JP2020146261A - Biological information measurement device and biological information measurement program - Google Patents

Abstract

To accurately measure biological information correlated with an output of blood.SOLUTION: A biological information measurement device 10 measures variation in blood oxygen concentration with the stop of breathing of a measured person by using an IR light signal expressing variation in a received light amount of IR light and an infrared light signal expressing variation in a received light amount of infrared light with which the measured person is irradiated, and gives information to the measured person to restart breathing when the blood oxygen concentration is lowered than that before the stop of breathing.SELECTED DRAWING: Figure 17

Description

The present invention relates to a biometric information measuring device and a biometric information measuring program.

Patent Document 1 describes a method for measuring the circulation time of oxygen transport, which calculates a change in oxygen saturation based on an absorbance signal of arterial blood extracted from a living body using a sensor. In this method of measuring the circulation time of oxygen transport, the amount of oxygen taken into the living body is changed and the time point at which the change is made is used as a reference point, and the time from the reference point until the oxygen saturation of arterial blood changes is measured.

Japanese Unexamined Patent Publication No. 2006-23102

Biological information that correlates with blood output may be measured by changes in blood oxygen concentration. Therefore, until now, the person to be measured has stopped breathing and resumed breathing after a predetermined time has elapsed as the length at which the change in oxygen concentration in blood required for measuring biological information appears. Biological information is measured by changing the oxygen concentration inside.

However, there are individual differences in the length of time until a change in blood oxygen concentration required for measurement of biological information appears. Therefore, in the case of a subject whose blood oxygen concentration, which is necessary for measuring biological information, changes earlier than other subjects, it is necessary to stop breathing more than necessary, and in some cases, it becomes stuffy. Sometimes. In addition, in the case of a subject whose blood oxygen concentration required for measurement of biological information appears later than that of other subjects, the blood required for measurement of biological information even after a specified time has passed. The change in oxygen concentration may not appear, and in such a case, the measurement accuracy of biological information is lowered.

The present invention is a biometric information measuring device capable of accurately measuring biometric information that correlates with the amount of blood pumped, as compared with the case where breathing is resumed with the passage of a predetermined time after stopping breathing. And to provide a biometric information measurement program.

In order to achieve the above object, the biometric information measuring device according to the first aspect includes a first signal representing a change in the amount of received light having a first wavelength irradiated to the person to be measured, and the person to be measured. A measurement that measures biological information that correlates with changes in blood oxygen concentration associated with respiratory arrest and resumption using a second signal that represents a change in the amount of light received with a second wavelength that is radiated to the subject. It is provided with a unit and a notification unit that notifies the measurement unit to resume breathing when it is measured that the biometric information is lower than that before stopping breathing.

The biometric information measuring device according to the second aspect is the biometric information measuring device according to the first aspect, when the measuring unit satisfies a predetermined reduction condition indicating a deterioration of the biometric information. , It is measured that the biometric information is lower than that before stopping breathing.

The biometric information measuring device according to the third aspect is set in the biometric information measuring device according to the second aspect under the condition that the lowering condition is lower than the predetermined reference threshold value.

The biometric information measuring device according to the fourth aspect is the statistic of the biometric information in a predetermined period after the lowering condition is lower than the reference threshold value in the biometric information measuring device according to the third aspect. The condition is set that the amount is lower than the reference threshold.

The biometric information measuring device according to the fifth aspect is the biometric information measuring device according to the third aspect, wherein the decrease condition is a decrease in the biological information in a predetermined period after the biological information is lower than the reference threshold value. Is set on the condition that the degree of the above exceeds the degree of decrease of the predetermined standard.

The biometric information measuring device according to the sixth aspect is the biometric information measuring device according to any one of the third to fifth aspects, wherein the light having the first wavelength and the light having the second wavelength are The reference threshold value differs depending on the part of the subject to be irradiated.

The biometric information measuring device according to the seventh aspect is set in the biometric information measuring device according to the second aspect under the condition that the degree of reduction of the biometric information exceeds the degree of reduction of a predetermined standard. ..

In the biometric information measuring device according to the eighth aspect, in the biometric information measuring device according to the seventh aspect, the degree of deterioration of the biometric information is represented by the slope of a graph showing a change in the biometric information.

The biometric information measuring device according to the ninth aspect is the biometric information measuring device according to any one of the first to eighth aspects, and the measuring unit is restarted by the notification of the notifying unit due to the decrease of the biometric information. The time from the resumption time of respiration of the subject to the appearance of the inflection point of the biological information is the light in which oxygen taken into the body by resumption of respiration has the first wavelength and the second. It is measured as the oxygen cycle time, which represents the time required to reach the site to be irradiated with light having the wavelength of.

The biological information measuring device according to the tenth aspect includes a respiratory waveform extraction unit that extracts the respiratory waveform of the person to be measured from the first signal or the second signal in the biological information measuring device according to the ninth aspect. The measurement unit uses the resumption time of respiration obtained from the respiration waveform of the subject extracted by the respiration waveform extraction unit as the resumption time of respiration of the subject.

In the biological information measuring device according to the eleventh aspect, in the biological information measuring device according to the ninth aspect, the time when the measuring unit notifies the resumption of respiration by the notification unit is defined as the resumption time of respiration of the person to be measured. ..

The biometric information measuring device according to the twelfth aspect is the biometric information measuring device according to the ninth aspect, in which the measuring unit notifies the resumption of respiration by the notification unit, and then the person to be measured resumes respiration. The time when the notification of resumption of notification is received is defined as the time for resuming breathing of the subject.

The biometric information measuring device according to the thirteenth aspect is the biometric information measuring device according to any one of the ninth to twelfth aspects, before and after the measuring unit starts measuring the oxygen cycle time. The biological information of different parts of the person to be measured is measured.

The biometric information measuring device according to the fourteenth aspect is the biometric information measuring device according to the thirteenth aspect, in which the other part measuring the biometric information before the measuring unit starts measuring the oxygen circulation time. After measuring the biometric information at the site where the biometric information decreases faster than the above and starting the measurement of the oxygen circulation time, the person to be measured is compared with other sites for which the biometric information is being measured. The biometric information of a site where it takes time for the biometric information to change in response to a change in breathing is measured.

The biometric information measuring device according to the fifteenth aspect measures the biometric information of the ear canal of the person to be measured until the measuring unit starts measuring the oxygen cycle time in the biometric information measuring device according to the fourteenth aspect. Then, after the measurement of the oxygen cycle time is started, the biological information of the fingertip of the person to be measured is measured.

The biometric information measuring device according to the 16th aspect is the biological information measuring device according to any one of the first to fifteenth aspects, wherein the first signal is associated with a change in the arterial blood volume of the person to be measured. A correction unit for correcting at least one of the first signal and the second signal is provided so that the difference between the amount of change and the amount of change in the second signal becomes small, and the measurement unit is the correction unit. The change in the biometric information is measured using the difference between the value of the first signal and the value of the second signal corrected by at least one of them.

The biometric information measuring device according to the seventeenth aspect is the biometric information measuring device according to any one of the first to fifteenth aspects, wherein the measuring unit has a change amount of the first signal and the second signal. The change in the biological information is measured using the ratio of the amount of change in.

The biometric information measurement program according to the eighteenth aspect is a program for causing the computer to function as each part of the biometric information measurement device according to any one of the first to seventeenth aspects.

According to the first aspect and the eighteenth aspect, the biological information that correlates with the cardiac output is accurately measured as compared with the case where the breathing is stopped and the breathing is resumed with the passage of a predetermined time. It has the effect of being able to.

According to the second aspect, there is an effect that it is possible to quantitatively determine whether or not the decrease in biological information has decreased, as compared with the case where a common decrease condition indicating that the decrease in biological information has decreased is not set.

According to the third aspect, there is an effect that it is possible to determine whether or not the biological information has deteriorated only by the latest measurement data without using the measurement data measured so far.

According to the fourth aspect, it is possible to determine whether or not the biological information has decreased even when the biological information shows a fluctuation that becomes equal to or higher than the reference threshold again in a predetermined period after the biological information has decreased from the reference threshold. It has the effect of being able to do it.

According to the fifth aspect, it is possible to determine whether or not the biological information has decreased even when the biological information shows a fluctuation that becomes equal to or higher than the reference threshold again in a predetermined period after the biological information has decreased from the reference threshold. It has the effect of being able to do it.

According to the sixth aspect, there is an effect that it can be accurately determined that the biological information has decreased as compared with the case where the reference threshold value is set to the same value regardless of the site where the biological information is measured. ..

According to the seventh aspect, there is an effect that it is possible to determine whether or not the biometric information has decreased without setting a reference threshold value in advance.

According to the eighth aspect, there is an effect that the degree of deterioration of biological information can be visually expressed.

According to the ninth aspect, there is an effect that the oxygen cycle time can be measured by irradiating the person to be measured with two lights having different wavelengths.

According to the tenth aspect, there is an effect that the resumption time of respiration can be obtained from the respiration waveform obtained by measuring the oxygen cycle time.

According to the eleventh aspect, there is an effect that the resumption time of respiration can be easily obtained as compared with the case where the resumption time of respiration is obtained from the respiration waveform.

According to the twelfth aspect, there is an effect that the resumption time of respiration can be accurately obtained as compared with the case where the time when the notification unit notifies the resumption of respiration is set as the resumption time of respiration.

According to the thirteenth aspect, there is an effect that the oxygen cycle time can be measured accurately as compared with the case where the biological information of the same site is continuously measured until the measurement of the oxygen cycle time is completed.

According to the fourteenth aspect, it is possible to reduce the burden on the person to be measured due to the measurement of the oxygen cycle time, as compared with the case where the biological information of the same site is continuously measured until the measurement of the oxygen cycle time is completed. It has the effect of.

According to the fifteenth aspect, until the measurement of the oxygen cycle time is started, it can be determined earlier whether the biological information has decreased or not, as compared with the case where the biological information of the fingertip of the person to be measured is measured. Have.

According to the 16th aspect, the change in the biological information is measured more accurately than the case where the change in the biological information is measured by using the ratio of the change amount of the first signal and the change amount of the second signal. It has the effect of being able to.

According to the seventeenth aspect, in the measurement of biometric information, as compared with the case where the change in biometric information is measured by using the difference between the value of the first signal and the value of the second signal corrected by at least one of them. It has the effect that the required time can be shortened.

It is a schematic diagram which shows the measurement example of the blood flow information and the oxygen saturation in blood. It is a graph which shows an example of the change of the received light amount by the reflected light from a living body. It is a schematic diagram which provides the explanation of the Doppler shift which occurs when a blood vessel is irradiated with a laser beam. It is a schematic diagram provided for the explanation of the speckle generated when a blood vessel is irradiated with a laser beam. It is a graph which shows an example of the spectrum distribution for each frequency in a unit time. It is a graph which shows an example of the change of the blood flow rate per unit time. It is a graph which shows an example of the change of the absorbance of the light absorbed by a living body. It is a graph which shows an example of the absorbance characteristic by hemoglobin. It is a schematic diagram which provides the explanation of the measurement principle of a respiratory waveform. It is a schematic diagram which provides the explanation of the measurement principle of a pumping amount. It is a graph for demonstrating an example of the measuring method of LFCT. It is a block diagram which shows an example of the electric structure of the biological information measuring apparatus. It is a figure which shows an example of arrangement of a light emitting element and a light receiving element in a biological information measuring apparatus. It is a figure which shows another example of arrangement of a light emitting element and a light receiving element in a biological information measuring apparatus. It is a graph which shows an example of the sampling timing of data in a light receiving element. It is a block diagram which shows an example of the functional structure of the biological information measuring apparatus. It is a flowchart which shows an example of the flow of the measurement process in a biological information measuring apparatus. It is a graph which shows an example of the amplitude of an IR light signal and the amplitude of a red light signal. It is a graph which shows an example of the relationship between a coefficient and a pulse wave difference. It is a graph which shows an example of the time series data of an IR optical signal, and the time series data of a red light signal. It is a graph which shows an example of the time series data of the IR optical signal and the time series data of a red light signal after correction. It is a graph which shows an example of LFCT specified from the pulse wave difference. It is a graph which shows the LFCT specified from the amplitude ratio.

Hereinafter, an example of a mode for carrying out the present invention will be described in detail with reference to the drawings.

First, with reference to FIG. 1, a method for measuring blood flow information and oxygen saturation in blood, which are examples of biological information related to blood in particular, will be described.

FIG. 1 is a schematic diagram showing a measurement example of blood flow information and oxygen saturation in blood according to the present embodiment.

As shown in FIG. 1, the blood flow information and the oxygen saturation in the blood are the living body 8 obtained by irradiating the body (living body 8) of the subject with light from the light emitting element 1 and receiving the light by the light receiving element 3. It is measured using the intensity of reflected or transmitted light of arteries 4, veins 5, capillaries, etc., that is, the amount of reflected light or transmitted light received.

(Measurement of blood flow information)
FIG. 2 is a graph showing an example of a change in the amount of received light due to the reflected light from the living body 8 according to the present embodiment.

In FIG. 2, the horizontal axis of the graph 80 represents the passage of time, and the vertical axis represents the amount of light received by the light receiving element 3.

As shown in FIG. 2, the amount of light received by the light receiving element 3 changes with the passage of time because it is affected by three optical phenomena that appear when the living body 8 including blood vessels is irradiated with light. It is believed that there is.

As the first optical phenomenon, a change in light absorption due to a change in the amount of blood existing in the blood vessel being measured due to pulsation can be considered. Since blood contains blood cell cells such as red blood cells and moves in blood vessels such as capillaries 6, the number of blood cell cells moving in blood vessels also changes as the blood volume changes, and the light receiving element 3 May affect the amount of light received.

As the second optical phenomenon, the influence of Doppler shift can be considered.

FIG. 3 is a schematic diagram for explaining the Doppler shift that occurs when the blood vessel according to the present embodiment is irradiated with a laser beam.

As shown in FIG. 3, when a coherent light 40 having a frequency of ω ₀ , such as a laser beam, is irradiated from the light emitting element 1 to a region including a capillary 6 which is an example of a blood vessel, blood cells moving in the capillary 6 are used. The scattered scattered light 42 causes a Doppler shift having a difference frequency Δω ₀ determined by the moving speed of blood cells. On the other hand, the frequency of the scattered light 42 scattered by a tissue (stationary tissue) such as skin that does not contain a moving body such as a blood cell cell maintains the same frequency ω ₀ as the frequency of the irradiated laser light. Therefore, the frequency ω ₀ + _{Δω 0} of the laser light scattered by the blood vessels 6 such capillaries, the frequency omega ₀ of the laser light scattered by stationary tissue will interfere with each other, the beat signal receiving element 3 having a difference frequency [Delta] [omega ₀ The amount of light received by the light receiving element 3 changes with the passage of time. The difference frequency Δω ₀ of the beat signal observed by the light receiving element 3 depends on the moving speed of the blood cell cells, but is included in the range up to about several tens of kHz.

Further, as a third optical phenomenon, the influence of speckle can be considered.

FIG. 4 is a schematic diagram provided for explaining a speckle generated when a blood vessel according to the present embodiment is irradiated with a laser beam.

As shown in FIG. 4, when a coherent light 40 such as a laser beam is irradiated from a light emitting element 1 to a blood cell 7 such as a red blood cell moving in a blood vessel in the direction of arrow 44, the laser light colliding with the blood cell 7 Scatters in various directions. Scattered light interferes randomly because they are out of phase. This produces a random speckled light intensity distribution. The light intensity distribution pattern formed in this way is called a "speckle pattern".

As described above, since the blood cell 7 moves in the blood vessel, the light scattering state in the blood cell 7 changes, and the speckle pattern changes with the passage of time. Therefore, the amount of light received by the light receiving element 3 changes with the passage of time.

Next, an example of how to obtain blood flow information will be described. When the amount of light received by the light receiving element 3 with the passage of time shown in FIG. 2 is obtained, the data included in the predetermined unit time T ₀ range is cut out, and the data is subjected to, for example, a Fast Fourier Transform. By executing: FFT), the spectral distribution for each frequency ω can be obtained.

FIG. 5 is a graph showing an example of the spectral distribution for each frequency ω at the unit time T _{0 according} to the present embodiment.

In FIG. 5, the horizontal axis of the graph 82 represents the frequency ω, and the vertical axis represents the spectral intensity.

Here, the blood volume is proportional to the value obtained by normalizing the area of the power spectrum represented by the shaded area 84 surrounded by the horizontal axis and the vertical axis of the graph 82 by the total amount of light. Further, since the blood flow velocity is proportional to the frequency average value of the power spectrum represented by the graph 82, the value obtained by integrating the product of the power spectrum at the frequency ω and the frequency ω with respect to the frequency ω is divided by the area of the shaded area 84. Is proportional to.

Since the blood flow rate is represented by the product of the blood volume and the blood flow velocity, it can be calculated from the above formula for calculating the blood volume and the blood flow velocity. Blood flow rate, blood flow velocity, and blood volume are examples of blood flow information, and blood flow information is not limited thereto.

FIG. 6 is a graph showing an example of a change in blood flow rate per unit time T _{0 according} to the present embodiment.

In FIG. 6, the horizontal axis of the graph 86 represents time, and the vertical axis represents blood flow rate.

As shown in FIG. 6, blood flow fluctuates with time, and the tendency of the fluctuation is classified into two types. For example, the fluctuation range 90 of the blood flow rate in the section T ₂ is larger than the fluctuation range 88 of the blood flow rate in the section T ₁ of FIG. This change in blood flow rate in the interval T ₁ is mainly whereas the change in blood flow caused by the motion of the pulse, the change in blood flow in the interval T ₂ are, for example, the cause of such congestion and neural activity This is thought to be due to the accompanying change in blood flow.

(Measurement of oxygen saturation)
Next, the measurement of oxygen saturation in blood will be described. The oxygen saturation in blood is an example of the oxygen concentration in blood, and is an index showing how much hemoglobin in blood is bound to oxygen. As the oxygen saturation in blood decreases, anemia, etc. Symptoms are more likely to occur.

FIG. 7 is a graph showing an example of a change in the amount of light absorbed by the living body 8 according to the present embodiment.

In FIG. 7, the horizontal axis of the graph 92 represents time, and the vertical axis represents the amount of absorbance.

As shown in FIG. 7, the absorbance in the living body 8 tends to fluctuate with the passage of time.

Furthermore, looking at the breakdown of the fluctuation of the absorbance in the living body 8, the absorbance mainly fluctuates depending on the artery 4, and the absorbance does not fluctuate in the other tissues including the vein 5 and the quiescent tissue as compared with the artery 4. It is known that the amount of fluctuation is such that it can be regarded. This is because the arterial blood pumped from the heart moves in the blood vessel with a pulse wave, so that the artery 4 expands and contracts with time along the cross-sectional direction of the artery 4, and the thickness of the artery 4 changes. .. In FIG. 7, the range indicated by the arrow 94 indicates the amount of variation in the amount of absorbance corresponding to the change in the thickness of the artery 4.

In FIG. 7, if the amount of light received at time t _a is I _a and the amount of light received at time t _b is I _b , the amount of change ΔA in the amount of light absorption due to the change in the thickness of the artery 4 is expressed by Eq. (1). Will be done.

(Number 1)
ΔA = ln (I _b / I _a ) ・ ・ ・ (1)

FIG. 8 is a graph showing an example of the absorbance characteristics of hemoglobin according to the present embodiment.

In FIG. 8, the vertical axis represents the absorbance and the horizontal axis represents the wavelength.

As shown in FIG. 8, hemoglobin (hemoglobin oxide) bound to oxygen flowing through the artery 4 easily absorbs light in the infrared (IR) region having a wavelength of about 880 nm and is not bound to oxygen. Hemoglobin (reduced hemoglobin) is known to easily absorb light in the red region having a wavelength in the vicinity of about 665 nm. Further, it is known that the oxygen saturation is proportional to the ratio of the amount of change ΔA in the amount of absorption at different wavelengths.

Therefore, the absorbance when the living body 8 is irradiated with IR light using infrared light (IR light) and red light, which are more likely to show a difference in absorbance between oxidized hemoglobin and reduced hemoglobin than in other wavelength combinations. the amount of variation .DELTA.A _IR, red light by calculating each ratio between the change amount .DELTA.A _red of light absorption when irradiated to the living body 8, the oxygen saturation S is calculated by the equation (2). In equation (2), k is a constant of proportionality.

(Number 2)
S = k (ΔA _Red / ΔA _IR ) ・ ・ ・ (2)

That is, when calculating the oxygen saturation in blood, a plurality of light emitting elements 1 that irradiate light having different wavelengths, specifically, a light emitting element 1 that irradiates IR light and a light emitting element 1 that irradiates red light. Although some of the light emitting periods may overlap, it is desirable that the light is emitted so that the light emitting periods do not overlap. Then, the reflected light or transmitted light from each light emitting element 1 is received by the light receiving element 3, and the equations (1) and (2) or these equations are modified from the amount of light received at each light receiving time. Oxygen saturation is measured by calculating a known formula.

As a known formula obtained by modifying the above formula (1), for example, the formula (1) may be developed and the amount of change ΔA in the amount of light absorption may be expressed as the formula (3).

(Number 3)
ΔA = lnI _b −lnI _a ··· (3)

Further, the equation (1) can be modified as the equation (4).

(Number 4)
ΔA = ln (I _b / I _a ) = ln (1 + (I _b -I _a ) / I _a ) ... (4)

Usually, because it is _{(I b -I a) «I a} , ln order to _{(I b / I a) ≒} (I b -I a) / I a is satisfied, instead of equation (1), light Equation (5) may be used as the amount of change in the amount of absorption ΔA.

(Number 5)
ΔA ≒ (I _b -I _a ) / I _a ... (5)

When it is necessary to distinguish between the light emitting element 1 that irradiates IR light and the light emitting element 1 that irradiates red light, the light emitting element 1 that irradiates IR light is hereinafter referred to as "light emitting element LD1". The light emitting element 1 that irradiates red light is referred to as "light emitting element LD2". Further, as an example, the light emitting element LD1 is used as the light emitting element 1 used for calculating the blood flow rate, and the light emitting element LD1 and the light emitting element LD2 are used as the light emitting element 1 used for calculating the oxygen saturation in blood.

Further, when measuring the oxygen saturation in blood, it is known that the measurement frequency of the amount of received light is about 30 Hz to 1000 Hz, so that the light emitting frequency representing the number of blinks per second of the light emitting element LD2. About 30 Hz to 1000 Hz is sufficient. Therefore, from the viewpoint of power consumption in the light emitting element LD2, it is preferable that the light emitting frequency of the light emitting element LD2 is lower than the light emitting frequency of the light emitting element LD1, but the light emitting frequency of the light emitting element LD2 is matched with the light emitting frequency of the light emitting element LD1. , The light emitting element LD1 and the light emitting element LD2 may be made to emit light alternately.

Next, with reference to FIG. 9, the principle of measuring the respiratory waveform from the pulse wave signal obtained from the peripheral part of the living body 8 will be described. Examples of peripheral parts referred to here include fingertips of hands, toes, ear lobes, and the like. The peripheral part includes a part before the elbow, a part before the knee, and the like. The respiratory waveform is a waveform of a signal indicating the respiratory state of the living body 8, and is a waveform of a time-series signal indicating a time change of exhalation and inspiration.

FIG. 9 is a schematic diagram for explaining the measurement principle of the respiratory waveform according to the present embodiment.

As shown in FIG. 9, the amplitude of the pulse wave signal is reduced by the following steps during inspiration.
(S1) The intrathoracic pressure decreases to negative pressure, and the lungs expand.
(S2) The amount of venous return increases.
(S3) The amount of blood flowing into the right atrium increases.
(S4) The vascular bed of the lung expands, and the amount of blood stored in the lung increases.
(S5) The amount of blood returning from the lungs to the left atrium decreases.
(S6) The stroke volume of the left ventricle decreases.
(S7) The amplitude of the pulse wave signal decreases.

On the other hand, at the time of exhalation, the amplitude of the pulse wave signal is increased by the following steps.
(S8) Blood squeezed from the lungs flows into the left ventricle.
(S9) The amplitude of the pulse wave signal increases.

That is, since the influence of the "lung pumping motion" caused by respiration is superimposed on the pulsation generated by the "heart pumping motion", it is possible to measure the respiratory waveform from the pulse wave signal obtained from the peripheral part of the living body 8. It becomes.

Next, with reference to FIG. 10, the principle of measuring the oxygen circulation time (LFCT), which is an example of an index having a correlation with the stroke amount of blood from the heart, will be described. The stroke amount referred to here includes not only the above-mentioned cardiac output but also a single stroke amount, a cardiac index and the like. The cardiac output is defined as the amount of blood pumped into an artery by contraction of the heart per unit time (for example, 1 minute). A single stroke is defined as the volume of blood pumped into an artery by a single contraction of the heart. Cardiac index is defined as a coefficient obtained by dividing cardiac output by the body surface area of the subject. In addition, LFCT is defined as the time required for oxygen taken in by breathing to reach the fingertips through the lungs and heart.

FIG. 10 is a schematic diagram for explaining the measurement principle of the pumping amount according to the present embodiment.

As shown in FIG. 10, there is a correlation between the above-mentioned pumping amount and LFCT. For example, assuming that the cardiac output, which is an example of the cardiac output, is CO, the cardiac output CO is calculated by the following equation (6).

(Equation 6)
CO = (a ₀ x S) / LFCT ... (6)

Here, a ₀ is a constant, and for example, a ₀ = 50 is used. Further, S is the body surface area (m ² ) of the subject, and the unit of LFCT is seconds.

FIG. 11 is a graph for explaining an example of the LFCT measurement method according to the present embodiment.

In FIG. 11, the vertical axis represents the reciprocal of oxygen saturation, and the horizontal axis represents time.

As shown in FIG. 11, the LFCT according to the present embodiment is measured from the above-mentioned change in oxygen saturation. That is, the LFCT is obtained by measuring the time from the time when the breathing is stopped for a certain period of time and then the breathing is resumed to the inflection point indicating that the oxygen saturation has begun to recover.

In the above LFCT measurement, for detecting the change in blood oxygen concentration, as an example, the ratio of the amount of change in the IR optical signal and the amount of change in the red light signal, that is, two pulse wave signals having different wavelengths (here). In, the amplitude ratio of IR optical signal and red optical signal) is used. When this amplitude ratio is used, it is difficult to accurately measure the blood oxygen concentration in, for example, a living body having atrial fibrillation or a living body in which blood flow is reduced due to the influence of environmental temperature or mental state. In some cases. Therefore, as will be described later, the blood oxygen concentration may be measured using the difference between the amount of change in the IR optical signal and the amount of change in the red light signal.

FIG. 12 is a block diagram showing an example of the electrical configuration of the biological information measuring device 10 according to the present embodiment.

As shown in FIG. 12, the biological information measuring device 10 according to the present embodiment includes a light emission control unit 12, a drive circuit 14, an amplifier circuit 16, an A / D (Analog / Digital) conversion circuit 18, a control unit 20, and a display unit. 22, a light emitting element LD1, a light emitting element LD2, and a light receiving element 3 are provided. The light emitting element LD1, the light emitting element LD2, the light receiving element 3, and the amplifier circuit 16 constitute a sensor unit. Further, the light emission control unit 12, the drive circuit 14, the amplifier circuit 16, the A / D conversion circuit 18, the control unit 20, and the display unit 22 constitute a main body unit. In the present embodiment, these sensor units and the main body unit are configured as separate bodies, and communication is possible via wired or wireless communication. The sensor unit and the main body unit may be integrally configured. Further, the sensor unit is attached so as to be in close contact with the living body 8 so that external light is not input. The sensor unit according to the present embodiment is attached to the fingertip of the living body 8 as an example, but can also be attached to other peripheral parts such as an earlobe.

The light emission control unit 12 outputs a control signal for controlling the light emission cycle and the light emission period of the light emitting element LD1 and the light emitting element LD2 to the drive circuit 14 including the power supply circuit for supplying the drive power to the light emitting element LD1 and the light emitting element LD2. .. The light emission control unit 12 may be realized as a part of the control unit 20.

When the drive circuit 14 receives the control signal from the light emission control unit 12, it supplies drive power to the light emitting element LD1 and the light emitting element LD2 according to the light emitting cycle and the light emitting period instructed by the control signal, and the light emitting element LD1 and the light emitting element Drive LD2.

The light receiving element 3 is an example of a light receiving unit, and receives light of a first wavelength from the light emitting element LD1 and receives a first light receiving signal corresponding to the received light of the first wavelength, and a light emitting element LD2 to a second light receiving element 3. It receives light of the wavelength of, and outputs a second light receiving signal corresponding to the received light of the second wavelength. In the present embodiment, the wavelength range corresponding to the infrared region is applied as the first wavelength, and the wavelength range corresponding to the red region is applied as the second wavelength. An IR optical signal is applied to the first light receiving signal, and a red light signal is applied to the second light receiving signal.

The amplifier circuit 16 converts a current corresponding to the intensity of light generated by the light receiving element 3 into a voltage, and amplifies the current to a voltage level defined as an input voltage range of the A / D conversion circuit 18.

The A / D conversion circuit 18 takes the voltage amplified by the amplifier circuit 16 as an input, and quantifies and outputs the amount of light received by the light receiving element 3 represented by the magnitude of the voltage.

The control unit 20 includes a CPU (Central Processing Unit) 20A, a ROM (Read Only Memory) 20B, and a RAM (Random Access Memory) 20C. The biological information measurement program is stored in the ROM 20B.

The display unit 22 notifies the measurement result of the biological information. For the display unit 22, for example, a liquid crystal display (LCD), an organic EL (Electro Luminescence) display, or the like is used. The display unit 22 integrally has a touch panel.

FIG. 13 is a diagram showing an example of arrangement of the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 in the biological information measuring device 10 according to the present embodiment. Further, FIG. 14 is a diagram showing another example of arrangement of the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 in the biological information measuring device 10 according to the present embodiment.

As shown in FIG. 13, the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 are arranged side by side toward one surface of the living body 8. In this case, the light receiving element 3 receives the light of the light emitting element LD1 and the light emitting element LD2 transmitted near the surface of the living body 8.

The arrangement of the light emitting element LD1, the light emitting element LD2, and the light receiving element 3 is not limited to the arrangement example of FIG. For example, as shown in FIG. 14, the light emitting element LD1 and the light emitting element LD2 and the light receiving element 3 may be arranged at positions facing each other with the living body 8 interposed therebetween. In this case, the light receiving element 3 receives the light of the light emitting element LD1 and the light emitting element LD2 that have passed through the living body 8.

Here, as an example, both the light emitting element LD1 and the light emitting element LD2 will be described as being surface emitting laser elements, but the present invention is not limited to this, and end surface emitting laser elements may be used. Further, the light emitted from each of the light emitting element LD1 and the light emitting element LD2 does not have to be laser light. In this case, a light-emitting diode (LED) or an organic light-emitting diode (OLED) may be used for each of the light-emitting element LD1 and the light-emitting element LD2.

FIG. 15 is a graph showing an example of data sampling timing in the light receiving element 3 according to the present embodiment. In FIG. 15, the positions of the circles indicate the sampling timing.

In FIG. 15, the vertical axis represents the output voltage of the light receiving element 3, and the horizontal axis represents time.

As shown in FIG. 15, when the output voltage corresponding to the light received from the light emitting element LD1 by the light receiving element 3 is IR ₁ , IR ₂ , ..., IR _n , IR (t) is used as time series data. = IR ₁ , IR ₂ , ..., IR _n can be obtained. Similarly, when the output voltage corresponding to the light received by the light receiving element 3 from the light emitting element LD2 is Red ₁ , Red ₂ , ..., Red _n , the time series data is Red (t) = Red ₁ , Red ₂ , ..., Red _n are obtained. At this time, both the light emitting element LD1 and the light emitting element LD2 may be provided with a period during which no light is emitted to obtain outputs Dark ₁ , Dark ₂ , ..., Dark _n in a dark state. In this case, IR (t) may be IR _1- Dark ₁ , IR _2- Dark ₂ , ..., IR _n- Dark _n . Similarly, Red (t) may be Red _1- Dark ₁ , Red _2- Dark ₂ , ..., Red _n- Dark _n . It is desirable to sample these data in a state where the output is stable near the end of the light emission period.

FIG. 16 is a block diagram showing an example of the functional configuration of the biological information measuring device 10.

As shown in FIG. 16, the biological information measuring device 10 according to the present embodiment is a functional unit of a removing unit 30, a correction unit 31, a measuring unit 32, a detecting unit 33, a specific unit 34, an estimating unit 35, and a notification unit 36. including. Further, the specific unit 34 includes an extraction unit 37. The removing unit 30 is not an essential component of the biological information measuring device 10, but may be provided as needed.

The CPU 20A functions as each functional unit shown in FIG. 16 by executing the biometric information measurement program stored in the ROM 20B.

First, the configuration of each part when the removing part 30 is not provided will be described.

The correction unit 31 according to the present embodiment receives each of the IR light signal and the red light signal output from the light receiving element 3, and changes the IR light signal with the change in the arterial blood volume of the living body 8 (hereinafter, ΔIR). The IR light signal is corrected so that the difference between the amount of change in the red light signal (hereinafter referred to as ΔRed) becomes small. This change in arterial blood volume represents the amplitude of the pulsation associated with the heartbeat. The IR optical signal is an example of the first signal, and the red light signal is an example of the second signal.

It is desirable that the above correction is a correction that makes ΔIR and ΔRed the same. Here, ΔIR is expressed as the amplitude of the IR optical signal, and ΔRed is expressed as the amplitude of the red light signal. In this case, the above correction is performed by multiplying the value of the IR optical signal (IR (t)) by the coefficient α represented by the amplitude ratio (ΔRed / ΔIR) of ΔIR and ΔRed. That is, the corrected output of IR (t) is α × IR (t).

The measuring unit 32 according to the present embodiment measures the blood oxygen concentration in the living body 8, specifically, the oxygen saturation, based on the IR light signal and the red light signal corrected by the correction unit 31. Then, when the measuring unit 32 measures that the blood oxygen concentration of the person to be measured who has stopped breathing to measure the LFCT is lower than that before the breathing is stopped, the measuring unit 32 notifies the notification unit 36. Since oxygen saturation is an example of blood oxygen concentration, the biological information that correlates with the change in blood oxygen concentration will be collectively referred to as "blood oxygen concentration" hereafter.

When the measuring unit 32 notifies that the blood oxygen concentration of the person to be measured has decreased, the notification unit 36 notifies the person to be measured to resume breathing.

Further, since the measuring unit 32 measures the LFCT after the subject resumes breathing, as an example, the difference between the IR light signal and the red light signal corrected by the correction unit 31 (hereinafter, this difference is referred to as “pulse wave”). "Difference") is measured. For example, when the pulse wave difference is β (t), β (t) can be obtained by the following equation (7).

(Number 7)
β (t) = α × IR (t) -Red (t) ... (7)

The detection unit 33 according to the present embodiment detects an inflection point of the blood oxygen concentration accompanying a change in the intake oxygen amount of the living body 8 based on the pulse wave difference β (t) measured by the measurement unit 32. As an example of the method of changing the amount of inspired oxygen, a method of holding a breath or the like can be mentioned. Further, the change in the amount of inspired oxygen referred to here is a change that affects the blood oxygen concentration for at least several seconds, and depends on a normal respiratory state (for example, breathing at an average respiratory rate and depth). It does not include slight changes. In other words, in the normal respiratory state, there is no change in the inspiratory oxygen amount, and when the inspiratory oxygen amount is changed from the normal respiratory state by stopping breathing, weakening the breathing, inhaling a gas having a high oxygen concentration, etc., the inspiratory oxygen amount changes. It is judged that it was done.

The specific unit 34 according to the present embodiment specifies the time from the time when the intake oxygen amount of the living body 8 changes to the inflection point of the blood oxygen concentration detected by the detection unit 33. The time when the inspiratory oxygen amount changes is, for example, the time when respiration is resumed from the state of respiratory arrest.

The specific unit 34 includes an extraction unit 37 that extracts the respiratory waveform of the subject from the pulse wave signal represented by the IR optical signal or the red light signal. Therefore, the specific unit 34 may specify the time point when the subject resumes respiration from the respiratory waveform extracted by the extraction unit 37. In the present embodiment, the time specified by the specific unit 34 is defined as LFCT.

The extraction unit 37, which is an example of the respiratory waveform extraction unit according to the present embodiment, is not an essential component of the biological information measuring device 10, and the specific unit 34 does not restart the respiration of the subject from the respiratory waveform. It is not necessary when specifying by other methods.

The estimation unit 35 according to the present embodiment estimates the output amount from the LFCT specified by the specific unit 34. For example, the cardiac output, which is an example of the stroke volume, is estimated using the above equation (6).

Here, each of the IR light signal and the red light signal contains a component representing a change in blood volume due to pulsation, nerve activity, etc., and a component representing a change in oxygen concentration due to a change in inspiratory oxygen amount. .. Then, according to the pulse wave difference β (t), the coefficient α (= ΔRed / ΔIR) is multiplied by IR (t), and the difference between α × IR (t) and Red (t) is adopted. The components representing changes in arterial blood volume are offset, and only the components representing changes in oxygen concentration are extracted.

In the above, the coefficient α is set to (ΔRed / ΔIR) in order to correct the IR optical signal, but the coefficient α may be set to (ΔIR / ΔRed) in order to correct the red light signal. In this case, the pulse wave difference β (t) is obtained by the following equation (8).

(Equation 8)
β (t) = IR (t) -α × Red (t) ... (8)

Further, in the above, the case of correcting either the IR optical signal or the red light signal, which is an example of the two pulse wave signals, has been described, but even if both the IR optical signal and the red light signal are corrected. Good. Further, in the above, the red light signal is subtracted from the IR light signal, but the IR light signal may be reduced from the red light signal. In that case, the direction of the inflection point appearing in β (t) is different.

The pulse wave signal when the coefficient α is obtained and the pulse wave signal to which the obtained coefficient α is applied are temporally different from each other. That is, in the above correction, the coefficient α represented by the amplitude ratio of ΔIR and ΔRed before changing the intake oxygen amount is multiplied by IR (t) or Red (t) after changing the intake oxygen amount. It is done in. For example, it is desirable to use the pulse wave signal at rest before respiratory arrest as the pulse wave signal when obtaining the coefficient α.

Next, the configuration of each part when the removing part 30 is provided will be described.

The removing unit 30 according to the present embodiment removes a DC component from each of the IR light signal and the red light signal output from the light receiving element 3, and removes each of the IR light signal and the red light signal after removing the DC component. Output to the correction unit 31. As an example, a high-pass filter or a band-pass filter is applied to the removing unit 30. In this case, the IR optical signal from which the DC component has been removed by the removing unit 30 is used as the first signal, and the red light signal from which the DC component has been removed by the removing unit 30 is used as the second signal.

The correction unit 31 receives the IR light signal and the red light signal from which the DC component has been removed by the removal unit 30, and derives a coefficient α represented by the amplitude ratio of the amplitude of the received IR light signal and the amplitude of the red light signal. To do. After that, the correction unit 31 derives the above with respect to IR (t), which is the value of the IR optical signal received from the light receiving element 3 without going through the removal unit 30, or Red (t), which is the value of the red light signal. Correction is performed by multiplying by the coefficient α. Since the operations of the measurement unit 32, the detection unit 33, the specific unit 34, the estimation unit 35, the notification unit 36, and the extraction unit 37 are the same, the description thereof will be omitted.

Next, the operation of the biological information measuring device 10 will be described. FIG. 17 is a flowchart showing an example of a flow of measurement processing executed by the CPU 20A of the biometric information measuring device 10 when the biometric information measuring device 10 is activated by the operation of the person to be measured or the person in charge of measurement.

The biometric information measurement program that defines the measurement process is stored in advance in, for example, the ROM 20B of the biometric information measuring device 10. The CPU 20A of the biometric information measuring device 10 reads the biometric information measuring program stored in the ROM 20B and executes the measurement process.

In step 100, the CPU 20A acquires the amplitude (ΔIR) of the IR light signal obtained from the light receiving element 3, and acquires the amplitude (ΔRed) of the red light signal obtained from the light receiving element 3. In this step 100, first, each of ΔIR and ΔRed is acquired as the pulse wave amplitude while the subject is in a resting state.

FIG. 18 is a graph showing an example of the amplitude of the IR optical signal and the amplitude of the red light signal according to the present embodiment.

In FIG. 18, the vertical axis represents the output voltage of the light receiving element 3, and the horizontal axis represents time.

As shown in FIG. 18, the correction unit 31 acquires ΔIR from IR (t), which is time-series data of IR optical signal values, and ΔRed from Red (t), which is time-series data of red light signal values. To get.

In step 102, the CPU 20A derives a coefficient α represented by an amplitude ratio of ΔIR and ΔRed based on the ΔIR and ΔRed acquired in step 100. As an example, the coefficient α is derived by the method shown below.
(A) The amplitude ratio obtained at an arbitrary timing is adopted. In this case, it may be after the start of LFCT measurement.
(B) The average value of a plurality of amplitude ratios obtained in a certain period is adopted. In the case of this method, a coefficient α suitable for measurement can be obtained as compared with the case where the coefficient α is derived by adopting the amplitude ratio of only one point.
(C) After the measurement is completed, as an example, as shown in FIG. 19, the coefficient α is changed between 0 and 1, and the value having the smallest pulsation frequency component appearing in the pulse wave difference β (t) is adopted. However, when the coefficient α is (ΔRed / ΔIR), the condition of ΔIR> ΔRed is satisfied. In the case of this method, it is not necessary to derive the coefficient α during the measurement, so that the measurement time is shortened, for example.

FIG. 19 is a graph showing an example of the relationship between the coefficient α and the pulse wave difference β (t) according to the present embodiment.

In FIG. 19, the vertical axis represents the pulse wave difference β (t). Further, in this example, α = ΔRed / ΔIR, β (t) = α × IR (t) -Red (t).

The upper figure of FIG. 19 shows the overall waveform and the enlarged waveform of the pulse wave difference β (t) when the coefficient α = 0.2. The left figure is the overall waveform, and the right figure is the enlarged waveform.

The middle figure of FIG. 19 shows the overall waveform and the enlarged waveform of the pulse wave difference β (t) when the coefficient α = 0.3583. The left figure is the overall waveform, and the right figure is the enlarged waveform.

The lower figure of FIG. 19 shows the overall waveform and the enlarged waveform of the pulse wave difference β (t) when the coefficient α = 0.6. The left figure is the overall waveform, and the right figure is the enlarged waveform.

From the above, it can be seen that when the coefficient α = 0.3583, the frequency component of the pulsation appearing in the pulse wave difference β (t) becomes the smallest. Therefore, according to the method (c) above, the coefficient α = 0.3583 is adopted, and the pulse wave difference β (t) in which the inflection point of the oxygen concentration is at the correct position can be obtained.

In step 104, the CPU 20A receives an instruction to start the measurement of the LFCT while the person to be measured keeps a resting state. As an example, the measurement start instruction is given by the person to be measured or the person in charge of measurement instructing the measurement start via the touch panel of the display unit 22 or the like.

In step 106, the CPU 20A instructs the person to be measured to start holding a breath. Specifically, for example, it may be performed by displaying a message such as "Please hold your breath" on the display unit 22, or it may be an instruction by voice or vibration.

As described above, LFCT is the time from when breathing is stopped so that the blood oxygen concentration decreases, and then after the respiration is resumed until the blood oxygen concentration begins to recover. Therefore, in order to measure LFCT, it is necessary to hold breathing for, for example, about 20 seconds so that the blood oxygen concentration decreases. However, there are individual differences in the time from when breathing is stopped until the blood oxygen concentration decreases, and it is a burden for some subjects to stop breathing for a uniform long time. Therefore, it is desirable to resume breathing of the subject when the blood oxygen concentration begins to decrease.

Therefore, a predetermined lowering condition indicating that the blood oxygen concentration of the person to be measured is lower than before stopping breathing is set, and the CPU 20A determines when the change in the blood oxygen concentration satisfies the lowering condition. , It is determined that the blood oxygen concentration of the subject is lower than that before the stop of breathing, the subject is instructed to resume breathing, and the measurement of LFCT is started.

The preset conditions for lowering the blood oxygen concentration may be any condition as long as it can be quantitatively determined that the blood oxygen concentration of the subject has decreased.

For example, it is set as a condition for lowering the blood oxygen concentration that the blood oxygen concentration falls below a predetermined reference threshold value. A value common to each subject may be used as the reference threshold, but since there are individual differences in the blood oxygen concentration before the subject stops breathing, that is, the blood oxygen concentration in normal times. A reference threshold set according to the blood oxygen concentration in normal times may be used for each person to be measured. The reference threshold value is stored in the ROM 20B in advance, for example, but is a value that can be changed by the person in charge of measurement.

However, even if the subject stops breathing, the measured blood oxygen concentration does not decrease monotonically due to measurement error, etc., and it is actually seen as an overall tendency with a slight increase or decrease. It will decrease in some cases.

Therefore, if the blood oxygen concentration of the subject falls below the reference threshold and then the blood oxygen concentration falls above the reference threshold again, at what point the subject is instructed to resume breathing. It is difficult to decide whether to start the LFCT measurement.

Therefore, the blood oxygen concentration is lower than the reference threshold value, and the statistic of the blood oxygen concentration in the specified period provided immediately after the blood oxygen concentration is lower than the reference threshold value is lower than the reference threshold value. May be set as a condition for lowering the blood oxygen concentration. The specified period, which is an example of the predetermined period according to the present embodiment, is a value stored in the ROM 20B in advance and can be changed by the person in charge of measurement.

The statistic of blood oxygen concentration in a specified period is a representative value of blood oxygen concentration in a specified period, such as an average value, a minimum value, and a median value of blood oxygen concentration measured in a specified period.

Immediately after the blood oxygen concentration drops below the reference threshold, the blood oxygen concentration tends to be higher than the reference threshold again. Therefore, the blood oxygen concentration measured in the latter half of the specified period is more statistical. A weighted average of blood oxygen concentrations weighted so as to have a large effect on the amount may be used.

Further, in order to grasp the tendency of the overall change of the blood oxygen concentration without being influenced by a slight increase or decrease of the blood oxygen concentration, the CPU 20A calculates and calculates the degree of decrease of the blood oxygen concentration in the specified period. Depending on the degree of decrease in blood oxygen concentration, it may be determined whether the blood oxygen concentration of the subject is lower than that before stopping breathing.

Specifically, the CPU 20A applies the least squares method to the measured blood oxygen concentration to calculate a regression line showing the tendency of the overall change in the blood oxygen concentration. Since the regression line is represented by a graph with the vertical axis representing the blood oxygen concentration and the horizontal axis representing the time, the slope of the calculated regression line represents the degree of decrease in the blood oxygen concentration. Therefore, it is set as the condition for lowering the blood oxygen concentration that the slope of the regression line exceeds the standard lowering degree, which is an example of the lowering degree of the predetermined standard according to the present embodiment.

The reference decrease degree is the slope of the regression line measured when the blood oxygen concentration begins to decrease. Therefore, when the slope of the regression line exceeds the reference decrease degree, it indicates that the blood oxygen concentration has started to decrease. The reference reduction degree is determined in advance based on, for example, measurement data of blood oxygen concentration obtained from a plurality of subjects and the result of computer simulation, and is stored in ROM 20B in advance. A value common to each subject may be used as the reference reduction degree, but as with the reference threshold value, the degree of decrease in blood oxygen concentration when breathing is stopped also varies from person to person, so that for each person to be measured. You may use different reference reduction degrees for.

Furthermore, as described above, since the attachment site of the sensor unit for measuring the blood oxygen concentration does not necessarily have to be the fingertip of the person to be measured, for example, the sensor unit is attached to the earlobe of the person to be measured to obtain blood oxygen. The concentration may be measured. In this case, the distance from the body surface to the blood vessels, the amount of fat in the body, etc. differ depending on the site where the blood oxygen concentration is measured, so that the biological information that correlates with the blood oxygen concentration in normal times also differs. There is. Therefore, it is preferable to use different reference threshold values depending on the site where the blood oxygen concentration is measured.

The conditions for lowering the blood oxygen concentration shown above were based on the premise that the blood oxygen concentration was lower than the reference threshold, but when it is difficult to set the reference threshold, the blood oxygen concentration May be compared with the degree of reference reduction without comparing with the reference threshold. Specifically, it is set as a condition for lowering the blood oxygen concentration that the degree of decrease in the blood oxygen concentration exceeds the reference lowering degree.

The CPU 20A divides the period after the subject stops breathing into a period of a predetermined length (referred to as a "division period"), and calculates a regression line showing a change in blood oxygen concentration for each division period. By comparing with the reference degree of decrease, it is determined whether the blood oxygen concentration of the subject is lower than that before stopping breathing.

In step 108, the CPU 20A determines whether or not the blood oxygen concentration has decreased due to the respiratory arrest of the subject, depending on whether or not the measured blood oxygen concentration satisfies the condition for reducing the blood oxygen concentration. To do. If the blood oxygen concentration of the subject is not decreased, the determination of whether the blood oxygen concentration satisfies the decrease condition is repeatedly executed. On the other hand, when the blood oxygen concentration of the person to be measured decreases, the process proceeds to step 110.

Depending on the person to be measured, it may take some time for the blood oxygen concentration to decrease depending on the physical condition, and breathing may not continue until it is determined that the blood oxygen concentration has decreased. In such a case, the person to be measured is forced to bear an excessive burden. Therefore, if the blood oxygen concentration of the subject does not decrease even after the predetermined waiting time elapses after instructing the subject to start breath holding in step 106, the waiting time After that, the person to be measured may be instructed to resume breathing for a while, and then the measurement process may be restarted from step 100.

In step 110, the CPU 20A instructs the subject to resume breathing due to the decrease in the blood oxygen concentration of the subject. Specifically, for example, it may be performed by displaying a message instructing the display unit 22 to resume breathing, or may be an instruction by voice or vibration. The CPU 20A starts the measurement of LFCT from the resumption time of respiration.

The resumption time of breathing of the subject may be, for example, the time when the subject is instructed to resume breathing, but even if the subject is instructed to resume breathing, the subject actually breathes. There may be a time lag before resuming. Therefore, the CPU 20A may perform a countdown or the like toward the timing of instructing the resumption of respiration to notify the person to be measured in advance of the timing of resuming respiration.

Further, for example, the person to be measured is provided with a button for notifying the CPU 20A of the resumption notification by pressing the button, and the person to be measured is instructed to resume respiration from the biological information measuring device 10 and then the person to be measured resumes respiration. You may let yourself press the button. In this case, the CPU 20A sets the time when the resumption notification is received as the resumption time of the person to be measured.

Further, the CPU 20A may use a known method to extract the respiratory waveform of the subject from the pulse wave and specify the respiration restart time from the extracted respiratory waveform.

Specifically, the CPU 20A extracts peak inflection points and bottom inflection points from a graph showing changes in pulse waves, and known interpolation such as spline interpolation between peak inflection points and bottom inflection points, respectively. The peak waveform and bottom waveform generated by interpolation by the method are generated. The "peak inflection point" is the point where the pulse wave value changes from rising to falling, and the "bottom inflection point" is the point where the pulse wave value changes from falling to rising.

Then, the CPU 20A generates a difference waveform between the peak waveform and the bottom waveform, performs a fast Fourier transform on the generated difference waveform, and calculates a frequency component included in the difference waveform. Further, the CPU 20A obtains the maximum frequency component from the calculated frequency component, sets the frequencies of the components adjacent to the obtained maximum frequency component to the cutoff frequency, and then uses, for example, a bandpass filter to set the respective cutoff frequencies. The respiratory waveform is extracted by leaving only the frequency components included in the interval and removing the other frequency components.

In step 112, the CPU 20A determines whether or not a predetermined time has elapsed after resuming respiration. This predetermined time is preset as a time for follow-up observation, and is, for example, 60 seconds or the like. Since the arrival time of oxygen differs depending on the measurement site, it is advisable to set a time for follow-up observation suitable for the measurement site in advance. When the predetermined time has elapsed, the process proceeds to step 114, and when it is determined that the predetermined time has not elapsed, the determination process of step 112 is repeatedly executed until the predetermined time elapses, and the predetermined time elapses. Wait until. The CPU 20A continues to measure IR (t) and Red (t) while waiting until a predetermined time elapses.

In step 114, the CPU 20A corrects by multiplying the coefficient α derived in step 102 by the IR (t) or Red (t) obtained by the above measurement. In the present embodiment, the coefficient α (ΔRed / ΔIR) is corrected by multiplying the IR (t), but when the Red (t) is corrected, the coefficient α may be ΔIR / ΔRed.

FIG. 20 is a graph showing an example of the time series data of the IR optical signal and the time series data of the red light signal according to the present embodiment.

In FIG. 20, the vertical axis represents the output voltage of the light receiving element 3, and the horizontal axis represents time.

As shown in FIG. 20, graph g1 represents IR (t), which is time-series data of IR optical signals. Further, the graph g2 represents Red (t) which is time series data of the red light signal.

FIG. 21 is a graph showing an example of time-series data of the corrected IR optical signal and time-series data of the red light signal according to the present embodiment.

In FIG. 21, the vertical axis represents the output voltage of the light receiving element 3, and the horizontal axis represents time.

As shown in FIG. 21, graph g3 represents α × IR (t) in which IR (t) is multiplied by a coefficient α to adjust the offset. Further, the graph g4 represents Red (t) which is time series data of the red light signal.

Next, in step 116, the CPU 20A uses the above equation (7) to obtain a pulse wave difference β (t) from α × IR (t) obtained by correction in step 114 and Red (t). Measure. When Red (t) is corrected, the pulse wave difference β (t) may be calculated using the above equation (8).

In step 118, the CPU 20A detects an inflection point of the blood oxygen concentration accompanying a change in the intake oxygen amount of the subject based on the pulse wave difference β (t) calculated in step 116.

In step 120, the CPU 20A specifies the time from the time when the intake oxygen amount of the person to be measured changes to the inflection point detected in step 118 as LFCT, and ends a series of processes by the biometric information measurement program. .. In the present embodiment, the process up to the specification of the LFCT has been described, but the pumping amount may be calculated using the specified LFCT. Specifically, for example, the specified LFCT may be applied to the above equation (6) to calculate the cardiac output.

FIG. 22 is a graph showing an example of LFCT identified from the pulse wave difference β (t) according to the present embodiment. In FIG. 22, the vertical axis represents the pulse wave difference β (t), and the horizontal axis represents time. Further, FIG. 23 is a graph showing the LFCT specified from the amplitude ratio according to the comparative example. In FIG. 23, the vertical axis represents the amplitude ratio of ΔIR and ΔRed, and the horizontal axis represents time.

As shown in FIG. 22, the time from the time when respiration is resumed to the inflection point indicated by the maximum value of the pulse wave difference β (t) (= α × IR (t) -Red (t)) is defined as LFCT. To do.

In FIG. 22, graph g5 represents the pulse wave difference β (t) as a moving average of one-sided width n data (n = 64 in this example). Further, the graph g6 represents the pulse wave difference β (t) when the coefficient α = 0.3583. By setting the pulse wave difference β (t) as the moving average of the one-sided width n data in this way, the residual pulse wave component due to the difference in blood oxygen concentration is removed, so that more accurate LFCT can be obtained.

Further, according to the graphs g5 and g6 shown in FIG. 22, the value of the pulse wave difference β (t) rises immediately after the breath-holding period ends and the respiration is resumed, and the value increases after reaching one peak. You can see that it is descending. Since the pulse wave difference β (t) increases when the blood oxygen concentration decreases, the blood oxygen concentration is the lowest at the peak time, and the inflection point where the decrease begins is the oxygen in the blood due to the resumption of respiration. It indicates that it has begun to be taken in. Therefore, the time from resumption of breathing to the peak is specified as LFCT.

On the other hand, in the comparative example shown in FIG. 23, the LFCT is specified from the amplitude ratio (ΔRed / ΔIR). Therefore, for example, in the case of a subject having a small pulse wave amplitude, a peak position different from the original peak position may be detected, and the LFCT may not be accurately specified.

As described above, it has been explained that the attachment site of the sensor unit for measuring the blood oxygen concentration does not necessarily have to be the fingertip of the person to be measured. However, for example, when the sensor unit is attached to the earlobe, the earlobe is the fingertip. Since it is closer to the heart than the heart, the phenomenon of decrease in blood oxygen concentration is measured earlier than the measurement of blood oxygen concentration with a fingertip. Therefore, in measuring LFCT, it is preferable to measure the blood oxygen concentration with the earlobe in order to shorten the period during which the subject stops breathing as much as possible and reduce the burden on the subject.

On the other hand, when the blood oxygen concentration is measured with the ear flap, it takes less time to observe the change in the blood oxygen concentration than when the blood oxygen concentration is measured with the fingertip because of the proximity to the heart. The effect of timing shift when resuming respiration becomes relatively large, and the measurement accuracy of LFCT decreases.

Therefore, the sensor unit is attached to the fingertip and the earlobe of the person to be measured, respectively, and the CPU 20A executes the determination process of step 108 using the blood oxygen concentration measured by the earlobe to instruct the resumption of respiration. To do. By doing so, the time for the person to be measured to hold his / her breath is shortened as compared with the case where the determination process of step 108 is performed using the blood oxygen concentration measured with the fingertip. Then, after instructing the subject to resume breathing, it is preferable to start the measurement of LFCT using the blood oxygen concentration measured with the fingertip.

The attachment portion of the sensor unit is an example, and may be a combination of other portions different from the combination of the fingertip and the earlobe. That is, the CPU 20A may measure the blood oxygen concentration at different sites of the person to be measured and execute the measurement process shown in FIG. 17 before and after starting the measurement of LFCT.

The measurement of biological information that correlates with the amount of blood pumped, such as LFCT, may be measured in real time during the measurement of blood oxygen concentration, but the measured blood oxygen concentration is used, for example, in a non-volatile storage medium. It may be memorized and measured by analyzing the change in the memorized blood oxygen concentration after the measurement of the blood oxygen concentration is completed. As the non-volatile storage medium, for example, a semiconductor memory, an HDD (Hard Disk Drive), an optical disk, or the like is used.

As described above, according to the biological information measuring device 10 according to the present embodiment, the person to be measured is stopped to breathe in order to measure the change in the blood oxygen concentration accompanying the stop of breathing, and the blood oxygen of the person to be measured is measured. The LFCT is measured by instructing the resumption of respiration when it is detected that the concentration has begun to decrease.

Although the present invention has been described above using the embodiments, the present invention is not limited to the scope described in the embodiments. Various changes or improvements can be made to the embodiments without departing from the gist of the present invention, and the modified or improved forms are also included in the technical scope of the present invention. For example, the order of processing may be changed without departing from the gist of the present invention.

In this embodiment, a mode in which the measurement process shown in FIG. 17 is realized by software has been described as an example, but a process equivalent to each flowchart of the measurement process shown in FIG. 17 can be performed by, for example, an ASIC (Application Specific Integrated Circuit). It may be implemented in the hardware and processed by hardware. In this case, the processing speed can be increased as compared with the case where the measurement processing is realized by software.

Further, in the above-described embodiment, the embodiment in which the biometric information measurement program is installed in the ROM 20B has been described, but the present invention is not limited to this. The biometric information measurement program according to the present invention can also be provided in a form recorded on a computer-readable storage medium. For example, the biometric information measurement program according to the present invention may be provided in the form of being recorded on an optical disk such as a CD (Compact Disc) -ROM or a DVD (Digital Versatile Disc) -ROM. Further, the biometric information measurement program according to the present invention may be provided in the form of being recorded in a semiconductor memory such as a USB (Universal Serial Bus) memory and a flash memory.

Further, the biometric information measuring device 10 may acquire the biometric information measuring program according to the present invention from an external device connected to the communication line through the communication line.

1 Light emitting element 3 Light receiving element 4 Artery 5 Vein 6 Capillaries 7 Blood cells 8 Living body 10 Biological information measuring device 12 Light emitting control unit 14 Drive circuit 16 Amplifier circuit 18 A / D conversion circuit 20 Control unit 20A CPU
20B ROM
20C RAM
22 Display unit 30 Removal unit 31 Correction unit 32 Measuring unit 33 Detection unit 34 Specific unit 35 Estimating unit 36 Notification unit 37 Estimating unit 40 Coherent light 42 Scattered light 44 Arrow

Claims (18)

A first signal representing a change in the amount of received light having a first wavelength irradiated to the person to be measured and a second signal representing a change in the amount of light received having a second wavelength irradiated to the person being measured. Using the signal of No. 2, a measuring unit that measures biological information that correlates with changes in blood oxygen concentration associated with respiratory arrest and resumption, and a measuring unit.
When the measuring unit measures that the biological information is lower than that before stopping breathing, a notification unit that notifies to resume breathing, and a notification unit.
Biological information measuring device equipped with. The living body according to claim 1, wherein the measuring unit measures that the biological information is lower than before the breathing is stopped when the change of the biological information satisfies a predetermined lowering condition indicating the deterioration of the biological information. Information measuring device. The biometric information measuring device according to claim 2, wherein the reduction condition is set to a condition that the biometric information is lower than a predetermined reference threshold value. The living body according to claim 3, wherein the lowering condition is set to a condition that the statistic of the biological information in a predetermined period after the biological information is lower than the reference threshold is lower than the reference threshold. Information measuring device. Claim 3 in which the reduction condition is set to a condition that the degree of reduction of the biometric information in a predetermined period after the biometric information is lower than the reference threshold value exceeds the degree of reduction of the predetermined standard. The biometric information measuring device described. The method according to any one of claims 3 to 5, wherein the reference threshold value differs depending on the portion of the person to be measured to be irradiated with the light having the first wavelength and the light having the second wavelength. Biometric information measuring device. The biometric information measuring device according to claim 2, wherein the reduction condition is set to a condition that the degree of reduction of the biological information exceeds the degree of reduction of a predetermined standard. The biometric information measuring device according to claim 7, wherein the degree of deterioration of the biometric information is represented by the slope of a graph showing the change in the biometric information. The measuring unit sets the time from the resumption time of the breathing of the person to be measured resumed by the notification of the notification unit due to the decrease of the biological information to the appearance of the distorted point of the biological information in the body by resuming the respiration. 1 to 8 of claims 1 to 8, which are measured as an oxygen cycle time representing the time until the oxygen taken into the body reaches the portion irradiated with the light having the first wavelength and the light having the second wavelength. The biometric information measuring device according to any one item. A respiratory waveform extraction unit for extracting a respiratory waveform of the subject from the first signal or the second signal is provided.
The biometric information measuring device according to claim 9, wherein the measuring unit uses the respiration restart time obtained from the respiration waveform of the person to be measured extracted by the respiration waveform extraction unit as the respiration resumption time of the person to be measured. The biometric information measuring device according to claim 9, wherein the measuring unit uses the time when the notification unit notifies the resumption of respiration as the resumption time of respiration of the person to be measured. The measuring unit claims that after the notification unit notifies the resumption of respiration, the time when the resumption notification for notifying that the person to be measured has resumed respiration is received as the resumption time of respiration of the person to be measured. 9. The biological information measuring device according to 9. The biometric information according to any one of claims 9 to 12, wherein the measuring unit measures the biometric information of different parts of the subject before and after starting the measurement of the oxygen cycle time. measuring device. Before starting the measurement of the oxygen circulation time, the measuring unit measures the biological information of the portion where the biological information decreases faster than that of the other portion measuring the biological information, and the oxygen circulation. After starting the time measurement, the living body of the part where it takes time for the biometric information to change with respect to the change in the respiration of the person to be measured as compared with other parts for which the biometric information is measured. The biometric information measuring device according to claim 13, wherein the information is measured. The measuring unit measures the biological information of the ear canal of the person to be measured until the measurement of the oxygen cycle time is started, and after the measurement of the oxygen cycle time is started, the measurement unit is the fingertip of the person to be measured. The biometric information measuring device according to claim 14, which measures biometric information. The first signal and the second signal so that the difference between the change amount of the first signal and the change amount of the second signal due to the change of the arterial blood volume of the subject is small. Equipped with a correction unit that corrects at least one of
The measurement unit measures the change in the biological information by using the difference between the value of the first signal and the value of the second signal corrected by at least one of the correction units. The biological information measuring device according to any one item. The one according to any one of claims 1 to 15, wherein the measuring unit measures the change of the biological information by using the ratio of the change amount of the first signal and the change amount of the second signal. Biometric information measuring device. A biometric information measurement program for causing a computer to function as each part of the biometric information measuring device according to any one of claims 1 to 17.