JP2019166152A - Biological information measurement device, and biological information measurement program - Google Patents

Abstract

To allow for measurement of an oxygen circulation period of a subject without direct detection of respiration.SOLUTION: A biological information measurement device 10 comprises: a photoelectronic sensor 11 receiving light having a first wavelength and light having a second wavelength and having transmitted a measurement portion of a subject, then outputting a first light reception signal corresponding to the light having the first wavelength and second light reception signal corresponding to the light having the second wavelength; a respiration re-start period identification part 41 identifying a first period at which respiration of the subject is started again, based on variation of amplitude of the first light reception signal; an oxygen saturation degree recovery period identification part 31 identifying a second period at which an oxygen saturation degree on the measurement portion is shifted from decrease to increase, based on the first and second light reception signals; and an oxygen circulation period calculation part 32 calculating a period since the first period to the second period as an oxygen circulation period, based on identification results of the respiration restart period identification part 41 and the oxygen saturation degree recovery period identification part 31.SELECTED DRAWING: Figure 4

Description

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

  Patent Document 1 discloses a signal acquisition unit that acquires an airflow signal that indicates a temporal change in respiratory airflow, an oxygen saturation signal that indicates a temporal change in oxygen saturation, a first time in the airflow signal, and the first A circulation time measuring device having a circulation time calculation unit for measuring 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 one time Is disclosed.

Table 2015-190413

  In recent years, development of measurement methods for measuring biological information using oxygen circulation time indicating the time required for oxygen taken into the body to be transported to a predetermined site has been promoted.

  Conventional oxygen circulation time measurement uses a period during which the subject is in an apneic state during sleep, and the detection means such as an airflow sensor attached to the subject's nostril, for example, the breathing state of the subject It was done by detecting with.

  In this case, since a detection means such as an airflow sensor is attached to the measurement subject's nostril and the measurement subject's breathing state is directly detected, the detection means for detecting the respiratory condition is not attached to the nose mouth and In comparison, the burden on the person to be measured increases. Similarly, when measuring oxygen circulation time not only during sleep but also during awakening, if a detection means such as an airflow sensor is attached to the subject's nostril and the respiratory state is detected directly, Compared with the case where no detection means for detecting is attached, the burden on the measurement subject increases.

  An object of the present invention is to provide a biological information measuring device and a biological information measuring program capable of measuring the oxygen circulation time of a measurement subject without attaching a sensor to the nostril and directly detecting respiration.

  In order to achieve the above object, the biological information measuring apparatus according to the first aspect of the present invention receives the first wavelength light and the second wavelength light transmitted through the measurement site of the measurement subject, and An output unit that outputs a first received light signal corresponding to light of a second wavelength and a second received light signal corresponding to light of the second wavelength; and based on fluctuations in amplitude of the first received light signal. Based on the first specifying unit that specifies the first time when the breathing of the measurer is resumed, and the first light receiving signal and the second light receiving signal, the oxygen saturation at the measurement site increases from a decrease to an increase. A time period from the first time to the second time is determined based on the second specific part for specifying the second time to turn, and the identification results of the first specific part and the second specific part. A calculation unit that calculates the circulation time.

  According to a second aspect of the present invention, the first received light signal is a received light signal having a larger amplitude corresponding to the pulsation of the measurement subject than the second received light signal.

  According to a third aspect of the present invention, the light of the first wavelength is light in a non-red region, the light of the second wavelength is light of a red region, and the first received light signal is This is a light reception signal corresponding to light in a non-red region.

  According to a fourth aspect of the present invention, the first wavelength is a wavelength of 750 nm or more and 1000 nm or less, and the second wavelength is a wavelength of 620 nm or more and less than 750 nm.

  In the invention according to claim 5, the light of the first wavelength is light in a green region.

  The invention according to claim 6 is light in which the light of the first wavelength and the light of the second wavelength are emitted toward one surface side of the measurement site and received on the one surface side. .

  According to a seventh aspect of the present invention, the first specifying unit has a first inflection point of the first received light signal or a fluctuation range of a second inflection point that appears next to the first inflection point. Is determined as the first time period when the first fluctuation range changes to the second fluctuation range larger than the first fluctuation range.

  The invention according to claim 8 interpolates between the first inflection points adjacent to each other in the first light reception signal and between the second inflection points adjacent to each other in the first light reception signal. An interpolation unit that interpolates, and the first specifying unit includes a first envelope connecting the first inflection points interpolated by the interpolation unit or the second variable interpolated by the interpolation unit. The first time is specified based on the second envelope connecting the music points.

  The invention according to claim 9 is characterized in that the calculation unit is based on a relationship between oxygen circulation time representing time until oxygen taken into the body of the subject reaches the measurement site and information on cardiac output. A third specifying unit that specifies information related to the cardiac output of the measurement subject from the time calculated in step (b).

  A biological information measuring program according to a tenth aspect of the present invention is a biological information measuring program for causing a computer to function as each part of the biological information measuring device according to any one of the first to ninth aspects.

  According to the first and tenth aspects of the present invention, there is an effect that the oxygen circulation time of the measurement subject can be measured without directly detecting respiration.

  According to the second aspect of the present invention, the amplitude corresponding to the pulsation of the person to be measured of the first light reception signal is smaller than the amplitude corresponding to the pulsation of the person to be measured of the second light reception signal, The oxygen circulation time can be accurately calculated.

  According to the third aspect of the present invention, the oxygen circulation time can be accurately compared with the case where the light of the first wavelength is light outside the non-red region and the light of the second wavelength is light outside the red region. Can be calculated.

  According to the invention of claim 4, the first wavelength is a wavelength less than 750 nm, the first wavelength is a wavelength greater than 1000 nm, and the second wavelength is a wavelength less than 620 nm, or Compared to the case where the second wavelength is 750 nm or more, the oxygen circulation time can be calculated with high accuracy.

  According to the fifth aspect of the present invention, there is an effect that it is possible to extract a respiration waveform with higher accuracy than in the case where the light of the first wavelength is IR light.

  According to the sixth aspect of the present invention, breathing is performed with higher accuracy than when light of the first wavelength that is emitted toward one surface side of the measurement site and received on the other surface side is used. The effect is that the waveform can be extracted.

  According to the seventh aspect of the present invention, the first time at which respiration is resumed can be identified from the fluctuation range of the first inflection point or the second inflection point of the first light receiving signal. It has the effect.

  According to the eighth aspect of the present invention, it is compared with a case where interpolation is not performed between adjacent first inflection points of the first light reception signal and between adjacent second inflection points of the first light reception signal. Thus, the first time when the breathing is resumed can be specified with high accuracy.

  According to the seventh aspect of the present invention, there is an effect that information relating to the cardiac output of the measurement subject can be specified without directly detecting respiration.

It is a schematic diagram which shows the example of a measurement of the oxygen saturation in blood. It is a graph which shows the example of a change of the light absorption amount of the light absorbed by the biological body. It is a figure which shows an example of the light absorption amount with respect to each wavelength of an oxygenated hemoglobin and a reduced hemoglobin. It is a figure which shows the structural example of a biometric information measuring apparatus. It is a figure which shows the example of arrangement | positioning of a light emitting element and a light receiving element. It is a figure which shows the other example of arrangement | positioning of a light emitting element and a light receiving element. It is a figure which shows the structural example of a respiration waveform extraction part. It is a figure which shows an example of a respiration waveform. It is a figure which shows an example of the 1st envelope which connected 1st inflection points, and the 2nd envelope which connected 2nd inflection points. It is a figure which shows an example of the 1st envelope after a interpolation process, and a 2nd envelope. It is a figure which shows the example of a change of the oxygen saturation in the blood accompanying the stop and restart of respiration. It is a figure which shows an example of the respiration waveform at the time of stopping respiration. It is a figure which shows an example of the respiration waveform at the time of restarting respiration. It is a figure which shows the principal part structural example of the electric system in a biological information measuring device. It is a flowchart which shows an example of the flow of a biometric information measurement process. It is a flowchart which shows an example of the flow of a respiration waveform extraction process.

  Hereinafter, the present embodiment will be described with reference to the drawings. In addition, the same code | symbol is provided to the component and process with the same function throughout all the drawings, and the overlapping description is abbreviate | omitted.

  The biological information measuring device 10 is a device that measures biological information related to the circulatory system among information related to the biological body 8 (biological information). The circulatory system is a general term for a group of organs for transporting a body fluid such as blood while circulating in the body.

  There are a plurality of indices in the biological information related to the circulatory system. As one of indices indicating the state of the heart that sends blood to the blood vessels, for example, the cardiac output (CO: Cardiac Output).

  Cardiac output is used for examination of various heart diseases or confirmation of medication effects.

  As a method for measuring cardiac output, for example, a pulmonary artery catheter is inserted into a subject to be measured for cardiac output, and a physiological solution cooled to near 0 ° C. is injected into a blood vessel, A method is used in which blood is heated with a thermal filament placed in the tube, the temperature of the blood is changed, and the relationship between the temperature change of the blood and the time is read with a thermistor at the tip of the catheter.

  However, the measurement method of cardiac output using a catheter requires a surgical procedure because it is necessary to insert the catheter into the blood vessel of the measurement subject, and is less invasive in the measurement subject than other measurement methods. Get higher.

  Therefore, there is a method for measuring cardiac output using oxygen saturation obtained from the pulse wave of the subject so that the burden on the subject is less than that of measuring the cardiac output using a catheter. It has been studied. The pulse wave is an index indicating a change in the pulsation of blood vessels accompanying the delivery of blood by the heart.

  First, with reference to FIG. 1, the measurement method of the oxygen saturation in blood among biological information is demonstrated. The oxygen saturation in the blood is an example of an index indicating the oxygen concentration in the blood, an index indicating how much hemoglobin in the blood is bound to oxygen, and the oxygen saturation in the blood is It shows that symptoms such as oxygen deficiency are more likely to occur as it decreases.

  As shown in FIG. 1, the oxygen saturation level in the blood is stretched in the body of the subject that is irradiated with light from the light emitting element 1 toward the body (living body 8) of the subject and received by the light receiving element 3. It is measured using the intensity of light reflected or transmitted by the circulating artery 4, vein 5, capillary 6 or the like, that is, the amount of reflected or transmitted light received.

  FIG. 2 is a conceptual diagram showing the amount of change in the amount of light absorbed by the living body 8, for example. As shown in FIG. 2, the light absorption amount in the living body 8 tends to vary with time.

  Further, looking at the breakdown of the fluctuation of the light absorption amount 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 regarded as. 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. 2, the range indicated by the arrow 94 indicates the amount of fluctuation in the amount of absorption corresponding to the change in the thickness of the artery 4.

In FIG. 2, assuming that 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 can be _expressed by equation (1). Is done.

(Equation 1)
ΔA = ln (I _b / I _a ) (1)

  On the other hand, FIG. 3 is a diagram showing an example of the light absorption amount for each wavelength of hemoglobin (oxygenated hemoglobin) combined with oxygen flowing through the artery 4 and hemoglobin not combined with oxygen (reduced hemoglobin). In FIG. 3, a graph 96 represents the light absorption amount of oxyhemoglobin, and a graph 97 represents the light absorption amount of reduced hemoglobin.

  As shown in FIG. 3, oxyhemoglobin is easier to absorb light in the infrared (IR) region 99 having a wavelength around 850 nm than reduced hemoglobin. It is known that light of the red region 98 having a wavelength around about 660 nm is easily absorbed. The infrared region 99 is an example of a non-red region.

  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 onto 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 (2), k is a proportionality constant.

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

  That is, when the oxygen saturation level in the blood is calculated, the living body 8 is irradiated with a plurality of light emitting elements 1 that irradiate light of different wavelengths. Specifically, the light emitting element 1 that emits IR light and the light emitting element 1 that emits red light are used for the living body 8. In this case, the light emission periods of the light emitting element 1 that irradiates IR light and the light emitting element 1 that emits red light may overlap, but preferably the light emission is performed 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)

  Hereinafter, 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 referred to as “light-emitting element 1A”. The light-emitting element 1 that irradiates is referred to as “light-emitting element 1B”.

  According to such a method, since the oxygen saturation level in the blood is measured by bringing the light-emitting element 1 and the light-receiving element 3 close to the body surface of the person to be measured, the catheter is inserted into the blood vessel to increase the oxygen saturation level in the blood. The burden on the person to be measured is less than the measurement.

  And the biometric information measuring apparatus 10 calculates cardiac output by the method mentioned later using the measured patient's oxygen saturation.

  FIG. 4 is a diagram illustrating a configuration example of the biological information measuring apparatus 10. As shown in FIG. 4, the biological information measuring apparatus 10 includes a photoelectric sensor 11, a pulse wave processing unit 12, a respiratory waveform extraction unit 13, an oxygen saturation measuring unit 14, an oxygen circulation time measuring unit 17, and a cardiac output measuring unit. 18 is included.

  The biological information measuring apparatus 10 detects that the measurement subject's respiratory state has changed without directly detecting respiration. Here, “the change in the respiratory state” does not mean a periodic change in inspiration or expiration in the normal respiratory state, but the breathing is stopped when the respiratory state is stopped from the normal respiratory state or when the respiratory state is stopped. This means a change in the respiratory state where the oxygen intake per unit time clearly changes, such as when resuming. In other words, it means a change in the respiratory state that exceeds the variation in oxygen intake for each inspiration in a normal respiratory state.

  The photoelectric sensor 11 is a light-emitting element 1A that irradiates IR light having a wavelength of about 850 nm as a center wavelength and a wavelength of 750 nm or more and 1000 nm or less, a wavelength of about 660 nm or more and a wavelength of 620 nm or more and less than 750 nm. A light emitting element 1B that emits red light and a light receiving element 3 that receives IR light and red light are provided.

  Here, the photoelectric sensor 11 is an example of an output unit. The IR light is an example of light having a first wavelength. The IR light irradiated from the light emitting element 1A is received by the light receiving element 3, and the signal converted into an electric signal and output is the first light receiving signal. It is an example. The red light is an example of light of the second wavelength, the red light emitted from the light emitting element 1B is received by the light receiving element 3, and the signal converted into an electric signal and output is an example of the second light receiving signal. It is.

  FIG. 5 shows an arrangement example of the light emitting element 1 </ b> A, the light emitting element 1 </ b> B, and the light receiving element 3 in the photoelectric sensor 11. As shown in FIG. 5, the light emitting element 1 </ b> A, the light emitting element 1 </ b> B, 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 IR light and red light reflected by blood or the like in the capillary 6 of the living body 8. In other words, the light from the light emitting element 1A and the light emitting element 1B is emitted toward one surface side of the measurement site in the living body 8, and is received by the light receiving element 3 on the same one surface side.

  However, the arrangement of the light emitting element 1A, the light emitting element 1B, and the light receiving element 3 is not limited to the arrangement example of FIG. For example, as shown in FIG. 6, the light emitting element 1 </ b> A, the light emitting element 1 </ b> B, 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 IR light and red light transmitted through the living body 8. In other words, the light from the light emitting element 1A and the light emitting element 1B is emitted toward one surface side of the measurement site in the living body 8, and after passing through the living body 8, is received by the light receiving element 3 on the other surface side. The

  Here, as an example, the light-emitting element 1A and the light-emitting element 1B are described as surface-emitting laser elements such as VCSEL (Vertical Cavity Surface Emitting Laser), but are not limited thereto, and may be edge-emitting laser elements. Further, the light emitting element 1A and the light emitting element 1B may be LEDs (Light Emitting Diodes). The light emitting element 1A and the light emitting element 1B may be a combination of a laser element and an LED.

  The photoelectric sensor 11 is provided with a clip (not shown) for attaching the photoelectric sensor 11 to the measurement site of the measurement subject's body so that ambient light such as illumination light in the measurement environment does not enter the photoelectric sensor unit. In addition, the photoelectric sensor 11 is attached so as to come into contact with the body surface of the person to be measured by a clip (not shown). In order to receive the IR light and the red light reflected or transmitted by the measurement subject's living body 8 with the light receiving element 3 as accurately as possible, the photoelectric sensor 11 is preferably disposed so as to be in contact with the body surface of the measurement subject. However, within the range in which the IR light and the red light reflected by the measurement subject's living body 8 or the IR light and the red light transmitted through the measurement subject's living body 8 are received by the light receiving element 3, the photoelectric sensor 11 is placed on the body surface. You may attach in the position away from.

  The photoelectric sensor 11 converts the received light amounts of IR light and red light received by the light receiving element 3 into, for example, voltage values and outputs them to the pulse wave processing unit 12.

  Since a predetermined amount of light is emitted from the light emitting element 1A and the light emitting element 1B, the amount of absorption of IR light and red light in the living body 8 is determined from the amount of received light of IR light and red light received by the photoelectric sensor 11. can get.

  Therefore, the pulse wave processing unit 12 uses the received light amounts of the IR light and the red light received from the photoelectric sensor 11, and the pulse wave signal representing the pulse wave of the measurement subject obtained from the IR light and the red light. A pulse wave signal representing the pulse wave of the measurement subject obtained from the above is generated. The pulse wave processing unit 12 amplifies the voltage value so that the voltage values corresponding to the received amounts of received IR light and red light are included in a predetermined range suitable for generating a pulse wave signal.

  The pulse wave processing unit 12 outputs the generated pulse wave signals to the respiratory waveform extraction unit 13 and the oxygen saturation measurement unit 14.

  The respiration waveform extraction unit 13 extracts a respiration waveform representing the respiration state of the measurement subject from the pulse wave signal output from the pulse wave processing unit 12.

  As shown in FIG. 7, the respiratory waveform extraction unit 13 includes an acquisition unit 50, an inflection point detection unit 54, and an interpolation unit 56.

  The acquisition unit 50 acquires the pulse wave signal output from the pulse wave processing unit 12. FIG. 8 shows a pulse wave signal S1 as an example of the pulse wave signal.

  The inflection point detection unit 54 detects the first inflection point and the second inflection point that appears next to the first inflection point from the pulse wave signal output from the acquisition unit 50. Here, in the present embodiment, the first inflection point refers to a point where the value of the pulse wave signal turns from rising to falling, that is, a point on the peak side. The second inflection point refers to a point at which the value of the pulse wave signal changes from falling to rising, that is, a point on the bottom side. Note that the first inflection point is a point on the bottom side where the value of the pulse wave signal turns from descending to rising, and the second inflection point is the point on the peak side where the value of the pulse wave signal turns from rising to descending. It is good. In FIG. 9, as an example of the first envelope connecting the detected first inflection points H1, the first envelope S3-1 is used as the second envelope connecting the second inflection points H2. The second envelope S3-2 is shown as an example of the envelope. Note that a frequency lower than the frequency corresponding to the pulsation may be removed before detecting the first inflection point and the second inflection point.

  If there are only the first inflection point and the second inflection point, there is a possibility that the number of data is too small to extract a respiration waveform with high accuracy.

  Therefore, the interpolation unit 56 interpolates between the adjacent first inflection points and interpolates between the adjacent second inflection points. Specifically, for example, interpolation is performed using a known interpolation method such as spline interpolation. The interpolation cycle is 50 Hz (0.02 second interval) as an example, but is not limited thereto. FIG. 10 shows a first envelope S4-1 and a second envelope S4-2 as an example of the first envelope and the second envelope after the interpolation processing by the interpolation unit 56.

  The first envelope or the second envelope after the interpolation process is output as a respiratory waveform to the respiratory stop timing specifying unit 40 and the respiratory restart timing specifying unit 41.

  In the respiratory waveform extraction method according to the present embodiment, the respiratory waveform is extracted using the pulse wave signal obtained from the red light when the respiratory waveform is extracted using the pulse wave signal obtained from the IR light. The accuracy of the respiration waveform is likely to be higher than when extracting. Therefore, the respiration waveform extraction unit 13 in the present embodiment extracts a respiration waveform using a pulse wave signal obtained from IR light. As shown in FIG. 3, since IR light is more easily absorbed by oxyhemoglobin than red light, the amplitude of the pulse wave signal corresponding to the change in blood volume in the artery 4 is obtained from the red light. This is because a tendency to become larger than the amplitude of the signal is seen. That is, the IR light reception signal is a light reception signal having a larger amplitude corresponding to the measurement subject's pulsation than the red light reception signal. Therefore, the respiratory waveform extracted from the pulse wave signal obtained from the IR light has a clearer waveform variation than the respiratory waveform extracted from the pulse wave signal obtained from the red light, and a highly accurate respiratory waveform is obtained. . The method for extracting a respiratory waveform in the present embodiment is a method for extracting a respiratory waveform from slight amplitude fluctuations of a pulse wave signal. Therefore, as described above, a pulse wave signal obtained from IR light is used, or red light is used. Depending on whether the pulse wave signal obtained from is used, the extracted respiratory waveform is affected. It is also possible to amplify the received light signal of red light so as to have the same amplitude as that of the received light signal of IR light, and use the amplified received light signal of red light for extraction of a respiratory waveform. However, in this method, noise superimposed on the red light reception signal is also amplified, and it is difficult to obtain a light reception signal similar to the IR light reception signal.

The oxygen saturation measuring unit 14 measures the oxygen saturation of the measurement subject from the pulse wave signal output from the pulse wave processing unit 12. Specifically, the oxygen saturation measuring unit 14 uses the pulse wave signal to change the amount of change ΔA _{IR in} the IR light amount due to the change in the blood volume in the artery 4 and the amount of change ΔA _{Red in the} amount of red light absorption. Are calculated according to equation (1). Then, the oxygen saturation measurement unit 14 uses the calculated change amount ΔA _IR and change amount ΔA _Red to measure the oxygen saturation of the measurement subject, for example, from the equation (2), and the measured oxygen saturation is used as the oxygen circulation. Output to the time measuring unit 17.

Hereinafter, as an example, an example in which the oxygen saturation measuring unit 14 measures the oxygen saturation of the measurement subject will be described. The oxygen saturation measurement unit 14 is a value indicating a time change of the oxygen saturation of the measurement subject. Any value may be measured as long as it is present. For example, the oxygen saturation measuring unit 14 may measure a value having a correlation with the temporal change of the oxygen saturation, such as the reciprocal of the oxygen saturation, or the ratio between the change amount ΔA _Red and the change amount ΔA _IR .

  The graph of FIG. 11 shows an example of changes in blood oxygen saturation at a specific part of the subject, with the horizontal axis representing time and the vertical axis representing the reciprocal of oxygen saturation.

When the subject stops breathing at time t ₀ , the blood oxygen saturation in the subject begins to decrease. Even if the subject resumes breathing after the elapse of a predetermined time (time t ₁ ) as a period during which the subject stops breathing, the oxygen taken into the blood by resuming breathing is specified from the lungs Since it takes time to reach this region, the blood oxygen saturation level in the measurement subject decreases even after time t ₁ . Among them, since oxygen taken into the blood by resuming breathing reaches a specific site from the lungs, the oxygen saturation level in the blood of the measurement subject starts to increase. A portion where the oxygen saturation level in the blood changes from decreasing to increasing is referred to as an “oxygen saturation inflection point”, and if the time at which the oxygen saturation inflection point appears is time t ₂ , the oxygen circulation time is time t _1. And the time t ₂ .

  That is, the oxygen circulation time represents the time required for oxygen to be transported from the lung to a specific site, and is also referred to as “oxygen transport time”.

  Since the measurement accuracy of the oxygen circulation time measured from the oxygen saturation tends to vary depending on the variation of the breathing stop period, a specified time that defines the breathing stop period is provided.

  The specified time is obtained in advance by an experiment using an actual apparatus of the biological information measuring apparatus 10 or a computer simulation based on the design specifications of the biological information measuring apparatus 10 so that the measurement accuracy of the oxygen circulation time in the biological information measuring apparatus 10 is increased. It is a value.

  As shown in FIG. 4, the oxygen circulation time measurement unit 17 includes a detection unit 30, an oxygen saturation recovery time specifying unit 31, and an oxygen circulation time calculation unit 32. The detection unit 30 includes a breathing stop timing specifying unit 40 and a breathing restart timing specifying unit 41.

  The respiration stop time specifying unit 40 specifies the respiration stop time when the respiration stops based on the fluctuation of the amplitude of the respiration waveform output from the respiration waveform extraction unit 13. Specifically, breathing is performed when the fluctuation range of the first inflection point or the second inflection point of the respiration waveform changes from the first fluctuation range to the second fluctuation range smaller than the first fluctuation range. Identified as a stop time. In this case, the first fluctuation range is the fluctuation range of the first inflection point or the second inflection point in the breathing state, and the second fluctuation range is stopping breathing. It is a fluctuation range of the first inflection point or the second inflection point in the state.

For example, the case where the breathing stop time is specified for the breathing waveform S7-1 obtained from the pulse wave signal as shown in FIG. 12 will be described. FIG. 12 shows a respiration waveform S7-2 obtained from the temperature of nasal breath for reference. As shown in FIG. 12, the first inflection point Pt ₁ , the second inflection point Bt ₂ , and the first inflection point Pt ₃ in time order (t ₁ , t ₂ , t ₃ ,...). , The second inflection point Bt ₄ ..., The amplitude _An is calculated by the following equation.

(Equation 6)
A _n = Pt _n −Bt _{n + 1} (6)

In the above formula (6), n is an odd number. Then, by comparing the amplitude A _n-1 immediately preceding the amplitude A _n, when the amplitude A _n was smaller than a predetermined threshold value than the amplitude A _n-1, i.e., from a state in which breathing breathing if the amplitude is greatly reduced as in the case of change in a stopped state, to identify the position of the first inflection point Pt _n (time) as respiratory arrest time. In the case of the example in FIG. 12, the amplitude A ₇ is smaller than the predetermined threshold value compared with the amplitude A ₅ , so the time point t ₇ is specified as the breathing stop time.

Incidentally, if the period during which breathing long, the amplitude _A instead of _n one comparison of the previous and the amplitude _{A n-1} of the plurality previous than the amplitude _{A n} amplitude _{A n-1, A n-2,} You may compare with the average value of.

  The breathing resumption timing specifying unit 41 specifies the breathing resumption timing when the breathing of the measurement subject is resumed after stopping the breathing based on the fluctuation of the amplitude of the breathing waveform output from the breathing waveform extraction unit 13. Specifically, breathing is performed when the fluctuation range of the first inflection point or the second inflection point of the respiratory waveform changes from the first fluctuation range to the second fluctuation range larger than the first fluctuation range. Identified as a resumption time. In this case, the first fluctuation range is a fluctuation range of the first inflection point or the second inflection point in a state where breathing is stopped, and the second fluctuation range is breathing. It is a fluctuation range of the first inflection point or the second inflection point in the state.

  In addition, the respiration restart time specific | specification part 41 is an example of a 1st specific part, and the respiration restart time is an example of a 1st time.

For example, the case where the respiration restart time is specified for the respiration waveform S8-1 shown in FIG. 13 will be described. For reference, FIG. 13 shows a respiration waveform S8-2 obtained from the temperature of nasal breath. As shown in FIG. 13, the first inflection point Pt ₁ , the second inflection point Bt ₂ , the first inflection point Pt ₃ , In the case of the inflection points Bt ₄ ..., The amplitude _An is calculated by the above equation (6).

When the amplitude A _n compares a and preceding amplitude A _n-1, the amplitude A _n is larger predetermined threshold or higher than the amplitude A _n-1, i.e., the state not breathing If breathing has amplitude greatly increases as in the case where change state to resume from, identifies the position of the first inflection point Pt _n (time) as the breathing resumes timing. Note that when a long breath hold, the amplitude _{A n} and not by comparison with the previous amplitude _{A n-1,} the amplitude _A plurality of amplitudes prior _{n A n-1, A n} -2, ·· You may compare with the average value.

  Based on the oxygen saturation measured by the oxygen saturation measuring unit 14, the oxygen saturation recovery time specifying unit 31 specifies the oxygen saturation recovery time when the oxygen saturation is about to recover. That is, as described above, the oxygen saturation inflection point at which the oxygen saturation turns from decreasing to increasing is specified as the oxygen saturation recovery time. The oxygen saturation recovery time specifying unit 31 is an example of a second specifying unit, and the oxygen saturation recovery time specifying unit 31 is an example of a second time.

  The oxygen circulation time calculation unit 32 is taken into the body of the subject based on the breathing restart time specified by the breathing restart time specifying unit 41 and the oxygen saturation recovery time specified by the oxygen saturation recovery time specifying unit 31. The oxygen circulation time representing the time until oxygen reaches the measurement site of the subject is calculated. The oxygen circulation time calculation unit 32 is an example of a calculation unit.

Specifically, the respiratory resumed timing specified by breathing resumption timing specifying unit 41 t _1, the oxygen saturation recovery time specified by the oxygen saturation recovery timing specifying unit 31 and t _2, from t ₁ to t ₂ Is measured as the oxygen circulation time.

  Then, the oxygen circulation time measuring unit 17 outputs the measured oxygen circulation time to the cardiac output measuring unit 18.

  In addition, although the measurement site | part of oxygen circulation time is determined by the attachment position of the photoelectric sensor 11 in a to-be-measured person, in this Embodiment, the photoelectric sensor 11 is mounted | worn with a to-be-measured person's fingertip, oxygen is supplied from a lung to a fingertip. Measure oxygen circulation time when transported. This is because the oxygen circulation time becomes longer due to the longer distance from the lungs compared to other parts, so the oxygen circulation time is more accurate than when the photoelectric sensor 11 is attached to other parts. It is because it is obtained.

  Therefore, the oxygen circulation time from the lung to the fingertip is sometimes referred to as LFCT (Lung to Finger Circulation Time). Also in the present embodiment, an example in which the photoelectric sensor 11 is attached to the fingertip of the measurement subject and the LFCT is measured by the oxygen circulation time measurement unit 17 will be described, but the attachment site of the photoelectric sensor 11 is not limited to the fingertip. Any part may be used as long as the measurement error of the obtained oxygen circulation time is included in a predetermined range. As such a part, for example, a part (end part) on the end side of the subject's neck, shoulder, or hip joint may be mentioned. Specifically, the photoelectric sensor 11 may be attached to any part of the measurement subject such as the earlobe, wrist, ankle, elbow or knee. The “fingertip” refers to the fingertip of the measurement subject's hand, but the photoelectric sensor 11 may be attached to the fingertip of the foot.

  The cardiac output measuring unit 18 specifies the cardiac output of the person to be measured from the oxygen circulation time calculated by the oxygen circulation time calculating unit 32 based on the relationship between the oxygen circulation time and information related to the cardiac output. . The cardiac output measuring unit 18 is an example of a third specifying unit.

  Specifically, the cardiac output CO is calculated by an arithmetic expression obtained in advance that represents the relationship between LFCT and cardiac output, for example.

  The cardiac output measuring unit 18 may measure information related to cardiac output in addition to cardiac output. “Information related to cardiac output” is information that is correlated with cardiac output, and includes, for example, a cardiac coefficient and stroke volume.

  The “cardiac coefficient” is a value obtained by dividing the cardiac output of the measured person by the body surface area of the measured person in order to correct the difference in cardiac output due to the difference in the physique of the measured person. The “stroke volume” is a value indicating the volume of blood that the heart pumps into the artery 4 by one contraction, and the cardiac output is divided by the one-minute heart rate of the person to be measured. Is required.

  The biological information measuring device 10 described above is configured using, for example, a computer. FIG. 14 is a diagram illustrating a configuration example of a main part of the electrical system in the biological information measuring apparatus 10 configured using the computer 20.

  The computer 20 includes a central processing unit (CPU) 21, a read only memory (ROM) 22, a random access memory (RAM) 23, a nonvolatile memory 24, and an input / output interface (I / O) 25. The CPU 21, ROM 22, RAM 23, nonvolatile memory 24, and I / O 25 are connected via a bus 26. The CPU 21 functions as a pulse wave processing unit 12, a respiratory waveform extraction unit 13, an oxygen saturation measurement unit 14, an oxygen circulation time measurement unit 17, and a cardiac output measurement unit 18.

  The non-volatile memory 24 is an example of a storage device that maintains stored information even when power supplied to the non-volatile memory 24 is cut off. For example, a semiconductor memory is used, but it may be a hard disk.

  For example, the photoelectric sensor 11, the input unit 27, the display unit 28, and the communication unit 29 are connected to the I / O 25.

  The photoelectric sensor 11 is connected to the I / O 25 by wire or wireless. The biological information measuring device 10 and the photoelectric sensor 11 may be separated from each other so that the biological information measuring device 10 and the photoelectric sensor 11 are integrated. It is good also as a structure accommodated in the same housing.

  The input unit 27 is a unit that receives an instruction from the user of the biological information measuring apparatus 10 and notifies the CPU 21 of the instruction. The input unit 27 includes, for example, a button, a touch panel, a keyboard, a mouse, and the like. Here, the user of the biological information measuring apparatus 10 includes, for example, an operator such as a medical worker who operates the measured person and the biological information measuring apparatus 10.

  The display unit 28 is a unit that visually displays, for example, information processed by the CPU 21 to the user of the biological information measuring device 10. For the display unit 28, for example, a display device such as a liquid crystal display, an organic EL (Electro Luminescence), and a projector is used.

  Note that the display unit 28 is not necessarily a unit necessary for the biological information measuring apparatus 10, and any type of unit may be used as long as it notifies the user of the biological information measuring apparatus 10 of, for example, an instruction to resume breathing. It may be connected to O25.

  For example, when the information notified from the biological information measuring device 10 is notified to the user of the biological information measuring device 10 by voice, for example, a speaker unit may be connected instead of the display unit 28. Moreover, when notifying the information notified from the biological information measuring device 10 to the user of the biological information measuring device 10 through the bodily sensation, for example, a vibration unit may be connected instead of the display unit 28. Furthermore, the information notified from the biological information measuring device 10 may be notified to the user of the biological information measuring device 10 using a plurality of units such as the display unit 28 and the speaker unit.

  The communication unit 29 includes a communication protocol for connecting the biological information measuring device 10 with a communication line such as the Internet, for example, and performs data communication between another external device connected to the communication line and the biological information measuring device 10. The connection form to the communication line in the communication unit 29 may be wired or wireless. If the biological information measuring device 10 does not need to perform data communication with other external devices connected to the communication line, it is not always necessary to connect the communication unit 29 to the I / O 25.

  The unit connected to the I / O 25 is not limited to the example described above, and other units such as a printing unit may be connected to the I / O 25, for example.

  Next, the operation of the biological information measuring apparatus 10 will be described with reference to FIG.

  FIG. 15 is executed by the CPU 21 when an instruction for measuring the cardiac output is received from the user of the biological information measuring apparatus 10 via the input unit 27 with the photoelectric sensor 11 attached to the fingertip of the measurement subject. It is a flowchart which shows an example of the flow of the biometric information measurement process performed. When the biological information measuring apparatus 10 accepts the measurement instruction of the cardiac output, it continues to extract the respiratory waveform of the measurement subject and at the same time measure the oxygen saturation at least until the measurement of the cardiac output is completed. .

  A biological information measurement program that defines the biological information measurement process is stored in advance in the ROM 22 of the biological information measurement device 10, for example. The CPU 21 of the biological information measuring device 10 reads a biological information measuring program stored in the ROM 22 and executes a biological information measuring process.

  In step S100, a pulse wave signal is generated. That is, using the respective received light amounts of IR light and red light received from the photoelectric sensor 11, a pulse wave signal representing the pulse wave of the measurement subject obtained from the IR light and the measurement subject obtained from the red light. Each of the pulse wave signals representing the pulse wave is generated. The generation of the pulse wave signal is repeatedly executed until at least the oxygen saturation recovery time is detected in step S118 described later.

  In step S102, a respiration waveform extraction process shown in FIG. 16 is executed.

  As shown in FIG. 16, in the respiration waveform extraction process, first, in step S200, a pulse wave signal is acquired.

  In step S202, a first inflection point and a second inflection point are detected from the pulse wave signal acquired in step S200.

  In step S204, the first inflection point and the second inflection point detected in step S202 are interpolated between the adjacent first inflection points, and the adjacent second inflection point is determined. Interpolate between. The first envelope or the second envelope after the interpolation processing is used as a respiratory waveform.

  In step S104 of FIG. 15, the oxygen saturation is measured. That is, the change amount of the IR light absorption amount and the change amount of the red light absorption amount are calculated from the pulse wave signal generated in step S100, and the oxygen saturation is measured using both of the calculated change amounts.

  In step S106, the subject is instructed to stop breathing. Specifically, a message that prompts the user to stop breathing while inhaling and exhaling is displayed on the display unit 28. Further, when a speaker unit is connected to the biological information measuring device 10, the CPU 21 outputs, for example, a sound prompting to stop breathing from the speaker unit.

  In step S108, the respiratory waveform is referred to and it is determined whether or not the subject has stopped breathing. That is, it is determined whether or not the fluctuation width of the first inflection point or the second inflection point of the respiratory waveform has changed from the first fluctuation width to a second fluctuation width that is smaller than the first fluctuation width. .

  If it is determined that the person to be measured has not stopped breathing, that is, breathing has been continued, the process of step S108 is repeatedly executed to monitor the breathing waveform of the person to be measured. On the other hand, if it is determined that the subject has stopped breathing, the process proceeds to step S110.

  In step S110, it is determined whether or not the breathing stop period has reached a specified time. When the breathing stop period has not reached the specified time, the process of step S110 is repeatedly executed to monitor the breathing stop period of the measurement subject. On the other hand, when the breathing stop period reaches the specified time, the process proceeds to step S112.

  In step S112, the subject is instructed to resume breathing. Specifically, a message prompting to resume breathing is displayed on the display unit 28. Further, when the speaker unit is connected to the biological information measuring device 10, the CPU 21 outputs, for example, a sound prompting to resume breathing from the speaker unit.

  In step S114, the respiratory waveform is referred to and it is determined whether or not the subject has resumed breathing. That is, it is determined whether or not the fluctuation width of the first inflection point or the second inflection point of the respiratory waveform has changed from the first fluctuation width to a second fluctuation width that is larger than the first fluctuation width. .

  When it is determined that the person to be measured has not resumed breathing, that is, breathing has been stopped, the process of step S114 is repeatedly executed to monitor the breathing waveform of the person to be measured. On the other hand, if it is determined that the measurement subject has resumed breathing, the process proceeds to step S116.

  In step S112, the measurement subject is instructed to resume breathing at the timing when the breathing stop period reaches the specified time. However, when the resumption of breathing is suddenly instructed, the subject is instructed to resume breathing. There may be a delay between when you receive the breath and when you actually resume breathing. Therefore, in order to inform the person to be measured how much more breathing should be stopped during the breathing stop period, the remaining time until the specified time is reached is sequentially displayed on the display unit 28 to indicate to the person to be measured. The end time of the breathing stop period may be notified in advance.

At step S116, it acquires from the timer (not shown) incorporated in the time point of time t _1, for example, CPU21 of detecting resumption of respiration of the subject, and stores the time t ₁ obtained in RAM23 as breathing resumes timing.

  In step S118, it is determined whether the oxygen saturation recovery time has been identified. That is, it is determined whether or not an oxygen saturation inflection point has been detected, in other words, whether or not the oxygen saturation has returned from a decrease to a recovery.

  If the oxygen saturation continues to decrease and no inflection point is detected, the process of step S118 is repeatedly executed to monitor the change in oxygen saturation. On the other hand, when the oxygen saturation inflection point is detected, the process proceeds to step S120.

In step S120, it acquires the time t ₂ at the time of detecting the oxygen saturation inflection point, and stores the RAM23 the time t ₂ obtained as oxygen saturation recovery time. Then, the difference between time t ₂ and time t ₁ stored in RAM 23 in step S116 is calculated as LFCT.

  In step S122, the cardiac output is measured from the equation (7), for example, using the LFCT acquired in step S120. Further, information related to cardiac output may be calculated using the measured cardiac output.

  Note that the breathing stop period during which LFCT is accurately measured varies depending on, for example, the age, sex, and physical condition of the subject. Therefore, based on the information of the person to be measured set by the user of the biological information measuring apparatus 10 in the biological information measuring apparatus 10 via the input unit 27, the CPU 21 sets a specified time for defining the breathing stop period for each person to be measured. You may adjust it. Further, the user of the biological information measuring device 10 may adjust the specified time.

  The specified time may be set in units of 1 second, for example, and a time selected from a plurality of previously prepared times such as 15 seconds, 20 seconds, and 25 seconds may be set as the specified time. There is no limitation on the set unit of the specified time, and it may be, for example, a millisecond unit or a 5-second unit.

  The set specified time for each person to be measured is stored in, for example, the non-volatile memory 24. Prior to the instruction to measure the cardiac output, information for identifying the person to be measured such as the name or patient number of the person to be measured is the biometric information measurement. When input to the apparatus 10, the CPU 21 uses the specified time associated with the person to be measured for the determination in step S110 of FIG.

  In the present embodiment, the case where the measurement of LFCT is started after waiting for the respiration of the measurement subject to be resumed in step S114 of FIG. 15 has been described. If the period until the subject's breathing is resumed after instructing the resumption of breathing is delayed, the breathing stop period becomes longer than the specified time, which is compared with the case where the breathing stop period is set to the specified time. LFCT measurement accuracy may be reduced.

  Therefore, the CPU 21 may measure the LFCT when the period from when the resumption of respiration is instructed until the respiration of the measurement subject is resumed is within the allowable delay period that is a predetermined period. In other words, when the period from when the respiration is instructed until the measurement subject's respiration is resumed exceeds the allowable delay period, the CPU 21 stops the execution of the processes after step S116 in FIG. The biological information measurement process shown in FIG. 15 may be terminated without measuring the LFCT.

  Thus, according to biological information measuring device 10 concerning this embodiment, based on change of the amplitude of the 1st received light signal corresponding to the light of the 1st wavelength which permeate | transmitted the measurement site | part of the to-be-measured person, to-be-measured Specify when to resume breathing when the person has resumed breathing. Further, based on the first received light signal and the second received light signal corresponding to the light having the second wavelength transmitted through the measurement site of the measurement subject, the oxygen saturation recovery at which the oxygen saturation level at the measurement site starts to decrease and increases is restored. Identify the time. Then, the time from the breath resumption time to the oxygen saturation recovery time is calculated as the oxygen circulation time. Thus, the oxygen circulation time of the measurement subject is measured without directly detecting respiration.

  As mentioned above, although this invention was demonstrated using the said embodiment, this invention is not limited to the range as described in the said embodiment. Various changes or improvements can be added to the above-described embodiment without departing from the gist of the present invention, and forms to which the changes or improvements are added are also included in the technical scope of the present invention.

  For example, in the above embodiment, the received light amounts of the IR light and the red light received by the light receiving element 3 are input to the pulse wave processing unit 12, but the pulse wave processing unit 12 is omitted and the light receiving element The received light amounts of the IR light and the red light received at 3 may be directly input to the respiratory waveform extraction unit 13 and the oxygen saturation measurement unit 14.

  Moreover, in the said embodiment, although IR light was used as an example of the light of a non-red area | region, it replaced with IR light and used the light (green light) of the green area | region which is light with a wavelength of 500 nm or more and less than 560 nm. May be. Furthermore, light of a non-red region other than IR light or green light may be used as long as the biological information to be measured is light having a wavelength that can be measured. Here, since the green light is more easily absorbed by oxyhemoglobin than the IR light, the received light signal has a larger amplitude corresponding to the pulsation of the measurement subject than the received light signal of the IR light. Therefore, when it is desired to obtain a respiratory waveform with higher accuracy, green light may be used as light in the non-red region. However, since green light is easily absorbed by the living body, when using green light, it is better to adopt the configuration shown in FIG. 5 than the configuration shown in FIG. By adopting the configuration shown in FIG. 5, it is difficult to detect a change in oxygen saturation slightly compared to the configuration shown in FIG. 6, but it is easier to extract a respiratory waveform with higher accuracy than in the case of IR light. Become.

  Moreover, although the said embodiment demonstrated as an apparatus which measures oxygen circulation time, you may comprise another biological information measuring device using the one part function in this embodiment. For example, the biological information measurement device that measures the oxygen saturation and respiration information such as a respiration waveform may be configured by deleting the oxygen circulation time measurement unit and the cardiac output measurement unit in the above embodiment. Specifically, the oxygen saturation may be measured by the oxygen saturation measuring unit 14 and the respiratory waveform may be extracted by the respiratory waveform extracting unit 13 and output to the display unit 28 or the like for display. Further, information other than the respiratory waveform may be output as long as it is information related to respiration (respiration information). For example, a detection unit that detects a respiratory rate, a respiratory cycle, the number of respiratory stops, and the like from a respiratory waveform may be newly added, and may function as a respiratory information measuring unit that measures respiratory information together with the respiratory waveform extracting unit 13. Then, the measured respiration information may be output together with the oxygen saturation measured by the oxygen saturation measuring unit 14. According to such a configuration, there is an effect that the light emitting element can be shared for the measurement of oxygen saturation and the measurement of respiratory information.

  In the above-described embodiment, the form in which the biological information measurement process is realized by software has been described as an example. However, the process equivalent to the flowcharts illustrated in FIGS. 15 and 16 is implemented in, for example, an ASIC (Application Specific Integrated Circuit). However, it may be processed by hardware. In this case, the detection process can be speeded up.

  In the above embodiment, the biological information measurement program is installed in the ROM 12. However, the present invention is not limited to this. The biological information measurement program according to the present invention can be provided in a form recorded in a computer-readable storage medium. For example, the biological information measurement program according to the present invention may be provided in a form recorded on an optical disc such as a CD (Compact Disc) -ROM or a DVD (Digital Versatile Disc) -ROM. The biological information measurement program according to the present invention may be provided in a form recorded in a semiconductor memory such as a USB memory and a flash memory. Furthermore, the biological information measuring device 10 may acquire the biological information measuring program according to the present invention from an external device connected to the communication line via the communication unit 29.

DESCRIPTION OF SYMBOLS 1 (1A, 1B) ... Light emitting element 3 ... Light receiving element 4 ... Artery 5 ... Vein 6 ... Capillary blood vessel 8 ... Living body 10 ... Living body information measuring device 11 ... Photoelectric sensor 12 ... Pulse wave processing unit 13 ... Respiration waveform extraction unit 14 ... Oxygen saturation measurement unit 17 ... Oxygen circulation time measurement unit 18 ... Cardiac output measurement unit 20 ... Computer 21 ... CPU
30 ... Detection unit 31 ... Oxygen saturation recovery time specifying unit 32 ... Oxygen circulation time calculating unit 40 ... Respiration stop time specifying unit 41 ... Respiration resumption time specifying unit 50 ... Acquisition unit 54 ... Inflection point detector 56 ... Interpolator

Claims (10)

The first wavelength light and the second wavelength light transmitted through the measurement site of the measurement subject are received, and the first received light signal and the second wavelength light corresponding to the first wavelength light are received. An output unit for outputting a corresponding second received light signal;
A first specifying unit for specifying a first time when the breathing of the measurement subject is resumed based on a change in amplitude of the first light reception signal;
Based on the first light reception signal and the second light reception signal, a second identification unit that identifies a second time when the oxygen saturation at the measurement site starts to decrease and increases;
A calculation unit that calculates the time from the first time to the second time as the oxygen circulation time based on the identification results of the first specifying unit and the second specifying unit;
A biological information measuring device comprising: The biological information measuring device according to claim 1, wherein the first light reception signal is a light reception signal having a larger amplitude corresponding to the pulsation of the measurement subject than the second light reception signal. The light of the first wavelength is light in a non-red region;
The light of the second wavelength is light in the red region,
The biological information measuring device according to claim 1, wherein the first light reception signal is a light reception signal corresponding to light in the non-red region. The first wavelength is not less than 750 nm and not more than 1000 nm,
The biological information measuring device according to claim 3, wherein the second wavelength is a wavelength of 620 nm or more and less than 750 nm. The biological information measuring device according to claim 3, wherein the light having the first wavelength is light in a green region. The biological information measurement according to claim 5, wherein the light having the first wavelength and the light having the second wavelength are light emitted toward one surface side of the measurement site and received by the one surface side. apparatus. The first specifying unit is configured such that a fluctuation range of a first inflection point of the first light receiving signal or a second inflection point that appears next to the first inflection point is determined from the first fluctuation range. The biological information measuring device according to any one of claims 1 to 6, wherein a time when the fluctuation range is larger than the first fluctuation range is specified as the first time period. An interpolation unit for interpolating between the first inflection points adjacent to each other in the first light reception signal and interpolating between the second inflection points adjacent to each other in the first light reception signal;
The first specifying unit includes a first envelope connecting the first inflection points interpolated by the interpolation unit or a second envelope connecting the second inflection points interpolated by the interpolation unit. The biological information measuring device according to claim 7, wherein the first time period is specified based on an envelope of. Based on the relationship between the oxygen circulation time representing the time until oxygen taken into the body of the subject reaches the measurement site and the information related to cardiac output, the oxygen circulation time calculated by the calculation unit is used. The biological information measuring device according to claim 1, further comprising a third specifying unit that specifies information related to the cardiac output of the measurement subject.   The biological information measurement program for functioning a computer as each part of the biological information measuring device as described in any one of Claims 1-9.