JP2023134265A - Oxygen saturation degree measuring device and oxygen saturation degree measuring method - Google Patents

Abstract

To provide an oxygen saturation degree measuring device and an oxygen saturation degree measuring method capable of reducing a frequency of measurement interruptions attributed to a positional deviation of a sensor at a position inside the wrist.SOLUTION: An oxygen saturation degree measuring device 10C includes: a band 12 wound around the wrist of a person to be measured; light emitting elements (a first light emitting element LED1, a second light emitting element LED2, and a third light emitting element LED3) for irradiating the artery (radial artery 24) of the wrist with light; a first light reception element PD1 and a second light reception element PD2 for receiving reflection light from the artery (radial artery 24); a light reception element determination part for determining the light reception element by which a pulse wave signal with a larger amplitude of a first pulse wave signal acquired from the reflection light received by the first light reception element PD1 and a second pulse wave signal acquired from the reflection light received by the second light reception element PD2 is received, as a light reception element for measurement; and a measuring part for measuring an oxygen saturation degree of the artery irradiated with light on the basis of the pulse wave signal received by the determined light reception element for measurement.SELECTED DRAWING: Figure 11

Description

The present disclosure relates to an oxygen saturation measuring device and an oxygen saturation measuring method.

Photoplethysmography (PPG) is a well-known method that measures oxygen saturation (S _{PO 2} ) in arterial blood by percutaneously irradiating light onto arteries in the human body from above the skin. ing. Since pulsations appear strongly on the skin of the human body, especially on the arteries under the skin of the wrist, when measuring oxygen saturation at the wrist, a pulse wave signal with a relatively large amplitude can be obtained.

As an example of an oxygen saturation measuring device, Patent Document 1 discloses a technique for measuring physiological data using a wristwatch-type measuring device worn on the wrist. The measuring device of Patent Document 1 is a wearable system that includes a band that is wrapped around the wrist and a sensor unit that is provided on the band. The sensor unit includes a light emitting element such as an LED that emits an optical signal, and a light receiving element such as a photodiode that serves as a sensor that receives the optical signal. The sensor unit is arranged within a part of the plate surface of a plate-shaped sensor plate having approximately the same thickness overall.

Moreover, Patent Document 1 discloses a technique of rotating a circular sensor unit arranged on the inner surface of the band, which is the surface that contacts the skin, as a method of changing the arrangement position of the sensor. Further, Patent Document 1 also discloses a sensor slide that is arranged on the inner surface of the band and slides in the circumferential direction of the wrist.

When measuring oxygen saturation using a wristwatch-type measuring device, a band is wrapped around the wrist and a sensor unit is placed on the skin on the inside of the wrist near an artery such as the brachioradial artery. Then, an optical signal is emitted from the light emitting element of the sensor unit to the pulsating arterial blood.

The irradiated optical signal is reflected by the arterial blood, and the reflected optical signal is acquired as a pulse wave signal by the light receiving element of the sensor unit. A value obtained by calculating the intensity of the acquired pulse wave signal using a predetermined calculation formula can be used as a measured value of oxygen saturation. Note that in the present disclosure, "intensity of pulse wave signal" means the amplitude of the pulse wave signal.

Further, Patent Document 2 discloses a wristwatch-type wearable system as a biological information acquisition device that includes a band that is wrapped around the wrist or arm, and a sensor module (sensor unit) provided in the band. In the biological information acquisition device of Patent Document 2, in order to measure a blood sugar level, a blood vessel to be measured is irradiated with light, and the transmitted light that has passed through the blood vessel is received by a plurality of light receiving sections (light receiving elements). Patent Document 2 states that oxygen saturation can be measured based on the intensity of transmitted light that has passed through an artery.

Special table 2017-516539 publication Japanese Patent Application Publication No. 2017-136182

Here, when the wristwatch-type measuring device is worn on the inside of the wrist of the person to be measured, there is a problem in that the sensor unit tends to move away from its initial position near the artery to be measured. Specifically, for example, after the band is worn on the wrist of the person being measured, the band may shift on the skin surface due to sweaty skin at the area where the band is worn. Alternatively, a person to be measured who feels uncomfortable wearing the band may temporarily remove the band from his wrist and then re-wrap it around his wrist. Furthermore, even if the wrist is slightly bent, for example, the palmaris longus tendon tends to protrude relatively largely from the skin at the wrist. The raised palmaris longus tendon pushes the band or sensor unit outward, increasing the distance between the sensor unit and the skin surface of the wrist.

In other words, even if the optical element as a sensor is placed at the initial position on the wrist, after placement, the placement position of the sensor changes in each of the extending direction of the forearm, the circumferential direction of the wrist, and the radial direction of the wrist. , the position is likely to shift from the initial position. For this reason, the intensity of the pulse wave signal acquired by the light receiving element decreases due to the positional shift, resulting in a problem in that the measurement of oxygen saturation is likely to be interrupted.

Here, in the case of Patent Document 1, by rotating the sensor unit, it is possible to slide the position of the optical element within the sensor unit on a circumference having a constant radius from the center of rotation. However, the range of change in the position of the optical element is limited only to the circumference having a constant radius from the center of rotation. Specifically, the range of position change is limited only to a certain circumference within a plane defined by two directions: the extending direction of the forearm and the circumferential direction of the wrist. For this reason, the range of positions that can be adjusted in the event of positional deviation of the sensor is small.

Furthermore, in Patent Document 2, transmitted light transmitted through an artery is used to measure oxygen saturation. For this reason, for example, when reflected light is used to measure oxygen saturation, it is difficult to apply the technique of Patent Document 2 as is to the problem of sensor positional deviation.

The present disclosure has been made with a focus on the above-mentioned problems, and includes an oxygen saturation measuring device and an oxygen saturation measuring method that can reduce the frequency of measurement interruptions caused by misalignment of the sensor at the inner side of the wrist. The purpose is to provide

An oxygen saturation measurement device according to one aspect of the present disclosure includes a band wrapped around the wrist of a subject, a light emitting element that irradiates light to an artery in the wrist, and a first light emitting element that receives reflected light from the artery in the wrist. a second light-receiving element that is placed apart from the first light-receiving element and receives the reflected light from the wrist artery; Among the pulse wave signal and the second pulse wave signal acquired from the reflected light received by the second light receiving element, the light receiving element that has received the pulse wave signal having a larger amplitude is used as the measuring light receiving element. The apparatus includes a light receiving element determining section that determines the light receiving element, and a measuring section that measures the oxygen saturation level of the artery irradiated with light based on the pulse wave signal received by the determined measuring light receiving element.

In the oxygen saturation measurement device according to the above aspect, when measuring oxygen saturation, the light receiving element that receives the pulse wave signal having the larger amplitude is selected from among the first light receiving element and the second light receiving element. It is determined as a light receiving element for measuring oxygen saturation. Then, the oxygen saturation level is measured based on the pulse wave signal received by the determined measurement light receiving element.

That is, a plurality of reflected lights of light emitted from the same light emitting element are received, and the amplitudes of pulse wave signals of the plurality of received reflected lights are compared. Through the comparison, the pulse wave signal having the largest amplitude is quantitatively selected as the pulse wave signal for oxygen saturation measurement. Therefore, the frequency of interruptions in oxygen saturation measurement due to misalignment of the sensor at the inner side of the wrist can be reduced.

Further, in the above aspect, the first light receiving element and the second light receiving element may be arranged along the circumferential direction of the wrist.

According to the above configuration, a more appropriate measurement light receiving element can be determined between two different positions along the circumferential direction of the wrist.

Further, in the above aspect, it is determined whether the first pulse wave signal and the second pulse wave signal satisfy a preset reference value based on a viewpoint of achieving a preset measurement accuracy. The measuring device may further include a determination unit, and perform a process of determining a measuring light receiving element from among the light receiving elements that have received a pulse wave signal that satisfies the reference value.

According to the above configuration, it is determined whether the first pulse wave signal and the second pulse wave signal satisfy a preset reference value based on the viewpoint of achieving a preset measurement accuracy. . Then, a process is performed to determine a measuring light receiving element from among the light receiving elements that have received a pulse wave signal that satisfies the reference value. Among the acquired pulse wave signals, only the pulse wave signals that satisfy the reference value are extracted for measurement, so that the measurement accuracy of oxygen saturation can be further improved.

Further, in the above aspect, the light emitting element includes a first light emitting element that irradiates light to an artery in the wrist, and a first light emitting element that is arranged apart from the first light emitting element along the circumferential direction of the wrist and that irradiates light to the artery in the wrist. a second light emitting element that emits light, the second light emitting element is arranged apart from the first light receiving element, and the second light receiving element is arranged apart from the second light receiving element, and the second light emitting element emits light. The first light receiving element, the second light receiving element, and the third light receiving element are arranged along the circumferential direction of the wrist, and the first light receiving element receives reflected light from the artery. a first amplitude distribution based on the first pulse wave signal, the second pulse wave signal, and the third pulse wave signal acquired from the reflected light of the light of the element; a distribution creation unit that creates a second amplitude distribution based on the first pulse wave signal, the second pulse wave signal, and the third pulse wave signal acquired from reflected light; A criterion set using the first amplitude distribution and the second amplitude distribution to correspond to the fact that the light emitting element is located above the artery among the first light emitting element and the second light emitting element. a light emitting element determination unit that determines the light emitting element for which a distribution satisfying the conditions has been created as the light emitting element for measurement, and determines the oxygen saturation based on the pulse wave signal of the reflected light of the determined light emitting element for measurement. may be measured.

According to the above configuration, the reflected light of the first light emitting element is received by each of the first light receiving element, the second light receiving element, and the third light receiving element, and the received reflected light is reflected by the wrist. A first amplitude distribution along the circumferential direction is created. Further, the reflected light of the second light emitting element is received by each of the first light receiving element, the second light receiving element, and the third light receiving element, and the received reflected light is transmitted along the circumferential direction of the wrist. A second amplitude distribution is created.

Then, out of the created first amplitude distribution and second amplitude distribution, a light emitting element is created that satisfies the reference condition set in accordance with the fact that the light emitting element is located above the artery. is determined as the light emitting element for measurement. Then, the oxygen saturation level is measured based on the pulse wave signal of the reflected light from the determined light emitting element for measurement. That is, the light emitting element located above the artery from among the plurality of light emitting elements is determined as the light emitting element for measurement. Therefore, the measurement accuracy of oxygen saturation can be further improved.

Further, in the above embodiment, current is continued to be applied only to the light emitting element determined as the measurement light emitting element among the first light emitting element and the second light emitting element, and the light emitting element is not determined as the measurement light emitting element. The light emitting device may further include a control unit that stops energizing the light emitting element.

According to the above configuration, power supply to the light emitting elements that have not been determined as measurement light emitting elements is stopped, so power can be saved.

An oxygen saturation measuring method according to another aspect of the present disclosure includes irradiating light onto an artery to be measured using the light-emitting element of the oxygen saturation measuring device according to the above-described one aspect, and emitting light from the artery irradiated with the light. From the reflected light, a first pulse wave signal is obtained using the first light receiving element, a second pulse wave signal is obtained using the second light receiving element, and the first pulse wave signal and the second pulse wave signal are combined. The pulse wave signal is monitored, and the light receiving element that receives the pulse wave signal having the larger amplitude between the monitored first pulse wave signal and the monitored second pulse wave signal is determined as the light receiving element. The measuring section is used to determine the oxygen saturation as a measuring light receiving element, and the measuring section is used to measure oxygen saturation based on the pulse wave signal received by the determined measuring light receiving element.

According to the oxygen saturation measuring method according to the other aspect described above, as in the case of the oxygen saturation measuring device according to one aspect of the present disclosure, the oxygen saturation is measured at the position on the inside of the wrist due to the positional deviation of the sensor. The frequency of measurement interruptions can be reduced.

According to the oxygen saturation measuring device and the oxygen saturation measuring method according to the present disclosure, it is possible to reduce the frequency of interruptions in measurement due to misalignment of the sensor at the inner side of the wrist.

FIG. 1 is a cross-sectional view illustrating an oxygen saturation measuring device according to a first embodiment of the present disclosure. FIG. 1 is a perspective view illustrating an oxygen saturation measuring device according to a first embodiment. FIG. 2 is a plan view illustrating a sensor unit of the oxygen saturation measuring device according to the first embodiment. 4 is a sectional view taken along line 4-4 in FIG. 3. FIG. It is a sectional view explaining the oxygen saturation measuring device concerning the modification (the 1st modification) of a 1st embodiment. It is a sectional view explaining the oxygen saturation measuring device concerning the modification (the 2nd modification) of a 1st embodiment. It is a top view explaining the slider part of the oxygen saturation measuring device based on 2nd Embodiment. 8 is a sectional view taken along line 8-8 in FIG. 7. FIG. 8 is a sectional view taken along line 9-9 in FIG. 7. FIG. FIG. 7 is a plan view illustrating the arrangement of a light emitting element and a light receiving element of an oxygen saturation measuring device according to a third embodiment. It is a flow chart explaining the oxygen saturation measuring method using the oxygen saturation measuring device concerning a 3rd embodiment. FIG. 12(A) is a graph illustrating the amplitude distribution of the reflected light of the light emitted from the first light emitting element of the oxygen saturation measuring device according to the third embodiment, and FIG. 12(B) is 12(C) is a graph illustrating the distribution of the amplitude of the reflected light of the light irradiated from the second light emitting element of the oxygen saturation measuring device according to the third embodiment, and FIG. It is a graph explaining the distribution of the amplitude of the reflected light of the light irradiated from the 3rd light emitting element of a saturation measuring device. FIG. 7 is a plan view illustrating another arrangement pattern of light emitting elements and light receiving elements.

First to third embodiments of the present disclosure will be described below. In the description of the drawings below, the same or similar parts are denoted by the same or similar symbols. However, the drawings are schematic, and the relationship between the thickness and planar dimensions, the ratio of the thickness of each device and each member, etc. differ from the reality. Therefore, specific thickness and dimensions should be determined with reference to the following explanation. Furthermore, the drawings include portions that differ in dimensional relationships and ratios.

-First embodiment-
The first embodiment is characterized in that, in a contact section where a sensor is disposed and has a contact surface that comes into contact with the skin, the contact surface has a curved shape. The first embodiment will be described below with reference to FIGS. 1 to 6.

<Oxygen saturation measuring device>
As shown in FIG. 1, the oxygen saturation measuring device 10A according to the first embodiment includes a band 12, a base 14, a contact section 16, a light emitting element, a light receiving element, and a measuring section 18. In the oxygen saturation measuring device 10A illustrated in FIG. 1, the light receiving elements include a first light receiving element PD1, a second light receiving element PD2, a third light receiving element PD3, a fourth light receiving element PD4, and a fifth light receiving element PD1. A light receiving element PD5 is provided. Further, inside the wrist in FIG. 1, a radius 20, a radial styloid process 20A, a flexor carpi radialis tendon 22, and a radial artery 24 are illustrated.

(band)
The band 12 is wrapped around the wrist of the subject. The material of the band 12 is arbitrary, such as resin, cloth, metal, etc. The band 12 is also provided with a clasp for adjusting and fixing the length when it is wrapped around the wrist. As shown in FIG. 2, the band 12 is provided with a calculation display section 26.

(base)
A base 14 is provided on the inner surface of the band 12. Specifically, in the first embodiment, the base 14 may be fixed to the band 12, for example by adhesive. However, the fixing method is not limited to adhesion, and a fixing plate member may be interposed between the circuit board and the band 12, and the circuit board may be fixed to the plate member by screwing or the like.

The base 14 has a flat joint surface 14A between the band 12 and the contact portion 16. In the first embodiment, both a light emitting element and a light receiving element are bonded to the bonding surface 14A of the base 14. In the present disclosure, at least one of the light emitting element and the light receiving element may be bonded to the bonding surface 14A.

Further, in the present disclosure, the base 14 may be the circuit board itself on which the light emitting element and the light receiving element are mounted, or a combination of the circuit board and a fixing plate member, or a combination of the circuit board and a buffer. It may also be a combination of other members. That is, the base 14 of the present disclosure only needs to have a bonding surface 14A to which at least one of the light emitting element and the light receiving element is bonded.

As shown in FIG. 3, a light emitting element and a light receiving element are arranged on the joint surface 14A of the base 14. Note that illustration of the circuit board on which the light emitting element and the light receiving element are mounted is omitted.

(Light emitting element)
The light emitting element is, for example, an electronic component such as a light emitting diode (LED). The light emitting element is placed at a preset position with respect to the contact portion 16, and irradiates light to the artery of the wrist. In the first embodiment, a first light emitting element LED1, a second light emitting element LED2, and a third light emitting element LED3 are provided as light emitting elements. The first light emitting element LED1, the second light emitting element LED2, and the third light emitting element LED3 are arranged apart from each other and arranged along the circumferential direction of the wrist. Note that in the present disclosure, the number of light emitting elements is one or more and arbitrary.

As shown in FIG. 3, the first light emitting element LED1, the second light emitting element LED2, and the third light emitting element LED3 each include one or more red light sources RED and one or more infrared light sources IR. has a set of light sources. That is, in the first embodiment, two types of light are emitted from one light emitting element. Two types of reflected light received by one light receiving element are used to measure oxygen saturation. Note that in the present disclosure, the number of types of light sources is not limited to two types, and may be one type, or three or more types.

(Measurement principle of oxygen saturation)
Here, the principle of measuring oxygen saturation in the first embodiment in which two types of irradiation light and two types of reflected light are used will be explained. Specifically, for example, red light in a wavelength range of about 620 nm to about 700 nm has a characteristic that its absorbance greatly changes depending on the presence or absence of oxygen bonded to hemoglobin. On the other hand, near-infrared light in the wavelength range of about 850 nm to about 960 nm has a characteristic that its absorbance does not change significantly depending on the presence or absence of oxygen bonded to hemoglobin.

For this reason, changes in the intensity of the pulse wave signal of the reflected red light are monitored over time, and the pulse wave signal fluctuating component (AC) included in the monitored pulse wave signal and the fixed component (DC) that does not fluctuate. Calculate. Then, by dividing the variable component by the fixed component (AC/DC), the perfusion index (PI) value of the red light is calculated as PI _RED . In addition, as in the case of red light, the PI value (PI _IR ) of reflected near-infrared light is calculated by monitoring changes in the intensity of the pulse wave signal of reflected near-infrared light over time. do.

Then, the ratio (PI _RED / _{PI IR )} between the PI value of red light (PI RED ) and the PI value of near-infrared light (PI _IR ) is calculated. Then, by using the calculated ratio (PI _RED /PI _IR ) in the following equation (1), the oxygen saturation level can be calculated.

Oxygen saturation [%] = a × (PI _RED / PI _IR ) + b ... Formula (1)

Coefficients a and b in equation (1) can be determined by experiment. Note that in the present disclosure, the method for measuring oxygen saturation is not limited to this, and other methods may be used.

(Light receiving element)
The light receiving element is, for example, an electronic component such as a photodiode (PD). The light receiving element is arranged at a preset position with respect to the contact part 16, and receives reflected light from the artery of the wrist via the contact surface 16A of the contact part 16. The first light receiving element PD1, the second light receiving element PD2, the third light receiving element PD3, the fourth light receiving element PD4, and the fifth light receiving element PD5 are arranged apart from each other and in the circumferential direction of the wrist. arranged along. Note that in the present disclosure, the number of light receiving elements is one or more and arbitrary.

In the first embodiment, one "sensor unit" is configured by one or more light emitting elements and one or more light receiving elements corresponding to the one or more light emitting elements. In the present disclosure, multiple sensor units may be provided. Further, both the number of light emitting elements and the number of light receiving elements included in one "sensor unit" can be set arbitrarily.

Further, the oxygen saturation measuring device 10A according to the first embodiment is a reflective type in which the intensity of the pulse wave signal is measured using reflected light, but the present disclosure is not limited to the reflective type, and the pulse wave signal is measured using transmitted light. It may also be a transmission type in which the intensity of is measured.

(light shielding part)
As shown in FIG. 4, a light shielding portion 14B is provided between the light emitting element and the light receiving element in the base 14. The light blocking portion 14B prevents the light receiving element from directly receiving light from the light emitting element. Note that while using the light shielding part 14B, it is preferable to make the distance between the light emitting element and the light receiving element as close as possible from the viewpoint of shortening the optical path length and improving measurement accuracy as a result.

(contact part)
Contact portion 16 is attached to band 12 . Further, the contact portion 16 has translucency for light irradiated onto the artery of the wrist and light reflected from the artery of the wrist. Specifically, for example, a light-transmitting member such as a lens may be used. The contact portion 16 disposed above the light emitting element in FIG. 4 is, for example, a diffuser lens capable of enlarging the irradiation area. Further, although not shown, a diffusing agent may be disposed above the light emitting element together with the diffusing lens or instead of the diffusing lens. Further, the contact portion 16 disposed above the light receiving element in FIG. 4 may be, for example, a condenser lens capable of collecting reflected light.

Further, the contact portion 16 has a contact surface 16A that protrudes from the band 12 toward the wrist. In the first embodiment, the contact surface 16A has a curved shape. The contact surface 16A comes into contact with the skin of the wrist when measuring oxygen saturation.

As shown in FIGS. 3 and 4, the contact portion 16 has a dome shape. In the contact surface 16A corresponding to the outer surface of the dome, the center part in the left-right direction (direction E in which the forearm extends) in FIG. Curves smoothly without any friction. The curvature is preferably 0.167 or more, for example, from the viewpoint of improving wearability for the person being measured. Although not shown in the drawings, similarly, the center portion of the contact portion 16 in the circumferential direction C of the wrist is flat, and both left and right end portions are smoothly curved.

Further, in the present disclosure, as will be described later in a second embodiment, the contact surface 16A does not need to have a flat portion, as shown in FIGS. 8 and 9. The contact surface 16A may have a curved shape with an overall constant curvature.

Note that in this specification, "the forearm extending direction E" overlaps with any of the directions in which the radius 20 extends, the ulna, and the artery. Moreover, the "direction E in which the forearm extends" strictly speaking differs depending on the subject. That is, the "extending direction E of the forearm" is not uniquely determined by coordinates in a three-dimensional space, but is determined based on the extending direction of the radius 20, the ulna extending direction, and the artery extending direction for each subject. determined individually.

(Maximum width of contact part)
In the first embodiment, the maximum width of the contact portion 16 is set to 3 mm or more and 7 mm or less. In this embodiment, as shown in FIG. 1, the maximum width W of the contact portion 16 is determined by measuring the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22 along the circumferential direction C of the wrist. means the maximum width of the case. Note that in the present disclosure, the maximum width of the contact portion may be set based on a distance set by other parts of the wrist other than the gap between the radial styloid process and the flexor carpi radialis tendon.

That is, in this embodiment, the maximum width W of the contact portion 16 is set in consideration of the state in which the contact portion 16 is arranged inside the recess of the gap. In other words, the width G of the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22 is the minimum value measured along the circumferential direction C on the surface of the wrist, and the width G of this minimum value is The maximum width W of the contact portion 16 is set so that the contact portion 16 can be placed inside the recess of the gap.

In the first embodiment, if the lower limit of the maximum width W of the contact portion 16 is less than 3 mm, the electronic components such as the light emitting element and the light receiving element will become too small, so there is a concern that manufacturing costs will increase or manufacturing will not be possible. On the other hand, if the upper limit of the maximum width W of the contact portion 16 exceeds 7 mm, it is placed in the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22 in the wrist of a female child, where the width of the gap is relatively narrow. things become difficult.

Note that in the present disclosure, the maximum width W of the contact portion 16 can be changed as appropriate. Further, the upper limit of the maximum width W of the contact portion 16 may be changed depending on the gender and age of the subject to be measured. For example, the height and weight of a 17-year-old boy can be set to be approximately 30% larger than the height and weight of a 5-year-old child. Therefore, for example, the upper limit of the maximum width W of the contact portion 16 for women aged 17 or older can be set to about 10 mm.

Further, the height and weight of a man can be set to be approximately 10% larger than the height and weight of a woman, for example. Therefore, the upper limit of the maximum width W of the contact portion 16 for male children can be set to about 8 mm. Further, for example, the upper limit of the maximum width W of the contact portion 16 for men aged 17 or older can be set to about 11 mm.

(Measurement part)
In the first embodiment, the measurement unit 18 is provided in a calculation display unit 26 attached to the band 12. The calculation display section 26 is located on the back side, which is the outside of the wrist. A light receiving element is connected to the measuring section 18. Data of a pulse wave signal of reflected light is inputted to the measurement unit 18 over time from a light receiving element.

The measurement unit 18 is configured as a computer including, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a storage device, an I/O port, and the like. The RAM, storage device, I/O port, etc. are configured to be able to exchange data with the CPU via an internal bus.

The measurement unit 18 measures the oxygen saturation level of the radial artery 24 irradiated with light, based on the pulse wave signal acquired from the reflected light, by a method using a ratio of PI values, or the like.

(Calculation display section)
The calculation display unit 26 displays the calculation results by the measurement unit 18 to the outside. The calculation display section 26 may be provided with a storage device that temporarily stores measurement results. Note that in the present disclosure, the calculation display section 26 is not essential. If the calculation display part 26 is not provided, the measurement part 18 can be arranged, for example, on the contact part 16 or the base part 14 as part of the calculation device.

Further, the storage device can also be placed on a member other than the calculation display section 26, such as the contact section 16 or the base section 14. Even if the calculation display section 26 is not provided, it is possible to obtain the calculation results by the measurement section 18, for example, via a communication section that is connected to the calculation device and enables communication with the outside. be.

<First modification example>
As shown in FIG. 5, the light emitting element and the light receiving element may be arranged on the contact surface 16A of the contact portion 16. In FIG. 5, a first light receiving element PD1, a second light receiving element PD2, a third light receiving element PD3, a fourth light receiving element PD4, and a fifth light receiving element PD5 are arranged on the joint surface 14A of the base 14. A case where the contact surface 16A is arranged instead of the contact surface 16A is illustrated.

By disposing the light emitting element and the light receiving element on the contact surface 16A of the contact portion 16, the distance between the light emitting element and the radial artery 24 and the distance between the light receiving element and the radial artery 24 can be determined by the distance between the light emitting element and the light receiving element. and can be made shorter than when they are arranged on the joint surface 14A of the base 14. Note that when the light emitting element and the light receiving element are arranged on the contact surface 16A of the contact part 16, the contact part 16 has translucency as long as the light emitting element and the light receiving element are connected to the measuring part 18. is not required.

<Second modification example>
As shown in FIG. 6, one contact portion 16 may be placed across both the first light emitting element LED1 and the first light receiving element PD1. Further, one contact portion 16 may be provided for all of the plurality of light emitting elements and the plurality of light receiving elements. Since the number of contact parts 16 in FIG. 6 is one, the structure of the oxygen saturation measuring device can be simplified, and the manufacturing burden can be reduced.

<Oxygen saturation measurement method>
Next, a method for measuring oxygen saturation using the oxygen saturation measuring device 10A according to the first embodiment will be described. First, the band 12 of the oxygen saturation measuring device 10A is wrapped around the wrist of the person to be measured. The artery to be measured is, for example, the radial artery 24. Note that in the present disclosure, the artery to be measured is not limited to the radial artery 24, and may be any other artery. The contact surface 16A is then brought into contact with the skin near the radial styloid process 20A on the inside of the wrist.

Then, as shown in FIG. 1, the contact portion 16 is placed inside the depression in the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22. Then, light is irradiated from the light emitting element to the radial artery 24 located below the depression. Then, the reflected light from the radial artery 24 is received by the light receiving element. Then, the measurement unit 18 measures the oxygen saturation level based on the pulse wave signal acquired from the reflected light.

(Operations and effects of the first embodiment)
According to the oxygen saturation measurement device 10A according to the first embodiment, the contact surface 16A of the contact portion 16 protruding from the band 12 toward the wrist has a curved shape. For example, after bringing the curved contact surface 16A into contact with the vicinity of the radial styloid process 20A on the inside of the wrist, the contact portion 16 is moved along the depression in the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22. If the contact portion 16 is moved toward the inside of the recess, it is easy to arrange the contact portion 16 inside the recess of the gap. That is, by utilizing the shape of the structural depressions formed by the bones, muscles, and tendons of the human body, the contact part 16 can be brought into contact with the skin surface on the inside of the wrist, as in the case where the contact part 16 is plate-shaped. There is no need to grope the location of the artery beforehand.

Further, in the first embodiment, the contact portion 16 has translucency for light irradiated onto the wrist artery and light reflected from the wrist artery. Further, a base 14 having a flat bonding surface 14A is provided between the band 12 and the contact portion 16, and at least one of a light emitting element and a light receiving element is bonded to the bonding surface 14A of the base 14.

Here, when electronic components such as a light emitting element and a light receiving element are mounted on the curved contact surface 16A, the electronic components directly contact the skin during measurement. Therefore, sebum, dirt, and the like from the skin tend to adhere to the electronic components, resulting in accelerated deterioration of the electronic components.

On the other hand, in the first embodiment, at least one of the electronic components of the light emitting element and the light receiving element is bonded on the flat bonding surface 14A between the band 12 and the contact portion 16. , avoid direct contact with skin. Therefore, deterioration of electronic components can be prevented.

Further, in the first embodiment, the maximum width W of the contact portion 16 is 3 mm or more and 7 mm or less. For this reason, when measuring the oxygen saturation level of the radial artery 24 with the contact portion 16 disposed in the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22, the wearer may feel uncomfortable when wearing it. It is possible to efficiently achieve both suppression and continuation of measurement.

Further, in the first embodiment, since the artery to be measured is the radial artery 24, it is particularly advantageous in measuring the oxygen saturation level in the radial artery 24.

Further, according to the oxygen saturation measuring method using the oxygen saturation measuring device 10A according to the first embodiment, the curved contact surface 16A is brought into contact with the skin near the radial styloid process 20A on the inside of the wrist, The contact portion 16 is arranged inside the depression in the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22. Then, the oxygen saturation level is measured based on the pulse wave signal obtained from the reflected light from the radial artery 24.

For example, even if the contact surface 16A has not reached the deepest part of the recess when the contact surface 16A is brought into contact with the vicinity of the radial styloid process 20A, since the contact surface 16A has a curved shape, the contact surface 16A can be easily fed into the hollow along the curved surface of the hollow. Therefore, as in the case of the oxygen saturation measurement device 10A of the present disclosure, the arrangement position of the contact portion 16 on the inside of the wrist can be easily determined, and interruption of oxygen saturation measurement can be suppressed.

-Second embodiment-
The second embodiment is characterized in that a contact portion 16 having a contact surface 16A that contacts the skin of the wrist and where a sensor is disposed can be slid by operating from the outside of the band 12. A second embodiment of the present disclosure will be described below with reference to FIGS. 7 to 9.

Note that, in the following, members in the second embodiment having the same names as members in the first embodiment have the same functions as in the first embodiment, so redundant explanations will be omitted, and there are differences in structure with the first embodiment. I will mainly explain the differences. Further, if the effects derived from the configuration of the second embodiment are similar to those of the first embodiment, duplicate explanations will be omitted, and the effects that are different from the first embodiment will be mainly explained. .

<Oxygen saturation measuring device>
As shown in FIG. 7, the oxygen saturation measuring device 10B according to the second embodiment includes a band 12, a slider section 30, a contact section 16, an operation section 40, a light emitting element, a light receiving element, and a measuring section. 18.

(band)
In the second embodiment, the band 12 includes a first body part 12A, a second body part 12B provided apart from the first body part 12A in the circumferential direction C of the wrist, and a pair of guide parts. Ru. The pair of guide parts is formed by a first guide part 12C and a second guide part 12D. The pair of guide parts connect the first body part 12A and the second body part 12B, respectively, and are provided apart from each other in the direction E in which the forearm extends. The pair of guide portions extend along the circumferential direction C of the wrist with the through hole 12E in between. The through hole 12E is formed by being surrounded by the first body part, the second body part, the first guide part, and the second guide part. The through hole 12E extends along the circumferential direction C of the wrist.

In the second embodiment, the four members consisting of the first body part 12A, the second body part 12B, the first guide part 12C, and the second guide part 12D are integrally made of the same material. The disclosure is not limited to this. Some or all of the four members may be made individually and connected to each other.

(through hole)
In the second embodiment, the through hole 12E has a rectangular shape in plan view, but the second embodiment is not limited to this, and may have other shapes, such as a linear shape. Note that in the present disclosure, "plan view" means a state viewed along the thickness direction of the band 12 (that is, the radial direction D of the wrist). Further, in the present disclosure, the through hole 12E is not essential as long as the contact portion 16 can be slid from the outside of the band 12 while the band 12 is wrapped around the wrist.

(slider part)
As shown in FIG. 7, the slider section 30 is arranged inside the through hole 12E of the band 12. The slider section 30 includes a base section 32, a pair of clamping sections, and an operating section 40. The pair of clamping parts are formed by a first clamping part 34A and a second clamping part 34B. As the material of the slider section 30, materials such as resin and metal can be appropriately adopted.

(base part)
The base portion 32 is arranged inside the through hole 12E of the band 12. Note that "the base portion 32 is disposed inside the through hole 12E" may be any state in which the base body portion 32 is disposed inside the through hole 12E in plan view, as shown in FIG. In other words, as shown in FIG. 8, in the radial direction D of the wrist, a portion of the base portion 32 in the vertical direction is not prevented from protruding outside the through hole 12E.

(Holding part)
As shown in FIG. 7, a pair of clamping parts formed by the first clamping part 34A and the second clamping part 34B are provided at both ends of the band of the base part 32 in the width direction (i.e., the direction E in which the forearm extends). It will be done. The first holding portion 34A is provided at one end (left end in FIG. 7) of the base portion 32 in the width direction of the band 12, and slidably holds the first guide portion 12C in the radial direction D of the wrist.

The second holding part 34B is provided at the other end of the base part 32 in the width direction of the band 12 (the right end in FIG. 7), and slidably holds the second guide part 12D in the radial direction D of the wrist. That is, the first clamping part 34A and the second clamping part 34B are slidable with respect to the first guide part 12C and the third guide part 12D, and the base part 32 is slidable with respect to the first guide part 12C and the third guide part 12D. It is provided with a gap or in contact with 12D to the extent that it does not fall off.

Although the second embodiment exemplifies a configuration in which the base portion 32 is slid inside the through hole 12E by a pair of guide portions and a pair of clamping portions, the present disclosure is not limited to this. In the present disclosure, as a configuration in which the base portion 32 is slid inside the through hole 12E, for example, each of the first guide portion 12C and the second guide portion 12D has a plurality of fastening portions along the circumferential direction C of the wrist. may be formed.

The plurality of fastening parts may be through holes formed with narrow hole widths, for example, like cuts. For example, the fasteners can be formed as a set of fasteners by being arranged on the first guide part 12C and the second guide part 12D, respectively, on a straight line along the direction E in which the forearm extends. A plurality of sets of fasteners may be formed along the circumferential direction C of the wrist.

Further, a set of fasteners corresponding to the set of fasteners may be provided at both ends of the base portion 32 in the direction E in which the forearm extends. The fastener may have a shape in which the distal end is larger in diameter than the proximal end, for example, like a cufflink. The distal end of the fastener can be inserted into the through hole, and can be detachably attached by being sandwiched between the cuts in the fastener at the base end position. By changing the mounting position of the fasteners among the plurality of fasteners provided along the circumferential direction C of the wrist, it is possible to slide the base portion 32 inside the through hole 12E.

(Operation unit)
As shown in FIG. 8, in the second embodiment, the operating section 40 is connected to the slider section 30 and arranged on the outside of the band 12 on the side opposite to the wrist. Note that in the present disclosure, the operation section 40 may be connected to the slider section 30 or the contact section 16. By operating the operating section 40, the slider section 30 can slide along the circumferential direction C of the wrist.

As shown in FIG. 9, in the second embodiment, both between the base portion 32 and the first guide portion 12C and between the base portion 32 and the second guide portion 12D in the direction E in which the forearm extends. , a void A is formed. The void A is a part of the through hole 12E. Therefore, the slider portion 30 can slide inside the formed gap A also along the direction E in which the forearm extends.

Note that in the present disclosure, the gap A may be formed between at least one of the base portion 32 and the first guide portion 12C and between the base portion 32 and the second guide portion 12D. Further, in the present disclosure, the void A is not essential.

(pressure device)
The oxygen saturation measuring device 10B according to the second embodiment further includes a pressurizing device 50 that applies force to the contact portion 16 from the side opposite to the wrist toward the wrist. Note that in the present disclosure, the pressurizing device 50 is not essential.

Specifically, as shown in FIG. 8, the base portion 32 is provided with a hole 32A that penetrates along the radial direction D of the wrist, and a female screw portion is formed on the inner surface of the provided hole 32A. Further, a rod-shaped member 42 is provided on the wrist side of the operating portion 40, and a male threaded portion is formed on the surface of the rod-shaped member 42 in correspondence with a female threaded portion of the hole 32A of the base portion 32.

That is, the pressurizing device 50 of the second embodiment is a screw feeding mechanism that adjusts the amount of protrusion from the slider portion 30 in the radial direction D of the wrist. Note that in the present disclosure, the pressurizing device is not limited to this. For example, other mechanisms may be used, such as a mechanism that applies a force toward the wrist to the contact portion 16 using a spring force.

Further, a plate-shaped connecting member 44 is provided at the end of the rod-shaped member 42 on the wrist side, and a base portion 14 is provided on the wrist side of the connecting member 44 . A contact portion 16 is provided on the opposite side of the base portion 14 from the connecting member 44 . In the second embodiment, the contact portion 16 is attached to the slider portion 30 via a pressure device 50. Therefore, the contact portion 16 slides along the circumferential direction C of the wrist together with the slider portion 30.

After the placement position of the sensor is determined by sliding the slider section 30, the determined placement position of the sensor is fixed by turning the screw so as to increase the amount of protrusion of the pressurizing device 50 from the slider section 30. Further, even after the sensor placement position is once fixed, the fixation of the sensor placement position can be loosened by turning the screw of the pressurizing device 50 so as to reduce the amount of protrusion from the slider portion 30. At the same time, it is possible to slide the slider section 30 again. That is, the sensor arrangement position can be changed to a desired position without loosening or removing the band 12 while the band 12 remains wrapped around the wrist of the subject.

Note that in the present disclosure, the contact portion 16 may be directly attached to the slider portion 30 without using the pressurizing device 50. Further, the contact portion 16 may be indirectly attached to the slider portion 30 via a member other than the pressure device 50. Further, in the second embodiment, the plate-shaped operation unit 40 is illustrated, but the present disclosure is not limited to this. For example, a protrusion that protrudes upward may be provided on the upper part of the base portion 32 in FIG. 8 so that the person to be measured can pinch it with his or her fingers.

<Oxygen saturation measurement method>
Next, a method for measuring oxygen saturation using the oxygen saturation measuring device 10B according to the second embodiment will be described. As in the case of the first embodiment, first, the band 12 of the oxygen saturation measuring device 10B is wrapped around the wrist of the person to be measured. The artery to be measured is, for example, the radial artery 24. The contact surface 16A is then brought into contact with the skin near the radial styloid process 20A on the inside of the wrist.

In the second embodiment, before placing the contact part 16 in the recess of the gap, by sliding the slider part 30, the contact part 16 is brought to an initial position near the artery to be measured on the inner skin surface of the wrist. can be placed. Alternatively, after placing the contact part 16 at the initial position, by sliding the slider part 30 to adjust the position, the contact part 16 can be placed on the skin surface on the inside of the wrist near the artery to be measured. It can be placed in a different position.

(Operations and effects of the second embodiment)
In the oxygen saturation measuring device 10B according to the second embodiment, the slider portion 30 is arranged inside the through hole 12E of the band 12 and is slidable along the circumferential direction C of the wrist. Further, a contact portion 16 having a contact surface 16A that contacts the wrist is attached to the slider portion 30. Further, an operating section 40 is connected to the slider section 30 or the contact section 16 and is arranged on the outside of the band 12 on the side opposite to the wrist. That is, even when the band 12 is wrapped around the wrist, it is possible to slide the slider section 30 by operating the operating section 40 from outside the band 12. Therefore, the subject can slide the contact part 16 attached to the slider part 30 along the circumferential direction C of the wrist without loosening the band 12 and without exposing the inner surface of the band 12. It becomes possible.

Therefore, according to the second embodiment, even when the sensor is worn on the wrist, the position of the sensor relative to the artery to be measured can be easily adjusted.

Further, in the second embodiment, the base portion 32 of the slider portion 30 is arranged inside the through hole 12E of the band 12. In addition, at both ends of the base portion 32 of the slider portion 30, there are correspondingly provided holding portions that slidably sandwich each of the pair of guide portions in the radial direction D of the wrist. Therefore, by sliding the pair of clamping parts with respect to the pair of guide parts, it becomes possible to slide the slider part 30.

Further, in the second embodiment, in the width direction of the band (that is, the direction E in which the forearm extends), between the base portion 32 and the first guide portion 12C, and between the base portion 32 and the second guide portion 12D. A gap A is formed between at least one of them. Moreover, the slider part 30 can slide inside the formed gap A along the direction E in which the forearm extends. In addition to the circumferential direction C of the wrist, the contact portion 16 attached to the slider portion 30 can be slid along the direction E in which the forearm extends, making it easier to adjust the placement position of the sensor.

Furthermore, the slider portion 30 is movable to any position within a plane defined by two directions, the circumferential direction C of the wrist and the extending direction E of the forearm, inside the through hole 12E formed in the band 12. . In other words, the slider section 30 can slide independently in two directions without being influenced by each other in the two directions. Therefore, compared to the case where the arrangement position is changed only on the circumference having a constant radius from the center of rotation as in Patent Document 1, the adjustable range of the arrangement position is wide.

Furthermore, the second embodiment includes a pressurizing device that applies force to the contact portion 16 from the side opposite to the wrist toward the wrist. Therefore, the position of the contact portion 16 relative to the artery to be measured in the wrist can be stably maintained.

Further, according to the oxygen saturation measuring method using the oxygen saturation measuring device 10B according to the second embodiment, even when the oxygen saturation measuring device 10B is worn on the wrist, the sensor for the artery to be measured can be used. The placement position can be easily adjusted.

-Third embodiment-
The third embodiment is characterized in that two or more light receiving elements for measuring oxygen saturation are provided, and a measuring light receiving element is quantitatively selected from the two or more light receiving elements. A third embodiment of the present disclosure will be described below with reference to FIGS. 10 to 12.

Note that, in the third embodiment, members having the same names as members in the first or second embodiment have the same functions as those in the first or second embodiment, so redundant explanation will be omitted, and The differences in configuration from the second embodiment will be mainly explained. Regarding the effects derived from the configuration of the third embodiment, if the effects are similar to those of the first or second embodiment, redundant explanation will be omitted, and effects different from those of the first or second embodiment will be omitted. I will mainly explain the effects.

<Oxygen saturation measuring device>
The oxygen saturation measuring device 10C according to the third embodiment illustrated in FIG. 10 includes three light emitting elements and five light receiving elements as in the first embodiment, and the slider described in the second embodiment. A slider section similar to section 30 is provided. Note that illustrations of the base, contact portion, slider portion, etc. are omitted in FIG. 10 for ease of viewing.

On the other hand, the third embodiment differs from the second embodiment in that the measuring section 18 includes a light receiving element determining section, a determining section, a distribution creating section, a light emitting element determining section, and a control section. Note that in the present disclosure, some or all of the light receiving element determining section, the determining section, the distribution creating section, the light emitting element determining section, and the control section may be arranged separately from the measuring section 18.

(pulse wave signal)
Furthermore, in the third embodiment, the "first pulse wave signal" is a pulse wave signal acquired from the reflected light received by the first light receiving element PD1. Moreover, the "second pulse wave signal" is a pulse wave signal acquired from the reflected light received by the second light receiving element PD2. Moreover, the "third pulse wave signal" is a pulse wave signal acquired from the reflected light received by the third light receiving element PD3. Moreover, the "fourth pulse wave signal" is a pulse wave signal acquired from the reflected light received by the fourth light receiving element PD4. Moreover, the "fifth pulse wave signal" is a pulse wave signal acquired from the reflected light received by the fifth light receiving element PD5.

(Light receiving element determining section)
The light receiving element determining section is connected to each light receiving element. In the third embodiment, the light-receiving element determining unit selects one of the first pulse wave signal, the second pulse wave signal, the third pulse wave signal, the fourth pulse wave signal, and the fifth pulse wave signal. The light receiving element that receives the pulse wave signal having the larger amplitude is determined as the measuring light receiving element.

Note that in the present disclosure, at least two light receiving elements may be used. That is, in the present disclosure, the light-receiving element determining unit selects the light-receiving element that has received a pulse wave signal having a larger amplitude between the first pulse wave signal and the second pulse wave signal as the light-receiving element for measurement. It may be determined as an element. Furthermore, when determining the light receiving element for measurement, any type of light to be irradiated can be selected from among red light and infrared light. However, from the viewpoint of comparison, it is preferable that the same type of light is used.

(Judgment Department)
The determination section is connected to each light receiving element. In the third embodiment, the determination unit is configured such that the first pulse wave signal, the second pulse wave signal, the third pulse wave signal, the fourth pulse wave signal, and the fifth pulse wave signal are set in advance. It is determined whether a preset reference value is satisfied based on the viewpoint of achieving measurement accuracy. Note that in the present disclosure, the determination unit determines whether at least the first pulse wave signal and the second pulse wave signal satisfy a reference value based on the viewpoint of achieving a preset measurement accuracy. do it.

Note that when multiple pulse wave signals that meet the standard value are acquired, extraction conditions are set to extract a more appropriate pulse wave signal from among the multiple pulse wave signals, for example, from the perspective of increasing the measurement accuracy of oxygen saturation. May be set. As an extraction condition, for example, a light receiving element from which a pulse wave signal having the largest amplitude among a plurality of pulse wave signals satisfying a reference value is acquired can be determined as a measurement light receiving element.

(Distribution creation department)
When the reflected light of the light of the first light emitting element LED1 is received by each of the first light receiving element PD1, the second light receiving element PD2, and the third light receiving element PD3, the distribution creation unit calculates the received reflection light. The amplitude distribution along the circumferential direction C of the wrist of light is created as a "first amplitude distribution." Further, the distribution creation unit determines whether the reflected light from the second light emitting element LED2 is received by each of the first light receiving element PD1, the second light receiving element PD2, and the third light receiving element PD3. The amplitude distribution of the reflected light along the circumferential direction C of the wrist is created as a "second amplitude distribution".

Further, the distribution creation unit determines whether the reflected light of the third light emitting element LED3 is received by each of the first light receiving element PD1, the second light receiving element PD2, and the third light receiving element PD3. The amplitude distribution of the reflected light along the circumferential direction C of the wrist is created as a "third amplitude distribution". Note that in the present disclosure, the distribution creation unit may create at least the first amplitude distribution and the second amplitude distribution. Furthermore, when creating the amplitude distribution, the timing of light irradiation from each light emitting element may be staggered.

(Light emitting element determining section)
The light-emitting element determination unit determines a criterion set in accordance with the fact that the light-emitting element is located above the artery among the created first amplitude distribution, second amplitude distribution, and third amplitude distribution. A light emitting element for which a distribution satisfying the conditions has been created is determined as a light emitting element for measurement. Oxygen saturation is measured based on the determined pulse wave signal of the reflected light from the light emitting element for measurement. Note that in the present disclosure, the light emitting element determining unit may determine the light emitting element for measurement based on at least the first amplitude distribution and the second amplitude distribution.

(control unit)
The control unit continues to energize only one light emitting element determined as the measurement light emitting element among the first light emitting element LED1, the second light emitting element LED2, and the third light receiving element PD3. On the other hand, the control unit stops energizing the other two light emitting elements that have not been determined as measurement light emitting elements. Note that in the present disclosure, the control unit may at least determine whether or not to energize between the first light emitting element LED1 and the second light emitting element LED2.

<Oxygen saturation measurement method>
Next, a method for measuring oxygen saturation using the oxygen saturation measuring device 10C according to the third embodiment will be described. As in the first and second embodiments, in step S1 in FIG. 11, first, the band 12 of the oxygen saturation measuring device 10C is wrapped around the wrist of the person to be measured. The artery to be measured is, for example, the radial artery 24.

Next, the contact surface 16A is brought into contact with the skin near the radial styloid process 20A on the inside of the wrist. Then, in step S2, the sensor unit is placed inside the gap between the radial styloid process 20A and the flexor carpi radialis tendon 22.

Next, in step S3, the arrangement position of the sensor unit is adjusted by moving the arrangement position of the sensor unit inside the gap using, for example, the slider section 30. The adjustment determines the placement position of the sensor unit. Next, in step S4, the determined arrangement position is fixed using a pressurizing device.

(Determination process of light emitting element for measurement)
Next, in step S5, the distribution creation unit is used to create a first amplitude distribution due to the reflected light of the first light emitting element LED1 and a second amplitude distribution due to the reflected light of the second light emitting element LED2. , and a third amplitude distribution based on the reflected light of the third light emitting element LED3.

Then, using the light-emitting element determination section, a light-emitting element for which a distribution satisfying the reference condition has been created among the created first amplitude distribution, second amplitude distribution, and third amplitude distribution is measured. It is determined as a light-emitting element for use. Note that the reference condition is set so that the light emitting element is located above the artery.

In FIG. 12(A), five data points representing the first amplitude distribution acquired by five light receiving elements arranged along the circumferential direction C of the wrist are illustrated. Further, in FIG. 12(B), five data points representing the second amplitude distribution acquired by five light receiving elements arranged along the circumferential direction C of the wrist are illustrated. Moreover, in FIG. 12(C), five data points representing the third amplitude distribution acquired by five light receiving elements lined up along the circumferential direction C of the wrist are illustrated.

Furthermore, in FIG. 12(A), a first locus L1 of a broken line connecting five data points is arranged to overlap with the five data points. Similarly, in FIG. 12(B), a second trajectory L2 indicated by a broken line is superimposed, and in FIG. 12(C), a third trajectory L3 indicated by a broken line is superimposed. The three trajectories are the first light emitting element LED1, the second light emitting element LED2, and the third light emitting element LED1, with the confirmation light receiving element having a constant length of about 1000 pixels arranged along the circumferential direction C of the wrist. These are respective amplitude distributions created using the light emitting element LED3. Illustration of the confirmation light receiving element is omitted. Further, the conditions for creating the amplitude distribution using the confirmation light-receiving element are the same as the conditions for creating the amplitude distribution using the five light-receiving elements.

Here, in the circumferential direction C of the wrist, the amplitude when the light emitting element is located above the artery is lower than the amplitude when the light emitting element is located shifted from above the artery in the circumferential direction C of the wrist. Note that "the light emitting element is located above the artery" means a state in which the light emitting element and the artery at least partially overlap in plan view, as shown in FIG.

Therefore, in the three light receiving elements arranged from one end side (for example, the left side in FIG. 12(B)) to the other end side (for example, the right side in FIG. 12(B)) along the circumferential direction C of the wrist, The amplitude decreases from the first light receiving element to the second light receiving element along the arrangement direction. Further, the amplitude increases from the second light receiving element to the third light receiving element.

That is, the reference condition is that the amplitude decreases and increases along the circumferential direction C. In other words, in the amplitude distribution in FIG. 12(B), a concave portion that is concave toward the bottom is drawn.

In the third embodiment, in the second amplitude distribution in FIG. 12(B), the amplitude of the second light receiving element PD2, the amplitude of the third light receiving element PD3, and the amplitude of the fourth light receiving element PD4 are It can be determined that the reference condition is satisfied by drawing a concave portion based on the amplitude. As a result, the second light emitting element LED2, which has obtained the second amplitude distribution in FIG. 12(B), is determined as the measurement light emitting element.

On the other hand, in the first amplitude distribution in FIG. 12(A), the amplitude increases from the first light receiving element PD1 to the second light receiving element PD2, but from the second light receiving element The amplitude continues to decrease until reaching the light receiving element PD5. Therefore, since no concave portion is drawn in the first amplitude distribution, it is determined that the reference condition is not satisfied.

In addition, in the third amplitude distribution in FIG. 12(C), the amplitude continues to increase from the first light receiving element PD1 to the fourth light receiving element PD4, but from the fourth light receiving element PD4 to the fifth light receiving element PD4. The amplitude decreases until the photodetector PD5. Thereafter, the amplitude is approximately constant from the fifth light receiving element PD5 toward the end of the determination target range located at the other end of the wrist in the circumferential direction C. That is, the amplitude does not turn to increase. Therefore, since no concave portion is drawn in the third amplitude distribution, it is determined that the reference condition is not satisfied.

Note that when multiple amplitude distributions that meet the standard conditions are formed, extraction conditions may be set to extract a more appropriate distribution from among the multiple distributions, for example, from the perspective of increasing the measurement accuracy of oxygen saturation. . As the extraction condition, for example, the difference between the central amplitude value that forms the bottom of the recess and the larger amplitude value of the amplitude values at both ends that are located on both sides of the bottom and form the two tops of the recess is calculated. Then, among the plurality of amplitude distributions in which the calculated difference satisfies the reference condition, the light-emitting element in which the largest distribution is formed can be determined as the light-emitting element for measurement.

Next, power is stopped to the first light emitting element LED1 and the third light emitting element LED3, which were not determined as the measuring light emitting element, and to the second light emitting element LED2, which was determined as the measuring light emitting element. continues to be energized. Then, the reflected light of the light emitted by the second light emitting element LED2 is received by the five light receiving elements.

For this reason, five pulse waves consisting of a first pulse wave signal, a second pulse wave signal, a third pulse wave signal, a fourth pulse wave signal, and a fifth pulse wave signal are detected by the five light receiving elements. I get a signal. Then, in step S6 in FIG. 11, five pulse wave signals are monitored. Then, a PI value is calculated for each of the five pulse wave signals. The PI value can be calculated for each of the PI value of red light (PI _RED ) and the PI value of near-infrared light (PI _IR ).

(Comparison process between PI value and reference value)
Next, in step S7, it is determined by comparison whether the calculated PI value is greater than or equal to a preset reference value. The comparison can be performed, for example, by the light receiving element determining section. Further, the reference value can be set for each of the PI value of red light (PI _RED ) and the PI value of near-infrared light (PI _IR ). Note that in the present disclosure, comparison processing with a reference value is not essential.

If all the PI values are less than a preset reference value, it is determined that the arrangement position of the light receiving element is not suitable for measurement, that is, it is determined that the positional shift of the light receiving element has occurred. Then, the process moves to step S3, and the arrangement position of the sensor unit is adjusted again. The arrangement position can be adjusted, for example, by sliding the slider section 30.

(Determination process of light emitting and receiving elements for measurement)
On the other hand, if one or more PI values are equal to or greater than a preset reference value, the process moves to step S8. Then, among the one or more pulse wave signals from which a PI value equal to or higher than the reference value is obtained, the light receiving element that receives the pulse wave signal having the largest amplitude is determined as the light receiving element for measurement using the light receiving element determination unit. do.

(Oxygen saturation measurement process)
Next, in step S9, a PI value is calculated using the measurement unit 18 based on the pulse wave signal received by the determined measurement light receiving element. Next, in step S10, oxygen saturation is calculated based on the calculated PI value. Next, in step S11, the calculated oxygen saturation data is stored in the storage device.

Next, in step S12, if the number of oxygen saturation data is less than a preset designated number, the process moves to step S13. Then, as in step S7, it is determined whether a positional shift of the light receiving element has occurred by comparing the PI value with a reference value.

In step S13, if it is determined that no positional deviation of the sensor unit has occurred because the PI value is greater than or equal to the reference value, the process moves to step S9 and the subsequent processes are repeated. On the other hand, if it is determined that the sensor unit is displaced because the PI value is not equal to or greater than the reference value, the process moves to step S6, and the five pulse wave signals are monitored again. Then, a PI value is calculated for each of the five pulse wave signals. Thereafter, by repeating the processes from step S7 onwards, the light receiving element for measurement is determined again. The oxygen saturation data is then stored in the storage device.

On the other hand, in step S12, if the number of saved oxygen saturation data is equal to or greater than a preset designated number, the process ends. The oxygen saturation measurement method according to the third embodiment is configured by executing the above series of processes until the number of stored oxygen saturation data satisfies the specified number that can be stored in the storage device. .

Note that in the present disclosure, if it is determined in step S13 that a positional shift of the sensor unit has occurred, after the band 12 is once removed from the wrist, the process may proceed to step S1, for example, without proceeding to step S6. is not excluded. That is, the arrangement position of the sensor unit may be adjusted by rewinding the band 12. Alternatively, the process may proceed to step S3, and the arrangement position of the sensor unit may be adjusted using, for example, the slider section 30.

(Operations and effects of the third embodiment)
In the oxygen saturation measuring device 10C according to the third embodiment, when measuring oxygen saturation, among the five light receiving elements, the light receiving element that has received the pulse wave signal having the largest amplitude receives the light for oxygen saturation measurement. determined as an element. Then, the oxygen saturation level is measured based on the pulse wave signal received by the determined measurement light receiving element.

That is, in the present disclosure, a plurality of reflected lights of light emitted from the same light emitting element are received, and the amplitudes of pulse wave signals of the plurality of received reflected lights are compared. Through the comparison, the pulse wave signal having the largest amplitude is quantitatively selected as the pulse wave signal for oxygen saturation measurement. Therefore, according to the oxygen saturation measuring device 10C according to the third embodiment, it is possible to reduce the frequency of interruptions in oxygen saturation measurement due to misalignment of the sensor at the inner side of the wrist.

Further, in the third embodiment, the first light receiving element PD1, the second light receiving element PD2, the third light receiving element PD3, the fourth light receiving element PD4, and the fifth light receiving element PD5 are arranged in the circumferential direction of the wrist. arranged along. Therefore, a more appropriate measurement light receiving element can be determined among five different positions along the circumferential direction of the wrist.

Furthermore, in the third embodiment, it is determined whether the five acquired pulse wave signals satisfy a preset reference value based on the viewpoint of achieving preset measurement accuracy. Then, a process is performed to determine a measuring light receiving element from among the light receiving elements that have received a pulse wave signal that satisfies the reference value. On the other hand, if all five pulse wave signals do not satisfy the reference value, the process of adjusting the arrangement position of the light receiving element is repeated until a pulse wave signal that satisfies the reference value appears. Among the acquired pulse wave signals, only the pulse wave signals that satisfy the reference value are extracted for measurement, so that the measurement accuracy of oxygen saturation can be further improved.

Furthermore, in the third embodiment, a first amplitude distribution, a second amplitude distribution, and a third amplitude distribution are created. Then, among the created first amplitude distribution, second amplitude distribution, and third amplitude distribution, the reference condition set corresponding to the light emitting element being located above the artery is satisfied. The light emitting element for which the distribution has been created is determined as the light emitting element for measurement. Then, the oxygen saturation level is measured based on the pulse wave signal of the reflected light from the determined light emitting element for measurement. That is, the light emitting element located above the artery from among the plurality of light emitting elements is determined as the light emitting element for measurement. Therefore, the measurement accuracy of oxygen saturation can be further improved.

Furthermore, in the third embodiment, power supply to light emitting elements that have not been determined as measurement light emitting elements is stopped, so power can be saved. Note that the present disclosure is not limited to controlling the energization to the light emitting element, and the control of the energization to the measurement light receiving element may be performed together with the control of the energization to the light emitting element, or independently. That is, the power supply to the light receiving element that is not determined as the measuring light receiving element may be stopped, and the power supply may be continued only to the light receiving element determined as the measuring light receiving element. Power saving can also be achieved by controlling the power supply to the measuring light receiving element.

Further, according to the oxygen saturation measuring method using the oxygen saturation measuring device 10C according to the third embodiment, it is possible to suppress interruption of oxygen saturation measurement due to misalignment of the sensor at the inner side of the wrist.

<Other embodiments>
Although the present disclosure has been described with reference to the disclosed embodiments above, the discussion and drawings forming a part of this disclosure should not be understood to limit the present disclosure. For example, in the first embodiment, as shown in FIG. 3, a group including one or more light emitting elements and a group including one or more light receiving elements are arranged along the direction E in which the forearm extends. However, the present disclosure is not limited thereto.

In FIG. 13, a case is illustrated in which a group including two light emitting elements and a group including three light receiving elements are arranged along the circumferential direction C of the wrist. That is, in the present disclosure, the arrangement direction of the group including one or more light emitting elements and the group including one or more light receiving elements may be the direction E in which the forearm extends, or the direction C in the circumferential direction of the wrist. Good too.

Furthermore, the present disclosure may be configured by partially combining the respective configurations shown in FIGS. 1 to 13. The present disclosure includes various embodiments not described above, and the technical scope of the present disclosure is determined only by the matters specifying the invention in the claims that are reasonable from the above description.

10A, 10B, 10C Oxygen saturation measuring device 12 Band 12A First main body part 12B Second main body part 12C First guide part 12D Second guide part 12E Through hole 14 Base part 14A Joint surface 14B Light shielding part 16 Contact part 16A Contact surface 18 Measuring part 20 Radius 20A Radial styloid process 22 Flexor carpi radialis tendon 24 Radial artery 26 Calculation display part 30 Slider part 32 Base part 32A Hole 34A First clamping part 34B Second clamping part 40 Operation part 42 Rod-shaped member 44 Connection member 50 Pressure device A Gap C Wrist circumferential direction D Wrist radial direction E Forearm extending direction G Gap width W Maximum width of contact part IR Infrared light source L1 First locus L2 Second locus L3 Third locus LED1 First light emitting element LED2 Second light emitting element LED3 Third light emitting element PD1 First light receiving element PD2 Second light receiving element PD3 Third light receiving element PD4 Fourth light receiving element PD5 Fifth light receiving element RED Red light source

Claims (6)

A band wrapped around the wrist of the person to be measured;
A light-emitting element that emits light to the artery in the wrist,
a first light-receiving element that receives reflected light from an artery in the wrist;
a second light-receiving element that is placed apart from the first light-receiving element and receives reflected light from an artery in the wrist;
The first pulse wave signal obtained from the reflected light received by the first light receiving element and the second pulse wave signal obtained from the reflected light received by the second light receiving element. a light-receiving element determination unit that determines a light-receiving element that has received a pulse wave signal having a large amplitude as a measurement light-receiving element;
a measurement unit that measures the oxygen saturation of the artery irradiated with light based on the pulse wave signal received by the determined measurement light receiving element;
Oxygen saturation measuring device equipped with. The first light receiving element and the second light receiving element are arranged along the circumferential direction of the wrist.
The oxygen saturation measuring device according to claim 1. further comprising a determination unit that determines whether the first pulse wave signal and the second pulse wave signal satisfy a preset reference value based on a viewpoint of achieving a preset measurement accuracy;
performing a process of determining a measurement light receiving element from among the light receiving elements that have received a pulse wave signal that satisfies the reference value;
The oxygen saturation measuring device according to claim 1 or 2. The light emitting elements include a first light emitting element that irradiates light to an artery in the wrist, and a second light emitting element that is disposed apart from the first light emitting element along the circumferential direction of the wrist and irradiates light to the artery in the wrist. comprising a light emitting element;
a third light receiving element disposed apart from the first light receiving element and also apart from the second light receiving element, the third light receiving element receiving reflected light from the artery of the wrist in order to obtain a third pulse wave signal; Equipped with an element,
The first light receiving element, the second light receiving element, and the third light receiving element are arranged along the circumferential direction of the wrist,
a first amplitude distribution based on the first pulse wave signal, the second pulse wave signal, and the third pulse wave signal acquired from the reflected light of the first light emitting element; creating a second amplitude distribution based on the first pulse wave signal obtained from the reflected light of the second light emitting element, the second pulse wave signal, and the third pulse wave signal; A distribution creation section,
Using the first amplitude distribution and the second amplitude distribution, determine whether the light emitting element is located above the artery among the first light emitting element and the second light emitting element. a light-emitting element determining unit that determines a light-emitting element for which a distribution satisfying the reference conditions set by
Measuring oxygen saturation based on the pulse wave signal of the reflected light of the determined light emitting element for measurement,
The oxygen saturation measuring device according to any one of claims 1 to 3. Continuing to energize only the light-emitting element determined as the light-emitting element for measurement among the first light-emitting element and the second light-emitting element, and stopping energization to the light-emitting element that was not determined as the light-emitting element for measurement. further comprising a control unit for stopping;
The oxygen saturation measuring device according to claim 4. Irradiating light to an artery to be measured using the light emitting element of the oxygen saturation measuring device according to any one of claims 1 to 5,
Obtaining a first pulse wave signal using a first light receiving element and obtaining a second pulse wave signal using a second light receiving element from reflected light from an artery irradiated with light,
monitoring a first pulse wave signal and a second pulse wave signal;
The light receiving element that has received the pulse wave signal with the larger amplitude of the monitored first pulse wave signal and the monitored second pulse wave signal is selected as the measurement light receiving element using the light receiving element determination unit. decided as,
Measuring oxygen saturation using a measurement unit based on the pulse wave signal received by the determined measurement light receiving element;
How to measure oxygen saturation.