JPH05135A - Blood model - Google Patents

Abstract

PURPOSE:To achieve higher reproducibility of a measured value for calibration test by setting a mixing ratio of an orange fluorescent dye and a red fluorescent dye to that indicating a photo absorption characteristic similar to blood. CONSTITUTION:A blood model 19 herein used is a acrylic resin as base which is mixed with an orange powder fluorescent dye at a mixing ratio of 50-75% and a red powder fluorescent dye at a mixing ratio of 50-25% to impart a photoabsorption characteristic similar to blood and injection molded into a plate. The tip of the blood model 19 is curved in shape so that a detection waveform similar to a pulse wave of an organism can be picked up from a photodetecting section 16 when the blood model 19 moves is or out between a light emitting section 15 and the photodetecting section 16. This enables optical calibration test of a pulse oximeter containing a measuring probe, that has hereto before been hard to perform thereby achieving higher reproducibility of a measured value for calibration test.

Description

Detailed Description of the Invention

[Object of the Invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blood model used for performing a calibration test of a pulse oximeter.

[0002]

2. Description of the Related Art A pulse oximeter emits light of, for example, two wavelengths, which have different optical transmissivities between oxyhemoglobin and deoxyhemoglobin, into a fingertip of a person or the like, and about two wavelengths that appear with pulsation of arterial blood. The ratio of the pulsation fluctuation of the transmitted light is calculated, and the oxygen saturation in the blood is calculated by using this ratio as a function. By the way, in the calibration method using the pulse oximeter, conventionally, the calibration was performed electrically only by the apparatus main body without including the measurement probe. As another test method, calibration is performed by actually measuring the fingertip of a normal person, and it is confirmed whether the same person's fingertip is attached to the measurement probe multiple times to show the same measurement value. Was there.

[0003]

However, in the method of actually measuring and calibrating the fingertip of a person, the reproducibility of the measured value is poor, and it is difficult to judge whether the measured value is reliable. Therefore, it is conceivable to calibrate the pulse oximeter using a finger model that has an absorption characteristic similar to that of a human finger, but it is difficult to realize a blood model that approximates the absorption characteristic of blood, and pulse oximeters using finger models are difficult to realize. The calibration test of the meter was difficult.

The present invention has been proposed in order to solve such a conventional problem, and can improve the reproducibility of measured values for a calibration test, and can calibrate a pulse oximeter with high reliability. The aim is to provide a blood model for doing so. [Constitution of Invention]

[0005]

In order to achieve this object, the blood model according to the present invention comprises an orange fluorescent dye mixed in a ratio of 50 to 75% and a red fluorescent dye in a ratio of 50 to 25%. , And has an absorption characteristic similar to that of blood.

[0006]

According to the above-mentioned structure, by mixing the orange fluorescent dye and the red fluorescent dye at a predetermined ratio, it is possible to give an absorption characteristic close to that of blood and change the mixing ratio of these. This constitutes a blood model that can be used for calibration tests with different oxygen saturations.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a blood model according to the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a block diagram of a pulse oximeter calibration test apparatus using this blood model. In this figure, a measurement probe 3 connected to the pulse oximeter body 1 by a signal cable 2
A human finger model 4 is attached to the human body, and a pulsation generator 5 that constitutes a part of the finger model 4 is driven by a drive unit 6 to reciprocate in the finger model 4. Driving power is supplied to the driving unit 6 from the power supply unit 7, and a control signal for driving the pulsation generating unit 5 at an appropriate speed is input from the control unit 8. Further, in the position detection unit 9, the sensor
The position of the pulsation generator 5 is detected based on the input signal from 10, and the detection result is displayed on the position detection display 11. As shown in FIG. 2, the measurement probe 3 is spring-biased so that the upper holding plate 13 and the lower holding plate 14 which can be opened and closed with the pin 12 as a fulcrum are closed inward. 2 for emitting light of different wavelengths λ1 and λ2 for measuring oxygen saturation
A light emitting portion 15 composed of two light emitting diodes is provided, and a light receiving portion 16 is provided on the inner surface of the lower holding plate 14 so as to face the light emitting portion 15. The finger model 4, which is mounted between the upper holding plate 13 and the lower holding plate 14 of the measurement probe 3 during the calibration test, includes a tissue model 17 and a pulsation generator 5 that moves in the tissue model 17. The tissue model 17 is made of, for example, styrofoam resin, and has a constant light absorption characteristic for each wavelength so as to approximate a living tissue. The tissue model 17 is provided with an insertion hole 20 in the front-rear direction in which the pulsation generator 5 having the blood model 19 attached to the translucent substrate 18 is inserted. As shown in FIGS. 3 and 4, slide guide pins 21 and 21 are provided on both side walls of the board 18, and the guide pins 21 and 21 are formed in the slide grooves 22 and 22 formed on both sides of the insertion hole 20, respectively. The pulsation generating section 5 can be moved within the range tissue model 17 of the slide groove 22 by being fitted into. Also, the output shaft 23 of the motor that constitutes the drive unit 6
A disc 24 is fixed to the disc 24, and a connecting rod 26 is rotatably attached to the disc 24 at an eccentric position. The base of the base plate 18 of the pulsation generator 5 is attached to the tip of the connecting rod 26 via a rotatable coupling 27.
As a result, the rotational movement of the motor is transmitted as a linear movement to the pulsation generating section 5 via the disc 24, and the pulsation generating section 5 becomes a light emitting section.
The finger model 4 is reciprocally moved in the front-rear direction so as to move in and out between the light receiving unit 16 and the light receiving unit 16. Further, the tissue model 17 is provided with a sensor 10 for confirming whether the finger model 4 is properly inserted between the light emitting portion 15 and the light receiving portion 16 when the finger model 4 is attached to the measurement probe 3. A detection output is sent from the sensor 10 to the position detecting unit 9 when the light from the light emitting unit 15 is received, and the position detecting unit 9 turns on the display unit 11 formed of a light emitting diode based on the sensor detection signal. Therefore, by confirming the lighting state of the display unit 11, it is possible to confirm whether or not the finger model 4 is completely attached to the probe 3. It should be noted that the upper surface and the lower surface of the finger model 4 are not slippery.
4a and 4a are attached. Next, the configuration of the blood model 19 on the substrate 18 will be described. The blood model 19 has a mixing ratio of 50 to 7 in order to have absorption characteristics similar to blood.
5% orange powder fluorescent dye and mixing ratio 50 ~ 25
% Of red powder fluorescent dye, and injection-molded into a plate shape based on an acrylic resin. The fluorescent dyes used here are orange 240 and red 300 of Lumogen F (trade name of BASF). The chemical name of this fluorescent dye is Perylen. By changing the mixing ratio of the orange powder fluorescent dye and the red powder fluorescent dye within the above range, the absorption characteristic patterns P1, P2, P3 (see FIG. 9) corresponding to the calibration test of different oxygen saturation S can be obtained. The blood model 19 that the user has can be configured. Here, by increasing the mixing ratio of the orange powder fluorescent dye, the blood model 19 used for the calibration test when the oxygen saturation S is high is configured. Further, the shape of the tip portion 19a of the blood model 19 is cut out in a curved sectional shape as shown in FIG. By making the tip shape of the blood model 19 into a curved shape in this way, when the blood model 19 enters and leaves between the light emitting unit 15 and the light receiving unit 16 as shown by the solid line and the virtual line, detection close to the pulse wave of the living body The waveform can be extracted from the light receiving unit 16. If the tip shape of the blood model 19 is cut off at a right angle, a sharp detection waveform close to a rectangular wave different from the pulse wave of the living body will result. Here, the blood model 19 is subjected to a surface treatment such that the absorption characteristics approximate to the scattering of transmitted light in the living body are obtained, and the linear light entering the blood model 19 and the model 19 are generated. The scattered light is converted into long-wavelength fluorescence and re-emitted, and most of it is guided to the edge portion 19b by total reflection as shown by the dotted line, and the remaining transmitted light is used as a pulsation detection component. In this way, by guiding the most part to the edge portion 19b, it is possible to make a large difference in the signal level of the pulsation change. The blood model 19 is removable so that it can be replaced when the light absorption characteristics change due to dirt or the like.

FIG. 6 is a schematic comparison between the living body and the finger model 4 in order to explain the actual light-absorbing characteristics and the light-absorbing characteristics of the finger model 4, and FIG.
Shows a schematic diagram of a living body 30 divided into a tissue layer 28 and a blood layer 29, and FIG. 6 (b) shows a schematic diagram of the finger model 4. In the figure, D is the thickness of the tissue, ΔD is the thickness of the blood, I ₀ is the amount of incident light,
I represents the amount of transmitted light only in the tissue portion, and (I-ΔI) represents the amount of transmitted light obtained by subtracting the dimmed portion in blood due to pulsation. By moving the blood model 19 in the tissue model 17 as described above, the finger model 4 can be used to simulate the light absorption characteristics approximate to the characteristics of the living body 30 in which the light absorption changes with the pulsation of blood. it can. Here, ΔA is given by the following equation, where ΔA is the change in absorbance due to pulsation, E is the extinction coefficient of the light absorber, and C is the concentration of the light absorber. ΔA = Log [I / (I-ΔI)] = ECΔD Further, assuming that the changes in the absorbance at the first and second wavelengths λ1 and λ2 are ΔA1 and ΔA2, respectively, and the extinction coefficients of the absorber are E1 and E2, respectively, the absorption is The coefficient ratio Φ is given by the following equation. [Phi] = [Delta] A1 / [Delta] A2 = E1 / E2 Using this [Phi] as a function, the oxygen saturation S can be obtained by the following equation. S = f (Φ) FIG. 7 shows an S-Φ relationship curve of an actual human fingertip portion, and the finger model 4 needs to obtain characteristics approximate to this S-Φ relationship curve. The materials of the tissue model 17 and the blood model 19 are determined so as to obtain this characteristic. FIG. 8 shows the absorption characteristics of oxyhemoglobin and reduced hemoglobin, and the absorption characteristics of the blood model 19 when the finger model 4 is used as a simulator for performing a calibration test with an oxygen saturation S of 97%. Pattern P1 is shown. Further, in FIG. 9, the oxygen saturation S is 8
The light absorption characteristic patterns of the blood model 19 when the blood model 19 is configured as a simulator at 3% and 60% are shown, respectively. In the figure, A1 and A2 on the right side
Is the absorption characteristic patterns P1 and P for wavelengths λ1 and λ2
2 and 3 show the pulsation fluctuation waveforms of the absorbance (pseudo sine wave) observed in the blood model 19 corresponding to P3, and A1 and A2 on the left side respectively show the pulsation fluctuation waveforms of the absorbance observed in the actual living body.

Next, the operation of signal processing inside the pulse oximeter when the finger model 4 is attached to the measurement probe 3 and a calibration test is performed will be described based on the timing chart of FIG. First, the light emission drive unit 31 outputs a drive pulse (a) for turning on the light emitting diodes of the light emission unit 15 corresponding to wavelengths λ1 and λ2, respectively, and two light emitting diodes are synchronized with the drive pulse (a). The lights are turned on alternately. The light emitted from the light emitting unit 15 is received by the light receiving unit 16 after passing through the finger model 4, and the light reception output is the light reception amplification unit.
Supplied to 32. The received light signal amplified by the amplifier 32 is sent to the multiplexer 33, and the synchronization pulse on the λ1 side is sent.
The signals corresponding to the respective wavelengths are separated based on (b) and the synchronization pulse (c) on the λ2 side. As for the separated signal output from the multiplexer 33, the signal on the λ1 side is held by the hold unit 34, the AC component AC1 (f) corresponding to the pulsation fluctuation is extracted by the AC unit 35 in the next stage, and the DC unit 36 also The DC component DC1 (g) corresponding to the tissue component is extracted. Also λ2
The signal on the side is held by the hold unit 37, and the AC of the next stage is held.
The AC component AC2 (h) corresponding to the pulsation fluctuation component is extracted in the unit 38, and the DC component DC2 (i) corresponding to the tissue component is extracted in the DC unit 39. These AC parts 35, 36 and DC
The output signals from the units 36 and 39 are converted into digital signals by the A / D conversion unit 40 and then supplied to the CPU 41, where the C
In PU41, as shown by the following equation, the calculation for obtaining the changes ΔA1 and ΔA2 in the absorbance corresponding to the respective wavelengths λ1 and λ2 is performed. ΔA1 = AC1 / DC1 ΔA2 = AC2 / DC2 Subsequently, the calculation unit 42 at the next stage performs a calculation for obtaining the ratio Φ of the absorption coefficient as shown in the following equation. Φ = ΔA1 / ΔA2 From the ratio Φ of the extinction coefficient, the oxygen saturation S is calculated in the calculation unit 43 in the next stage, and the oxygen saturation S obtained on the display unit 44 is calculated.
The value of is displayed.

[0010]

As described above, according to the blood model of the present invention, since the blood model is constructed by mixing the orange fluorescent dye and the red fluorescent dye in a predetermined ratio, the blood model of the living body can be obtained. This finger model enables the optical calibration test of the pulse oximeter including the measurement probe, which has been able to have similar absorption characteristics and was difficult in the past. Therefore, by performing the calibration test of the pulse oximeter with the finger model using this blood model, the reproducibility of the measurement value for the calibration test can be improved, and the pulse oximeter can be calibrated with high reliability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a pulse oximeter calibration test apparatus using a blood model according to the present invention together with a pulse oximeter.

FIG. 2 is a cross-sectional view showing a finger model attached to a measurement probe.

FIG. 3 is a plan view of the finger model.

FIG. 4 is a front view of the finger model.

FIG. 5 is a diagram for explaining a shape of a blood model used for a finger model and a state of scattering of transmitted light in the blood model.

FIG. 6 is a schematic diagram for explaining absorption characteristics of a living body and a finger model.

FIG. 7 is a graph showing a relationship curve between the oxygen saturation S of a human fingertip and the extinction coefficient ratio Φ.

FIG. 8 is a characteristic diagram showing the absorption characteristics of oxygenated hemoglobin and reduced hemoglobin and the absorption characteristics of a blood model.

FIG. 9 is a diagram showing each absorption characteristic pattern of a blood model used for a calibration test of different oxygen saturation.

FIG. 10 is a timing chart showing an operation of signal processing in the pulse oximeter.

[Explanation of symbols]

1 pulse oximeter body 3 measurement probe 4 finger model 5 pulsation generator 6 drive unit 7 power supply unit 8 control unit 9 position detection unit 10 sensor 11 position detection display unit 15 light emitting unit 16 light receiving unit 17 tissue model 18 substrate 19 blood model 20 Insertion hole 21 Guide pin 22 Slide groove 23 Output shaft 24 Disc 26 Connection rod 27 Coupling 28 Tissue layer 29 Blood layer 30 Living body

Claims (2)

[Claims] 1. A blood model comprising an orange fluorescent dye and a red fluorescent dye mixed in a predetermined ratio and having an absorption characteristic similar to blood. 2. Orange fluorescent dye is 50-75%,
Red fluorescent dye is mixed in a ratio of 50-25%,
A blood model having an absorption characteristic similar to that of blood.