JPH03165740A - Blood flow detector - Google Patents

Abstract

PURPOSE:To precisely detect the amplitude of blood flow pulse waves by removing the effect on the pulse wave amplitude caused by the difference of the organization quantity at the fitted section of an organism via the fitting of a pulse wave detecting means to the organism under a constant-pressure load and the correction of the pulse wave amplitude by the organization quantity signal of a pulse wave amplitude correcting means. CONSTITUTION:A pulse wave detecting means has a clip 100 pinching an ear lobe M, and both clip pieces 100a, 100b hold the ear lobe M via a constant contact force regardless of the thickness with a constant-pressure spring 104 and maintain a constant blood vessel cross section shape. The detected light reception quantity of infrared rays from a light emitting diode 105a by a photo-transistor 105b is changed to effect the pulse wave amplitude when the thickness of the ear lobe M differs, the blood flow quantity change of the ear lobe M is detected by a pulse wave amplitude correcting means via the transmission type photoelectric pulse wave method, a signal corresponding to the organization quantity of the ear lobe M and a signal corresponding to the blood flow change are calculated from the detected pulse wave signal, the signal corresponding to the blood flow change is corrected by the signal corresponding to the organization quantity, and the sense of heat is detected based on the corrected signal. The amplitude of blood flow pulse waves can be precisely detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blood flow detector that detects the pulsation of blood flow in a living body.

(Prior Art) Conventionally, this type of device is attached to the earlobe of a living body to detect changes in skin blood flow.
For example, a pair of light-emitting and light-receiving elements is brought into contact with the skin of the earlobe, and the light-receiving element detects changes in the transmittance of light emitted from the light-emitting element depending on the skin blood flow rate, thereby detecting the pulsation of blood flow. .

In this case, in order to bring the pulse wave detection means constituted by a pair of light emitting and light receiving elements into contact with the skin (earlobe) and maintain that state, for example, Japanese Utility Model Application Publication No. 57-103705, Japanese Utility Model Application No. 1-84605 As shown in the publication, light-emitting and light-receiving elements are provided in a pair of detection cases facing each other in the shape of a clip, and the mounting member consisting of the detection case in the shape of a clip covers the earlobe etc. by the action of a compression spring. The mounting part is sandwiched between them.

[Problem to be solved by the invention]

However, in the clip structure using the above-mentioned compression spring, the amount of opening of the clip pieces constituting the detection case changes depending on the thickness of the part to be worn, such as the earlobe.

Due to the characteristics of the compression spring, if the thickness of the part to be worn, such as the earlobe, changes, the pinching force of the detection case will change.
The contact pressure between the pulse wave detection means and the skin also changes.

Here, if the contact pressure between the pulse wave detection means and the skin is large, it will compress the blood vessels at and around the contact position of the pulse wave detection means, changing the cross-sectional shape of the blood vessels, and affecting the normal pulsation flow. This makes it difficult to detect correct blood flow signals.

The present inventors had previously proposed in Japanese Patent Application No. 1-108101 a method for detecting the temperature range of a living body from the amplitude of blood flow pulse waves, but the above-mentioned change in blood vessel cross-sectional shape due to contact pressure was not detected. (see Figure 5), which affects the pulse wave amplitude VPF.
We found a problem that when trying to detect the temperature range from the amplitude of the pulse wave, a large error is included due to changes in contact pressure.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a blood flow detector that can accurately detect the amplitude of blood flow pulse waves regardless of the thickness of the part to be worn such as an earlobe. purpose.

[Means for Solving the Problems] In order to achieve the above object, the present invention, as shown in the basic configuration of FIG. A pulse wave detection means detects a change in blood flow under the skin in the part to be worn corresponding to a heartbeat, and generates a pulse wave signal, A set weight signal corresponding to the amount of tissue at the attachment part and a pulse wave amplitude corresponding to the change in the blood flow rate are calculated, and this pulse wave amplitude is corrected by the tissue type signal to calculate the corrected pulse wave amplitude. A technical means is adopted in which the pulse wave amplitude correction means outputs the pulse wave amplitude.

[Effect]

The operation of the above configuration will be explained.

The pulse wave detection means, which is attached to the skin of a living body by applying a constant pressure load and clamping it, detects a change in blood flow under the skin in the attached part corresponding to the heartbeat of the living body, and generates a pulse wave signal. do.

Based on the pulse wave signal from the pulse wave detecting means, the pulse wave amplitude correcting means generates a tissue type signal corresponding to the amount of tissue in the attached part of the living body and a pulse wave amplitude corresponding to the change in the blood flow rate. This pulse wave amplitude is corrected by the tissue type signal to generate this corrected pulse wave amplitude.

That is, the influence on the pulse wave amplitude caused by the difference in the assembly weight of the part to which the living body is attached is due to the attachment of the pulse wave detection means to the living body with a constant pressure load and the change in pulse wave amplitude caused by the set Ia amount signal of the pulse wave amplitude correction means. removed by correction.

〔Example〕

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

FIG. 2 is a block diagram of an electric circuit of a temperature range sensor to which the first embodiment of the blood flow detector of the present invention is applied, and FIG. 3 is a structure of a pulse wave detection means constructed on the clip-shaped attachment member. FIG.

In FIG. 3, the pulse wave detection means is equipped with a clip 100 made of a black material that holds the earlobe M of the living body.
0b from the outside and fixed pressure spring 104.
Both clips 10 are rotated around the time axis 102 when pressed against the
The tip portions 0a and 100b are tilted outward from each other to release the earlobe M from being held. On the other hand, when the gripping pressure on the clip pieces 100aS and 100b is released, the clip 100 is moved around the shaft 102 by the action of the constant pressure spring 104.
100b inwardly to each other to remove the earlobe M.
It is designed to hold the

Furthermore, in FIG. 3, 103 is a clip piece 100b.
This is a shaft for rotatably fixing the spring bobbin 104a of the constant pressure spring 104 to the shaft 102, and by arranging it toward the center of the clip 100 with respect to the shaft 102, it creates an earlobe holding force.

Further, 104 is a constant pressure spring configured to provide a constant earlobe holding force (contact pressure) even if the degree of opening of the clip pieces 100a and 100b, that is, the thickness of the earlobe changes. This constant pressure spring 104 has a tightly wound spiral thin plate (for example, a cob ring manufactured by Osaka Heat Treatment Co., Ltd.) wound around a spring bobbin 104a.
04b is fixed to the clip piece 100a, and the spring bobbin 104a is rotatable about the shaft 103.
It holds the earlobe with a constant contact force regardless of the thickness of the earlobe.

Next, in FIG. 3, reference numeral 105 denotes an optical pulse wave detection means composed of an infrared light emitting diode 105a having a peak wavelength around 900nW+ and a phototransistor 105b, and a clip piece 100a and a phototransistor 105b, respectively. It is supported in the inner surface recess of 100b by suitable means in parallel to the bottom wall of the recess and is disposed opposite to the bottom wall of the recess.

In addition, 106 and 107 are spacers formed in a disc shape from a black foam material, and clip pieces 100a and 100 are inserted into the hollow portions of the spacers so that a light emitting diode 105a and a phototransistor 105b are fitted therein.
It is fixed to the opening end of the recess b. This spacer 10
6 and 107 are convex than the opening surfaces of the light emitting diode 105a and the phototransistor 105b, and when the earlobe M is held between the clip 100, they contract in the direction of the plate thickness and the openings of the light emitting diode 105a and the phototransistor 105b are formed. It has a function of bringing the surface into uniform contact with the surface of the earlobe M.

And 108 and 109 are light emitting diodes 105a.
and a cover that protects a connection portion for outputting terminal signals of the phototransistor 105b to the outside, and 101 is a lead wire that outputs signals from the light emitting diode 105a and the phototransistor 105b.

The operation of the pulse wave detecting means configured as described above will be explained below.

When the light emitting diode 105a emits light due to its conduction,
The light from the light emitting diode 105a enters the earlobe M and is absorbed by the earlobe tissue and blood in the open earlobe M, and the rest is transmitted through the phototransistor 105.
The light is received by the phototransistor 10 and is photoelectrically converted by the phototransistor 10.
5b as a pulse wave signal. In this case, the amplitude {circle around (2)} of the pulse wave signal corresponds to the amount of light received by the phototransistor 105b, that is, the amount of change in blood flow in the earlobe M. Note that FIG. 4 illustrates the waveform of the pulse wave signal.

Here, the shape of the arteriole blood vessel in the earlobe M is determined by the clip 10.
0 and the earlobe contact pressure caused by the constant pressure spring 104, the cross-sectional shape changes. That is, the cross-sectional shape of the blood vessel in the absence of contact pressure is approximately circular, but when contact pressure is applied, the cross-sectional shape of the blood vessel changes to an elliptical shape. Changes in the blood vessel cross-sectional shape due to this contact pressure affect the pulse wave amplitude V□ output from the phototransistor 105b, as shown in FIG. 5 described above. By the way, the contact pressure of the earlobe changes depending on the amount of opening of the clamping piece, for example in the structure using a compression spring shown in the above-mentioned Japanese Utility Model Publication No. 1-84605, so the contact pressure changes depending on the thickness of the earlobe. However, there is a problem in that the cross-sectional shape of the blood vessel changes accordingly, and as a result, the pulse wave amplitude changes. On the other hand, in the mounting member structure of this embodiment, the clip pieces 100a, 10
Since a constant contact pressure is obtained regardless of the amount of opening of 0b, a constant cross-sectional shape of the blood vessel can be maintained even if the thickness of the earlobe changes.

However, the pulse wave amplitude in the pulse wave signal from the pulse wave detecting means configured as described above still includes an optical error due to the difference in earlobe thickness, so it is necessary to electrically correct it. That is, since the infrared light emitted from the light emitting diode 105a is also absorbed by the tissue of the earlobe M, the tissue! (Here, mainly the thickness of the earlobe) changes the amount of light received by the phototransistor 105b, which also affects the pulse wave amplitude. FIG. 6 shows the optical error characteristics due to this difference in earlobe thickness.

Here, the intertissue signal is the earlobe skin tissue (
This signal corresponds to the amount of permeation absorbed by the ear (excluding blood and bone), and is proportional to the thickness of the earlobe. In this embodiment, the earlobe thickness correction means calculates the thickness of the earlobe using this intertissue signal, and calculates the simultaneously detected pulse wave amplitude using equation (1).
As shown in Figure 2, the thickness of the earlobe is 4 m according to the Kaiso-sensing signal.
It was decided to correct it to m.

CVFP= VPPX (K X v4c10.8
2) ... (1) Here, CV is the corrected pulse wave amplitude, Vdc is the intertissue signal, K is the matting constant, and 0.82 is the intertissue signal when the earlobe thickness is 4 mm.

Next, the earlobe thickness correction means and the thermal sensation detection means as the pulse wave amplitude correction means will be explained using the electric circuit block diagram shown in FIG.

The infrared light that enters the earlobe M from the light emitting diode 105a is absorbed by the earlobe tissue and blood, and the remaining transmitted light is photoelectrically converted by the phototransistor 105b, and blood flow changes in the earlobe M are converted into voltage change signals, that is, pulse waves. The signal is input to an AC amplifier 30 and a low-pass filter 31 as a signal.

The AC amplifier 30 amplifies only the alternating current component of the pulse wave signal, that is, the blood flow rate change component, and outputs it to the pulse generator 32 and peak hold circuit 33. The pulse generator 32 creates a heartbeat pulse signal synchronized with the heartbeat from the alternating current component of the pulse wave signal, and inputs it to the CPU 3B. Further, the peak hold circuit 33 peak-holds the maximum value and the minimum value from the AC component of the input pulse wave signal, that is, the pulse wave amplitude, and inputs them to the differential amplifier 34 . In the differential amplifier 34,
The minimum value of the input pulse wave amplitude is subtracted from the maximum value, and the DC voltage corresponding to the pulse wave amplitude is input to the A/D converter 37.

On the other hand, the low-pass filter circuit 31 applies a low-pass filter (in this embodiment, the center frequency is 1) to the input pulse wave signal.
&) to remove blood flow change components, and input to the differential amplifier 35. In the differential amplifier 35, the low pass filter 31
The input signal from the reference value setting circuit 36 and the input signal from the reference value setting circuit 36 are differentially amplified, and an intertissue signal that can be applied to the above equation (1) is converted to A.
/D converter 37.

The A/D converter 37 converts the DC voltage and interstitial signal corresponding to the pulse wave amplitude into A/D according to the control signal from the CPU 3B.
D conversion is performed and each digital signal is input to CPU3B.

The CPU 38 calculates the corrected pulse wave amplitude CVPF and the thermal sensation amount according to the control flowchart shown in FIG.

First, in step 40, it is determined whether or not a heartbeat pulse is generated from the heartbeat pulse generation circuit 32 (in this embodiment, it is determined by the rise of the heartbeat pulse signal). If a heartbeat pulse is generated, the process proceeds to step 41, and the A/D A control signal is sent to the converter 37 to start A/D conversion of the pulse wave amplitude and the interstitial signal, and the respective values are taken into the CPU 38 as digital signals. Thereafter, in step 42, the respective average values are calculated cumulatively until the number n of captured data reaches 100 in step 43, which will be described later. The determination in step 43 as to whether or not the number of captured data n has reached 100 corresponds to whether or not the number of data, that is, 100 heartbeats has been input. When the number n of data is 100 or less, the processes from steps 40 to 43 are repeated until the number n of data reaches 100. When the number n of data reaches 100, in step 44, based on the above formula (]), A corrected pulse wave amplitude CVPP is calculated from the pulse wave amplitude calculated in step 42 and the average value of the m-sensitive signal. In the next step 45, the amount of thermal sensation is calculated from the relationship between the pulse wave amplitude and the thermal sensation shown in FIG. Clear and step 4
Return to 0 and repeat the same process.

In other words, what is shown in Fig. 2 detects changes in blood flow in the earlobe using a transmission photoplethysmography method, and from the detected pulse wave signal, a signal corresponding to the amount of tissue in the earlobe and a signal corresponding to the change in blood flow are generated. By calculating the signal corresponding to the tissue amount, i and u of the other signal corresponding to the blood flow change are calculated.
The m + m error is corrected using equation (1), and a warm sensation is detected based on a signal corresponding to the corrected blood flow change.

Figure 8 shows the temperature range-pulse wave amplitude characteristics, and shows the pulse wave amplitude detected in the earlobe of each subject and the pulse wave amplitude at that time when the environmental temperature of each subject was varied in various ways. This shows the relationship between the thermal sensations reported by each subject when they were divided into 7 ranks from ``cold'' to ``hot''. It can be confirmed that the pulse wave amplitude changes in response to the change in pulse wave amplitude.Here, the VFP characteristic shows the correlation before implementation of this example, and the CV, characteristic shows the correlation obtained by implementing this example. By implementing this example, the correlation coefficient of the warm pulse wave amplitude (calculated by exponential interpolation) is increased from 0.914 to 0.97.
Improved to 2.

An example of a vehicle air conditioner in which the present invention is applied to a temperature sensor will be described with reference to the block diagram of FIG. 9.

For example, the pulse wave detection means shown in FIG. 3 is attached to the earlobe of a vehicle occupant, and the blood flow pulse wave in the arteriole within the earlobe is optically detected. The pulse wave amplitude is corrected by the earlobe thickness correction means explained in the figure. In other words, the earlobe thickness correction means is a means for correcting the optical detection error of the pulse wave detection means that optically detects the pulse wave of the earlobe. Corrects detection errors due to differences in thickness. Then, based on this corrected pulse wave amplitude, as shown in the previous publication 1ll (Japanese Patent Application No. 1-108101),
A corresponding thermal sensation is calculated by the thermal sensation detection means, and based on this temperature range amount, the air conditioning control means controls the air conditioning so that the temperature range of the occupant is, for example, in a windowless state that is neither hot nor cold.

According to the air conditioning control with the above configuration, even if there are individual differences in the part to which the pulse wave detecting means is attached to the driver or passenger, the amplitude of the blood flow pulse wave can be detected with high accuracy. Even when detecting a warm sensation, there is no large error,
As a result, good air conditioning control can be achieved.

Note that it goes without saying that the present invention is applicable not only to vehicle air conditioners but also to various types of air conditioners.

Moreover, although the above embodiment was applied to a temperature range sensor that detects a thermal sensation from pulse wave amplitude, it can also be applied to a sensor that detects various amounts of movement of a living body.

Further, as shown in FIG. 3, in the above embodiment, a structure in which the contact pressure is constant is shown using a tightly spiral thin plate spring, but the structure is not limited to this, and the structure in which the contact pressure is constant is not limited to this. If so, for example, an air bag or the like may be used.

Furthermore, although the above embodiment employs a photoplethysmographic heart rate sensor consisting of a light emitting diode and a phototransistor, the present invention is not limited to this; for example, a blood flow impedance sensor that detects changes in blood flow may be used. It can also be employed in the impedance plethysmography method, etc., which detects changes.

〔Effect of the invention〕

As described above, the blood flow detector according to the present invention eliminates the influence on the pulse wave amplitude caused by the difference in the tissue amount of the part to which the living body is attached. Since it is removed by correcting the pulse wave amplitude using the tissue mass signal of the correction means, for example, when it is attached to the earlobe of a living body, the blood flow pulse wave is removed regardless of the thickness of the attached part such as the earlobe. This has an excellent effect in that the amplitude can be detected with high precision.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is an electric circuit block diagram of a temperature range sensor to which the first embodiment of the present invention is applied, and FIG. 3 is a structure of the pulse wave detection means shown in FIG. 2. 4 is a pulse wave signal waveform diagram from the pulse wave detecting means shown in FIG. 2, and FIG. 5 is a characteristic diagram showing the influence of the contact pressure of the pulse wave detecting means on the living body on the pulse wave amplitude. , FIG. 6 is a characteristic diagram showing optical error characteristics to pulse wave amplitude due to differences in earlobe thickness, FIG. 7 is a control flowchart of CPU 38 in FIG. 2, and FIG.
The figure is a characteristic diagram showing the correlation between pulse wave amplitude and thermal sensation.
FIG. 3 is a block configuration diagram when the device shown in FIG. 2 is used for air conditioning control. 31...Low pass filter circuit, 33...Peak hold circuit, 34.35...Differential amplifier, 36...
Reference value setting circuit, 37... A/D converter, 38...
cpu, 100...clip, 102...axis, 10
4... constant pressure spring, 105a... light emitting diode, 105b... phototransistor.

Claims (1)

[Scope of Claims] It is attached to the skin of a living body by applying a constant pressure load and clamping it, and detects changes in blood flow under the skin in the part to be worn corresponding to the heartbeat of the living body, and detects changes in blood flow under the skin in response to the heartbeat of the living body, and detects changes in blood flow under the skin in response to the heartbeat of the living body. A pulse wave detection means that generates a pulse wave signal, and a tissue amount signal corresponding to the tissue amount in the attached part of the living body, and a pulse wave amplitude corresponding to a change in the blood flow amount based on the pulse wave signal from the pulse wave detection means. A blood flow detector comprising pulse wave amplitude correction means for calculating the pulse wave amplitude, correcting the pulse wave amplitude using the tissue mass signal, and outputting the corrected pulse wave amplitude.