JPS6384520A - Reflection type heart rate meter - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention relates to a pulse meter, more specifically a pulse meter that detects the pulse by irradiating light onto the wall of the external auditory canal and detecting the reflected light. Regarding the meter.

(Prior Art) Pulse rate is a very important measurement value when examining the condition of the heart. In the past, doctors often manually compressed the artery in the patient's forearm and measured the pulse rate based on pressure fluctuations in the artery, but in recent years, pressure fluctuations have been automatically measured using a pressure quadrangle transducer, and the pulse rate has been measured. Devices have emerged to measure This involves wrapping a cuff around the upper arm that compresses the forearm and artery, inserting a pressure transducer between the cuff and the upper arm, and measuring the pulse based on changes in arterial pressure applied to the pressure transducer.

Furthermore, devices that measure pulse using electrocardiograms or fingertip absorbance have recently been developed. Devices that measure pulses using electrocardiograms measure pulses (more precisely, heartbeats) from electrocardiogram waveforms by attaching electrodes to the chest or arm.

A device that measures the pulse based on the absorbance of the fingertip is a device that attaches an absorbance meter to the fingertip of the hand, detects changes in the blood volume of the fingertip due to changes in arterial pressure as absorbance, and measures the pulse using RII. These devices allow automatic pulse measurement.

On the other hand, due to the increase in the number of people playing sports, the number of deaths from diseases such as heart failure during exercise is increasing, so devices that measure pulses during exercise are being introduced so that people can exercise at a moderate level without putting their health at risk. Demand is increasing. However, with conventional pulse measurement devices, the sensor must be attached to the arm, chest, fingertips, etc., which can lead to erroneous measurements due to body movement or sweating, and the sensor may impede movement, making it difficult to measure the pulse during exercise. difficult to use.

(Problems to be Solved by the Invention) As described above, it has been difficult for the conventional pulse measuring device to measure the pulse during exercise due to erroneous measurements due to body movement and sweating and poor mobility when worn.

An object of the present invention is to solve the problems of the prior art and provide a pulse meter that can easily measure pulses during exercise.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a light source that irradiates a living body with light, and a light receiver that receives light emitted from the light source and reflected by the living body, which is inserted into the external auditory canal. The insertion portion is equipped with a holder for holding the external auditory canal wall so as to face it.

(Function) Light emitted from the light source provided at the insertion portion into the external auditory canal is irradiated onto the external auditory canal wall. Because a superficial vascular network runs on the surface of the external auditory canal wall like other parts of the body, the reflectance changes as the amount of hemoglobin increases or decreases due to increases or decreases in blood pressure. Therefore, the pulse can be detected by receiving the reflected light from the wall of the external auditory canal with a light receiver and detecting a change in the output signal of the light receiver.

In this case, the holder inserted into the external auditory canal wall maintains a stable positional relationship between the light source and receiver and the external auditory canal wall regardless of body movements, and the external auditory canal is one of the areas in the human body that sweats the least. , reflected light is less affected by sweat.

(Embodiment) FIG. 1 shows the configuration of a reflex pulse meter according to an embodiment of the present invention. In the figure, 1 is a cross-section of the head of the subject, in which a part 3a of the holder 3 is inserted into the external auditory canal 2.

The holder 3 is made of a sponge-like synthetic resin, and is configured so that the insertion portion 3a is brought into close contact with the wall of the external auditory canal so that its relative position with respect to the external auditory canal does not shift.

The holder 3 includes a light emitting diode (LED) 4 as a light source.
A photodiode 5 as a light receiver is embedded so that its light-emitting surface and light-receiving surface are exposed on the circumferential surface of the insertion section 3a and facing the wall of the external auditory canal. The light is received by the photodiode 5. In this example, the LED 4 and the photodiode 5 are constituted by separate chips, and the light emitting surface and light receiving surface thereof are provided a predetermined distance apart from the surface of the external auditory canal wall. This is an LED
4 and photodiode 5 are configured on separate chips,
This is to ensure that the light emitted from the LED 4 and reflected by the wall of the external auditory canal is incident on the photodiode 5, taking into account that there is a certain distance between them.

The LED 4 used has, for example, an emission center wavelength of λ-565nffl and an output of 2.5 mW. Of course, other light sources may be used.

As shown in Figure 5, part of the light emitted from the LED 4 is reflected by the epidermal surface of the external auditory canal wall, but the remaining part penetrates into the epidermal tissue or superficial blood vessels and is scattered and absorbed. . A portion of the light scattered by the epidermal tissue, superficial blood vessels, or other tissues is emitted from the external auditory canal wall surface and exits the body again.
Similar to the light reflected on the surface of the external auditory canal epidermis, the reflected light is received by the photodiode 5. The amount of light scattered and reflected by tissues in the body decreases when the tissue absorbs a lot of light, and increases when the absorption of light decreases. The main substance that causes light absorption in living tissues is hemoglobin, and at wavelengths for which hemoglobin absorbs a large amount of light, the amount of reflected light decreases.

An example of the light absorption characteristics of hemoglobin (and oxidized hemoglobin) is shown in Figure 3 (Reference 1; Joint Venture Hiroshi "Biophysical Properties - Optical Properties", Medical Electronics and Bioengineering.

(From Vol. 15, No. 1, ppA8-56). As shown in the figure, absorption increases at wavelengths of ~430 nm and 500 rv ~600 nm.

Due to the absorption spectrum of hemoglobin, the reflectance of the skin is as shown in Figure 4 (Reference 2: J, Gltvelt et al.

“Pulsed multirequency ph
otoplethysmooraph”Med, &
Biol, EnQ, & Comput, 1984
．． vol 22゜1) I), 212-215). In FIG. 4, the area indicated by the arrow is the area where the reflectance is reduced due to hemoglobin. When the reflectance of the skin is measured in a wavelength range where the reflectance is reduced due to light absorption by hemoglobin, the reflectance changes depending on the increase or decrease in hemoglobin m due to the increase or decrease in blood pressure.

Here, the blood volume in the surface tissue of the recessed wall of the external ear increases or decreases due to increases and decreases in blood pressure associated with heart beats. Therefore, if reflected light is measured at a wavelength that is largely absorbed by hemoglobin, the amount of reflected light will decrease or increase as blood pressure increases or decreases. That is, the pulse can be measured by measuring the amount of reflected light.

On the other hand, the degree of light penetration into tissues such as the epidermis increases as the wavelength becomes longer, and light with a wavelength of 500 nm or more penetrates 230 μm or more, and the light also reaches superficial blood vessels. However, 430n
The light penetration into the epidermis is low for light with a wavelength of less than 100 μm.
It penetrates only below m. Therefore, less light with a wavelength of 430 nm or less reaches superficial blood vessels, and changes in the amount of reflected light due to changes in blood pressure are small.

Therefore, in order to measure the pulse with good S/N, it is necessary to
It is appropriate to use light with a wavelength of +m to 600nra, and in this example, an LE with an emission center wavelength of 565nm
D was used.

In addition, light with a wavelength close to the ultraviolet region of 45'Onm or less may cause harm such as skin cancer if continued irradiation to the human body for a long period of time, so from this point of view as well, the light to be irradiated should be
Light with a wavelength of 00 nm to 600 ni is suitable. More preferably, 5 is the absorption peak wavelength of oxidized hemoglobin.
Light around 40 nl or around 570 nl is optimal.

Note that the LED 4 is supplied with a constant current from the LED drive circuit 8, so that temporal fluctuations in illuminance are reduced.

The output signal of the photodiode 5 is led to the detection means via a cable 7, and first converted into a voltage signal of an appropriate magnitude by a current-voltage converter (1-V converter) 9. The output signal from this 1-V converter 9 may contain external light such as sunlight or indoor light in addition to the light reflected from the skin, or may contain fluctuation components of reflectance due to body movement. Therefore, the pulse signal component is extracted by a filter (bandpass filter > 10
times/minute, so the filter 10 has a frequency of 0.6 Hz to
A bandpass filter that passes a 2.5Hz frequency component is used. Depending on the pulse measurement conditions, the filter 10 may be omitted.

The output signal of the filter 10 is divided into two signal paths and input to the comparator 11. That is, on one path, the signal is directly input to one input of the comparator 11 without undergoing signal processing, and on the other path, it is input as a threshold value to the input of the comparator 11 via the peak hold circuit 12 and attenuator 13.

The solid line in FIG. 2 (a) is the output signal waveform of the filter 10, and the result of determining it with the comparator 14 using the output of the attenuator 13 as the threshold value vth as shown in FIG.
b). The output signal of the comparator 14 thus obtained is input to the counter 14, where the pulse rate per unit time (for example, per minute) is determined and displayed on the display 15.

The output signal of the comparator 11 is also input to the gate circuit 17, and the output signal of the oscillator 16 oscillating in the audible band is passed therethrough. The output signal of this gate circuit 17 is
The transducer 2 embedded in the tip of the insertion section 3a of
is converted into sound. That is, an audible sound is emitted from the transducer 2 in synchronization with the pulse.

Note that, in FIG. 1, a reset signal is periodically input to the peak hold circuit 12 from a timing circuit 18. This allows for a
Even if iivth is erroneously set to a high value, normal operation can be quickly restored by this reset.

In addition, in FIG. 1, LED drive circuit 8.1--converter 9. Filter 10. Comparator・11. Peak hold circuit 12. Attenuator 13. Counter 14, display 151
Oscillator 16. Gate circuit 17 and timing circuit 18
The electronic circuit section consisting of, for example, is housed in a small case,
It can be carried in the subject's chest pocket or the like. Note that these electronic circuit sections can be embedded in the holder 3 to further improve portability.

By using a reflex-type pulse meter such as the one described above, the person being measured can check their own pulse rate by sound or display while exercising, such as jogging, and can perform appropriate exercise according to their physical strength. It turns out.

The present invention can be implemented in various modifications other than the above embodiments. For example, the structure shown in FIG. 6 may be used as the holder 3 instead of the structure shown in FIG. 1. In FIG. 6, the LED 4 and the photodiode 5 are connected to a rod-shaped first holder 21 made of relatively hard resin, and this first holder 21.
and a second holder 22 made of a relatively soft (sponge-like) member such as resin, which is provided so as to cover the peripheral surface of the holder 21 and is in close contact with the wall of the external auditory canal. The tip of the first holder 21 is exposed from the second holder 22, and the LED 4 and photodiode 5 are provided in this exposed portion.

Further, in the above embodiment, the LED 4 and the photodiode 5 are constructed of separate chips, but they may be constructed of the same chip, in which case the distance between them will be very short. Therefore, the light-emitting surface and the light-receiving surface can be provided on the holder so that they are in contact with the wall of the external auditory canal.

Further, in the above embodiment, only the pulse sound is output from the transducer 6, but it is also possible to output music or the like at the same time in combination with a so-called headphone stereo or the like. Furthermore, instead of outputting a sound synchronized with the pulse rate, it is also possible to output an increase or decrease in the pulse rate as the pitch of the sound.

Further, other biological measurement sensors such as a temperature sensor for measuring body temperature may be incorporated into the holder.

[1 Effect of the Invention] According to the present invention, the pulse of a subject during exercise can be easily detected without being affected by body movement, sweating, etc., and without interfering with the mobility of the subject. Can be done. Further, since the pulse meter according to the present invention has good portability, it has the advantage that the person to be measured does not get tired even when using it for a long time.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a reflection type pulse meter according to an embodiment of the present invention, and FIG. 2 is a signal waveform diagram for explaining the operation of the detection section.
Figure 3 is an explanatory diagram showing the light absorption characteristics of hemoglobin, Figure 4 is a diagram showing the spectrum of light reflected from the skin, Figure 5 is an illustration to explain how light is reflected in a living body, and Figure 6 is an illustration showing the light absorption characteristics of hemoglobin. FIG. 3 is a diagram for explaining the structure of a holder in another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Head cross section, 2... External auditory canal, 3... Holder, 3a... Insertion part, 4... LED (light source), 5...
...Photodiode (light receiver), 6...Transducer for electrical-acoustic conversion, 7...Cable, 8...
LED drive circuit, 9... I-V converter, 10... Filter, 11... Comparator, 12... Peak hold circuit, 13... Attenuator, 14... Counter,
15... Display device, 16... Oscillator, 17... Gate circuit, 18... Timing circuit, 21.22...
Retainer. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Wavelength [nm] Figure 3 Wavelength [nm] Figure 4 Figure 5 Figure 6

Claims (8)

[Claims] (1) Reflection type pulse that includes a light source that irradiates light onto a living body, a light receiver that receives light emitted from the light source and reflected by the living body, and a detection means that detects the pulse from the output signal of this light receiver. The instrument has an insertion part inserted into the external auditory canal,
A reflection type pulsometer characterized in that the insertion portion is provided with a holder for holding the light source and the light receiver so as to face the wall of the external auditory canal. (2) The reflection type pulsometer according to claim 1, wherein the light source is a light emitting diode with a center emission wavelength of 500 nm to 600 nm. (3) The detection means detects 0.6Hz~ of the output signal of the optical receiver.
2. The reflex pulse meter according to claim 1, further comprising a filter that selectively passes a frequency component of 2.5 Hz. (4) The reflection according to claim 3, wherein the detection means detects the pulse by counting the number of times the output signal of the filter exceeds a predetermined threshold value with a counter per unit time. type pulse meter. (5) A signal source that generates an electrical signal when the output signal of the filter exceeds a predetermined threshold, and a transducer that converts the electrical signal into sound. 4. The reflex pulse meter according to item 4. (6) The reflex pulse meter according to claim 5, wherein the transducer is held by a holder. (7) Claim 3, characterized in that it has a peak detector that detects the peak value of the output signal of the filter and an attenuator that attenuates the output signal of the peak detector, and the output signal of the attenuator is used as a threshold value. 6. The reflex pulse meter according to any one of items 6 to 6. (8) The reflex pulse meter according to claim 7, further comprising a reset circuit that resets the peak detector at regular intervals.