JP2000107147A - Photoelectric pulse wave detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a decrease in detection accuracy attributed to physical motion of a subject. SOLUTION: A plurality of detectors 38a-38i which receive transmission light incident into a finger 20 from a light emitting element while transmitting it are arrayed in one direction almost facing the light emitting element while pinching the finger 20 with the light emitting element and a distribution waveform characteristic value calculating means 60 calculates a characteristic value of a distribution waveform indicating the distribution of photodetecting levels of the photodetectors 38a-38i in one direction, namely, a right/left area ratio R based on photodetecting signals M-SM1 respectively outputted from the photodetectors 38a-38i. A distribution waveform characteristic value judging means 62 judges physical motion of a subject based on the right/left area ratio R of the distribution waveform calculated by the distribution waveform characteristic value calculation means 60. Therefore, when the physical motion of the subject is judged, the waveform accuracy and reliability of a photoelectric pulse wave SMK sequentially outputted can be enhanced by blocking the output of the photoelectric pule wave SMK distorted under the influence of the physical motion or others.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric pulse wave detecting device for sequentially detecting and outputting photoelectric pulse waves pulsating in synchronization with a periodic change in the blood volume in a living body.

[0002]

2. Description of the Related Art A photoplethysmogram detection device outputs light as a photoplethysmogram by irradiating light into the skin of a living body and detecting the scattered light which is scattered by blood cells existing in a capillary tube under the skin. Devices are known. Since such a photoelectric pulse wave detecting device periodically pulsates in accordance with the increase and decrease of the blood cells, the volume pulse wave detecting device pulsating in response to the periodic change of the blood volume under the skin, Also known as a pleograph (Plethysmograph).

By the way, in the conventional photoelectric pulse wave detecting device,
Usually, a light emitting element that is brought into close contact with one surface, for example, an upper (back) surface of a finger, which is a part of a living body, to irradiate light thereto, and a surface opposite to the one surface of the finger corresponding to the light emitting element For example, a photoplethysmographic detection probe of a type that includes a light receiving element that is in close contact with the lower (abdominal) surface and detects scattered light in the finger and grips the finger is used.

[0004]

However, in the case of using the above-described photoelectric pulse wave detection probe, when the body movement of the living body, for example, the unconscious movement of the patient during operation or the bending of the finger occurs, the photoelectric pulse wave is detected. The finger held by the pulse wave detection probe and the light emitting element and light receiving element applied to the upper and lower surfaces of the finger move relatively, and the detection condition of the photoelectric pulse wave changes. There is a disadvantage that accuracy may be reduced.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoplethysmographic detector which does not cause a decrease in detection accuracy due to body movement of a subject. It is in.

[0006]

Means for Solving the Problems The inventors of the present invention have made various studies on the background described above, and as a result, when body movement or bending of a finger of the subject occurs, the skin of the living body and the light receiving element are connected. This is because light is greatly attenuated while propagating to the light receiving element through the gap and the photoelectric pulse wave is affected, and the light detected by the light receiving elements arranged in one direction It has been found that the intensity distribution is uniformly affected by changes in blood volume, but is unevenly affected when the subject's body movement or finger bending occurs and the distribution waveform is disturbed. The present invention has been made based on such findings.

That is, the gist of the present invention is as follows.
A photoelectric pulse wave detection device that sequentially detects and outputs photoelectric pulse waves pulsating in synchronization with a periodic change in blood volume in a living body, and (a) arranged to irradiate a part of the living body with light. And (b) a plurality of light-emitting elements are arranged substantially in one direction with the part of the living body interposed between the light-emitting element and the light-emitting element, and the light-emitting element is incident on a part of the living body from the light-emitting element. And a plurality of light receiving elements for receiving the transmitted light transmitted therethrough,
(c) distribution waveform characteristic value calculating means for calculating a characteristic value of a distribution waveform indicating a distribution of a light receiving level of the light receiving element in the one direction based on a light receiving signal output from each of the light receiving elements; A body movement determining unit that determines body movement of the living body based on a specific value of the distribution waveform calculated by the distribution waveform characteristic value calculating unit.

[0008]

According to this structure, a plurality of light receiving elements which enter the part of the living body from the light emitting element and receive the transmitted light transmitted therethrough are substantially opposed to the light emitting element, and are in contact with the light emitting element. A plurality of light receiving levels of the light receiving element are arranged in one direction based on the light receiving signals output from the light receiving element by the distributed waveform characteristic value calculating means, while being arranged in one direction with a part of the living body therebetween. The characteristic value of the distribution waveform indicating the distribution is calculated, and the body movement of the living body is determined by the body movement determining means based on the characteristic value of the distribution waveform calculated by the distribution waveform characteristic value calculating means. Therefore, when body movement is determined, it is possible to improve the waveform accuracy and reliability of the sequentially output photoelectric pulse wave by preventing the output of the photoelectric pulse wave distorted by the influence of the body movement. Thus, waveform analysis based on photoplethysmograms with low accuracy can be prevented.

[0009]

Another aspect of the present invention preferably further comprises an output blocking means for blocking the output of the photoelectric pulse wave when the body movement of the living body is determined by the body movement determining means. With this configuration, when the body movement is determined, the output of the photoelectric pulse wave distorted by the influence of the body movement is automatically stopped by the output blocking means, so that the sequentially output photoelectric pulse is prevented. The waveform accuracy and reliability of the wave can be improved.

Preferably, the body movement determining means determines the body movement of the living body based on a change in a characteristic value indicating the asymmetry of the distribution waveform calculated by the distribution waveform characteristic value calculating means. It is. Usually, the distribution waveform when the subject does not move has a relatively smooth symmetrical shape because the light receiving element is in close contact with the surface of the living body. There is an advantage that the body movement determination is performed when the symmetry of the actual distribution waveform changes as compared with the distribution waveform when there is no body movement of the person.

Preferably, the body movement determining means determines the body movement of the living body based on the characteristic value indicating the asymmetry of the distribution waveform itself calculated by the distribution waveform characteristic value calculating means. is there. As described above, the distribution waveform when there is no body movement of the subject shows a relatively smooth symmetrical shape because the light receiving element is in a state in which the light receiving element is in close contact with the surface of the living body. There is an advantage that the body motion determination is performed when the symmetry of the distribution waveform is reduced.

Preferably, the body movement determining means includes a characteristic value indicating the asymmetry of the distribution waveform calculated by the distribution waveform characteristic value calculating means and a characteristic value indicating the asymmetry of the distribution waveform itself. The body motion of the living body is determined based on the above. By doing so, the reliability of the body motion determination is further improved.

[0013]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a view for explaining a main part of the configuration of a photoelectric pulse wave detecting apparatus 10 according to one embodiment of the present invention. The photoelectric pulse wave detection device 10 according to the present embodiment includes a photoelectric pulse wave detection probe 12 attached to a part of a living body to collect a photoelectric pulse wave, and processes a signal from the photoelectric pulse wave detection probe 12 to obtain a reliable signal. And a display device 16 for displaying the photoplethysmogram output from the arithmetic and control unit 14 for the purpose of waveform monitoring or waveform analysis.

The photoelectric pulse wave detecting probe 12 has a pair of longitudinal pressing members 24 and 26 connected to each other so as to be relatively rotatable around a pin 22 so as to pinch the tip of a finger 20 of a living body.
And a hollow 1 which is fixed to the tip of each of the pair of pressing members 24 and 26, respectively, and is formed to have longitudinal concave grooves 28 and 30 along the longitudinal direction of the pressing members 24 and 26, respectively. A pair of elastic sheet members 32, 34, a light emitting element 36 provided in the groove 28 of one elastic sheet member 32 at an intermediate position in the longitudinal direction, and a groove 30 of the other elastic sheet member 34. A plurality of (in the present embodiment, nine) light receiving elements 38 arranged in the longitudinal direction and the finger 20 of the living body are held between the distal ends of the pressing members 24 and 26 with a predetermined pressing force. A spring 40 is provided for urging the base ends of the pressing members 24 and 26 in a direction separating from each other. Thus, the finger 20 is housed in the longitudinal grooves 28, 30 of the pair of elastic sheet members 32, 34, and the back and abdominal surfaces thereof are shielded from light by the inner wall surfaces thereof. 12.

In the state where the finger 20 is held by the photoelectric pulse wave detection probe 12 as described above, the plurality of light receiving elements 38 are substantially opposed to the light emitting element 36 and
The light receiving surface is arranged in the concave groove 30 of the elastic sheet member 34 such that its light receiving surface is in close contact with the finger 20 in a state of being arranged at equal intervals in one direction along the longitudinal direction of 0. In the present embodiment, of the nine light receiving elements 38 _{a to} 38 _i , the light receiving element 38 _e located at the center in the arrangement direction is the pressing members 24 and 26.
Are arranged so as to coincide with the light-emitting element 36 in the longitudinal direction of the finger 20, so that the distance between the light-receiving element _38e and the light-emitting element 36 is shorter than that between the other light-receiving elements when the finger 20 is sandwiched. Distance.

Further, the grooves 28 of the elastic sheet member 32 are provided.
The light emitting element 36 disposed therein has a wavelength range that is preferably scattered by blood cells such as hemoglobin, for example, 660.
A light emitting diode that outputs a wavelength in the range of about 900 nm to about 900 nm is used. More preferably, the wavelength is not affected by the oxygen saturation of hemoglobin, for example, 800 to 840 nm.
Light emitting diodes that output wavelengths in the order of magnitude are used. In addition, a photodiode, a phototransistor, or the like is preferably used for the plurality of light receiving elements 38.

The arithmetic and control unit 14 includes a CPU 42, an R
It is a so-called microcomputer comprising an AM 44, a ROM 46, and an interface 48.
While utilizing a temporary storage function of M44, according to pre-ROM46 program stored, inputted is converted from an analog signal to a digital signal by the A / D converter 50, a plurality of light receiving elements 38 _a to 38 DEG _i The sequentially output detection signals SM _{a to} SM _i are processed, and normally, the detection signal SM _e from the light receiving element 38 _e having the highest gain is sequentially output as a photoelectric pulse wave SMK. and prevents the output of the detection signal SM _e detected by _e, and generates a photoelectric pulse wave signal SMK undistorted, and outputs from the interface 48. The display device 16
Receives the photoelectric pulse wave signal SMK and displays the waveform of the photoelectric pulse wave.

FIG. 2 shows a control function of the arithmetic and control unit 14.
FIG. 3 is a functional block diagram for explaining a main part of FIG. Figure smell
The distribution waveform characteristic value calculation means 60 includes a plurality of light receiving elements.
38_a~ 38_iDetection signal SM sequentially output from_a~ S
M_iBased on the light receiving elements 38_a~ 38_iArray of
Longitudinal direction of the finger 20, ie, the pressing member 26 or
Or the groove 30 of the elastic sheet member 34 attached thereto.
The distribution of the light receiving level of each light receiving element 38 in the longitudinal direction is
A characteristic value indicating the asymmetry of the indicated distribution waveform is calculated. FIG.
Is that each light receiving element 38 is placed on the skin of a living body,
In a state where there is no body movement or finger 20 bending
Each detection signal SM_a~ SM_iThe maximum amplitude level of
Example of distribution waveform of average amplitude level or effective value level
FIG. 4 shows that each light receiving element is
The child 38 is moved relative to the belly of the finger 20 and
FIG. 3 in a state where an uneven gap is generated between
3 shows an example of the distribution waveform. Finger of each light receiving element 38
Those that are almost in contact with the belly of 20 are damped by gaps
Although the received light level is high because it detects scattered light that is not affected by
Those separated from the belly of the finger 20 will attenuate due to the gap
Detects the scattered light that is received, so the light reception level is low
Therefore, when a body motion occurs, the distribution waveform is not as shown in FIG.
A symmetry phenomenon occurs. Calculation method of the above distribution waveform characteristic value
The step 60 has, for example, an area S left and right from the center of the distribution waveform.
_L, S_RArea ratio R (= S_L/ S _R) Is the characteristic value
Is calculated as For convenience, the left side of the above distribution waveform
Side area S _LAs the light receiving element 38_a~ 38_dInspection from
Outgoing signal SM_a~ SM_dOf the distributed wave
Area S on the right side of the shape_RAs the light receiving element 38_f~ 38_iOr
Detection signal SM_f~ SM_iIs used.

The body movement determining means 62 determines the body movement of the non-measurement person based on the characteristic value of the distribution waveform generated by the distribution waveform calculating means 60. Usually, the distribution waveform when the subject does not move has a relatively smooth symmetry as shown in FIG. 3 because the light receiving element 38 is in a state of being in close contact with the belly of the finger 20. Since the shape is shown, the area ratio R which is a characteristic value of the distribution waveform when the subject does not move is shown.
_M (= S _L / S _R ) is stored in advance, and the actual area ratio R (= S _L / S _R ) is stored in the previously stored area ratio R.
Compared to _M, carry out the body movement determination when shifted actual case the symmetry of the distribution waveform is varied i.e. actual area ratio R is pre-stored predetermined value or more from the area ratio R _M, for example, 20% or more.

The photoelectric pulse wave selecting means 64, usually, but to sequentially output a detection signal SM _e by most high-gain receiving element 38 _e as a photoelectric pulse wave SMK, body motion is determined by the body movement judging means 62 If the, it prevents the output of the detection signal SM _e detected by the light receiving element 38 _e at that time. Thereby, only the photoelectric pulse wave signal SMK without distortion is output.

FIG. 5 is a flowchart for explaining a main part of the control operation of the arithmetic and control unit 14. In FIG. 5, in step (hereinafter, step is omitted) SA1, it is determined whether or not one pulse wave is generated, for example, by detection signal SM.
_The determination is made based on whether one cycle of _e has elapsed. If the determination at SA1 is denied, the system is put on standby.
If the result is affirmative, at SA2, the detection signal SM _a to SM _i of one period is read.

Next, the distribution waveform characteristic value calculating means 60
In SA3 corresponding to the above, the detection signals SM _{a to} SM _i
, A characteristic value indicating the symmetry of the distribution waveform of the signal level formed by, for example, the ratio of the left and right areas R (= S _L /
S _R ) is calculated. Then, in SA4 corresponding to the body movement judging means 62, with respect to previously stored area ratio in the absence of body motion _{R M (= S L / S} R), the actual area ratio newly calculated It is determined whether R has changed by a predetermined value or more, for example, by 20% or more. If the determination in SA4 is negative, although the detection signal SM _e detected by the light receiving element 38 _e in SA6 is output as a photoelectric pulse wave SMK, if it is positive, the detection signal SM _e Since the waveform may be distorted, the output of the photoplethysmogram SMK is blocked in SA5. In this embodiment, the above SA
5 and SA6 correspond to the photoelectric pulse wave sorting means 64.

[0024] As described above, according to this embodiment, a plurality of light receiving elements 30 _a to 30 _i for receiving the light transmitted by and it enters the 20 finger from the light emitting element 36 is the light-emitting elements 36 Is substantially opposed to the light emitting element 36 and the finger 2
A plurality of light-receiving elements 30 are arranged in one direction with respect to 0, and the light-receiving elements 30 are distributed by the distribution waveform characteristic value calculating means 60 (SA3).
light receiving signals SM _{a to} S output from _a to 30 _i respectively
Based on M _i , the light receiving element 30 _a in the one direction
To 30 _i characteristic value, that the left and right area ratio R of distribution waveforms showing the distribution of the received light level is calculated, and the body movement judging means 62 (S
According to A4), the body motion of the subject is determined based on the right-left area ratio R of the distribution waveform calculated by the distribution waveform characteristic value calculation means 60. Therefore, when the body motion is determined, the photoelectric pulse wave SMK distorted due to the influence of the body motion.
The output of the photoelectric pulse wave S
The waveform accuracy and reliability of the MK can be improved, and waveform analysis based on a low-accuracy photoplethysmogram is prevented.

While the embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, the body movement judging means 6 of the above embodiment
2 is the area ratio R _M (=
S _L / S _R ) and the newly calculated actual area ratio R
Is determined based on whether or not has changed by a predetermined value or more, for example, 20% or more. However, the body motion is determined based on the asymmetry of a new distribution waveform itself that is sequentially obtained. You may. That is, when the area ratio R (= S _L / S _R ) of the new distribution waveform exceeds a predetermined judgment reference range, for example, the range of 0.8 to 1.2, it is judged that the body motion has occurred. Is also good.

The body movement determining means 62 may determine the body movement of the subject based on the change in the asymmetry of the distribution waveform and the asymmetry of the distribution waveform itself. For example, the newly calculated actual area ratio R changes by a predetermined value or more, for example, by 20% or more with respect to the previously stored area ratio _RM (= S _L / S _R ) in a state where there is no body movement. If the area ratio R (= S _L / S _R ) of the appropriate distribution waveform exceeds a predetermined determination reference range, for example, the range of 0.8 to 1.2, it may be determined that a body motion has occurred. .

Further, in the above-described embodiment, the right and left area ratio R of the distribution waveform is used as the characteristic value of the distribution waveform. However, the amplitude ratio of the detection signal detected by the light receiving elements belonging to the left and right regions is used. , for example, the ratio of the amplitude of the detection signal SM _g amplitude and detected by light receiving element 38 _g of the detection signal SM _c detected by the light receiving element 38 _c may be used in a simplified manner.

In the above-described embodiment, the body movement determining means 6
If the body motion is determined by the step 2, the photoelectric pulse wave selecting means 6
4, the output of the photoelectric pulse wave SMK at that time was blocked, but the photoelectric pulse wave SMK output in the immediately preceding cycle
May be output in place of.

In the above-described embodiment, the photoplethysmogram SMK without distortion is output. However, inside the arithmetic and control unit 14, waveform analysis, evaluation of peripheral circulation state, estimation of peripheral blood pressure, pulse It may be processed for the purpose of wave timing detection or the like.

The photoplethysmogram detection probe 12 of the above-described embodiment is mounted with the finger 20 of the living body interposed therebetween in order to detect the photoelectric pulse wave. It may be attached to the part.

In the photoelectric pulse wave detection probe 12 of the above-described embodiment, the light output from the light emitting element 36 is propagated from the upper surface, ie, the back surface, of the finger 20 toward the lower surface, ie, the abdominal surface. It may be transmitted in the opposite direction. Further, the light output from the light emitting element 36 may be transmitted from one side of the finger 20 to the other side. In this case, the light emitting element 3
6 and the light receiving element 38 are attached to the both sides of the finger so that the photoelectric pulse wave detection probe 12 is attached.
There is an advantage that the influence on the zero bending is reduced.

Although not enumerated one by one, the present invention can be variously modified without departing from the spirit thereof.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a main part of a configuration of a photoelectric pulse wave detection device according to an embodiment of the present invention.

FIG. 2 is a functional block diagram illustrating a main part of a control function of the arithmetic and control unit according to the embodiment of FIG. 1;

FIG. 3 is a diagram showing a level distribution of a detection signal of each light receiving element in the embodiment of FIG. 1, and is a diagram showing a state where no body movement occurs.

FIG. 4 is a diagram showing a level distribution of a detection signal of each light receiving element in the embodiment of FIG. 1 and showing a state in which a body motion is occurring.

FIG. 5 is a flowchart illustrating a main part of a control operation of the arithmetic and control unit according to the embodiment of FIG. 1;

[Description of sign]

 10: Photoplethysmogram detection device 12: Photoplethysmogram detection probe 36: Light emitting element 38: Plurality of light receiving elements 60: Distribution waveform characteristic value calculation means 62: Body motion determination means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hidekatsu Inukai 2007 No. 1 Hayashi, Komaki-shi, Aichi F-term in Nippon Colin Co., Ltd. 4C017 AA09 AB03 AC27 BC11 CC01 FF15

Claims (2)

[Claims] 1. A photoelectric pulse wave detecting device for sequentially detecting and outputting a photoelectric pulse wave pulsating in synchronization with a periodic change in a blood volume in a living body, for irradiating a part of the living body with light. And a plurality of light-emitting elements arranged in one direction substantially opposing the light-emitting element and sandwiching a part of the living body between the light-emitting element and the light-emitting element. And a plurality of light receiving elements for receiving the transmitted light transmitted therethrough; and characteristic values of a distribution waveform indicating a distribution of light receiving levels of the light receiving elements in the one direction based on light receiving signals output from the light receiving elements. A distribution waveform characteristic value calculating means for calculating the distribution waveform characteristic value calculating means, and a body movement determining means for determining a body movement of the living body based on the characteristic value of the distribution waveform calculated by the distribution waveform characteristic value calculating means. A photoelectric pulse wave detection device characterized by the following. 2. The photoelectric pulse wave detecting apparatus according to claim 1, further comprising output blocking means for blocking the output of said photoelectric pulse wave when said body movement determining means determines the body movement of said living body.