JP2019166146A - Biological information measurement device and biological information measuring program - Google Patents

Abstract

To detect variation in a respiration state of a person being measured, without directly detecting the respiration.SOLUTION: A biological information measurement device 10 comprises: a respiratory waveform extracting unit 13 which extracts a respiratory waveform of a person being measured, from a pulse wave signal representing a pulse wave of the person being measured; and a detection unit 30 for detecting a fact that a variation range of a value corresponding to a difference between a first respiratory inflection point of the respiratory waveform and a second respiratory inflection point appearing next to the first respiratory inflection point has varied from a first variation range to a second variation range.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 detecting that the respiratory state of the measurement subject has changed without directly detecting respiration.

  In order to achieve the above object, the biological information measuring apparatus according to claim 1 is a respiratory waveform extracting unit that extracts a respiratory waveform of the measurement subject from a pulse wave signal representing the measurement subject's pulse wave; The fluctuation range of the value corresponding to the difference between the first respiratory inflection point of the respiratory waveform and the second respiratory inflection point appearing next to the first respiratory inflection point is changed from the first fluctuation range to the second. And a detection unit for detecting that the fluctuation range has been changed.

  According to a second aspect of the present invention, the detection unit detects that the fluctuation range has changed from the first fluctuation range to a second fluctuation range that is larger than the first fluctuation range.

  According to a third aspect of the present invention, the detection unit detects that the variation range has changed from the first variation range to a second variation range that is smaller than the first variation range.

  According to a fourth aspect of the present invention, the detection unit detects the number of times the difference has changed from the first fluctuation range to the second fluctuation range.

  According to a fifth aspect of the present invention, the respiratory waveform extraction unit includes a first removal unit that removes a second frequency component lower than the first frequency component corresponding to pulsation from the pulse wave signal, and the detection is performed. The unit performs the detection based on the pulse wave signal processed by the first removal unit.

  The invention according to claim 6 is characterized in that the breathing waveform extraction unit indicates a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal. An extraction unit that extracts a waveform; and a second removal unit that removes at least a part of a frequency component of 0.5 Hz or more and a frequency component of 0.1 Hz or less from the differential waveform, and the detection unit includes: The detection is performed based on the differential waveform processed by the second removal unit.

  The invention according to claim 7 is characterized in that the respiratory waveform extracting unit indicates a time change of a value corresponding to a difference between a first pulse wave inflection point and a second pulse wave inflection point from the pulse wave signal. An extraction unit that extracts a waveform; an analysis unit that performs frequency analysis on the differential waveform; and a second removal unit that removes frequency components other than the largest frequency component in the differential waveform based on the result of the frequency analysis; The detection unit performs the detection based on the differential waveform processed by the second removal unit.

  The invention according to claim 8 is characterized in that the respiratory waveform extraction unit indicates a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal. An extraction unit that extracts a waveform; a calculation unit that calculates a baseline representing a change tendency of the differential waveform from the differential waveform; and normalizing the differential waveform with the baseline so that the person to be measured is derived from the differential waveform A second removing unit that removes at least a part of the frequency component other than the frequency component corresponding to the respiration.

  The invention according to claim 9 includes an interpolation unit that interpolates between the adjacent first pulse wave inflection points and interpolates between the adjacent second pulse wave inflection points, and the extraction unit Is based on a peak waveform connecting the first pulse wave inflection points interpolated by the interpolation unit and a bottom waveform connecting the second pulse wave inflection points interpolated by the interpolation unit. The differential waveform is extracted.

  According to a tenth aspect of the present invention, the detection unit includes a respiratory resumption timing identifying unit that identifies a resumption timing of resuming respiration after having stopped breathing based on the respiration waveform. An oxygen saturation measuring unit that measures the oxygen saturation of the measurer, an oxygen saturation recovery time specifying unit that specifies an oxygen saturation recovery time for the oxygen saturation to recover based on the oxygen saturation, and Based on the resumption time of breathing and the recovery time of oxygen saturation, oxygen circulation for calculating an oxygen circulation time representing the time until oxygen taken into the body of the subject reaches the measurement site of the subject A time calculation unit.

  An eleventh aspect of the invention includes a cardiac output calculation unit that calculates information related to the cardiac output of the subject based on the oxygen circulation time.

  A twelfth aspect of the invention includes an acquisition unit that acquires a pulse wave signal that represents a pulse wave of the measurement subject, and a respiratory waveform extraction unit that extracts the respiratory waveform of the measurement subject from the pulse wave signal.

  A biological information measuring program according to a thirteenth 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 thirteenth aspects.

  According to invention of Claim 1, 13, it has the effect that it can detect that the to-be-measured person's respiration state changed, without detecting respiration directly.

  According to the second aspect of the present invention, it is possible to detect from the pulse wave signal that the respiration of the measurement subject has been resumed.

  According to the third aspect of the present invention, it is possible to detect from the pulse wave signal that the measurement subject has stopped breathing.

  According to the fourth aspect of the present invention, there is an effect that the number of changes in the breathing state of the measurement subject can be grasped from the pulse wave signal.

  According to the fifth aspect of the present invention, it is possible to extract the respiratory waveform with higher accuracy than in the case where the second frequency component lower than the first frequency component corresponding to the pulsation is not removed from the pulse wave signal. Has the effect.

  According to the sixth aspect of the present invention, it is possible to detect the change in the fluctuation range with high accuracy as compared with the case where the frequency component of 0.5 Hz or more and the frequency component of 0.1 Hz or less are not removed from the differential waveform. It has the effect.

  According to the seventh aspect of the present invention, it is possible to detect the change in the fluctuation range with high accuracy as compared with the case where the frequency component other than the largest frequency component is not removed from the differential waveform.

  According to the eighth aspect of the present invention, it is possible to detect the change in the fluctuation range with higher accuracy than in the case where the frequency component other than the frequency component corresponding to the breath of the measurement subject is not removed from the differential waveform. Has an effect.

  According to the ninth aspect of the invention, as compared with the case where the differential waveform is extracted without interpolating between the adjacent first pulse wave inflection points and between the adjacent second pulse wave inflection points. The differential waveform can be extracted with high accuracy.

  According to the tenth aspect of the invention, the oxygen circulation time can be calculated from the pulse wave signal.

  According to the eleventh aspect of the present invention, the cardiac output can be calculated from the pulse wave signal.

  According to the twelfth aspect of the present invention, the respiratory waveform can be extracted from the pulse wave signal.

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 showing an example of composition of a living body information measuring device concerning a 1st embodiment. 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 the respiration waveform extraction part which concerns on 1st Embodiment. It is a figure which shows an example of a respiration waveform. It is a figure which shows an example of the signal waveform after removing the 2nd frequency component from a pulse wave signal. It is a figure which shows an example of the bottom waveform which connected the 1st pulse wave inflection point and the 2nd pulse wave inflection point. It is a figure which shows an example of the peak waveform and bottom waveform after an interpolation process. It is a figure which shows an example of a difference waveform. It is a figure which shows an example of a respiration waveform. 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 the biometric information measurement process which concerns on 1st Embodiment. It is a flowchart which shows an example of the flow of the respiration waveform extraction process which concerns on 1st Embodiment. It is a figure which shows the structural example of the respiration waveform extraction part which concerns on 2nd Embodiment. It is a figure which shows an example of a difference waveform and a base line. It is a figure which shows an example of the waveform which divided the difference waveform by the base line. It is a figure which shows an example of the respiration waveform after smoothing. It is a flowchart which shows an example of the flow of the respiration waveform extraction process which concerns on 2nd Embodiment.

  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.

<First Embodiment>

  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.

  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 receives a light emitting element 1A that emits IR light having a center wavelength of about 850 nm, a light emitting element 1B that emits red light having a center wavelength of about 660 nm, and IR light and red light. A light receiving element 3 is provided. Note that IR light in this embodiment has a wavelength of 750 nm or more and 1000 nm or less, and red light has a wavelength of 620 nm or more and less than 750 nm.

  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 the capillaries 6 and the like of the living body 8.

  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.

  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 body part of the measurement subject so that ambient light such as illumination light in the measurement environment does not enter the photoelectric sensor unit. 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. Then, the pulse wave processing unit 12 generates each pulse wave signal from which noise components have been removed using a known filter or the like.

  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, a first removal unit 52, an inflection point detection unit 54, an interpolation unit 56, an extraction unit 58, an analysis unit 60, a cutoff frequency determination unit 62, And the 2nd removal part 64 is provided.

  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 first removal unit 52 removes a second frequency component lower than the first frequency component corresponding to the pulsation from the pulse wave signal acquired by the acquisition unit 50. Here, the first frequency component refers to a frequency component corresponding to pulsation, that is, a frequency component necessary for extracting a respiratory waveform. The second frequency component is a frequency component that is not related to pulsation, that is, a frequency component that is not necessary for extraction of a respiratory waveform, and is a frequency component corresponding to, for example, neural fluctuations. Note that a third frequency component higher than the first frequency component may be removed. Here, the third frequency component is a frequency component that is not related to pulsation, that is, a frequency component that is not necessary for extraction of a respiratory waveform, for example, a frequency component corresponding to body movement or the like. Thus, the 1st removal part 52 has a function as a band pass filter. FIG. 9 shows a signal waveform S2 as an example of a signal waveform after removing the second frequency component from the pulse wave signal S1 of FIG.

  The inflection point detector 54 detects the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal output from the first removal unit 52. Here, in the present embodiment, the first pulse wave inflection point refers to a point where the value of the pulse wave signal changes from rising to falling, that is, a point on the peak side. The second pulse wave 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 pulse wave inflection point is the bottom point where the value of the pulse wave signal turns from rising to rising, and the second pulse wave inflection point is the pulse wave signal value changing from rising to falling. A point on the peak side may be used. FIG. 10 shows an example of a peak waveform S3-1 as an example of a peak waveform connecting the detected first pulse wave inflection points H1, and an example of a bottom waveform connecting the second pulse wave inflection points H2. The bottom waveform S3-2 is shown. The “peak waveform” is time-series data representing the time change of the size of the first pulse wave inflection point, and as an example, a line connecting the first pulse wave inflection points with a straight line. expressed. The “bottom waveform” is time-series data representing the time change of the size of the second pulse wave inflection point. As an example, the “bottom waveform” is a line connecting the second pulse wave inflection points with a straight line. expressed.

  If only the first pulse wave inflection point and the second pulse wave inflection point are present, the second pulse wave inflection is located at a position (temporal position) corresponding to the first pulse wave inflection point. Since there is no point and there is no first pulse wave inflection point at the position corresponding to the second pulse wave inflection point, the difference between the peak side and the bottom side of the pulse wave signal at the same position in time is calculated. I can't ask for it.

  Therefore, the interpolating unit 56 interpolates between the adjacent first pulse wave inflection points and interpolates between the adjacent second pulse wave inflection points. Specifically, for example, interpolation is performed using a known interpolation method such as spline interpolation so that the difference between the peak side and the bottom side of the pulse wave signal can be obtained. That is, the bottom point is interpolated at the same position in time as the first pulse wave inflection point. Similarly, the peak point is interpolated at the same position in time as the second pulse wave inflection point. The interpolation cycle is 50 Hz (0.02 second interval) as an example, but is not limited thereto. FIG. 11 shows a peak waveform S4-1 and a bottom waveform S4-2 as an example of the peak waveform and the bottom waveform after the interpolation processing by the interpolation unit 56.

  The extraction unit 58 represents a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point appearing next to the first pulse wave inflection point from the pulse wave signal. Extract the differential waveform. Specifically, the difference between the first pulse wave inflection point and the bottom point interpolated at the same time position as the first pulse wave inflection point is calculated. Also, the difference between the second pulse wave inflection point and the peak point interpolated at the same time position as the second pulse wave inflection point is calculated. Thereby, a differential waveform is calculated. FIG. 12 shows a differential waveform S5 as an example of the differential waveform.

  The analysis unit 60 performs frequency analysis on the differential waveform extracted by the extraction unit 58. Specifically, the differential waveform is subjected to fast Fourier transform (FFT), and the frequency component included in the differential waveform is calculated.

The cut-off frequency determination unit 62 obtains the maximum frequency component f _max corresponding to the principal component of respiration among the frequency components calculated by the analysis unit 60, and sets the frequencies before and after the obtained maximum frequency component as cut-off frequencies f _c1 and f Determine as _c2 . Here, f _c1 = f _max −a, f _c2 = f _max + a, and a is a constant, for example, set to 0.05 Hz.

The 2nd removal part 64 removes frequency components other than the largest frequency component in a difference waveform based on the result of a frequency analysis. Specifically, the cutoff frequency determination unit 62 removes the cut-off frequency f _c1 following frequency component and the cut-off frequency f _c2 or more frequency components determined. Thus, the 2nd removal part 64 has a function as a band pass filter. The cut-off frequencies f _c1 and f _c2 may be determined in advance, and at least a part of the frequency component of f _c2 Hz or higher and the frequency component of f _c1 Hz or lower may be removed from the differential waveform. In this case, the cut-off frequency f _c1 is preferably 0.1 Hz as an example, and the cut-off frequency f _c2 is preferably 0.5 Hz as an example, but the cut-off frequency is not limited to these. Further, the cutoff frequencies f _c1 and f _c2 may be determined according to the half width of the maximum frequency component f _max . For example, the value of the constant a may be increased as the full width at half maximum of the maximum frequency component f _max is increased.

The waveform obtained by removing the frequency component equal to or lower than the cutoff frequency f _{c1 and} the frequency component equal to or higher than the cutoff frequency f _c2 from the differential waveform by the second removing unit 64 is a respiratory stop timing specifying unit 40 and a breath resumption timing specifying unit 41 as a respiratory waveform. Is output. FIG. 13 shows a respiratory waveform S6 as an example of the respiratory waveform.

  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. 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. 14 shows an example of changes in blood oxygen saturation at a specific site 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 respiratory stop timing specifying unit 40 specifies the respiratory stop timing when the breathing stopped based on the respiratory waveform output from the respiratory waveform extracting unit 13. Specifically, the second variation width of the value corresponding to the difference between the first respiratory inflection point and the second respiratory inflection point of the respiratory waveform is smaller than the first variation width from the first variation width. When it is detected that the fluctuation range is changed, the detected time is specified as the respiratory stop time. In this case, the first fluctuation range is a fluctuation range of the difference between the first respiratory inflection point and the second respiratory inflection point in the breathing state, and the second fluctuation range is the breathing It is the fluctuation range of the difference between the first respiratory inflection point and the second respiratory inflection point in the state where is stopped.

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. 15 will be described. For reference, FIG. 15 shows a respiration waveform S7-2 obtained from the temperature of the nasal breath. As shown in FIG. 15, the first respiratory inflection point Pt ₁ , the second respiratory inflection point Bt ₂ , and the first respiratory inflection in time order (t ₁ , t ₂ , t ₃ ,...). When the point Pt ₃ , the second respiratory inflection point Bt ₄ ... Are used, 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 breath inflection point Pt _n (time) as respiratory arrest time. In the case of the example in FIG. 15, the amplitude A ₇ is smaller than a predetermined threshold value as compared with the amplitude A _5, and therefore the time point t ₇ is specified as the respiratory stop timing.

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.

  Based on the respiratory waveform output from the respiratory waveform extracting unit 13, the respiratory restart timing specifying unit 41 specifies the respiratory restart timing when the breathing is resumed after stopping the breathing. Specifically, a second fluctuation range of a value corresponding to the difference between the first respiratory inflection point and the second respiratory inflection point of the respiratory waveform is larger than the first fluctuation width from the first fluctuation width. When it is detected that the fluctuation range is changed, the detected time is specified as the breathing restart time. In this case, the first fluctuation width is a fluctuation width of a difference between the first respiratory inflection point and the second respiratory inflection point in a state where the breathing is stopped, and the second fluctuation width is The fluctuation range of the difference between the first respiratory inflection point and the second respiratory inflection point in the breathing state.

For example, the case where the respiration restart time is specified for the respiration waveform S8-1 as shown in FIG. 16 will be described. FIG. 16 shows a respiration waveform S8-2 obtained from the temperature of nasal breath for reference. As shown in FIG. 16, as in the specific case of the respiratory stop timing, the first respiratory inflection point Pt ₁ , the second respiratory inflection point Bt ₂ , the first respiratory inflection point Pt ₃ , When the second respiratory inflection point Bt ₄ ... Is used, 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 the amplitude is greatly increased as in the case of changes in state of breathing resumes from identifies the location of the first breath 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.

  Note that the number of times the fluctuation range has changed from the first fluctuation range to the second fluctuation range may be detected. As a result, the number of times the breathing state has changed is counted.

  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 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.

Specifically, the resumption timing specified by the resumption timing specifying unit 41 is t ₁ , the recovery time of oxygen saturation specified by the recovery time specification unit 31 is t _2, and t ₁ and t ₂ The time represented by the difference 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 calculates the cardiac output of the measurement subject based on the oxygen circulation time calculated by the oxygen circulation time calculating unit 32.

  The cardiac output CO is obtained from LFCT using a known arithmetic expression shown in, for example, the expression (7).

(Equation 7)
CO = (a0 × S) / LFCT (7)

  Here, a0 is a constant, and for example, a0 = 50 is used. S is the body surface area (m2) of the measurement subject, and the unit of LFCT is second.

  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. 17 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. 18 is executed by the CPU 21 when an instruction to measure 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 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 infrared light. A pulse wave signal representing the person's 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, the respiration waveform extraction process shown in FIG. 19 is executed. The respiration waveform extraction process is repeatedly executed at least until the resumption of respiration is detected in step S114 described later.

  As shown in FIG. 19, in the respiration waveform extraction process, first, in step S200, a pulse wave signal is acquired.

  In step S202, a filtering process is performed on the pulse wave signal acquired in step S200. That is, the second frequency component lower than the first frequency component corresponding to the pulsation is removed from the pulse wave signal.

  In step S204, the first pulse wave inflection point and the second pulse wave inflection point are detected from the pulse wave signal filtered in step S202.

  In step S206, the first pulse wave inflection point and the second pulse wave inflection point detected in step S204 are interpolated between the adjacent first pulse wave inflection points and adjacent first pulse wave inflection points. Interpolate between two pulse wave inflection points.

  In step S208, the difference between the first pulse wave inflection point and the bottom point interpolated at the same position in time as the first pulse wave inflection point is calculated. Further, the difference between the second pulse wave inflection point and the bottom point interpolated at the same time position as the second pulse wave inflection point is calculated. Thereby, a differential waveform is generated.

  In step S210, Fourier transformation is performed on the differential waveform obtained in step S208.

In step S212, the cutoff frequency is determined based on the result of the Fourier transform in step S210. That is, the maximum frequency component f _max corresponding to the main component of respiration is obtained from the result of Fourier transform, and the frequencies before and after the obtained maximum frequency component are determined as cutoff frequencies f _c1 and f _c2 .

At step S214, the relative differential waveform generated in step S210, executes the filtering process for removing the cut-off frequency _{f c1} following frequency component and the cut-off frequency _{f c2} or more frequency components determined in step S212. Thereby, a respiratory waveform is extracted.

  In step S104 of FIG. 18, 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, the second fluctuation range in which the fluctuation range of the value corresponding to the difference between the first respiratory inflection point and the second respiratory inflection point of the respiratory waveform is smaller than the first fluctuation range from the first fluctuation range. It is determined whether or not it has changed.

  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, the second fluctuation range in which the fluctuation range of the value corresponding to the difference between the first respiratory inflection point and the second respiratory inflection point of the respiratory waveform is larger than the first fluctuation range from the first fluctuation range. It is determined whether or not it has changed.

  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 in FIG.

  In the present embodiment, the case where the measurement of LFCT is started after waiting for the breathing of the subject to be resumed in step S114 of FIG. 18 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 breathing is resumed exceeds the allowable delay period, the CPU 21 stops the execution of the processing after step S116 in FIG. The biological information measurement process shown in FIG. 18 may be terminated without measuring the LFCT.

  As described above, according to the biological information measuring apparatus 10 according to the first embodiment, the difference between the first respiratory inflection point of the respiratory waveform and the second respiratory inflection point that appears next to the first respiratory inflection point. The case where it is detected that the fluctuation range of the value corresponding to is changed from the first fluctuation range to the second fluctuation range larger than the first fluctuation range is specified as the breathing resumption timing. Further, the fluctuation range of the value corresponding to the difference between the first respiratory inflection point of the respiratory waveform and the second respiratory inflection point that appears next to the first respiratory inflection point is changed from the first fluctuation range to the first. A case where it is detected that the second fluctuation range is smaller than the fluctuation range is specified as the respiratory stop timing. Thereby, it is detected that the respiratory state of the measurement subject has changed without directly detecting respiration.

  In the present embodiment, the fluctuation range of the value corresponding to the difference between the first respiratory inflection point of the respiratory waveform and the second respiratory inflection point that appears next to the first respiratory inflection point is the first. In the above description, it has been described that the change from the first fluctuation width to the second fluctuation width is detected. However, the fluctuation width of the first pulse wave inflection point of the pulse wave signal is changed from the first fluctuation width to the second fluctuation width. The change may be detected, or the change width of the second pulse wave inflection point of the pulse wave signal may be detected to be changed from the first change width to the second change width. Also good.

Second Embodiment

  Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected about the same part as 1st Embodiment, and detailed description is abbreviate | omitted.

  FIG. 20 shows a configuration example of the respiratory waveform extraction unit 13A according to the second embodiment. The breathing waveform extraction unit 13A shown in FIG. 20 is different from the breathing waveform extraction unit 13 shown in FIG. 7 in that a baseline calculation unit 59 is provided instead of the analysis unit 60 and the cutoff frequency determination unit 62.

  The base line calculation unit 59 calculates a base line representing a change tendency of the differential waveform from the differential waveform, that is, a low frequency component of the differential waveform. Specifically, the baseline calculation unit 59 has a function as a moving average filter, and calculates a baseline of the difference waveform by executing a moving average process on the difference waveform. As described above, by using the moving average process, a baseline corresponding to the vertical change of the signal can be obtained. FIG. 21 illustrates a base line S11 of the differential waveform S10 as an example of the base line. The moving average process includes a simple moving average method, a polynomial fitting method, an adaptive smoothing method, and the like, and any method may be applied. However, the simple moving average method tends to increase the signal distortion when the average number of points is increased, and when applied to the calculation of the base line in the present embodiment, the required signal components are easily smoothed. On the other hand, the polynomial fitting method or the adaptive smoothing method requires more complicated processing than the simple moving average method. However, when applied to the calculation of the baseline in the present embodiment, the signal peak is compared with the simple moving average method. Smoothing while maintaining high frequency components representing the width and width. Therefore, when extracting a respiratory waveform with higher accuracy, a polynomial fitting method or an adaptive smoothing method may be used. Furthermore, when the polynomial fitting method is used, the Savitzky-Golay method, which is an example of the least square smoothing process, may be used. The Savitzky-Golay method can execute complicated processing relatively easily as compared with other methods, and is useful in the calculation of the baseline in the present embodiment. A method other than the moving average method may be used as the baseline calculation method.

  The second removal unit 64 divides the differential waveform by the baseline calculated by the baseline calculation unit 59, thereby generating a frequency component other than the frequency component corresponding to the measurement subject's breath from the differential waveform, specifically, a low frequency. Remove at least a portion of the components. FIG. 22 shows a waveform S12 obtained by dividing the differential waveform S10 by the base line S11. When calculating the waveform S12, it is sufficient if the differential waveform can be normalized by the baseline, and may be normalized by using a method other than division.

  In addition, the second removal unit 64 performs smoothing processing, specifically, for example, moving average processing on the waveform obtained by dividing the difference waveform by the base line, and removes high-frequency components. FIG. 23 shows a waveform S13 obtained by performing a least square smoothing process using the Savitzky-Golay method on the waveform S12. Here, the least square smoothing process using the Savitzky-Golay method is an example of a moving average process. As the moving average process, similar to the process in the baseline calculation unit 59, various moving average processes can be applied. Further, the smoothing process may be performed using a method other than the moving average method.

  Here, in the cardiac output measurement, it is desired to accurately measure the timing when the breathing is resumed and the timing when the breathing is stopped. However, in the first embodiment, since the frequency filter is used, There will be a time delay. On the other hand, in the second embodiment, the delay is suppressed by using the base line. Therefore, it is easy to specify the stoppage and resumption of breathing with higher accuracy than when using a frequency filter. Further, in the method for determining the stoppage of respiration in FIG. 15, when the frequency filter is used, the amplitude A5 tends to be smaller than that in the second embodiment, and in the method for determining resumption of respiration in FIG. Tend to be smaller in amplitude A9 than in the second embodiment. As described above, when determining whether to stop or restart breathing, it is more accurate to adopt the second embodiment.

  Next, the respiration waveform extraction process executed by the respiration waveform extraction unit 13A will be described with reference to the flowchart shown in FIG.

  The breathing waveform extraction process shown in FIG. 24 is different from the breathing waveform extraction process shown in FIG. 19 in that steps S211, S213, and S215 are executed instead of steps S210, S212, and S214.

  In step S211, the base line of the difference waveform is calculated by executing a least square smoothing process on the difference waveform obtained in step S208.

  In step S213, the differential waveform is divided by the baseline obtained in step S211.

  In step S215, the least square smoothing process is performed on the waveform obtained in step S213 to remove high frequency components.

  As described above, in the present embodiment, a base line representing a tendency of the change of the differential waveform is calculated from the differential waveform, and the differential waveform is divided by the calculated base line to obtain a component other than the frequency component corresponding to the breathing of the measurement subject. Is removed.

  Although the present invention has been described above using each embodiment, the present invention is not limited to the scope described in each embodiment. Various modifications or improvements can be added to the respective embodiments without departing from the gist of the present invention, and embodiments to which the modifications or improvements are added are also included in the technical scope of the present invention.

  For example, in each of the above embodiments, the received light amounts of the IR light and 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 to receive light. The received light amounts of the IR light and the red light received by the element 3 may be directly input to the respiratory waveform extraction unit 13 and the oxygen saturation measurement unit 14.

  In each of the above embodiments, an example of a combination of IR light and red light has been described. However, a combination of green light and red light may be used. Here, green light refers to light having a wavelength of 500 nm or more and less than 560 nm. Furthermore, three types of light emitting elements corresponding to each of IR light, red light, and green light are used, oxygen saturation is measured with IR light and red light, and a respiratory waveform is extracted with green light. May be.

  4 may be configured to include only the photoelectric sensor 11, the pulse wave processing unit 12, and the respiratory waveform extraction unit 13. In other words, it may be configured to have a measurement function related to oxygen saturation, oxygen circulation time, and cardiac output, or may not be configured. In addition, a respiration information calculation unit that calculates respiration information related to respiration such as respiration rate, respiration cycle, respiration depth, respiration frequency, and the like from the extracted respiration waveform is provided after the respiration waveform extraction unit 13, You may comprise as a biological information measuring device to calculate. In this case, it is preferable to use green light that can easily detect a pulse wave.

  In each of the embodiments, 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. 18, 19, and 24 is performed by, for example, ASIC (Application Specific It may be mounted on an integrated circuit and processed by hardware. In this case, the detection process can be speeded up.

  Moreover, although each embodiment mentioned above demonstrated the form in which the biometric information measurement program was installed in ROM12, it 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, 13A ... 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 52 ... First removal unit 54 ... Inflection point detection unit 56 ... Interpolation unit 58 ... Extraction unit 59 ... Base line calculation unit 60 ... Analysis unit 62 ... Cut-off frequency determination Part 64... Second removal part

Claims (13)

A respiration waveform extraction unit that extracts the respiration waveform of the measurement subject from a pulse wave signal representing the measurement subject's pulse wave;
The fluctuation range of the value corresponding to the difference between the first respiratory inflection point of the respiratory waveform and the second respiratory inflection point that appears after the first respiratory inflection point is changed from the first fluctuation width to the first fluctuation inflection point. A detection unit for detecting that the fluctuation range is 2;
A biological information measuring device comprising: The biological information measuring apparatus according to claim 1, wherein the detection unit detects that the fluctuation range has changed from the first fluctuation range to a second fluctuation range that is larger than the first fluctuation range. The biological information measuring device according to claim 1, wherein the detection unit detects that the fluctuation range has changed from the first fluctuation range to a second fluctuation range that is smaller than the first fluctuation range. The biological information measuring device according to claim 1, wherein the detection unit detects the number of times the difference has changed from the first fluctuation range to the second fluctuation range. The respiratory waveform extraction unit
A first removing unit that removes a second frequency component lower than the first frequency component corresponding to the pulsation from the pulse wave signal;
The biological information measuring device according to claim 1, wherein the detection unit performs the detection based on a pulse wave signal processed by the first removal unit. The respiratory waveform extraction unit
An extraction unit that extracts a difference waveform representing a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal;
A second removal unit for removing at least a part of a frequency component of 0.5 Hz or more and a frequency component of 0.1 Hz or less from the differential waveform;
With
The biological information measuring apparatus according to claim 1, wherein the detection unit performs the detection based on a differential waveform processed by the second removal unit. The respiratory waveform extraction unit
An extraction unit that extracts a difference waveform representing a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal;
An analysis unit for performing frequency analysis on the differential waveform;
A second removing unit that removes a frequency component other than the largest frequency component in the differential waveform based on the result of the frequency analysis;
With
The biological information measuring apparatus according to claim 1, wherein the detection unit performs the detection based on a differential waveform processed by the second removal unit. The respiratory waveform extraction unit
An extraction unit that extracts a difference waveform representing a time change of a value corresponding to a difference between the first pulse wave inflection point and the second pulse wave inflection point from the pulse wave signal;
A base line calculation unit for calculating a base line representing a change tendency of the differential waveform from the differential waveform;
A second removing unit that removes at least a part of a frequency component other than the frequency component corresponding to the breath of the measurement subject from the differential waveform by normalizing the differential waveform with the baseline;
The biological information measuring device according to any one of claims 1 to 5, further comprising: Interpolating between the adjacent first pulse wave inflection points, and interpolating between the adjacent second pulse wave inflection points,
The extraction unit includes a peak waveform connecting the first pulse wave inflection points interpolated by the interpolation unit, and a bottom waveform connecting the second pulse wave inflection points interpolated by the interpolation unit. The biological information measuring device according to any one of claims 6 to 8, wherein the differential waveform is extracted on the basis of. The detection unit includes a respiratory resumption timing identifying unit that identifies a respiratory resumption timing at which respiration is resumed after stopping breathing based on the respiratory waveform,
An oxygen saturation measuring unit for measuring the oxygen saturation of the measurement subject from the pulse wave signal;
Based on the oxygen saturation, the oxygen saturation recovery time specifying unit for specifying the oxygen saturation recovery time when the oxygen saturation is going to recover;
Oxygen for calculating an oxygen circulation time representing the time until oxygen taken into the measurement subject's body reaches the measurement site based on the resumption timing of breathing and the recovery time of oxygen saturation A circulation time calculation unit;
The biological information measuring device according to claim 1, comprising: The biological information measuring device according to claim 10, further comprising: a cardiac output calculating unit that calculates information related to the cardiac output of the subject based on the oxygen circulation time. An acquisition unit for acquiring a pulse wave signal representing the pulse wave of the measurement subject;
A respiration waveform extraction unit that extracts the respiration waveform of the measurement subject from the pulse wave signal;
A biological information measuring device comprising:   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 1-12.