JP2019166145A - Biological information measurement device and biological information measurement program - Google Patents

Abstract

To provide a biological information measurement device and a biological information measurement program capable of measuring a cardiac output non-invasively and accurately, compared with a case of not using a blood flow signal.SOLUTION: A biological information measurement device 10A comprises: an acquisition unit 30 for acquiring a blood flow signal indicating at least one of a blood volume and a blood flow speed at a peripheral part of a living body; and an identification unit 32 for identifying a cardiac output of a living body on the basis of the blood flow signal acquired by the acquisition unit 30 on the basis of a predetermined relationship between the blood flow signal of the living body and the cardiac output of the living body.SELECTED DRAWING: Figure 14

Description

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

  For example, Patent Document 1 describes a circulation time measuring device that measures an oxygen circulation time required for specifying cardiac output. This circulation time measuring device includes a signal acquisition unit that acquires an airflow signal indicating a time change of a respiratory airflow and an oxygen saturation signal indicating a time change of oxygen saturation, a predetermined first time in the airflow signal, A circulation time calculation unit that measures the oxygen circulation time of blood based on a time difference from the second time in the oxygen saturation signal indicating an increase in oxygen saturation corresponding to resumption of breathing at the first time. .

International Publication No. 2015/190413 Pamphlet

  By the way, the cardiac output represented by the cardiac output is one of the indexes indicating the state of cardiac function. As a representative method for measuring the stroke volume, there is a thermodilution method in which cold water is injected from a catheter inserted into a blood vessel. However, this thermodilution method is highly invasive to the living body and places a heavy burden on the living body.

  In addition, there are measurement methods using MRI (Magnetic Resonance Imaging) and an ultrasonic device, and measurement methods such as a bioimpedance method, but they are relatively less invasive than the above-mentioned thermodilution method. Specialized knowledge is required and it cannot be said that it is a simple measurement method.

  Further, in the measurement method using the oxygen circulation time, a blood flow signal indicating a blood volume, a blood flow velocity, or the like in a peripheral part of the living body may be measured. Since the blood flow signal obtained from the peripheral part of the living body is considered to have a high correlation with the stroke volume, there is a possibility that the stroke volume can be accurately measured non-invasively by using the blood flow signal. However, the measurement method using the oxygen circulation time does not consider measuring the stroke volume using the blood flow signal.

  It is an object of the present invention to provide a biological information measuring device and a biological information measuring program that can measure the stroke volume non-invasively and accurately compared to the case where a blood flow signal is not used.

  In order to achieve the above object, the biological information measuring device according to claim 1 includes an acquisition unit that acquires a blood flow signal indicating at least one of a blood volume and a blood flow velocity in a peripheral region of the living body, and blood of the living body. A specifying unit that specifies the amount of stroke of the living body from the blood flow signal acquired by the acquiring unit based on a predetermined relationship between the flow signal and the amount of stroke of the living body.

According to a second aspect of the present invention, in the biological information measuring apparatus according to the first aspect, the output of the living body is a cardiac output, and the predetermined relationship is a heartbeat of the living body. When the output is CO, the constant parameters are a ₀ and a ₁ , and the value indicated by the blood flow signal of the living body is BS,
CO = a ₀ + a ₁ × BS
It is assumed that the relationship is represented by

  Moreover, the biological information measuring device according to claim 3 further includes a storage unit according to the invention according to claim 1, further comprising a storage unit that stores in advance the values indicated by the amount of stroke of the living body and the blood flow signal of the living body. The predetermined relationship is a relationship stored in association with the predetermined relationship.

  According to a fourth aspect of the present invention, in the biological information measuring apparatus according to the third aspect of the present invention, the stroke volume of the living body is indicated by any one of a cardiac output, a stroke volume, and a cardiac coefficient. It is said that it is an amount.

  Moreover, the biological information measuring device according to claim 5 is the oxygen circulation time according to the invention according to claim 1, wherein the acquisition unit represents a time until oxygen taken into the living body reaches the peripheral site. And the specifying unit is acquired by the acquiring unit based on a predetermined second relationship of the blood flow signal of the living body, the oxygen circulation time of the living body, and the stroke volume of the living body. The stroke volume of the living body is specified from the blood flow signal and the oxygen circulation time.

Further, the biological information measuring apparatus according to claim 6 is the invention according to claim 5, wherein the amount of stroke of the living body is the amount of cardiac output, and the predetermined second relationship is: When the cardiac output of CO is CO, the oxygen circulation time of the living body is LFCT, the constant parameters are a ₀ , a ₁ , a ₂ , and the value indicated by the blood flow signal of the living body is BS,
CO = a ₀ + a ₁ × 1 / LFCT + a ₂ × BS
It is assumed that the relationship is represented by

  According to a seventh aspect of the present invention, there is provided the biological information measuring device according to the fifth aspect of the invention, in which the volume of the living body, the value indicated by the blood flow signal of the living body, and the oxygen circulation time of the living body are associated in advance. A storage unit is further provided, and the predetermined second relationship is a relationship stored in association with the predetermined relationship.

  Moreover, the biological information measuring device according to claim 8 is the invention according to any one of claims 1 to 7, wherein the acquisition unit determines a value indicated by the blood flow signal as a peripheral part of the living body. It is obtained from a signal obtained in accordance with the reflected light or transmitted light of the light irradiated to.

  Furthermore, in order to achieve the said objective, the biological information measurement program of Claim 9 makes a computer function as each part with which the biological information measurement apparatus of any one of Claims 1-8 is provided.

  According to the invention which concerns on Claim 1 and Claim 9, compared with the case where a blood-flow signal is not utilized, a stroke volume can be measured with sufficient accuracy non-invasively.

  According to the second aspect of the present invention, when the blood flow signal is used, the cardiac output can be measured with a simple calculation.

  According to invention of Claim 3, when using a blood-flow signal, the load of the arithmetic processing regarding a stroke amount can be reduced.

  According to the fourth aspect of the present invention, any one of cardiac output, stroke volume, and cardiac coefficient can be measured as the cardiac output.

  According to the fifth aspect of the present invention, the stroke volume can be measured more accurately and non-invasively than when the blood flow signal and the oxygen circulation time are not used.

  According to the sixth aspect of the present invention, when the blood flow signal and the oxygen circulation time are used, the cardiac output can be measured with a simple calculation.

  According to the seventh aspect of the present invention, when the blood flow signal and the oxygen circulation time are used, it is possible to reduce the load of calculation processing related to the stroke volume.

  According to the eighth aspect of the present invention, the value indicated by the blood flow signal can be easily obtained as compared with the case where the reflected light or transmitted light of the light irradiated to the peripheral part of the living body is not used. .

It is a schematic diagram which shows the measurement example of the blood flow information which concerns on embodiment, and the oxygen saturation in blood. It is a graph which shows an example of change of the amount of received light by reflected light from a living body concerning an embodiment. It is a schematic diagram with which it uses for description of the Doppler shift which arises when a laser beam is irradiated to the blood vessel which concerns on embodiment. It is a schematic diagram with which it uses for description of the speckle produced when the blood vessel which concerns on embodiment is irradiated with a laser beam. It is a graph which shows an example of spectrum distribution for every frequency in unit time concerning an embodiment. It is a graph which shows an example of change of blood flow volume per unit time concerning an embodiment. It is a graph which shows an example of change of the amount of light absorption of the light absorbed by the living body concerning an embodiment. It is a graph which shows an example of the light absorbency characteristic by the hemoglobin which concerns on embodiment. It is a schematic diagram with which it uses for description of the measurement principle of LFCT which concerns on embodiment. It is a graph for demonstrating an example of the measuring method of LFCT which concerns on embodiment. It is a block diagram which shows an example of the electrical constitution of the biological information measuring device which concerns on 1st Embodiment. It is a figure which shows an example of arrangement | positioning of the light emitting element and light receiving element in the biological information measuring device which concerns on embodiment. It is a figure which shows another example of arrangement | positioning of the light emitting element and light receiving element in the biological information measuring device which concerns on embodiment. It is a block diagram showing an example of functional composition of a living body information measuring device concerning a 1st embodiment. It is a figure which shows an example of the correlation with cardiac output and each parameter which concerns on embodiment. It is a scatter diagram used for the regression analysis which concerns on 1st Embodiment. It is a figure which shows an example of the lookup table which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of a process of the biometric information measurement program which concerns on 1st Embodiment. It is a block diagram which shows an example of the electrical constitution of the biological information measuring device which concerns on 2nd Embodiment. It is a block diagram which shows an example of a functional structure of the biological information measuring device which concerns on 2nd Embodiment. It is a scatter diagram used for the regression analysis which concerns on 2nd Embodiment. It is a figure which shows an example of the look-up table which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of a process of the biometric information measurement program which concerns on 2nd Embodiment.

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

[First Embodiment]
First, a method for measuring blood flow information and oxygen saturation in blood, which is an example of biological information related to blood, among biological information, will be described with reference to FIG.

FIG. 1 is a schematic diagram showing a measurement example of blood flow information and blood oxygen saturation according to the present embodiment.
As shown in FIG. 1, blood flow information and oxygen saturation in the blood mean that the inside of the living body 8 is irradiated with light from the light emitting element 1 toward the subject's body (living body 8) and received by the light receiving element 3. It is measured using the intensity of the reflected or transmitted light of the artery 4, vein 5, capillary 6, etc. stretched around, 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 time, because this is influenced by three optical phenomena that appear when light is applied to the living body 8 including blood vessels. It is believed that there is.

  As a 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. The blood contains blood cells such as red blood cells, and moves in blood vessels such as the capillaries 6, so that the number of blood cells moving in the blood vessels changes as the blood volume changes. May affect the amount of light received.

  As the second optical phenomenon, the influence of the 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 laser light.

As shown in FIG. 3, for example, when a region including a capillary vessel 6, which is an example of a blood vessel, is irradiated from a light emitting element 1 with coherent light 40 having a frequency ω ₀ such as a laser beam, 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 such as skin (stationary tissue) that does not include a moving body such as a blood 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 And the amount of light received by the light receiving element 3 varies with time. Note that 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, but is included in a range having an upper limit of about several tens kHz.

  As a third optical phenomenon, the influence of speckle is considered.

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

  As shown in FIG. 4, when coherent light 40 such as laser light is applied to blood cell 7 such as red blood cells moving in the direction of arrow 44 from light emitting element 1, laser light hitting blood cell 7. Scatters in various directions. Since the scattered lights have different phases, they interfere with each other randomly. This produces a random spotted light intensity distribution. The light intensity distribution pattern thus formed is called a “speckle pattern”.

  As already described, 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 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, data included in the range of a predetermined unit time T ₀ is cut out and, for example, fast Fourier transform (Fast Fourier Transform) is performed on the data. : FFT), the spectral distribution for each frequency ω can be obtained.

FIG. 5 is a graph showing an example of the spectrum distribution for each frequency ω in 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 hatched area 84 surrounded by the horizontal axis and the vertical axis of the graph 82 with the total light quantity. Further, since the blood flow velocity is proportional to the frequency average value of the power spectrum represented by the graph 82, a value obtained by dividing the product of the frequency ω and the power spectrum at the frequency ω with respect to the frequency ω by the area of the hatched region 84. Is proportional to

  In addition, since the blood flow volume is represented by the product of the blood volume and the blood flow velocity, it can be obtained from the calculation formula for the blood volume and the blood flow velocity. Blood flow volume, blood flow velocity, and blood volume are examples of blood flow information, and blood flow information is not limited to this.

FIG. 6 is a graph showing an example of a change in blood flow per unit time T _{0 according} to the present embodiment.
In FIG. 6, the horizontal axis of graph 86 represents time, and the vertical axis represents blood flow.

As shown in FIG. 6, the blood flow volume varies with time, but the variation tendency is classified into two types. For example, compared to the fluctuation range 88 of the blood flow rate in the interval T ₁ of the FIG. 6, the fluctuation range 90 of the blood flow in the interval T ₂ are large. This is because the change in the blood flow volume in the section T ₁ is mainly a change in the blood flow volume accompanying the movement of the pulse, whereas the change in the blood flow volume in the section T ₂ is a blood flow volume caused by causes such as congestion. It is thought that this is because of the change of.

(Measurement of oxygen saturation)
Next, measurement of blood oxygen saturation will be described. Blood oxygen saturation is an example of blood oxygen concentration and is an indicator of how much hemoglobin in the blood is bound to oxygen. As the blood oxygen saturation 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 light absorption.

  As shown in FIG. 7, the light absorption amount in the living body 8 tends to vary with time.

  Further, looking at the breakdown of the change in light absorption in the living body 8, the light absorption amount mainly fluctuates by the artery 4, and the light absorption amount does not fluctuate compared to the artery 4 in other tissues including the vein 5 and the stationary tissue. It is known that the amount of fluctuation can be considered. This is because arterial blood pumped out of 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 fluctuation of the light absorption corresponding to the change in the thickness of the artery 4.

In FIG. 7, assuming that the amount of received light at time t _a is I _a and the amount of received light 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 can be _expressed by equation (1). Is done.

(Equation 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 absorbance and the horizontal axis represents wavelength.

  As shown in FIG. 8, hemoglobin (oxygenated hemoglobin) combined with oxygen flowing through the artery 4 easily absorbs light in the infrared (IR) region having a wavelength of about 880 nm, and is not bonded to oxygen. It is known that hemoglobin (reduced hemoglobin) easily absorbs light in the red region having a wavelength around about 665 nm. Furthermore, 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, compared to other combinations of wavelengths, the absorption when IR light is irradiated on the living body 8 using infrared light (IR light) and red light, in which the difference in the amount of light absorption between oxidized hemoglobin and reduced hemoglobin tends to appear. By calculating the ratio between the change amount ΔA _IR of the amount and the change amount ΔA _Red of the light absorption amount when the living body 8 is irradiated with red light, the oxygen saturation S is calculated by the equation (2). In equation (2), k is a proportional constant.

(Equation 2)
S = k (ΔA _Red / ΔA _IR ) (2)

  That is, when calculating oxygen saturation in blood, a plurality of light emitting elements 1 that irradiate light of different wavelengths, specifically, a light emitting element 1 that irradiates IR light and a light emitting element 1 that irradiates red light, However, it is desirable to emit light so that the light emission 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 is obtained by modifying the expressions (1) and (2) or these expressions from the amount of light received at each light reception time point. The oxygen saturation is measured by calculating a known formula.

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

(Equation 3)
ΔA = lnI _b −lnI _a (3)

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

(Equation 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 ΔA in the amount of light absorption.

(Equation 5)
ΔA≈ (I _b −I _a ) / I _a (5)

  When it is necessary to distinguish between the light emitting element 1 that emits IR light and the light emitting element 1 that emits red light, the light emitting element 1 that emits IR light is hereinafter referred to as “light emitting element LD1”. The light emitting element 1 that emits red light is referred to as a “light emitting element LD2”. In addition, as an example, the light emitting element LD1 is used as the light emitting element 1 used for calculating blood flow, and the light emitting element LD1 and the light emitting element LD2 are used as light emitting element 1 used for calculating oxygen saturation in blood.

  In addition, when measuring oxygen saturation in blood, it is known that the measurement frequency of the amount of received light is about 30 Hz to about 1000 Hz. Therefore, the light emission frequency representing the number of flashes per second of the light emitting element LD2 Also, about 30 Hz to about 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 to the light emitting frequency of the light emitting element LD1. The light emitting element LD1 and the light emitting element LD2 may alternately emit light.

  Next, with reference to FIG. 9, the principle of measuring LFCT (Lung to Finger Circulation Time), which is an example of an index correlated with the amount of blood from the heart, will be described. The stroke volume here includes not only the above-mentioned cardiac output but also stroke volume, cardiac coefficient, and the like. The cardiac output is defined as the amount of blood pumped into the artery by contraction per unit time (for example, 1 minute) of the heart. Stroke volume is defined as the volume of blood pumped into an artery by a single contraction of the heart. The cardiac coefficient is defined as a coefficient obtained by dividing the cardiac output by the body surface area of the subject. LFCT is defined as the time taken for oxygen taken in by breathing to reach the fingertip through the lungs and heart. That is, LFCT is an example of an oxygen circulation time that represents a time until oxygen taken into the living body 8 reaches a peripheral site. The peripheral part here means the part on the distal side of the subject's neck, shoulder, and hip joint. For example, the fingertip of the hand, the tip of the toe, the wrist, the ankle, the earlobe, the part inside the elbow or knee Etc.

FIG. 9 is a schematic diagram for explaining the measurement principle of LFCT according to the present embodiment.
As shown in FIG. 9, the stroke volume and LFCT have a correlation. For example, when the cardiac output, which is an example of the cardiac output, is CO, the cardiac output CO is calculated by the following equation (6). However, _{a 0} and _{a 1} are constants parameter.

(Equation 6)
CO = a ₀ + a ₁ / LFCT (6)

FIG. 10 is a graph for explaining an example of the LFCT measurement method according to the present embodiment.
In FIG. 10, the vertical axis represents the reciprocal of oxygen saturation, and the horizontal axis represents time.

  As shown in FIG. 10, the LFCT according to the present embodiment is measured from the oxygen saturation in the blood described above. That is, LFCT is obtained by measuring the time from the point when respiration is resumed after stopping breathing for a certain period to the inflection point indicating that the oxygen saturation has recovered.

  Next, a biological information measuring apparatus that measures the stroke volume accurately and non-invasively using the blood flow information described above will be described.

  FIG. 11 is a block diagram illustrating an example of an electrical configuration of the biological information measuring apparatus 10A according to the first embodiment.

  As shown in FIG. 11, the biological information measuring apparatus 10A according to the present embodiment includes a light emission control unit 12, a drive circuit 14, an amplification circuit 16, an A / D (Analog / Digital) conversion circuit 18, a control unit 20, and a display unit. 22, a light emitting element LD 1, and a light receiving element 3. The light emitting element LD1, the light receiving element 3, and the amplifier circuit 16 constitute a sensor unit. Moreover, the light emission control part 12, the drive circuit 14, the amplifier circuit 16, the A / D conversion circuit 18, the control part 20, and the display part 22 comprise the main-body part. In the present embodiment, the sensor unit and the main body unit are configured separately, and can communicate with each other via wired or wireless communication. The sensor unit and the main body unit may be configured integrally. 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 be attached to other peripheral parts such as the 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 to the driving circuit 14 including a power supply circuit that supplies driving power to the light emitting element LD1. Note that 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, the drive circuit 14 supplies driving power to the light emitting element LD1 according to the light emission cycle and the light emission period instructed by the control signal to drive the light emitting element LD1.

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

  The amplifier circuit 16 amplifies a voltage corresponding to the intensity of light received by the light receiving element 3 to a voltage level defined as an input voltage range of the A / D conversion circuit 18. Here, as an example, the light receiving element 3 is an element that outputs a voltage according to the intensity of received light, but the light receiving element 3 may output a current according to the intensity of received light, In this case, the amplifier circuit 16 amplifies the current output from the light receiving element 3 to the current level defined as the input current range of the A / D conversion circuit 18.

  The A / D conversion circuit 18 receives the voltage amplified by the amplifier circuit 16 as an input, converts the received light amount of the light receiving element 3 represented by the magnitude of the voltage into a numerical value, and outputs it.

  The control unit 20 includes a central processing unit (CPU) 20A, a read only memory (ROM) 20B, and a random access memory (RAM) 20C. A biological information measurement program is stored in the ROM 20B. This biological information measuring program may be installed in advance in the biological information measuring apparatus 10A, for example. The biological information measurement program may be realized by being stored in a nonvolatile storage medium or distributed via a network and appropriately installed in the biological information measurement apparatus 10A. As examples of nonvolatile storage media, CD-ROM (Compact Disc Read Only Memory), magneto-optical disk, HDD, DVD-ROM (Digital Versatile Disc Read Only Memory), flash memory, memory card, etc. are assumed. The

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

  FIG. 12 is a diagram showing an example of the arrangement of the light emitting element LD1 and the light receiving element 3 in the biological information measuring apparatus 10A according to the present embodiment. FIG. 13 is a diagram showing another example of the arrangement of the light emitting element LD1 and the light receiving element 3 in the biological information measuring apparatus 10A according to the present embodiment.

  As shown in FIG. 12, the light emitting element LD <b> 1 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 reflected by the living body 8.

  The arrangement of the light emitting element LD1 and the light receiving element 3 is not limited to the arrangement example of FIG. For example, as shown in FIG. 13, the light emitting element LD1 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 that has passed through the living body 8.

  Here, as an example, the light emitting element LD1 is described as a surface emitting laser element. However, the present invention is not limited thereto, and may be an edge emitting laser element. The light emitted from the light emitting element LD1 may not be laser light. In this case, a light emitting diode (Light-Emitting Diode: LED) or an organic light-emitting diode (OLED) may be used as the light emitting element LD1.

  The CPU 20A of the biological information measuring device 10A according to the present embodiment functions as each unit shown in FIG. 14 by writing and executing the biological information measuring program stored in the ROM 20B in the RAM 20C.

FIG. 14 is a block diagram illustrating an example of a functional configuration of the biological information measuring apparatus 10A according to the first embodiment.
As illustrated in FIG. 14, the CPU 20 </ b> A of the biological information measurement device 10 </ b> A according to the present embodiment functions as an acquisition unit 30 and a specification unit 32.

  The acquisition unit 30 according to the present embodiment acquires a blood flow signal indicating at least one of the blood volume and the blood flow velocity in the peripheral region of the living body 8. Specifically, the acquisition unit 30 acquires a value indicated by the blood flow signal from a signal obtained according to reflected light or transmitted light of light irradiated on the peripheral portion of the living body 8. Since the blood flow signal according to the present embodiment is synonymous with the above-described blood flow information, the blood flow information will be described in the following unified description.

  In the present embodiment, one light emitting element LD1 that irradiates IR light for measuring blood flow information is used. For this reason, an IR optical signal is output from the light receiving element 3. The acquisition unit 30 receives the IR light signal output from the light receiving element 3, and calculates and acquires blood flow information from the received IR light signal. Note that this blood flow information is calculated based on the spectrum distribution for each frequency ω obtained by performing FFT on the IR optical signal as described with reference to FIG. 5 as an example.

  The specifying unit 32 according to the present embodiment outputs the living body 8 from the blood flow information acquired by the acquiring unit 30 based on a predetermined relationship between the blood flow information of the living body 8 and the stroke amount of the living body 8. Specify the amount. In the present embodiment, a case where the cardiac output is applied as an example of the stroke volume of the living body 8 will be described, but the same applies regardless of which stroke volume or cardiac coefficient is applied. The blood flow information is similarly applied to any of blood volume, blood flow velocity, and blood flow volume (= blood flow velocity × blood volume).

FIG. 15 is a diagram illustrating an example of the correlation between the cardiac output and each parameter according to the present embodiment.
The example shown in FIG. 15 shows the top three parameters extracted from the 30 parameters estimated to have correlation with cardiac output in descending order of the correlation coefficient with cardiac output. It is a thing. For these three parameters, “Mass” represents the blood volume, “1 / LFCT” represents the reciprocal of LFCT, and “BF” represents the blood flow. The number of subjects is “15”. “Mass” and “BF” are data when a fingertip is measured using a reflective sensor, and “1 / LFCT” is data when a fingertip is measured using a transmissive sensor. It is data. The case where both blood flow information and LFCT are used will be described later.

  Here, as an example of the “correlation coefficient” according to the present embodiment, a Pearson correlation coefficient is used. Pearson's correlation coefficient is a dimensionless quantity and takes a value between −1 and 1 inclusive. As an example, if the absolute value of the correlation coefficient is 0.4 or more, it is determined that there is a correlation (for example, there is a weak correlation between 0.4 and less than 0.7, and there is a strong correlation between 0.7 and 1 or less). . The “p value” is one of indices indicating correlation, and as a general standard, if it is less than 0.05, it is determined that there is a correlation.

Specifically, the predetermined relationship between the blood flow information of the living body 8 and the cardiac output of the living body 8 is that the cardiac output of the living body 8 is CO, the constant parameters are a ₀ , a ₁ , and the living body 8. When the value indicated by the blood flow information is BS, it is expressed by the following equation (7).

(Equation 7)
CO = a ₀ + a ₁ × BS (7)

The constant parameters a ₀ and a ₁ are determined so that the absolute value of the correlation coefficient is 0.4 or more by performing a regression analysis as shown in FIG.

FIG. 16 is a scatter diagram used for the regression analysis according to the first embodiment.
In FIG. 16, the vertical axis represents the estimated value of cardiac output (CO), and the horizontal axis represents the true value of cardiac output (CO). The unit is [l (liter) / min (minute)], and the number of subjects is “15”.

The regression analysis here refers to a scatter plot in which the measured values obtained by two different methods are plotted on the X axis (horizontal axis) and Y axis (vertical axis) for one subject. In this method, the correlation coefficient, the slope of the regression line, and the intercept are calculated. For example, assuming that the regression line is f (x) = αx + β, the least square method is applied, and the Y coordinate (= y) plotted in the scatter diagram and the Y coordinate (= f) on the regression line are applied. F (x) that minimizes the sum of the squares of the difference from (x)) (= (y−f (x)) ² ) is obtained.

In the example shown in FIG. 16, the measured value measured using the thermodilution method or the like is used as the CO true value as an example, and the constant parameters a ₀ and a ₁ of the above equation (7) are set as certain values as the CO estimated value. Use the derived estimate. Further, as the value BS indicated by the blood flow information, an average value of the blood volume Mass for 40 seconds is used.

From the scatter diagram shown in FIG. 16, the correlation coefficient R and the slope α and the intercept β of the regression line f (x) are obtained for the regression line f (x). Since regression analysis itself is a well-known technique, the description of the specific derivation process here is abbreviate | omitted. In the present embodiment, the constant parameters a ₀ and a ₁ are determined when the absolute value of the correlation coefficient R is 0.4 or more. As an example, the correlation coefficient R is determined to be 0.76, the constant parameter a ₀ is 13.032, and the constant parameter a ₁ is −1.698. When the absolute value of the correlation coefficient R is less than 0.4, a scatter diagram is created by changing the values of the constant parameters a ₀ and a _{1 in} the above equation (7), and the same processing is repeated.

  The result derived in advance based on the above equation (7) may be stored in advance as a lookup table as shown in FIG. Further, the look-up table is an example, and the value BS indicated by the blood flow information and the cardiac output CO may be stored in advance in association with each other, and other methods may be used.

FIG. 17 is a diagram illustrating an example of a lookup table according to the first embodiment.
As shown in FIG. 17, in the lookup table according to the present embodiment, a cardiac output CO, which is an example of the cardiac output of the living body 8, is associated with the value BS indicated by the blood flow information of the living body 8. Stored in advance. This lookup table is stored in the ROM 20B, which is an example of a storage unit.

  In this case, the predetermined relationship between the blood flow information of the living body 8 and the cardiac output of the living body 8 is a relationship represented by a lookup table. That is, in this case, the cardiac output CO can be obtained by referring to the lookup table shown in FIG. 17 based on the value BS indicated by the blood flow information.

  Next, the operation of the biological information measuring apparatus 10A according to the first embodiment will be described with reference to FIG. FIG. 18 is a flowchart illustrating an example of a processing flow of the biological information measurement program according to the first embodiment.

  First, when the biological information measuring apparatus 10A is turned on by the operation of the subject or the person in charge of measurement, the biological information measuring program is started and the following steps are executed.

  In step 100 of FIG. 18, the acquisition unit 30 acquires an IR light signal from the light receiving element 3.

  In step 102, the acquisition unit 30 calculates and acquires blood flow information from the IR light signal acquired in step 100. Note that this blood flow information is calculated based on the spectrum distribution for each frequency ω obtained by performing FFT on the IR optical signal as described with reference to FIG. 5 as an example.

  In step 104, the specifying unit 32 determines the output amount of the living body 8 from the blood flow information calculated in step 102 based on the predetermined relationship between the blood flow information of the living body 8 and the output amount of the living body 8. Is identified. For example, using the above equation (7), the cardiac output CO, which is an example of the cardiac output, is specified from the value BS indicated by the blood flow information.

Thus, according to the present embodiment, the stroke volume is measured non-invasively and accurately by using the predetermined relationship between the blood flow information of the living body and the stroke volume of the living body.
Moreover, since the oxygen circulation time is not used, it is not necessary to hold the breath and the burden on the subject is reduced.
Further, since only one light emitting element is required, the apparatus configuration is simplified.

[Second Embodiment]
In the first embodiment, the case where blood flow information is acquired using only the light emitting element LD1 has been described, but in this embodiment, blood flow information and oxygen circulation are obtained using both the light emitting element LD1 and the light emitting element LD2. A case where time is acquired will be described.

  FIG. 19 is a block diagram illustrating an example of an electrical configuration of the biological information measuring device 10B according to the second embodiment.

  As shown in FIG. 19, the biological information measuring apparatus 10B according to this embodiment includes a light emission control unit 12, a drive circuit 14, an amplification circuit 16, an A / D conversion circuit 18, a control unit 20, a display unit 22, and a light emitting element LD1. , A light emitting element LD2 and a light receiving element 3.

  The biological information measuring device 10B according to the present embodiment is different from the biological information measuring device 10A according to the first embodiment in that a light emitting element LD2 is provided. In addition, about the component which has the same function as 10 A of biological information measuring devices which concern on 1st Embodiment, the same code | symbol is attached | subjected and repeated description here is abbreviate | omitted.

  In the present embodiment, 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 each light of the light emitting element LD1 and the light emitting element LD2 reflected by the living body 8. Further, the light emitting element LD1, 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 light from the light emitting element LD1 and the light emitting element LD2 that have passed through the living body 8.

  Here, as an example, the light emitting element LD2 is described as being a surface emitting laser element similarly to the light emitting element LD1, but is not limited thereto, and may be an edge emitting laser element. Further, the light emitted from the light emitting element LD2 may not be laser light. In this case, a light emitting diode (LED) or an organic light emitting diode (OLED) may be used for the light emitting element LD2.

  The CPU 20A of the biological information measurement apparatus 10B according to the present embodiment functions as each unit illustrated in FIG. 20 by writing and executing the biological information measurement program stored in the ROM 20B in the RAM 20C.

FIG. 20 is a block diagram illustrating an example of a functional configuration of the biological information measurement device 10B according to the second embodiment.
As illustrated in FIG. 20, the CPU 20 </ b> A of the biological information measurement device 10 </ b> B according to the present embodiment functions as an acquisition unit 34 and a specification unit 36.

  The acquisition unit 34 according to the present embodiment further acquires LFCT that is an example of the oxygen circulation time of the living body 8 in addition to the blood flow information of the living body 8. This LFCT is calculated based on the oxygen saturation level in the blood as described above.

  In the present embodiment, IR light is emitted from the light emitting element LD1, and red light is emitted from the light emitting element LD2. For this reason, the IR light signal and the red light signal are output from the light receiving element 3. The acquisition unit 34 receives the IR light signal and the red light signal output from the light receiving element 3, and calculates and acquires blood flow information from the received IR light signal. Furthermore, the acquisition unit 34 calculates and acquires LFCT from the received IR light signal and red light signal.

  The specifying unit 36 according to the present embodiment is acquired by the acquiring unit 34 based on a predetermined second relationship among the blood flow information of the living body 8, the LFCT of the living body 8, and the stroke volume of the living body 8. The stroke volume of the living body 8 is specified from the blood flow information and the LFCT. In the present embodiment, a case where the cardiac output is applied will be described as an example of the output of the living body 8 as in the first embodiment.

Specifically, the predetermined second relationship among the blood flow information of the living body 8, the LFCT of the living body 8, and the cardiac output of the living body 8 is that the cardiac output of the living body 8 is CO, When the oxygen circulation time is LFCT, the constant parameter is a ₀ , a ₁ , a ₂ , and the value indicated by the blood flow information of the living body 8 is BS, it is expressed by the following equation (8).

(Equation 8)
CO = a ₀ + a ₁ × 1 / LFCT + a ₂ × BS (8)

The constant parameters a ₀ , a ₁ , and a ₂ are determined such that the absolute value of the correlation coefficient is 0.4 or more by performing a regression analysis as shown in FIG.

FIG. 21 is a scatter diagram used for regression analysis according to the second embodiment.
In FIG. 21, the vertical axis represents the estimated value of cardiac output (CO), and the horizontal axis represents the true value of cardiac output (CO). The unit is [l (liter) / min (minute)], and the number of subjects is “15”.

In the example shown in FIG. 21, the measured values measured using the thermodilution method or the like are used as the CO true value as an example, and the constant parameters a ₀ , a ₁ , and a ₂ of the above equation (8) are used as the CO estimated values. An estimated value derived as a certain value is used. Further, the average value of blood volume Mass for 40 seconds is used as the value BS indicated by the blood flow information.

From the scatter diagram shown in FIG. 21, as in the case of the first embodiment, the correlation coefficient R and the slope α and the intercept β of the regression line f (x) are obtained for the regression line f (x). In the present embodiment, when the absolute value of the correlation coefficient R is 0.4 or more, the constant parameters a ₀ , a ₁ , and a ₂ are determined. As an example, it is determined that the correlation coefficient R is 0.82, the constant parameter a ₀ is 10.458, the constant parameter a ₁ is 21.184, and the constant parameter a ₂ is −1.395. In this case, in the first embodiment, the correlation coefficient R is 0.76, whereas in this embodiment, the correlation coefficient R is 0.82 and the correlation is higher. I understand. If the absolute value of the correlation coefficient R is less than 0.4, a scatter diagram is created by changing the values of the constant parameters a ₀ , a ₁ , and a _{2 in} the above equation (8), and the same processing is repeated. .

  The result derived in advance based on the above equation (8) may be stored in advance as a lookup table as shown in FIG. Also, the look-up table is an example and may be stored by other methods.

FIG. 22 is a diagram illustrating an example of a lookup table according to the second embodiment.
As shown in FIG. 22, the lookup table according to the present embodiment is an example of the amount of stroke of the living body 8 in association with the value BS indicated by the blood flow information of the living body 8 and the LFCT of the living body 8. A certain cardiac output CO is stored in advance. This lookup table is stored in the ROM 20B, which is an example of a storage unit.

  In this case, the predetermined second relationship among the blood flow information of the living body 8, the LFCT of the living body 8, and the cardiac output of the living body 8 is a relationship represented by a look-up table. That is, in this case, the cardiac output CO can be obtained by referring to the lookup table shown in FIG. 22 based on the values BS and LFCT indicated by the blood flow information.

  Next, the operation of the biological information measuring device 10B according to the second embodiment will be described with reference to FIG. FIG. 23 is a flowchart illustrating an example of a process flow of the biological information measurement program according to the second embodiment.

  First, when the biological information measuring device 10B is turned on by the operation of the subject or the person in charge of measurement, the biological information measuring program is started and the following steps are executed.

  In step 110 of FIG. 23, the acquisition unit 34 acquires an IR light signal and a red light signal from the light receiving element 3.

  In step 112, the acquisition unit 34 calculates and acquires blood flow information from the IR light signal acquired in step 110, and calculates and acquires LFCT from the acquired IR light signal and red light signal. As described above, the blood flow information is calculated based on the spectrum distribution for each frequency ω obtained by performing FFT on the IR optical signal. Further, as described above, LFCT is calculated based on the oxygen saturation obtained from the IR light signal and the red light signal.

  In step 114, the specifying unit 36 calculates the blood calculated in step 112 based on the predetermined second relationship among the blood flow information of the living body 8, the LFCT of the living body 8, and the stroke volume of the living body 8. The stroke volume of the living body 8 is specified from the flow information and the LFCT. For example, using the above equation (8), the cardiac output CO, which is an example of the cardiac output, is specified from the values BS and LFCT indicated by the blood flow information.

  As described above, according to the present embodiment, by using the second predetermined relationship between the blood flow information of the living body, the oxygen circulation time of the living body, and the amount of stroke of the living body, non-invasive and more accurate. The stroke volume is measured.

  Heretofore, the biological information measuring device has been exemplified and described as an embodiment. The embodiment may be in the form of a program for causing a computer to execute the function of each unit included in the biological information measuring apparatus. The embodiment may be in the form of a computer-readable storage medium storing this program.

  In addition, the configuration of the biological information measuring device described in the above embodiment is an example, and may be changed according to the situation without departing from the gist.

  Further, the processing flow of the program described in the above embodiment is an example, and unnecessary steps may be deleted, new steps may be added, or the processing order may be changed within a range not departing from the gist. Good.

  Moreover, although the said embodiment demonstrated the case where the process which concerns on embodiment was implement | achieved by a software structure using a computer by running a program, it is not restricted to this. The embodiment may be realized by, for example, a hardware configuration or a combination of a hardware configuration and a software configuration.

DESCRIPTION OF SYMBOLS 1 Light emitting element 3 Light receiving element 4 Artery 5 Vein 6 Capillary blood vessel 7 Blood cell 8 Living body 10A, 10B Living body information measuring device 12 Light emission control part 14 Drive circuit 16 Amplification circuit 18 A / D conversion circuit 20 Control part 20A CPU
20B ROM
20C RAM
22 Display unit 30, 34 Acquisition unit 32, 36 Identification unit
40 Coherent light 42 Scattered light 44 Arrow

Claims (9)

An acquisition unit for acquiring a blood flow signal indicating at least one of a blood volume and a blood flow velocity in a peripheral region of the living body;
Based on a predetermined relationship between the blood flow signal of the living body and the amount of stroke of the living body, a specifying unit that specifies the amount of stroke of the living body from the blood flow signal acquired by the acquiring unit;
A biological information measuring device comprising: The volume of the living body is the cardiac output,
The predetermined relationship is as follows: when the cardiac output of the living body is CO, the constant parameters are a ₀ and a ₁ , and the value indicated by the blood flow signal of the living body is BS,
CO = a ₀ + a ₁ × BS
The biological information measuring device according to claim 1, wherein the relationship is represented by: Further comprising a storage unit that stores in advance the values indicated by the volume of the living body and the blood flow signal of the living body,
The biological information measuring apparatus according to claim 1, wherein the predetermined relationship is the relationship stored in association with the predetermined relationship.   The biological information measuring device according to claim 3, wherein the stroke volume of the living body is an amount indicated by any one of a cardiac output, a stroke volume, and a cardiac coefficient. The acquisition unit further acquires an oxygen circulation time representing a time until oxygen taken into the living body reaches the peripheral site,
The identification unit is configured to obtain a blood flow signal acquired by the acquisition unit based on a predetermined second relationship of the blood flow signal of the living body, the oxygen circulation time of the living body, and the stroke volume of the living body, and The living body information measuring device according to claim 1 which specifies the amount of stroke of the living body from oxygen circulation time. The volume of the living body is the cardiac output,
The second predetermined relationship is that the cardiac output of the living body is CO, the oxygen circulation time of the living body is LFCT, the constant parameters are a ₀ , a ₁ , a ₂ , and the values indicated by the blood flow signals of the living body. In case of BS,
CO = a ₀ + a ₁ × 1 / LFCT + a ₂ × BS
The biological information measuring device according to claim 5, wherein the relationship is expressed by: Further comprising a storage unit that stores in advance the volume of the living body, the value indicated by the blood flow signal of the living body, and the oxygen circulation time of the living body in advance,
The biological information measuring apparatus according to claim 5, wherein the predetermined second relationship is a relationship stored in association with the predetermined second relationship.   The said acquisition part acquires the value shown by the said blood flow signal from the signal obtained according to the reflected light or the transmitted light of the light irradiated to the peripheral site | part of the said biological body. The biological information measuring device according to 1.   The biological information measurement program for functioning a computer as each part with which the biological information measuring device of any one of Claims 1-8 is provided.