JPH0412736A - Biomeasuring instrument - Google Patents

Abstract

PURPOSE:To decrease the errors by a difference in reflected light measuring parts and the errors by the color, etc., of the skin by providing the measuring parts at the plural points varying in the distance from a light source and computing the change rate of an exponent part by regarding the attenuation of the intensity of the reflected light with the distance from a light incident position as an exponential function. CONSTITUTION:This instrument is disposed with a 1st light receiving part 22 and a 2nd light receiving part 24 at the two points varying in the distance from the light source 20 provided with two pieces of light emitting diodes 20A, 20B which generate the light of different wavelengths in a housing 12 for housing main constituting parts. The quantity of the reflected light received by the two light receiving parts 22, 24 is considered to attenuate exponential-functionally in accordance with Lambert-Beer law with the distance and the change rate of the exponential part thereof is computed by a microcomputer 28. The errors by the movement of the measuring parts 22, 24 and the contact state of the light source 20 and the detector with the measuring parts 22, 24 are, therefore, decreased. Since the measurement is made by selectively making >=2 kinds of the light rays of the different wavelengths incident on a living body, the errors by the difference in, for example, the color of the skin, etc., are prevented.

Description

[Detailed description of the invention]

(Industrial Application Field 1) The present invention relates to a biomeasuring device that detects metabolism, such as oxygen consumption, in the living tissue by injecting light into the living tissue and from the intensity of the reflected light.

[Prior Art] Oxygen is supplied to each part of a living body by hemoglobin in blood. The light absorption characteristics of hemoglobin are different between the oxidized type (Hb○2), which has oxygen, and the reduced type (Hb), which does not have oxygen. There is a device that utilizes this to monitor changes in the amount of Hb and HbO2 in each partial tissue of a living body to monitor metabolism such as oxygen consumption within the living tissue. Conventionally, this type of reflective biomeasuring device includes a first type of reflective oximeter that projects light onto the surface of living tissue, and a second type that inserts a probe into a blood vessel and projects light there. There are several types of reflective oximeters. [Problems to be Solved by the Invention] The former reflection type oximeter, which injects light onto the surface of living tissue, makes light of five different wavelengths enter one point on the surface of living tissue, and calculates the relative reflected light intensity by The hematocrit value and SO2 value (blood oxygen saturation) are calculated by comparing with empirical experimental data, but the device is complicated and large, and there are also problems with the movement of the measurement site, the light source, detector, and measurement site. There is a problem in that errors are likely to occur due to the contact state of the contacts. In addition, errors due to differences in the measurement site of the living body, and furthermore, static tissue,
For example, there is a problem in that errors are likely to occur due to skin color, etc. Furthermore, the second type of reflex oximeter, in which the probe is inserted into the blood vessel, is an invasive method, and the information obtained is not information inside the living tissue, but information inside the veins and arteries. Therefore, there is a problem in that it is not possible to obtain data on exercise or local oxygen consumption. This invention has been made in view of the above-mentioned conventional problems, and is small and lightweight, has good portability, and can reduce the movement of the measurement site.
Alternatively, it is possible to reduce errors caused by contact conditions between the light source and detector and the measurement site, and errors caused by the location and color of biological tissue, and to obtain data on oxygen consumption during exercise and locally in a non-invasive manner. The purpose is to provide a biomeasuring device that can perform [Means for Solving the Problems] The present invention provides a biomeasuring device for injecting light into a living body from a light source and measuring metabolic changes such as oxygen consumption in the living body based on the intensity of the reflected light. parts are provided at two or more points at different distances from the light source, and the attenuation of the reflected light intensity at the measuring part with respect to the distance from the light incident position is regarded as an exponential function, and the amount of change in the index part is calculated. The above object is achieved by providing an arithmetic device. Further, the above object is achieved by setting the distance of the measuring section from the light source to a distance where attenuation can be regarded as an exponential function. Furthermore, the above object is achieved by arranging the light incident point on the living body and the plurality of measurement units on the same virtual straight line. Further, the above object is achieved by arranging the light source and the plurality of measuring sections in windows formed on the same surface of the same housing. Furthermore, the above object is achieved by making the casing attachable to a living body using a fitting. Furthermore, the above object is achieved by configuring the light source to selectively generate light of two or more types of wavelengths and to enter the light at one point on the living body. Further, the wavelength of the light generated by the light source is 600 to 1300.
The above object is achieved by adjusting the thickness to be in the nm range. Further, the above object is achieved by selecting the wavelength of the light source light between 805 nm. (Function) In this invention, measurement units for measuring the reflected light of the light incident on the living body are provided at two or more points at different distances from the light source, and the intensity of the reflected light at the measurement unit is determined based on the distance from the light incident position. Since the attenuation is regarded as an exponential function and the amount of change in the exponential part is calculated, it is possible to reduce errors caused by movement of the measurement site and the state of contact of the light source and detector with the measurement site. Furthermore, since two or more types of light with different wavelengths are selectively incident on the living body for measurement, errors due to differences in parts of the living body, such as differences in skin color, can be prevented. Furthermore, since it is sufficient to provide at least two measuring sections, the apparatus can be made simple and compact.

【Example】

Examples of the present invention will be described in detail below. As shown in FIG. 1, the biometric device 10 according to this embodiment includes a housing 12 in which the main components are housed, and a housing 12 for attaching the housing 12 to a biological tissue, such as a human arm 14. A band 16 is provided. Independent recesses 18A to 18C are formed in the arm 14 side surface of the housing 12, and these recesses 18A to 18G
A light source 20, a first light receiving section 22, and a second light receiving section 24 are respectively arranged. The light source 20 includes two light emitting diodes 2OA and 20B that emit light of different wavelengths, and these light emitting diodes 2.
Ball lens 20 placed on the light emitting surface side of OA, 20B
It is formed from C. Further, as shown in FIG. 3, the first light receiving section 22 and the second light receiving section 24 are both composed of photoelectric conversion photodiodes 22A, 24A and an amplifier 22B 124B that amplifies the outputs of the received light. ing. The recesses 18A to 18C are covered with a transparent resin 26, and the outer surface 26 of the transparent resin 26 forms a window that contacts the outer surface of the AI housing 12 and the surface of the living body. Furthermore, inside the housing 12, there is a microcomputer 28, a driver 30 that is controlled by the microcomputer 28 and blinks the light emitting diode 2OA120B in the light 120, and a driver 30 that converts the outputs of the amplifiers 22B and 24B into digital signals. A/D converters 32A and 32B that output the results to the microcomputer 28, and a telemeter 34 that outputs the results of calculations by the microcomputer 28 are built into the IC. Further, a liquid crystal display 36 for displaying calculation results by the microcomputer 28 is provided on the front surface of the housing 12 on the opposite side from the recesses 18A to 18C. Here, as shown in FIG.
placed above. Moreover, around the recesses 18A to 18C in the housing 12,
An adhesive tape 40 is provided so that the surface of the casing 72 on the light source and light receiving section side can be brought into close contact with the surface of the living body. Reference numeral 42 in FIG. 4 indicates a remote display device consisting of a receiver 42A for receiving the output from the telemeter 34 and a display 42B for displaying the contents. Here, a light emitting diode 20Δ constituting the light source 20
, 20B each have a wavelength of 67 in this example.
It has been chosen to generate light at 7 nm and 830 nm. Further, the straight-line distance a between the light source 20 and the first light receiving section 22 is 3
It is set to be 1 or more. The microcomputer 28 has a driver 3, which will be described in detail later.
0, the light emitting diodes 2OA, 20B of the light source 20
The first light receiving section 22 and the second light receiving section at this time emit light alternately.
The attenuation of each reflected light intensity in the light receiving section 24 is regarded as an exponential function with respect to the light incident position, that is, the distance from the light source 20,
It is configured to calculate the amount of change in the exponent part. Next, the operation of the apparatus of the above embodiment will be explained. First, the principle of measurement will be explained. As shown in FIG. 5, light emitting diodes 20A, 20
The amount of light incident on one point of the living body of the light of two wavelengths from B is I O
N J o and the amount of reflected light received by the first and second light receiving sections 22.24 at the distance 11a is ■. , J a , and distance b (a < b ), I b s J b
Let za' and b' be the substantial optical path lengths of the light. The attenuation of the reflected light m with respect to the distance is l ambert −3
It is assumed that it decays exponentially according to the eer law. At wavelength 1, 1(L=IOeXI) ((Xa' B)
-(1A)Ib=Io eXI)(-(Xb' -8
)...(1B) At wavelength 2, Jα=JOeXp(-βa'-B) ・(2A)
Jb=Jo exp(-βb'-8')-(2
B) Here, B and B' are components other than absorption of Hb and Hb 02, and α and β are absorbances due to Hb and Hboz. α8εHbl CHb +ε+bo21 CHboz β;ε+bJ Cab +ε+bo2J CHbo2. Here, CH
boz, CH is 1-1b, concentration of Hb 02 in living tissue, εHb I% εHbo2I is absorbance of Hll, Hboz for wavelength 1, CHb J sε+b
o2J is the absorbance of HbSHbOz for wavelength 2. For wavelength 1, log
(1(L/Io)=-(2a' Blog (I
b/Io)=-αb'-B'From the above formula, 0(1(IcL/Ib) -α<b'-a')+(8'-8>), and the attenuation of the amount of reflected light is log (IcL/Ib )=IC
, b, then Icb = (2(b' - a' ) + <B
B')... (3) Comparing equation (3) with the previous measurement, Icb(N1)=α(N-1>-(b'-a')+(B-8')
Iαb(N)=α(N) (b'-a')+(B-B') From the above formula, Inb (N) IcLb (N 1) = (α(N
>-α(N-1))(b'-a')α(N-1)
, rewrite α(N>, α<N)=ε+bl・Cab
(N> +ε+bo2I 0C+boz (N)α(N)−α(
N-1>=ε+bI・(CHb (N) −CHb (N −1) )(ε+
bo210(CHboz (N)CHboz(N 1
)) =εhbl life ΔCab +ε+boz10△CHboz Therefore, ε+bI 0△Cab +εHb 02 ■ 0ΔCHb 02=(IcLb(
N) Icb(N-1))/(b'-a')
... (4A) Similarly for wavelength 2, ε+bJ・△CHb + ε Hb02 -ノ 6 ΔC) Ib02=(J
cLb (N) Jab (N 1))/(b'-
a') ... (4B) (4A), (
From the formula 4B), the value of △CHb, CHb02, that is, Hbq
The change in the concentration of Hi, 02 is determined. Furthermore, by setting the number of measurement points (light receiving parts) to three or more, the measurement accuracy can be improved if Iαb and JLILb are obtained by linear regression on the logarithm, and even if there are three or more wavelengths (4A)
, the number of equations corresponding to equation (4B) increases, resulting in improved accuracy. In the above embodiment, the light emitting wavelengths of the light emitting diodes 2OA and 20B in the light source 20 are 670 nm and 8 nm.
As shown in Figure 6, this wavelength light has good optical transparency through living tissues, and the absorption characteristics of oxyhemoglobin (Hboz) and deoxyhemoglobin (Hb) are different. Under the conditions, 6
This is because a range of 00 to 130 Qnm is appropriate. especially,
As can be seen from Figure 6, at a wavelength of 805 nm, H
The absorbances of b and Hboz become equal. As mentioned above, the emission wavelength of the light emitting diodes 2OA and 20B is
The reason for choosing m in between is that Hb, H
This is because the change in absorbance of boz is reversed and the difference becomes large. In the case of the above emission wavelengths of 670nlll and 830nlW,
In the measurement experiment using rats, the straight distances a and b between the light source 20 and the first light receiving section 22 and the second light receiving section 24 relative to the light source 20
On the other hand, the path that light reflects and passes through living tissue is longer due to scattering, but the actual travel distance a'b' of light is 3 to 4 compared to the straight line distances a and b. It has doubled,
Moreover, no difference was found between the two wavelengths of light. In order to confirm the relationship between the aforementioned Lambert-Beer law and the change in the amount of reflected light due to concentration conversion of Hb and Hb02 inside the living body, the present inventor conducted an experiment on rats 44 as shown in FIG. I did it. In this experiment, a pair of peristaltic pumps 46 was used to
By replacing the blood of No. 4 with artificial blood (fluorocarbon) from the thigh 44A, the hematocrit (red blood cell volume ratio) of the blood is changed, and the concentration of hemoglobin in the living tissue of the rat 44 is changed, thereby increasing the amount of reflected light. was measured. The light source is a light emitting diode that outputs light with a wavelength of 660 r+m and a laser diode that outputs light with a wavelength of 830 nm, and the linear distance from the light source to the light receiving part is 3°5.5.
5.7.5.9.5 and 10.5n+n+. The measurement results are shown in FIG. 8 for a hematocrit of 42% and in FIG. 9 for a hematocrit of 5.5%, with the vertical axis representing the amount of reflected light (10 g) and the horizontal axis representing distance. From these figures, if the light receiving part is 3 mm or more away from the light source, the attenuation of the reflected light becomes a straight line, and lumbert-
It was confirmed that Beer's law holds true. In addition, the hematocrit value, which is considered to be proportional to the hemoglobin concentration in living tissue, is calculated by using the slope of the regression line of the measurement points in Figures 8 and 9 (corresponding to Inb and Jαb in the above formula) as the vertical axis. It was confirmed that when plotted on the horizontal axis, there is a linear relationship as shown in FIGS. 10 and 11. Note that FIGS. 10 and 11 are measurements taken on rats different from those shown in FIGS. 8 and 9, and it was confirmed that a linear relationship can be found even in different individuals. In addition, in human measurement experiments, the values measured at five points with a distance of 3 to 11 mm from the light source to the light receiving part are linearly regressed as described above, and the slope is plotted on the m axis and the time elapsed on the horizontal axis. When I removed it, it looked like Figure 12. In this case, as shown in FIG. 13, during the measurement, blood flow was stopped using a cuff (CUFF) 48 for blood pressure measurement. As shown in FIG. 12, blood deoxygenation was also measured in human arms. In the above embodiment, two types of light emitting diodes 2OA and 20B are used as the light source 20, but these may be replaced with laser diodes or other light sources as appropriate. Further, as shown in FIG. 14, a beam splitter 50 is arranged in each recess 18A, and two light emitting diodes 2O
The emitted light beams from A, 20B, a laser diode, etc. may be on the same optical axis.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment of the biometric device according to the present invention, FIG. 2 is an enlarged sectional view taken along the line ■-■ in FIG.
FIG. 3 is a circuit diagram showing the essential parts of the device according to the embodiment, FIG. 4 is an enlarged perspective view of the device according to the embodiment, and FIG. 5 is a schematic cross-sectional view showing the measurement principle according to the present invention. 6 is a diagram showing the relationship between the absorbance of oxyhemoglobin and deoxyhemoglobin and the wavelength of light, FIG. 7 is a block diagram showing the state in which a mouse is measured using the device of the present invention, and FIG. Figures 8 and 9 are pictorial diagrams showing the results of the measurement experiments on the same mouse, Figures 10 and 11 are diagrams showing the results of the experiments shown in Figures 8 and 9, and Figure 13 is FIG. 14, which is a perspective view showing a state in which a measurement experiment is performed using a human arm, is a sectional view similar to FIG. 2, which shows an embodiment in which the light source of the apparatus of the present invention is different. 10... Biometric device, 12... Housing, 14
...Arm, 16...Band, 18A
~18C...Recess, 20...Light source, 2OA, 2
0B... Light emitting diode, 22... First light receiving section, 22A, 24A... Photodiode, 24... Second light receiving section, 28... Microcomputer, 38...
Virtual straight line.

Claims (8)

[Claims] (1) In a biomeasuring device that injects light into a living body from a light source and measures metabolic changes such as oxygen consumption in the living body based on the intensity of the reflected light, the reflected light measuring section is placed at different distances from the light source. At least two points are provided, and an arithmetic device is provided which considers the attenuation of the reflected light intensity at the measuring section with respect to the distance from the light incident position as an exponential function and calculates the amount of change in the exponent part. Biometric device. (2) The biomeasuring device according to claim 1, wherein the distance of the measuring section from the light source is a distance at which attenuation can be regarded as an exponential function. (3) The biomeasuring device according to claim 1 or 2, wherein the point of light incidence on the living body and the plurality of measurement units are arranged on the same virtual straight line. (4) The biometric device according to claim 1, 2 or 3, wherein the light source and the plurality of measurement units are arranged in windows formed on the same surface of the same housing. (5) The biomeasuring device according to claim 4, wherein the housing is attachable to a living body using a fitting. (6) In any one of claims 1 to 5, the light source selectively generates light of two or more wavelengths, and
A biomeasuring device characterized in that it is configured to be incident on a single point on a living body. (7) The biomeasuring device according to claim 6, wherein the light source generates light with a wavelength in a range of 600 to 1300 nm. (8) In claim 7, the wavelength of the light source light is 805.
A biomeasuring device characterized in that it is selected between nm.