JP2019118460A - Arterial oxygen saturation measuring apparatus - Google Patents

Abstract

To provide a percutaneous arterial oxygen saturation measuring device which reduces restraint of a body and a load on the body and always obtains good measurement results.SOLUTION: An arterial oxygen saturation measuring device 1 is provided with: a body part 2 composed of a flexible substrate 4 on which light emitting elements 11 and 12 and light receiving elements 15 to 18 are mounted; and an elastic mounting belt 3. The body part 2 is curved along the curved shape of the upper arm of a person and fixed by the mounting belt so that the surface mounting the light emitting elements and the light receiving elements thereon is brought into close contact with the skin surface.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an arterial blood oxygen saturation measuring apparatus for measuring arterial blood oxygen saturation of a human or another animal percutaneously, that is, noninvasively and noninvasively.

Conventionally, sleep apnea syndrome (SAS: Sleep) that can not breathe during sleep
In order to examine Apnea Syndrome) and to obtain biological information during various activities and operations, there are widely used inspection methods for measuring oxygen saturation of arterial blood percutaneously. In general, a pulse oximeter is well known that irradiates arterial blood with light of two different wavelengths and changes the ratio of their absorption coefficients by pulsation of arterial blood as a measuring device of percutaneous arterial blood oxygen saturation. ing.

  Many pulse oximeters are of a type in which a probe is sandwiched between a finger tip and an earlobe, and the probe includes two light emitting elements that emit red light and infrared light, and a light receiving element that receives reflected light or transmitted light. (See, for example, Patent Documents 1 and 2). In a laboratory such as a hospital, in order to diagnose SAS, an overnight sleep polygraphy (PSG: PolySomnoGraphy) test is performed in which a patient sleeps overnight while wearing a measurement device such as a pulse oximeter.

  A respiratory state estimation device has been proposed for discriminating whether the SAS is obstructive or central by a test simpler than the PSG test (see, for example, Patent Document 3). This device is used by being attached to the chest of the sleeping user, and measures the respiratory fluctuation to detect whether or not the patient is in the respiratory arrest state, measures the movement of the trunk, and measures the user's trunk. Detect the presence or absence of movement.

  Recently, wearable devices have been proposed which have a function of measuring arterial blood oxygen saturation and which are worn on the wrist like a watch (see, for example, Patent Document 4). In this wearable device, a sensor unit including a light emitting unit and a light receiving unit is provided on the back surface of a case unit in contact with a living body at the time of wearing in order to obtain arterial blood oxygen saturation information.

JP-A-6-63032 JP 2002-224088 A JP, 2016-10616, A JP, 2017-164274, A

  However, the above-described pulse oximeter attached to the fingertip or earwax is not suitable for continuous attachment for a long time. For example, there is a risk that the probe may come off or shift due to body movement such as the subject turning over while sleeping. Also, depending on the physical condition of the user, there may be cases where the probe can not be attached to the finger tip or earlobe. Furthermore, it is difficult to perform daily operations and exercises while wearing the probe.

  The wearable device disclosed in Patent Document 4 prevents external light from entering the light receiving unit by bringing the sensor unit into close contact with the living body, thereby reducing the distance between the sensor unit and the living body to shorten the optical path length. It is said that the detection signal strength can be increased. However, since the case portion is fixed to the wrist by a band portion similar to a wristwatch, it is practically difficult to always keep the sensor portion in close contact with a living body. Therefore, ambient light may be incident depending on the movement of the body or the arm, and the arterial blood oxygen saturation may not be accurately measured.

  Therefore, the present invention has been made in view of the problems of the prior art described above, and its object is to irradiate arterial blood of a human or other animal living body with light of two different wavelengths and reflect them. In an arterial blood oxygen saturation measurement device that obtains arterial oxygen saturation percutaneously from changes in the ratio of light or transmitted light absorbance, the user can easily wear it without assistance from a specialist or another person. It can be fitted and used according to the site, and the physical restraint and load on the body are small, and long-time continuous wearing and its more accurate judgment are possible during sleeping, exercising and daily activities. There is little influence of noise due to ambient light and wiring, and it is possible to always obtain good measurement results without requiring strict light emission control, and even if some displacement or fluctuation of the mounting position occurs during use .

The arterial blood oxygen saturation measuring apparatus according to the present invention is a device for percutaneously measuring arterial blood oxygen saturation of a living body,
Flexible substrate,
Two light emitting elements mounted on one side of the flexible substrate to emit light of different wavelengths to arterial blood of a living body;
A light receiving element mounted on one surface of the flexible substrate to receive light emitted from the light emitting element reflected by arterial blood of a living body;
And a mounting belt wound around a mounting site of the living body in order to mount the flexible substrate on the living body side of the one side,
The flexible substrate has flexibility capable of bringing the light emitting element and the light receiving element into close contact with the surface of the living body when the flexible substrate is mounted on the mounting site of the living body by the mounting belt,
The oxygen saturation of arterial blood of the living body is measured from light emitted from the light emitting element received by the light receiving element.

  According to the present invention, the arterial blood oxygen saturation measuring apparatus is mounted in a state in which the flexible substrate is wound around the mounting portion of the living body by the combination of the flexible substrate and the mounting belt and the light emitting element and the light receiving element are in close contact with the living body surface. Because it is possible, the user can use it by himself, without the assistance of an expert or another person, and can use it easily, and does not restrain the body or put a heavy load on the body while wearing it. During exercise, even during daily activities, it can be worn continuously for a long time, thereby allowing more accurate judgment. Furthermore, since the state of adhesion of the light emitting element and the light receiving element to the living body surface is maintained during mounting, the influence of noise due to direct incidence of external light or emitted light is small, and good measurement results can always be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall perspective view schematically showing an arterial blood oxygen saturation measurement apparatus according to a preferred embodiment of the present invention. It is a top view which shows the back surface of the main-body part of the apparatus of FIG. It is a top view which shows the surface of the main-body part of the apparatus of FIG. Figure 2 is a side view of the body of the device of Figure 1; FIG. 6 is an oscillation circuit diagram for automatically recognizing a mounting state of the device on a living body. It is explanatory drawing which shows the mounting condition to the human body upper arm part. It is sectional drawing in the VI-VI line of FIG. It is a diagram for demonstrating the acquisition method of arterial blood oxygen saturation. (A) Figure and (b) are diagrams showing the photoplethysmogram of infrared light (wavelength 940 nm) and red light (wavelength 730 nm) measured using the apparatus of FIG. 1 on the upper arm of the user is there.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In the present embodiment, a case where the arterial blood oxygen saturation measuring apparatus is mounted on the upper arm of a subject and used will be described. In the accompanying drawings, similar components throughout the present specification are denoted by the same reference numerals.

  FIG. 1 shows an arterial blood oxygen saturation measuring device 1 of the present embodiment. The arterial blood oxygen saturation measuring apparatus 1 includes a main body 2 and a wearing belt 3 for winding the main body around an upper arm of a subject for wearing. The main body portion 2 is formed of a substantially rectangular flexible substrate 4 elongated in the winding direction to the upper arm portion. The flexible substrate 4 is formed of, for example, a flexible flexible substrate material of silicon resin system such as silicone rubber for medical use. Thereby, the main body portion 2 can be bent and wound so as to be in close contact with the upper arm portion along the curved shape.

  It is more advantageous if the flexible substrate material is stretchable at least in the winding direction. Such stretchable resin materials and circuit boards are already known, for example as described in WO 2016/125670.

  Annular belt engaging portions 6a and 6b having long holes 5a and 5b in the width direction orthogonal to the longitudinal direction are provided at both longitudinal end portions of the flexible substrate 4, respectively. The mounting belt 3 is a belt-like stretchable belt having stretchability in the winding direction around the upper arm, and is formed of a stretchable material such as woven fabric of rubber and fiber, knitted rubber, natural rubber, synthetic rubber, etc. It is done. The mounting belt 3 is inserted at one end 3a into the long hole 5a of one belt engaging portion 6a from the outside (surface side) so as to cover substantially the entire surface of the main body 2, and the other end 3b is The other belt engaging portion 6 b is inserted into the long hole 5 b from the outer side (surface side) from the outer side (surface side) to be mounted to the main body portion 2.

  After the other end 3b of the mounting belt 3 is inserted into the long hole 9a of the rectangular ring 9 for belt length adjustment, it is folded back and sewed on the outer surface of the mounting belt 3 or integrated by a suitable fastener or adhesive, for example. Combined with In use, as shown in FIG. 1, one end 3a of the wearing belt 3 is such that the whole surface of the upper arm in contact with the skin of the main body 2 is inside, and the whole arterial blood oxygen saturation measuring device 1 forms a large ring. , And the long hole 9a of the rectangular ring 9 is inserted from inside. The outer surface of the mounting belt 3 is provided with a fastener for folding back and detachably fixing one end 3 a drawn from the rectangular ring 9.

  As such a fastener, for example, it is possible to use a surface fastener composed of a hook-like raised sheet and a loop-like raised sheet that are attached releasably when pressed against each other. In the present embodiment, a hook-shaped raised sheet portion 7a is attached to the outer surface of the attachment belt 3 near one end 3a, and when the one end is folded from the rectangular ring 9, it is looped at a position facing the hook-shaped raised sheet portion 7a. The napping sheet 7b is attached.

  The means for fixing the one end 3a of the folded attachment belt 3 to the outer surface is not limited to the above-described surface fastener, and various other known fasteners can be used. Moreover, the attachment to the upper arm of the main body 2 by the attachment belt 3 is not limited to the method described above. For example, the mounting belt 3 is overlapped on the outer surface of the main body portion 2, and both ends thereof are inserted from the outside into the long holes 5a and 5b of the belt engaging portions 6a and 6b and extended as in FIG. It is also possible to form a loop and detachably fix it with a fastener, or to connect both ends together. By configuring as described above, the mounting belt 3 can be replaced with the main body 2.

  Further, a protective cover 8 is integrally provided on the outer surface of the mounting belt 3 at a portion corresponding to the main body 2 so as to cover substantially the entire main body 2 at the time of use. The protective cover 8 protects the electronic circuits and electronic components provided on the surface of the flexible substrate 4 of the main body 2 and wiring from damage and noise as described later, and outside light does not reach the back surface of the flexible substrate 4 provided with the optical element. Thus, a sheet material made of an opaque metal foil such as, for example, aluminum is preferred.

  FIG. 2 shows the back surface of the main body 2 directly in contact with the upper arm of the user when the arterial blood oxygen saturation measuring device 1 is used. As shown in the figure, the flexible substrate 4 has a belt-like portion 10a extending from one belt engaging portion 6a toward the other belt engaging portion 6b, and the other belt engaging continuously with the belt-like portion. And a widening portion 10b provided on the side of the portion 6b. The strip portion 10a is formed to have a substantially constant width which is longer in the winding direction (longitudinal direction of the flexible substrate 4) and narrower than the belt engaging portion 6a. The widening portion 10b is expanded in the width direction more than the strip portion 10a, and the width is formed in a rectangular shape larger than the length in the winding direction.

  In the widened portion 10b, two light emitting elements 11 and 12 are arranged at the same position along the winding direction and slightly apart in the width direction near the center in the width direction of the region near the strip 10a. . The light emitting element 11 on one side (upper side in the drawing) is an LED that emits infrared light. The other (lower in the drawing) light emitting element 12 is an LED that emits infrared light. In the present embodiment, the emission wavelength of the light emitting element 11 is set to 940 nm, and the emission wavelength of the light emitting element 12 is set to 730 nm.

  In the strip portion 10a, the third light emitting element 13 emitting green light is disposed at the center position in the width direction of the region on the belt engaging portion 6a side. Strip shaped barrier ribs 14 a and 14 b extending along the winding direction are provided on both sides in the width direction of the light emitting element 13.

  Two light receiving elements 15 to 18 are disposed on the outer side in the width direction of the partition walls 14a and 14b. For example, a photodiode can be used as the light receiving element. The four light receiving elements 15 to 18 are provided at the same position along the winding direction, and the adjacent two light receiving elements 15 and 16 and 17 and 18 are provided slightly apart from each other in the width direction.

  As described above, since the light emitting elements 11 and 12 and the light receiving elements 15 to 18 are disposed apart from each other by a considerable distance in the winding direction, the light emitting elements 11 and 12 when using the arterial blood oxygen saturation measuring device 1 Can be prevented from being directly incident on the light receiving elements 15-18. In particular, infrared light is effective in preventing its direct incidence because it has the property of diffracting. Further, since light emission from the third light emitting element 13 is blocked between the light receiving elements 15 to 18 by the partition walls 14a and 14b, direct incidence to the light receiving elements is blocked.

  The band-shaped portion 10a is further provided with a mounting electrode 19 which constitutes an automatic mounting recognition circuit of the arterial blood oxygen saturation measuring device 1 described later. The mounting electrode 19 is disposed near the center in the winding direction of the side edge of one of the strip portions 10a (lower side in the drawing) so as to secure a relatively large electrode area. The surface of the mounting electrode 19 is entirely covered with an insulating material film (not shown) of a suitable constant thickness.

  Wirings of the light emitting elements 11 to 13, the light receiving elements 15 to 18, and the mounting electrode 19 are formed on the back surface of the flexible substrate 4. Further, on the back surface of the flexible substrate 4, ground electrodes 20a and 20b plated with gold are formed on the belt engaging portion 6a, the belt engaging portion 6b, and a part of the widened portion 10b. The ground electrodes 20a and 20b are connected to the same potential as the ground electrode of the wiring.

  FIG. 3 shows the surface of the main body 2 facing away from the user's upper arm, i.e., facing outward when the arterial blood oxygen saturation measuring device 1 is used. As shown in the figure, a battery 21 is disposed in the widening section 10b for the power supply of the arterial blood oxygen saturation measuring device 1 so as to be in contact with the border with the strip section on the strip section 10a side. Thereby, the arterial blood oxygen saturation measuring device 1 can be used without the power cord. Therefore, the user is greatly restrained compared with the conventional device because the user does not restrain the body or restrict the movement much while sleeping or doing various activities or exercise during daily life. Continuous wear of time is possible.

  The battery 21 is preferably, for example, a rechargeable lithium ion battery, and a battery charging circuit 22 and an external connection terminal 23 therefor are provided in the region between the belt engaging portion 6b of the widened portion 10b (near the upper end in the figure). It is done. The external connection terminal 23 is preferably a terminal for USB connection so that the external connection terminal 23 can be easily connected to a mobile device such as a smartphone or a tablet or an external device such as a personal computer.

  Furthermore, LED constant current circuits 25 and 26 for the light emitting elements 11 and 12 are provided in the area between the battery 21 and the belt engaging portion 6 b in the widening portion 10 b. The LED constant current circuits 25 and 26 are connected to the corresponding light emitting elements 11 and 12, respectively, and to the CPU 28 provided in the strip portion 10a. The CPU 28 is disposed closer to the widened portion 10b than the center of the strip portion 10a, and incorporates a communication circuit for communicating with the outside wirelessly or by wire. For wireless communication with the outside, the CPU 28 is connected to an antenna 29 provided on the strip portion 10 a. For wireless communication, it is possible to use, for example, bluetooth (registered trademark), infrared light, and various other known wireless schemes.

  In the strip portion 10a, a current voltage conversion circuit 31 connected to the light receiving elements 15 to 18, a distribution circuit 32 connected to the current voltage conversion circuit, and an LPF for infrared wavelength connected to the distribution circuit. (Low-pass filter) circuit 33 and LPF circuit 34 for red wavelength, HPF (high pass filter) circuit 35 for red wavelength and HPF circuit 36 for red wavelength respectively connected to the respective LPF circuits are provided . The distribution circuit 32 distributes the infrared wavelength component and the red wavelength component output from the light receiving element to the LPF circuits 33 and 34, respectively. The HPF circuits 35 and 36 are connected to the CPU 28.

  As described above, the strip circuit 10a is provided with the transmission circuit 37 that constitutes an automatic attachment recognition circuit for automatically recognizing whether or not the arterial blood oxygen saturation measuring device 1 is attached to a living body (upper arm). . The transmission circuit 37 is connected to the mounting electrode 19 on the back surface of the strip 10 a and to the CPU 28.

  As shown in FIG. 3, a waterproof layer 40 is formed on substantially the entire surface of the main body 2 in the main body 2. The waterproof layer 40 is realized by applying a colorless and transparent resin coating agent so as to have sufficient waterproof / moisture resistance and to ensure sufficient transparency to the light emitting element and the light receiving element. . By providing such a waterproof layer 40, the elements, electrodes, wires and circuits provided on the front and back sides of the main body 2 are protected from sweat, water vapor and the like generated by a living body (upper arm of the user) at the time of use. can do.

  The waterproof layer 40 is formed on the entire surface of the main body 2 except the ground electrodes 20a and 20b. Thereby, when the arterial blood oxygen saturation measuring device 1 is attached to the upper arm of the user, the ground electrodes 20a and 20b have the same potential as the skin of the upper arm in contact therewith, for example, used near the user The output of the light receiving element can be protected from high frequency noise of a commercial power source, a radio or the like. Also, since the ground electrodes 20a and 20b are plated with gold as described above, it is possible to prevent corrosion due to perspiration and metal rash on the user's skin.

  Furthermore, a resin protective layer 41 is provided on the surface and the side of the main body 2. For the resin protective layer 41, for example, a flexible and elastic resin material such as a silicon resin is preferable. The resin protective layer 41 is formed, for example, by insert molding a room temperature curing type silicone resin material on the main body 2 on which the waterproof layer 40 is formed. As a result, the main body 2 can be protected from undesirable external impact, damage from external contact and the like, and at the same time, the weight of the arterial blood oxygen saturation measuring device 1 can be further reduced.

  FIG. 5 shows a typical example of the transmission circuit 37. Transmission circuit 37 includes Schmitt NAND gate G, resistor R connected between input 2 and output 3 thereof, and variable capacitance capacitor VC connected in series with input 2 of Schmitt NAND gate G and resistor R. Configured One electrode of the variable capacitance capacitor VC is a mounting electrode 19, and the other electrode is constituted by a living body (upper arm) to which the arterial blood oxygen saturation measuring device 1 is mounted. The waterproof layer 41 described above is formed on the surface of the mounting electrode 19 to insulate the mounting electrode.

  The capacitance of the variable capacitance capacitor VC varies with the distance between the electrodes, ie, the distance between the waterproof layer 41 and the living body. When the main body 2 is in close contact with the surface of the living body, the distance between the electrodes is determined only by the waterproof layer 41 and is minimized, so the capacitance is maximized and the oscillation frequency of the oscillation circuit 37 is minimized. When the main body 2 is not in close contact with the surface of the living body, the distance between the electrodes is increased, the capacitance is decreased, and the transmission frequency of the transmission circuit 37 is increased. Furthermore, when the main body 2 is not attached to the surface of the living body, the capacitance is substantially zero, so that the transmission frequency of the transmission circuit 37 is maximum. Therefore, the wearing state of the arterial blood oxygen saturation measuring apparatus 1 can be reliably determined from the magnitude of the transmission frequency and / or the change thereof.

  According to this embodiment, the switch of the arterial blood oxygen saturation measuring device 1 can be turned on and off automatically based on the transmission frequency of the transmission circuit 37. For example, when the transmission frequency becomes lower than a predetermined frequency, it is possible to determine that the wearing state is appropriate and automatically start the operation of the arterial blood oxygen saturation measuring device 1. In addition, if the transmission frequency becomes equal to or higher than another preset frequency, the arterial blood oxygen saturation measuring device 1 may be removed from the living body or it may be determined that it is improperly mounted, and the operation may be automatically stopped. it can.

  Furthermore, a gyro sensor 38 and an acceleration sensor 39 are provided in the strip portion 10 a and connected to the CPU 28 respectively. The gyro sensor 38 detects a change in posture of a portion (upper arm) of a living body (user) on which the arterial blood oxygen saturation measuring device 1 is mounted. The acceleration sensor 39 detects the magnitude of physical movement of the arterial blood oxygen saturation measuring device 1. From these detection data, it is possible to infer the physical condition and activity of the user.

  FIG. 6 shows a state in which the arterial blood oxygen saturation measuring device 1 is attached to the upper arm UA of the user. In this case, the arterial blood oxygen saturation measuring apparatus 1 arranges the main body 2 so as to measure the arterial blood oxygen saturation with the brachial artery Ab as a target artery.

  The arterial blood oxygen saturation measuring device 1 of the present embodiment can also be used by being attached to the user's forearm. FIG. 6 further illustrates in phantom lines the state in which the arterial blood oxygen saturation measuring device 1 is attached to the forearm FA of the user. In this case, the arterial blood oxygen saturation measuring apparatus 1 arranges the main body 2 so as to measure the arterial blood oxygen saturation with the radial artery Ar as a target artery or with the ulnar artery Au as a target artery.

  FIG. 7 is a cross-sectional view of the upper arm UA of the user wearing the arterial blood oxygen saturation measuring device 1 in FIG. 6 as viewed from below along the line VI-VI in FIG. The main body 2 is mounted on the inner side of the upper arm UA where the upper arm artery Au is running, and is fixed by the mounting belt 3 so as to be in close contact with the skin surface. Since the mounting belt 3 has at least stretchability in the winding direction, it is possible to bring the back of the main body 2 into close contact in an appropriate mounting state by tightening it somewhat strongly. By using the mounting belt 3 in this manner, the user can easily mount the arterial blood oxygen saturation measuring device 1 in an appropriate state, without assistance from a third party or a specialist, regardless of whereabouts. It can be removed and reinstalled.

  At this time, it is preferable that the light emitting elements 11 and 12 and the light receiving elements 15 to 18 be in close contact with the skin of the upper arm UA so as to slightly penetrate the skin. Thereby, light emitted from the light emitting elements 11 and 12 diffuses to the light receiving element 15 to 18 side along the skin surface, the light receiving element 15 to 18 directly receives light emitted from the light emitting element, and external light enters. Can be prevented.

  The light emitting elements 11 and 12 and the light receiving elements 15 to 18 are preferably arranged such that the angle between the optical axis Oe of the light emitting element and the optical axis Or of the light receiving element is 30 ° or more. In particular, since infrared light having a long wavelength has strong diffractive properties, the reflected light from the brachial artery Au and the diffracted light from the light emitting element are superimposed and incident on the light receiving element. When the angle between the optical axis Oe and the optical axis Or is small, the influence of the diffracted light from the light emitting element becomes large. In the present embodiment, by setting the angle between the optical axis Oe and the optical axis Or to 30 ° or more, part of the emitted light diffused from the light emitting elements 11 and 12 into the upper arm portion UA is reflected to the upper arm artery Au. The influence of noise generated by direct incidence on the light receiving elements 15 to 18 can be reduced. Further, in the present embodiment, by forming the flexible substrate 4 with the substrate material having elasticity in the winding direction described above, the flexible substrate 4 is extended corresponding to the peripheral length of the upper arm to be attached, and the light emitting element And the light receiving element can be adjusted to be disposed at more preferable angular positions.

  The light emitting elements 11 and 12 and the light receiving elements 15 to 18 are disposed such that the optical path length of the reflected light Lr with respect to the brachial artery Au is equal to the optical path length of the irradiation light Le or the difference in optical path length is as small as possible. It is preferable to do.

  FIG. 7 shows a state in which the arterial blood oxygen saturation measuring device 1 is attached to an average upper arm of an adult, and the light emitting elements 11, 12 and the light receiving elements 15 to 18 use reflected light from the brachial artery Au. To be arranged. When the user has a thin child or arm, the light emitting elements 11, 12 and the light receiving elements 15 to 18 may be disposed at opposite positions across the brachial artery Au or another target artery. In this case, arterial light oxygen saturation can be similarly measured by receiving light transmitted by the light emitting elements 11 and 12 and transmitted through the brachial artery Au and receiving the transmitted light by the light receiving elements 15 to 18.

  Generally, it is known that it is difficult to feel the burden (weight) if the weight of the attached device or the like is 5% or less because the weight of the attached device or the like is relative to the attached portion when the device or instrument is attached to the body . Since the average weight of an adult is assumed to be 6.5% of the weight, in the case of 50 kg of weight, the weight of one arm is 3.25 kg, and 5% thereof is 163 g. As described above, the arterial blood oxygen saturation measuring device 1 comprises the thin flexible substrate 4 and the small light emitting and receiving element mounted thereon, the main body 2 including the circuit, the thin film wiring and the small battery, and the mounting belt 3 Therefore, the total weight can be set to 150 g or less. Therefore, the arterial blood oxygen saturation measuring device 1 can be used without feeling the weight when at least an average adult is attached to the upper arm.

  FIG. 8 shows light absorption spectra of reduced hemoglobin Hb, oxygenated hemoglobin HbO2, and carbon monoxide hemoglobin HbCO. As shown in the figure, in the case of light having a wavelength longer than 800 nm, since the absorption coefficient is larger for oxygenated hemoglobin HbO2, reflected light or transmitted light in arterial blood of the light represents the amount of oxygenated hemoglobin in arterial blood. become. Conversely, in the case of light having a wavelength shorter than 800 nm, the light absorption coefficient is larger in reduced hemoglobin Hb, and thus the reflected light or transmitted light in arterial blood of the light represents the amount of reduced hemoglobin in arterial blood.

  The arterial blood oxygen saturation measuring apparatus 1 uses the characteristic that the light absorption spectrum is different between such oxygenated hemoglobin HbO2 and reduced hemoglobin Hb as in the above-described conventional apparatus, and reflected light of light of two different wavelengths. Or measure arterial blood oxygen saturation from transmitted light. In the conventional arterial blood oxygen saturation measurement apparatus, in order to eliminate the influence of carbon monoxide hemoglobin HbCO, the wavelength of red light is set to 660 nm, the wavelength of infrared light to 910 nm, and the emission wavelength of red light is strictly determined. May be in control.

  In the present embodiment, as described above, the red light of wavelength 730 nm and the infrared light of wavelength 940 nm are adopted. Therefore, red light is not influenced by carbon monoxide hemoglobin HbCO as shown in FIG. Therefore, even if the emission wavelengths of the light emitting elements 11 and 12 slightly shift or change, the influence on the measurement result is very small. Therefore, the light emission control can be configured relatively easily by using a cheaper light emitting element, and the arterial blood oxygen saturation measurement device 1 can be manufactured more inexpensively.

  Further, in the present embodiment, it is necessary to irradiate light with higher light intensity, because the optical path length of the emitted light and the reflected light or the transmitted light is very long as compared with the case of attaching to the fingertip or earlobe of the conventional device. . In the present embodiment, by using the red light and the infrared light of the wavelengths described above, it is possible to use a light emitting element with high light intensity, thereby attaching to a living body part having a long optical path length like an upper arm. Also, good measurement results can be secured.

  FIGS. 9A and 9B show photoplethysmograms of infrared light (wavelength 940 nm) and red light (wavelength 730 nm) measured using the arterial blood oxygen saturation measuring device 1 on the upper arm of the user, ie, the upper arm The change of the absorption coefficient by the pulsation of arterial blood is shown, respectively. The user's respiration waveform and pulsation waveform are superimposed on the photoplethysmogram of FIG. As conventionally known, the respiratory waveform can be separated by using an LPF circuit for the photoplethysmogram.

  Generally, since the pulsation included in the photoplethysmogram is four times per one respiration, the LPF circuit performs digital processing (LPF processing) at a frequency of 1/2 of the pulsation frequency, as shown in FIGS. The respiratory waveform can be extracted from each waveform of. Similarly, the HPF circuit is used for the photoplethysmogram, and digital processing (HPF processing) is performed at half the pulsation frequency to separate the pulsation waveform from each waveform in FIGS. 9A and 9B. It can be extracted.

  The pulsation frequency can be detected by fast Fourier transform of the photoplethysmogram. At this time, since the photoplethysmogram is divided into a respiratory frequency region and a pulsating frequency region by fast Fourier transform, its high frequency component is used as a pulsating frequency. Thus, according to the present embodiment, it is possible to measure the number of respirations simultaneously with measuring the arterial blood oxygen saturation measurement from the photoplethysmogram.

  Although the present invention has been described above in connection with the preferred embodiments, the present invention is not limited to the above embodiments, and various changes or modifications may be made within the technical scope thereof. Needless to say. For example, the number of light receiving elements can be reduced by setting such that one light receiving element receives different lights in time division.

DESCRIPTION OF SYMBOLS 1 arterial blood oxygen saturation measuring device 2 main body 3 mounting belt 4 flexible substrate 8 protective cover 11, 12 light emitting element 15-18 light receiving element 19 mounting electrode 21 battery 37 transmission circuit 40 waterproof layer 41 resin protective layer

Claims (9)

An apparatus for percutaneously measuring arterial blood oxygen saturation in a living body, comprising:
Flexible substrate,
Two light emitting elements mounted on one side of the flexible substrate to emit light of different wavelengths to arterial blood of a living body;
A light receiving element mounted on the one surface of the flexible substrate to receive light emitted from the light emitting element reflected by arterial blood of the living body;
And a mounting belt wound around a mounting site of the living body in order to mount the flexible substrate on the living body side of the one side of the flexible substrate.
The flexible substrate has flexibility to allow the light emitting element and the light receiving element to be in close contact with the surface of the living body and to be wound around the mounting site when mounted on the mounting site of the living body by the mounting belt.
An arterial blood oxygen saturation measuring apparatus, which measures oxygen saturation of arterial blood of the living body from light emitted from the light emitting element received by the light receiving element.   The arterial blood oxygen according to claim 1, wherein the light emitting element and the light receiving element are disposed on the one surface of the flexible substrate so as to be separated from each other along a winding direction to the mounting portion. Saturation measuring device.   The arterial blood oxygen saturation measuring apparatus according to claim 1 or 2, wherein the wearing belt has elasticity along the winding direction.   The device further comprises an automatic mounting recognition circuit having a mounting electrode mounted on the one surface of the flexible substrate, the mounting electrode facing the living body surface facing the mounting substrate when the flexible substrate is mounted by the mounting member. The arterial blood oxygen saturation measurement device according to any one of claims 1 to 3, wherein the surface is coated with an insulating material film so as to form a variable capacitance capacitor between them.   LPF circuit for performing LPF processing of the light emitted from the light emitting element received by the light receiving element to measure the respiration waveform and / or the number of respirations of the living body from the light emitted from the light emitting element received by the light receiving element The arterial blood oxygen saturation measuring apparatus according to any one of claims 1 to 4, further comprising an HPF circuit for processing.   The arterial blood oxygen saturation measuring apparatus according to any one of claims 1 to 5, further comprising an acceleration sensor and / or a gyro sensor mounted on the other surface of the flexible substrate.   The arterial blood oxygen saturation measuring apparatus according to any one of claims 1 to 6, further comprising a communication circuit and a wireless antenna mounted on the other surface of the flexible substrate.   The arterial blood oxygen saturation according to any one of claims 1 to 7, wherein one of the light emitting elements emits infrared light of a wavelength of 940 nm, and the other light emitting element emits red light of a wavelength of 730 nm. Measuring device.   The arterial blood oxygen saturation measuring apparatus according to any one of claims 1 to 8, wherein the weight of the whole apparatus is 150 g or less.

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