₁ + Ex ₁ ) / (Eb ₂ + K Ex ₁ ). _{(7) Eb 1 + Ex 1} = Φ 0 (Eb 2 + KEx 1) Ex 1 (1-Φ 0 K) = Φ 0 Eb 2 -Eb 1 Ex 1 = (Φ 0 Eb 2 -Eb 1) / (1-Φ ₀ K) (8) Ex ₂ = K (Φ ₀ Eb ₂ −Eb ₁ ) / (1−Φ ₀ K) (9) The formula of Φ after dye injection is as follows. Φ = ΔA ₁ / ΔA ₂ = [{(Eh ₁ + Ed ₁ Cd ′) (Eh ₁ + Ed ₁ Cd ′ + F)} ^1/2 + Ex ₁ ] / [{Eh ₂ (Eh ₂ + F)} ^1/2 + KEx ₁ ] (10) Cd '= Cd / Hb (11); Relative value of blood dye concentration Cd to hemoglobin concentration Hb. By this, {(Eh ₁ + Ed ₁ Cd ′) (Eh ₁ + Ed ₁ Cd ′ + F)} ^1/2 = Φ (Eb ₂ + KEx ₁ ) −Exx ₁ (12) (Ed ₁ Cd ′) ² + Ed ₁ Cd ′ (2Eh ₁ + F) + Eb ₁ ² − [Φ (Eb ₂ + KEx ₁ ) −Ex ₁ > ² = 0 Cd ′ = {− B + (B ² -4AC) ^1/2 } / 2A (13) A = Ed ₁ ² B = Ed ₁ (2Eh ₁ + F) C = Eb ₁ ² − [Φ (Eb ₂ + KEx ₁ ) −Ex ₁ ] ^{2 From} this, Cd ′ can be obtained. Next, the blood dye concentration Cd is calculated by the following equation. Cd = Cd'.Hb (14)

Hb is measured in advance for each subject and used in the calculation of blood dye concentration, or is measured afterwards and used to convert Cd 'into blood dye concentration.

In order to determine K in this equation, a dye was injected into the vein of volantea and the transmitted light at the earlobe and fingertip was continuously measured. In parallel with this, arterial blood was sampled at regular intervals. The dye concentration in blood was measured invasively, and the result of K = 0.5 was obtained from the comparison of both.

It was also proved that the blood dye concentration measurement using this K value shows sufficient accuracy.

To describe the above principle more generally,
Each of the two correction terms has a function f of one unknown X.
_{As 1} (X) and f ₂ (X), X is obtained based on the measured value of Φ before dye injection.

An apparatus based on the above principle will be described with reference to FIG.

The light source device 1 is composed of two LEDs 11 and 12 and an LED driving device 13 for driving them. LED11 has wavelength λ
The light of ₁ is generated, and the LED 12 generates the light of wavelength λ ₂ .
The light detection device 2 is arranged at a position facing the LEDs 11 and 12 of the light source device 1 with a predetermined gap. The photodetector 2 comprises a photosensor 21 and an amplifier 22 for amplifying the output of the photosensor 21. For example, a photodiode is used as the optical sensor 21.

The output of the photodetection device 2 is supplied to the dimming degree change calculation device 3. The dimming degree change calculation device 3 includes a multiplexer 31, a pair of reproduction circuits 32 and 33, a pair of logarithmic circuits 34 and 35, and a pair of change amount detection circuits 36 and 37. The multiplexer 31 is a circuit that distributes the signals corresponding to the light having the wavelengths λ ₁ and λ ₂ which are the output signals of the amplifier 22 of the photodetector ₂ to the reproduction circuits 32 and 33. This multiplexer 31 connects the LED driving device 13 of the light source device 1 to the LED 11,
It is connected to a timing device 100 which gives the blinking timing of 12 and distributes the signal from the amplifier 22 at the same timing as the blinking of the LEDs 11 and 12. Also timing device
The timing signal output from 100 also reaches the amplifier 22 of the photodetector. The gain of the amplifier 22 is switched according to the light having the wavelength λ ₁ and the wavelength λ ₂ by this timing signal. The reproduction circuits 32 and 33 are circuits that smooth the signals corresponding to the light of each wavelength given from the multiplexer 31. The logarithmic circuits 34 and 35 are circuits for obtaining the logarithm of the outputs of the reproducing circuits 32 and 33. The change detection circuits 36 and 37 are circuits that detect a change in the outputs of the logarithmic circuits 34 and 35. Specifically, the difference between the outputs of the logarithmic circuits 34 and 35 at _two time points t ₁ and t ₂ is detected.
(5) is calculated to obtain ΔA ₁ and ΔA ₂ . This calculation is
It is designed to be performed once for each pulsation of the outputs of the logarithmic circuits 34 and 35.

The dimming degree change ratio calculation device 4 is a device for obtaining the ratio ΔA ₁ / ΔA ₂ = Φ of the outputs of the change amount detection circuits 36 and 37. This output Φ is given to one terminal of the changeover switch 5. The changeover switch 5 is changed over by the mode changeover device 101, and the output Φ of the change ratio calculation device 4 is given to either the independent variable calculation device 6 or the blood dye relative concentration measurement device 8.

The mode changeover device 101 outputs a changeover signal to the changeover switch 5 by a timer or an operation of an operator.

The independent variable calculation device 6 is a device for substituting Φ (= Φ ₀ ) given from the change ratio calculation device 4 into the equation (8) to calculate Ex ₁ .

The correction term calculation device 7 calculates the equation (9) based on Ex ₁ calculated by the independent variable calculation device 6 and calculates Ex ₁ and E
It is a device that stores the value of x ₂ .

The blood dye relative concentration calculation device 8 calculates the blood from Φ given from the change ratio calculation device 4 and Ex ₁ and Ex ₂ (= KEx ₁ ) stored in the correction term calculation device 7 and the equation (13). This is a device for calculating the relative concentration of medium dye Cd '.

The hemoglobin concentration storage device 9 is a device for storing the hemoglobin concentration Hb of the subject when it is given.

The blood dye concentration calculation device 10 uses the Cd 'calculated by the blood relative concentration calculation device 8 and Hb stored in the hemoglobin concentration storage device 9 and the formula (14) to determine the blood dye concentration of the subject. This is a circuit for calculating Cd.

In this embodiment, the light source device 1 and the timing device 100 constitute the light generating means, the light detecting device 2 is the light detecting means, and the dimming degree change calculating device 3 is the change detecting means. The ratio calculation device 4 is a change ratio calculation means, the independent variable calculation device 6 is a first variable calculation means,
The correction term calculation device 7 is the function value calculation means, the blood dye relative concentration calculation device 8 is the second variable calculation means, the hemoglobin concentration storage device 9 is the hemoglobin concentration storage means, and the blood dye concentration calculation device. Reference numeral 10 is a dye concentration calculating means, and the changeover switch 5 and the mode changing device 101 constitute a changing means.

Next, the operation of the apparatus of this embodiment thus constructed will be described.

First, the mode switching device 101 switches the changeover switch 5 to the independent variable calculation device 6 side. Next, the subject is a living body tissue 102 such as an earlobe or a fingertip, which is a measurement site.
Is inserted into the gap between the light source device 1 and the light detection device 2. The operator activates the timing device 100. This allows the LED
11 and 12 light up alternately. The light generated by the LEDs 11 and 12 passes through the living tissue 102, is converted into an electric signal by the optical sensor 21, and is amplified by the amplifier 22.

The output signal of the amplifier 22 is distributed by the multiplexer 31 into signals corresponding to the lights of the wavelengths λ ₁ and λ ₂ . These signals are smoothed by the reproduction circuits 32 and 33. The outputs I ₁ and I ₂ of the reproduction circuits 32 and 33 are converted into logarithms by the logarithmic circuits 34 and 35 to be log I ₁ and log I ₂ . The change amount detection circuits 36 and 37 have two time points t ₁ and t in each pulsation.
₂ log I _1, log I ₂ respective differences, i.e. formula (4)
, .DELTA.A ₁ shown in (5), calculates a .DELTA.A _2, and outputs the attenuation variation ratio calculation unit 4.

The dimming degree change ratio calculation device 4 is a change amount detection circuit.
36, 37 outputs ΔA ₁ , ΔA ₂ to ΔA ₁ / ΔA ₂ = Φ ₀
To calculate. Φ ₀ is constant because it is before dye injection.
The independent variable calculation device 6 outputs the output Φ of the dimming degree change ratio calculation device 4.
Ex ₁ is calculated by substituting ₀ into equation (8). The correction term calculation device 7 uses the equation (9) calculated from Ex ₁ calculated by the independent variable calculation device 6.
Is calculated to obtain Ex ₂ , and Ex _{1 and} this Ex ₂ are stored.

Next, the operator injects the dye into the blood of the subject and informs the mode switching device 101 of the injection time. As a method of informing the mode switching device 101 of the time of dye injection, for example, there is a method in which a fit switch is connected to the mode switching device 101 and the operator steps on it. At this time, the mode switching device 101 uses the selector switch 5
Is switched to the blood dye relative concentration calculation device 8 side. Therefore, the output Φ of the dimming degree change ratio calculation device 4 is given to the blood dye relative concentration calculation device 8. At this time, φ changes depending on the dye concentration at the measurement site.

The blood pigment relative concentration calculation device 8 receives the given Φ and Ex ₁ , Ex ₂ stored in the correction term calculation device 7.
The relative concentration Cd 'is calculated from (= KEx ₁ ) and the equation (13). Next, the blood pigment concentration calculation device 10 uses the relative concentration C
Dd = Cd'.Hb is calculated from d ', the hemoglobin concentration stored in the hemoglobin concentration storage device 9, and the equation (14). The blood dye concentration Cd thus obtained is recorded and displayed on a recording device and a display device (not shown).

In this embodiment, the change detecting circuits 36 and 37, the extinction change ratio calculation device 4, the independent variable calculation device 7, the blood dye relative concentration calculation device 8 and the blood dye concentration calculation device 10 are independent devices. However, some or all of these may be replaced by a digital computer. In this case, the signal to be processed needs to be digitized by an A / D converter.

In the above embodiment, the device is used to obtain the blood dye concentration Cd. However, from this Cd, the blood stroke volume per unit time is further obtained, or Cd obtained at the stage before obtaining Cd. A device for obtaining the hemoglobin stroke volume per unit time from ′ (relative value of blood dye concentration to hemoglobin concentration) may be used.

[0044]

According to the present invention, the following effects can be obtained.

Less invasive than the conventional open blood method.

Compared with the conventional non-invasive method, the operation of pressing the earlobe to put it in an ischemic state is unnecessary and simple.

Since only the arterial blood is measured, the dye in the venous blood does not overlap and a good dye dilution curve can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light source device 2 photodetector device 3 extinction change calculation device 4 extinction change ratio calculation device 5 changeover switch 6 independent variable calculation device 7 correction term calculation device 8 blood dye relative concentration calculation device 9 hemoglobin concentration storage device 10 blood dye Concentration calculator

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 6, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0022

[Correction method] Change

[Correction content]

[0022] collected for determination of K in the equation, by injecting dye into a vein of volunteer, the transmitted light was measured continuously at the apex earlobe and finger, to which was concurrent, the arterial blood at regular intervals The blood dye concentration was measured invasively . Pair of both
The ratio gives K, in some cases K = 0.5, and
In one example, K = -1. In this way, K is the person
It is a constant uniquely obtained by each.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

The dimming degree change ratio calculation device 4 is a device for obtaining the ratio ΔA ₁ / ΔA ₂ = Φ of the outputs of the change amount detection circuits 36, 37. This output Φ is given to one terminal of the changeover switch 5. The changeover switch 5 is changed over by the mode changeover device 101, and the output Φ of the dimming degree change ratio calculation device 4 is given to either the independent variable calculation device 6 or the blood dye relative concentration measurement device 8.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

The independent variable calculation device 6 substitutes Φ (= Φ ₀ ) given from the extinction change ratio calculation device 4 into the equation (8) to obtain E.
A device that calculates x ₁ .

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

The blood dye relative concentration calculation device 8 has Φ given from the extinction degree change ratio calculation device 4 and Ex ₁ and Ex ₂ (= KEx ₁ ) stored in the correction term calculation device 7. And a device for calculating the blood dye relative concentration Cd 'from equation (13).

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Xie Yi Tai 1-31-4 Nishi-Ochiai, Shinjuku-ku, Tokyo Within Nihon Kohden Kogyo Co., Ltd. (72) Inventor Hideyuki Tomita 1-31 Nishi-ochiai, Shinjuku-ku, Tokyo No. 4 inside Nippon Koden Kogyo Co., Ltd.

Claims (3)

[Claims] 1. A light generating means for generating light of each of the first and second wavelengths, and light detection for receiving the light generated by the light generating means through living tissue and converting the transmitted light into an electric signal. Means and a change ΔA ₁ , in the degree of extinction of the biological tissue, based on a change in transmitted light of the first and second wavelengths detected by the light detecting means.
Given a change detecting means for detecting ΔA ₂ , a change ratio calculating means for calculating a ratio Φ between ΔA ₁ and ΔA ₂ detected by this change detecting means, and a Φ calculated by this change ratio calculating means,
= {C ₁ + f ₁ (X)} / {C ₂ + f ₂ (X)} (C ₁ ,
C ₂ : constant, f ₁ (X), f ₂ (X): a first variable calculating means for calculating X = X ₀ satisfying X (function having X as an independent variable), and the first variable calculating means F ₁ based on X ₀ calculated by
Given the function value calculation means for calculating and storing the values of (X ₀ ), f ₂ (X ₀ ), and Φ calculated by the change ratio calculation means,
= {F ₁₀ (Cd ′) + f ₁ (X ₀ )} / {f ₂₀ (Cd
′) + F ₂ (X ₀ )} (f ₁₀ (Cd ′), f ₂₀ (Cd
′): Function with Cd ′ as an independent variable, f ₁ (X ₀ ),
f ₂ (X ₀ ): function value calculated by the function value calculating means)
And a second variable calculating means for calculating Cd ′ satisfying the above condition, and Φ calculated by the change ratio calculating means are switched to the first variable calculating means or the second variable calculating means. A dye dilution curve measuring device comprising a switching means. 2. Light generating means for generating light of each of the first and second wavelengths, and light detection for receiving the light generated by the light generating means through living tissue and converting the transmitted light into an electric signal. Means and a change ΔA ₁ , in the degree of extinction of the biological tissue, based on a change in transmitted light of the first and second wavelengths detected by the light detecting means.
Given a change detecting means for detecting ΔA ₂ , a change ratio calculating means for calculating a ratio Φ between ΔA ₁ and ΔA ₂ detected by this change detecting means, and a Φ calculated by this change ratio calculating means,
= {C ₁ + f ₁ (X)} / {C ₂ + f ₂ (X)} (C ₁ ,
C ₂ : constant, f ₁ (X), f ₂ (X): a first variable calculating means for calculating X = X ₀ satisfying X (function having X as an independent variable), and the first variable calculating means F ₁ based on X ₀ calculated by
Given the function value calculation means for calculating and storing the values of (X ₀ ), f ₂ (X ₀ ), and Φ calculated by the change ratio calculation means,
= {F ₁₀ (Cd ′) + f ₁ (X ₀ )} / {f ₂₀ (Cd
′) + F ₂ (X ₀ )} (f ₁₀ (Cd ′), f ₂₀ (Cd
′): Function with Cd ′ as an independent variable, f ₁ (X ₀ ),
f ₂ (X ₀ ): function value calculated by the function value calculating means)
Cd ′ calculated by the second variable calculation means and Hb stored by the hemoglobin concentration storage means, and a second variable calculation means for calculating Cd ′ satisfying the above condition, a hemoglobin concentration storage means for storing the hemoglobin concentration Hb, and a Cd ′ calculated by the second variable calculation means and Hb stored by the hemoglobin concentration storage means. And by Cd '· H
Switching is performed between the dye concentration calculating means for calculating b to obtain the dye concentration Cd and the Φ calculated by the change ratio calculating means for the first variable calculating means or the second variable calculating means. A dye dilution curve measuring device comprising a switching means. 3. The first variable calculation means is f ₂ (X) = K ·
The dye dilution curve measuring device according to claim 1 or 2, which is calculated using a relationship of f ₁ (X) (K: constant).