Biological information measuring device and biological information measuring program

Abstract

To reduce time required for measuring oxygen circulation time for a plurality of times.SOLUTION: A biological information measurement device 10 gives a notice of halting a respiration that is a preparation action for measuring the oxygen circulation time at the next measurement to a person to be measured for oxygen circulation time before the end of follow-up time T3 in the previous measurement, in measuring the oxygen circulation time for a prescribed plurality of times, and controls measurement of the oxygen circulation time so that the measurement of the previous oxygen circulation time and the next measurement of the oxygen circulation time are overlapped with each other.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a biological information measuring device and a biological information measuring program. [Background technology]

[0002] Patent document 1 discloses a biometric information measuring device that includes a notification means for issuing a notification to a subject who has stopped breathing to resume breathing when a specified time that defines the period of breathing cessation is reached, and a measurement means for measuring the oxygen circulation time, which represents the time it takes for oxygen taken into the subject's body when breathing resumes to reach a predetermined location. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-166147 Summary of the Invention [Problem to be solved by the invention]

[0004] Until now, when measuring oxygen circulation time multiple times using a biological information measurement device, the change in blood oxygen saturation was measured until the end of a predetermined measurement time before the next measurement. Therefore, to measure oxygen circulation time three times, the time required for one oxygen circulation time measurement multiplied by 3 was required.

[0005] The technology disclosed herein aims to provide a bioinformation measuring device and a bioinformation measuring program that can shorten the time required to measure oxygen circulation time multiple times when measuring oxygen circulation time multiple times, compared to when starting the next measurement of oxygen circulation time after the end of a predetermined measurement time of oxygen circulation time. [Means for solving the problem]

[0006] The biological information measuring device according to the first aspect includes a processor, and when measuring oxygen circulation time a predetermined number of times, the processor notifies the subject of oxygen circulation time measurement to stop breathing, which is a preparatory action for measuring oxygen circulation time in the next measurement, before the end of the measurement period of the predetermined oxygen circulation time in the previous measurement.

[0007] In the second aspect of the bioinformation measuring device, in the bioinformation measuring device of the first aspect, the processor varies the breathing adjustment time, which is the period from when the subject who has stopped breathing is instructed to resume breathing to when the processor instructs the subject to stop breathing again in order to measure the oxygen circulation time in the next measurement, depending on the measurement status of the oxygen circulation time of the subject.

[0008] A third aspect of the biological information measuring device is the biological information measuring device of the second aspect, wherein the processor controls the breathing adjustment time so that the breathing adjustment time becomes longer as the measurement of the oxygen circulation time of the subject approaches the final measurement.

[0009] In the fourth aspect of the bioinformation measuring device, in the bioinformation measuring device of the second aspect, the processor controls the breathing adjustment time to be the period from when the subject, who has stopped breathing, is instructed to resume breathing until an inflection point is detected at which the oxygen saturation in the subject's blood changes from decreasing to increasing as the subject resumes breathing.

[0010] A fifth aspect of the biological information measuring device is the biological information measuring device of the fourth aspect, wherein the processor controls the final oxygen circulation time measurement for the subject so as not to end the measurement of the oxygen circulation time until the inflection point is detected.

[0011] A sixth aspect of the bioinformation measuring device is a bioinformation measuring device according to any one of the first to fifth aspects, wherein the processor controls the breathing hold time, which is the period from when the subject is instructed to stop breathing to when the subject is instructed to resume breathing, to shorten the breathing hold time as the measurement of the oxygen circulation time of the subject approaches the final measurement.

[0012] A seventh aspect of the bioinformation measuring device is a bioinformation measuring device according to any one of the first to fifth aspects, wherein the processor varies the breathing stop time, which is the period from when the subject is instructed to stop breathing to when the subject is instructed to resume breathing, depending on the difference between the lowest oxygen saturation value in the subject's blood and a predetermined oxygen saturation reference value which specifies the lowest oxygen saturation value required for measuring oxygen circulation time.

[0013] The bioinformation measuring device of the eighth aspect is the bioinformation measuring device of the seventh aspect, wherein the processor shortens the breath-hold time as the difference increases when the minimum value is equal to or less than the reference value, and lengthens the breath-hold time as the difference increases when the minimum value exceeds the reference value.

[0014] The biological information measurement program according to the ninth aspect is a program for causing a computer to execute a process for notifying a subject whose oxygen circulation time is being measured to stop breathing as a preparatory action for measuring the oxygen circulation time in the next measurement before the end of the measurement period of the oxygen circulation time in the previous measurement when the oxygen circulation time is measured a predetermined number of times. [Effects of the Invention]

[0015] According to the first and ninth aspects, when measuring the oxygen circulation time multiple times, the time required to measure the oxygen circulation time multiple times can be shortened compared to when the next measurement of the oxygen circulation time is started after the end of a predetermined measurement time of the oxygen circulation time.

[0016] According to the second aspect, there is an advantage that the time required to measure the oxygen circulation time multiple times can be shortened compared to when a common breathing control time is used for each measurement.

[0017] According to the third aspect, it is possible to reduce the burden on the subject involved in measuring the oxygen circulation time.

[0018] According to the fourth aspect, compared to measuring the oxygen circulation time using a breathing adjustment time that is set regardless of the change in the subject's oxygen saturation, it has the advantage that a breathing adjustment time that corresponds to the change characteristics of the subject's oxygen saturation can be set for each subject.

[0019] According to the fifth aspect, it is possible to improve the measurement accuracy in the final measurement of the oxygen circulation time compared to when the oxygen saturation measurement is terminated upon the end of a predetermined oxygen saturation observation period.

[0020] The sixth aspect has the advantage that the burden on the subject associated with measuring the oxygen circulation time can be reduced compared to when a common breath-hold time is used for each measurement.

[0021] According to the seventh aspect, there is an effect that the breath-holding time can be varied.

[0022] According to the eighth aspect, there is an effect that the accuracy of measuring the oxygen circulation time can be improved while reducing the burden on the subject, compared to when the breath-hold time is set in advance. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic diagram showing an example of measurement of blood oxygen saturation. [Figure 2] 10 is a graph showing an example of changes in the amount of light absorbed by a living body. [Figure 3]FIG. 2 is a diagram showing an example of the amount of light absorbed by oxygenated hemoglobin and reduced hemoglobin at each wavelength. [Figure 4] FIG. 1 is a diagram illustrating an example of the configuration of a biological information measuring device. [Figure 5] 1A and 1B are diagrams illustrating examples of the arrangement of light-emitting elements and light-receiving elements. [Figure 6] 10A and 10B are diagrams illustrating other examples of the arrangement of light-emitting elements and light-receiving elements. [Figure 7] FIG. 10 is a diagram showing an example of changes in blood oxygen saturation. [Figure 8] FIG. 2 is a diagram illustrating an example of the configuration of a main part of an electrical system in the biological information measuring device. [Figure 9] 10 is a flowchart showing the first half of an example of the flow of a biological information measurement process according to the first and second embodiments. [Figure 10] 10 is a flowchart showing the second half of an example of the flow of the biological information measurement process according to the first embodiment. [Figure 11] 10 is a graph showing an example of time variation in the oxygen saturation of a subject when biological information measurement processing according to the first embodiment is executed. [Figure 12] 10 is a graph showing an example of time-dependent changes in the oxygen saturation of a subject when the first LFCT measurement and the second LFCT measurement are not performed overlappingly. [Figure 13] 10 is a flowchart showing the second half of an example of the flow of biological information measurement processing according to the second embodiment. [Figure 14] 10 is a graph showing an example of time-dependent change in the oxygen saturation of a subject in the final LFCT measurement, in which an inflection point in the subject's oxygen saturation was detected before the elapse of the follow-up observation time. [Figure 15] 10 is a graph showing an example of time-dependent change in the oxygen saturation of a subject in the final LFCT measurement, in which an inflection point in the subject's oxygen saturation was detected after the elapse of a follow-up observation period. [Figure 16] 10 is a diagram illustrating an example of the relationship between an inflection point of oxygen saturation and a reference value of oxygen saturation. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present embodiment will be described below with reference to the drawings. Note that the same components and processes are given the same reference numerals throughout the drawings, and redundant description will be omitted.

[0025] First Embodiment The biological information measuring device 10 is a device that measures biological information, particularly biological information related to the circulatory system, among information (biological information) related to a living body 8. The circulatory system is a general term for a group of organs that circulate and transport body fluids, such as blood, within the body.

[0026] There are several indicators of biological information related to the circulatory system. One indicator that indicates the condition of the heart, which pumps blood into the blood vessels, is cardiac output (CO), which represents the amount of blood pumped out of the heart.

[0027] It is known that if cardiac output decreases below the reference value, there is a suspicion of left heart failure, and if cardiac output increases above the reference value, there is a suspicion of right heart failure. Cardiac output is used to examine various heart diseases or to confirm the effectiveness of medication.

[0028] One method for measuring cardiac output involves inserting a catheter with a balloon at its tip into the pulmonary artery of a subject whose cardiac output is being measured, measuring blood oxygen saturation while inflating and deflating the balloon, and then calculating cardiac output from the measured oxygen saturation. Blood oxygen saturation is an example of an index of blood oxygen concentration, indicating the degree to which hemoglobin in the blood is bound to oxygen. A decrease in blood oxygen saturation indicates a greater likelihood of developing symptoms such as anemia. Like cardiac output, blood oxygen saturation is also an example of biometric information and is used as an index of the subject's ability to absorb oxygen into the body. Hereinafter, blood oxygen saturation will be simply referred to as "oxygen saturation."

[0029] Measurement of oxygen saturation and cardiac output using a catheter requires surgical procedures because the catheter must be inserted into the subject's blood vessels, making the method more invasive than other measurement methods.

[0030] Therefore, a method of measuring oxygen saturation and cardiac output from the pulse wave of the subject is used, which places less strain on the subject than a catheter-based measurement method. The pulse wave is an index that shows changes in the pulsation of blood vessels caused by the heart's pumping of blood.

[0031] First, a method for measuring oxygen saturation, which is one of the biological information, will be described with reference to FIG.

[0032] As shown in Figure 1, oxygen saturation is measured by irradiating light from a light-emitting element 1 onto the body (living body 8) of the subject, receiving the light with a light-receiving element 3, and measuring the intensity of the light reflected or transmitted by arteries 4, veins 5, capillaries 6, etc. that are distributed throughout the subject's body, i.e., the amount of reflected or transmitted light received.

[0033] 2 is a conceptual diagram showing, for example, the amount of change in the amount of light absorbed by a living body 8. As shown in FIG. 2, the amount of light absorbed by the living body 8 tends to fluctuate over time.

[0034] Furthermore, looking at the breakdown of the variation in light absorption in the living body 8, it is known that the amount of light absorption varies mainly in the arteries 4, while in the veins 5 and other tissues including stationary tissue, the amount of variation is such that the amount of light absorption can be considered to be unchanged compared to the arteries 4. This is because arterial blood pumped from the heart moves within the blood vessels accompanied by a pulse wave, causing the arteries 4 to expand and contract over time along the cross-sectional direction of the arteries 4, resulting in changes in the thickness of the arteries 4. In FIG. 2, the range indicated by arrow 94 indicates the amount of variation in light absorption corresponding to changes in the thickness of the arteries 4.

[0035] In Figure 2, time t a The amount of light received at I a , time t b The amount of light received at I bThen, the amount of change ΔA in the amount of light absorbed due to a change in the thickness of the artery 4 is expressed by equation (1).

[0036] (Number 1)

[0037] ΔA=ln(I b / I a )···(1)

[0038] 3 is a diagram showing an example of the light absorption at each wavelength of hemoglobin bound to oxygen (oxyhemoglobin) and hemoglobin not bound to oxygen (reduced hemoglobin) flowing through artery 4. In FIG. 3, light absorption curve 96 represents the light absorption by oxygenated hemoglobin, and light absorption curve 97 represents the light absorption by reduced hemoglobin.

[0039] As shown in FIG. 3, it is known that oxygenated hemoglobin is more likely to absorb light in the infrared (IR) region 99 having a wavelength around approximately 850 nm than reduced hemoglobin, and that reduced hemoglobin is more likely to absorb light in the red region 98 having a wavelength around approximately 660 nm than oxygenated hemoglobin.

[0040] Furthermore, it is known that the oxygen saturation level is proportional to the ratio of the change ΔA in the amount of absorbance at different wavelengths.

[0041] Therefore, compared to other wavelength combinations, infrared light (IR light) and red light, which are more likely to cause a difference in the amount of absorbance between oxygenated hemoglobin and reduced hemoglobin, are used to irradiate IR light onto a living body 8. IR and the change in the amount of absorbance ΔA when red light is irradiated onto the living body 8 Red By calculating the ratio of these two values, the oxygen saturation S can be calculated using equation (2). In equation (2), k is a proportionality constant.

[0042] (Number 2)

[0043] S=k(ΔA Red / ΔA IR )···(2)

[0044] That is, when calculating oxygen saturation, a plurality of light-emitting elements 1, each emitting light of a different wavelength, are irradiated onto a living body 8. Specifically, a light-emitting element 1 that emits IR light and a light-emitting element 1 that emits red light are used on the living body 8. In this case, the light-emitting elements 1 that emit IR light and the light-emitting element 1 that emits red light may have overlapping light-emitting periods, but it is preferable that the light-emitting elements 1 emit light so that the light-emitting periods do not overlap. Then, the light reflected or transmitted by each light-emitting element 1 is received by the light-receiving element 3, and the oxygen saturation is measured by calculating equations (1) and (2) or known equations obtained by modifying these equations from the amount of light received at each light-receiving time.

[0045] As a known formula obtained by modifying the above formula (1), for example, the amount of change ΔA in the amount of light absorbed may be expressed as formula (3) by expanding formula (1).

[0046] (Number 3)

[0047] ΔA=lnI b -lnI a ···(3)

[0048] Moreover, equation (1) can be transformed into equation (4).

[0049] (Number 4)

[0050] ΔA=ln(I b / I a )=ln(1+(I b -I a ) / I a ) ···(4)

[0051] Usually, (I b -I a )≪I a Therefore, ln(I b / I a )≒(I b -I a ) / I a Therefore, instead of equation (1), equation (5) may be used as the change ΔA in the amount of light absorbed.

[0052] (Number 5)

[0053] ΔA≒(I b -I a ) / I a ···(5)

[0054] 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 will be referred to as "light-emitting element 1A" and the light-emitting element 1 that emits red light will be referred to as "light-emitting element 1B."

[0055] According to this method, oxygen saturation is measured by bringing the light-emitting element 1 and the light-receiving element 3 close to the body surface of the person being measured, which places less strain on the person being measured than measuring oxygen saturation by inserting a catheter into a blood vessel.

[0056] The cardiac output of the subject is calculated using the measured oxygen saturation, and the details of the calculation method will be explained later.

[0057] Fig. 4 is a diagram showing an example of the configuration of the biological information measuring device 10. As shown in Fig. 4, the biological information measuring device 10 includes a photoelectric sensor 11, a pulse wave processing unit 12, an oxygen saturation measuring unit 13, an oxygen circulation time measuring unit 14, a cardiac output measuring unit 15, a timer unit 16, and a notification unit 17.

[0058] The photoelectric sensor 11 includes a light-emitting element 1A that emits IR light having a central wavelength of approximately 850 nm, a light-emitting element 1B that emits red light having a central wavelength of approximately 660 nm, and a light-receiving element 3 that receives the IR light and the red light.

[0059] 5 shows an example of the arrangement of the light-emitting element 1A, the light-emitting element 1B, and the light-receiving element 3 in the photoelectric sensor 11. As shown in Fig. 5, the light-emitting element 1A, the light-emitting element 1B, and the light-receiving element 3 are arranged side by side facing 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 of the living body 8, etc.

[0060] 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 example arrangement shown in Fig. 5. For example, as shown in Fig. 6, the light-emitting element 1A and the light-emitting element 1B may be arranged opposite the light-receiving element 3 with the living body 8 interposed therebetween. In this case, the light-receiving element 3 receives IR light and red light that have passed through the living body 8.

[0061] Here, as an example, the light emitting element 1A and the light emitting element 1B are described as surface emitting laser elements such as VCSELs (Vertical Cavity Surface Emitting Lasers), but are not limited thereto and may be edge emitting laser elements. Furthermore, the light emitting element 1A and the light emitting element 1B may be LEDs (Light Emitting Diodes).

[0062] The photoelectric sensor 11 is provided with a clip (not shown) for attaching the photoelectric sensor 11 to a part of the body of the person being measured, and the photoelectric sensor 11 is attached so as to come into contact with the body surface of the person being measured by the clip (not shown) so as to prevent IR light and red light from leaking to the outside from the photoelectric sensor 11. In order for the light-receiving element 3 to receive the IR light and red light reflected by or transmitted through the living body 8 of the person being measured as accurately as possible, it is preferable to position the photoelectric sensor 11 so as to come into contact with the body surface of the person being measured, but the photoelectric sensor 11 may also be attached at a position away from the body surface within a range in which the IR light and red light reflected by or transmitted through the living body 8 of the person being measured is received by the light-receiving element 3.

[0063] The photoelectric sensor 11 converts the amount of IR light and red light received by the light receiving element 3 into, for example, a voltage value and notifies the pulse wave processing unit 12 of the voltage value.

[0064] Since a predetermined amount of light is emitted from light-emitting element 1A and light-emitting element 1B, the amount of IR light and red light absorbed by living body 8 can be obtained from the amount of IR light and red light received by photoelectric sensor 11, respectively.

[0065] Therefore, pulse wave processing unit 12 generates a pulse wave signal representing the subject's pulse wave obtained from IR light and a pulse wave signal representing the subject's pulse wave obtained from infrared light using the respective amounts of IR light and red light received from photoelectric sensor 11. Pulse wave processing unit 12 amplifies the voltage values ​​corresponding to the respective amounts of IR light and red light received so that they fall within predetermined ranges suitable for generating pulse wave signals. Pulse wave processing unit 12 then generates each pulse wave signal from which noise components have been removed using a known filter or the like. Pulse wave processing unit 12 notifies oxygen saturation measurement unit 13 of the generated pulse wave signals.

[0066] Upon receiving the pulse wave signal from the pulse wave processing unit 12, the oxygen saturation measurement unit 13 measures the oxygen saturation of the subject from the received pulse wave signal. Specifically, the oxygen saturation measurement unit 13 uses the pulse wave signal to calculate the amount of change ΔA IR and the change in the amount of red light absorbed ΔA Red and are calculated according to equation (1). Then, the oxygen saturation measurement unit 13 calculates the calculated change ΔA IR and the change ΔA Red The oxygen saturation level of the subject is measured using, for example, equation (2), and the measured oxygen saturation level is notified to the oxygen circulation time measuring unit 14.

[0067] In the following, an example will be described in which the oxygen saturation measurement unit 13 measures the oxygen saturation of the subject, but the oxygen saturation measurement unit 13 may measure any value that indicates the change in the oxygen saturation of the subject over time. For example, the oxygen saturation measurement unit 13 may measure the reciprocal of the oxygen saturation, or the amount of change ΔA Red and the change ΔA IR Alternatively, a value that correlates with the change in oxygen saturation over time, such as the ratio of

[0068] The oxygen circulation time measurement unit 14 detects an inflection point of the oxygen saturation by referring to the oxygen saturation of the subject measured by the oxygen saturation measurement unit 13, and measures the oxygen circulation time.

[0069] FIG. 7 is a graph showing an example of changes in oxygen saturation at a specific site of the subject, where the horizontal axis represents time and the vertical axis represents oxygen saturation.

[0070] When the subject stops breathing at time t1, the subject's oxygen saturation level begins to decrease. Even if the subject resumes breathing after the end of the breath-hold period (time t2), the oxygen taken into the blood by the resumption of breathing takes time to reach specific areas from the lungs, so the subject's oxygen saturation level continues to decrease even after time t2. Eventually, the oxygen taken into the blood by the resumption of breathing reaches specific areas from the lungs, so the subject's oxygen saturation level begins to increase. The point at which oxygen saturation changes from decreasing to increasing is called the "inflection point," and the time at which the inflection point appears is called time t 60 Then, the oxygen circulation time is between time t2 and time t 60 is expressed by the difference between

[0071] That is, oxygen circulation time refers to the time it takes for oxygen to be transported from the lungs to a specific site, and is also called "oxygen delivery time."

[0072] The oxygen circulation time measured from changes in oxygen saturation tends to vary in measurement accuracy depending on the variation in the breathing hold period, so the biological information measurement device 10 has a preset breathing hold period T1 that determines the length of the breathing hold period.

[0073] Specifically, if the subject resumes breathing while the oxygen saturation is decreasing, the oxygen saturation may begin to increase before it reaches the minimum value required for measuring the oxygen circulation time. If the oxygen circulation time is measured from a change in oxygen saturation that has not yet reached the minimum value required for measuring the oxygen circulation time, the measurement accuracy of the oxygen circulation time will be lower than if the oxygen circulation time is measured from a change in oxygen saturation that has reached the minimum value required for measuring the oxygen circulation time.

[0074] Therefore, the breathing hold time T1 is set so that, for as many subjects as possible, the minimum oxygen saturation value obtained by the subject stopping breathing is lower than the minimum oxygen saturation value required to measure the oxygen circulation time.

[0075] Therefore, the breath-hold time T1 is determined in advance by an experiment using the biological information measurement device 10 on an actual device, or the like.

[0076] Hereinafter, the minimum oxygen saturation value required for measuring the oxygen circulation time will be referred to as the “reference value H of oxygen saturation.” The reference value H of oxygen saturation will also be determined in advance through experiments using the biological information measurement device 10.

[0077] The lowest oxygen saturation value falling below the reference value H of oxygen saturation means that the lowest oxygen saturation value is equal to or less than the reference value H of oxygen saturation.

[0078] The oxygen circulation time measurement unit 14 determines the time when the inflection point of the oxygen saturation is detected as time t 60 and time t2 and time t 60 The time represented by the difference between the oxygen saturation inflection point and the oxygen circulation time is measured. Note that "detecting an inflection point" includes detecting a position within a range shifted forward or backward along the time axis from the inflection point of oxygen saturation, as long as the detection does not substantially affect the measurement of oxygen circulation time.

[0079] The oxygen circulation time measuring unit 14 notifies the notifying unit 17 and the cardiac output measuring unit 15 of the measured oxygen circulation time.

[0080] The measurement site for the oxygen circulation time is determined by the attachment position of the photoelectric sensor 11 on the subject. In this embodiment, as an example, the photoelectric sensor 11 is attached to a peripheral site of the subject. More specifically, the photoelectric sensor 11 is attached to a fingertip, and the oxygen circulation time when oxygen is transported from the lungs to the fingertip is measured. This is because the longer distance from the lungs compared to other sites results in a longer oxygen circulation time, and therefore a more accurate oxygen circulation time can be obtained compared to when the photoelectric sensor 11 is attached to other sites. Note that the "peripheral site" refers to a site on the peripheral side of the subject's body, such as the neck, shoulders, or hip joints.

[0081] Therefore, the oxygen circulation time from the lungs to the fingertips is sometimes referred to as LFCT (Lung to Finger Circulation Time). In this embodiment, too, an example will be described in which photoelectric sensor 11 is attached to the fingertips of the subject and LFCT is measured by oxygen circulation time measurement unit 14, but the location of photoelectric sensor 11 is not limited to the fingertips. Photoelectric sensor 11 may be attached to any part of the subject as long as the measurement error of the obtained oxygen circulation time falls within a predetermined range. Note that "fingertip" refers to the fingertips of the subject's hands, but photoelectric sensor 11 may also be attached to the toes.

[0082] The cardiac output measurement unit 15 measures the cardiac output of the subject using the LFCT received from the oxygen circulation time measurement unit 14. The cardiac output is calculated, for example, by a predetermined arithmetic expression that represents the relationship between the LFCT and the cardiac output.

[0083] In addition to the cardiac output, the cardiac output measurement unit 15 may measure information related to the cardiac output. "Information related to the cardiac output" is information that is correlated with the cardiac output, and includes, for example, the cardiac index and stroke volume.

[0084] The "cardiac index" is the value obtained by dividing the cardiac output of the subject by the subject's body surface area in order to correct for differences in cardiac output due to differences in the subject's physique. The "stroke volume" is a value indicating the amount of blood pumped into the artery 4 by one contraction of the heart, and is calculated by dividing the cardiac output by the subject's heart rate per minute.

[0085] The cardiac output measuring unit 15 notifies the notifying unit 17 of the measured cardiac output. Note that although the biological information measuring device 10 shown in FIG. 4 has the cardiac output measuring unit 15 for measuring cardiac output, measuring cardiac output is not essential for the biological information measuring device 10. Therefore, the biological information measuring device 10 does not necessarily have to include the cardiac output measuring unit 15.

[0086] The notification unit 17 notifies the subject to start holding their breath, and also measures the breathing hold time T1 in cooperation with the timer unit 16, and notifies the subject to resume breathing after the breathing hold time T1 has elapsed. The timer unit 16 is provided with a timer that measures time, and measures the time of a section with a specified start and end.

[0087] Furthermore, when measuring the oxygen circulation time of the same subject multiple times, the notification unit 17 notifies the subject to resume breathing, and then notifies the subject to resume cessation of breathing in order to measure the oxygen circulation time in the next measurement.

[0088] The period from when the subject is instructed to resume breathing until the subject is instructed to stop breathing again in order to measure the oxygen circulation time in the next measurement is the period during which the subject regulates their breathing in preparation for the next oxygen circulation time measurement. Therefore, hereafter, the length of this period will be referred to as the "breathing regulation time T2."

[0089] Furthermore, the notification unit 17 notifies at least one of the subject and a medical professional in charge of the subject of the oxygen circulation time measured by the oxygen circulation time measurement unit 14 and the cardiac output measured by the cardiac output measurement unit 15.

[0090] In this embodiment, "notification" refers to making instructions from the biological information measurement device 10 or information obtained by the biological information measurement device 10 recognizable to at least one of the subject and the medical professional in charge of the subject. Therefore, ways in which the biological information measurement device 10 notifies the subject of instructions, such as restarting or stopping breathing, include visual notification, such as displaying the instruction on a display, auditory notification, such as issuing an instruction by voice, and contact notification, such as transmitting an instruction by vibration. Furthermore, ways in which the biological information measurement device 10 notifies the subject of biological information, such as oxygen circulation time and cardiac output, measured by the biological information measurement device 10 include visual notification, such as displaying the measured biological information on a display, auditory notification, such as issuing the measured biological information by voice, notification using a storage device, such as storing the measured biological information in a storage device to which at least one of the subject and the medical professional in charge of the subject has read permission, notification using a recording medium, such as forming the measured biological information on a recording medium such as paper using an image forming device, and notification using a communication line, such as transmitting the measured biological information to an external device via a communication line.

[0091] 8 is a diagram showing an example of the configuration of a main part of an electrical system in the biological information measuring device 10 configured using a computer 20.

[0092] The computer 20 includes a CPU (Central Processing Unit) 21, which performs the processing of the pulse wave processing unit 12, oxygen saturation measurement unit 13, oxygen circulation time measurement unit 14, cardiac output measurement unit 15, timer unit 16, and notification unit 17 according to this embodiment, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 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 to each other via a bus 26. There are no restrictions on the operating system used in the computer 20.

[0093] The nonvolatile memory 24 is an example of a storage device that maintains stored information even if the power supplied to the nonvolatile memory 24 is cut off, and is, for example, a semiconductor memory, but may also be a hard disk.

[0094] To the I / O 25, for example, the photoelectric sensor 11, an input unit 27, a display unit 28, and a communication unit 29 are connected.

[0095] The photoelectric sensor 11 is connected by wire or wirelessly to the I / O 25. The vital information measuring device 10 and the photoelectric sensor 11 may be configured as separate units so as to be separated from each other, or may be configured so as to be housed in the same housing so as to be integrated.

[0096] The input unit 27 is an input device that receives instructions from, for example, a user of the biological information measuring device 10 and notifies the CPU 21. The input unit 27 includes, for example, a button, a touch panel, a keyboard, a mouse, etc. The user of the biological information measuring device 10 includes, for example, the subject and a medical professional in charge of the subject.

[0097] The display unit 28 is a display device that displays, for example, information processed by the CPU 21 to the user of the biological information measuring device 10. The display unit 28 may be, for example, a liquid crystal display, an organic EL (Electro Luminescence), a projector, or other display device.

[0098] The display unit 28 is not necessarily an essential unit for the biological information measurement device 10, and a unit appropriate for the form of notification of instructions to the user and biological information is connected to the I / O 25.

[0099] For example, when instructions from the biological information measuring device 10 and measured biological information are to be notified to the user of the biological information measuring device 10 by voice, a speaker unit may be connected to the I / O 25. When instructions from the biological information measuring device 10 are to be notified to the user of the biological information measuring device 10 through a physical sensation, a vibration unit may be connected to the I / O 25.

[0100] The communication unit 29 has a communication protocol for connecting the vital information measurement device 10 to a communication line such as the Internet, and performs data communication between the vital information measurement device 10 and other external devices connected to the communication line. The communication unit 29 may be connected to the communication line in a wired or wireless manner. If the vital information measurement device 10 does not need to perform data communication with other external devices connected to the communication line, the communication unit 29 does not need to be connected to the I / O 25.

[0101] The units connected to the I / O 25 are not limited to the above-mentioned examples, and other units such as a printing unit that prints measured biometric information on a recording medium may be connected to the I / O 25.

[0102] Next, the operation of the biological information measuring device 10 will be described with reference to Figures 9 and 10. Hereinafter, an example will be described in which, when the biological information measuring device 10 receives a measurement start instruction from the user via the input unit 27, the LFCT, which is an example of oxygen circulation time, is measured multiple times. The number of LFCT measurements is stored in advance in the nonvolatile memory 24 of the biological information measuring device 10. The number of LFCT measurements stored in the nonvolatile memory 24 can be changed by the user. The number of LFCT measurements performed by the biological information measuring device 10 in response to a single measurement start instruction needs to be two or more, and there is no restriction on the number of measurements. The number of LFCT measurements may be specified by the user when giving an instruction to start measurement.

[0103] For ease of explanation, it is assumed that the number of LFCT measurements is set to "two" in the nonvolatile memory 24 of the biological information measurement device 10. In other words, the biological information measurement device 10 performs two consecutive LFCT measurements in response to a single measurement start instruction.

[0104] 7, the time from when a subject who has stopped breathing resumes breathing until an inflection point in oxygen saturation appears varies from subject to subject. Therefore, in the biological information measurement device 10, a reference time is set to determine how long oxygen saturation measurement should continue after the subject resumes breathing. This reference time is called the "follow-up observation time T3."

[0105] The follow-up observation time T3 is set to be longer than the average LFCT, for example, so that the LFCT can be measured even for a subject whose oxygen saturation inflection point appears later than other subjects. Specifically, the follow-up observation time T3 is determined in advance by experiments using an actual device such as the biological information measuring device 10. The follow-up observation time T3 is an example of the "oxygen circulation time measurement period" according to this embodiment.

[0106] The nonvolatile memory 24 of the biological information measurement device 10 stores the follow-up observation time T3 as well as a predetermined breath-hold time T1 and a predetermined breath-regulation time T2.

[0107] As an example, the following relationship exists between the breath-hold time T1, the breath-control time T2, and the follow-up observation time T3.

[0108] Relationship 1: Breathing adjustment time T2 < follow-up observation time T3 Relationship 2: (breathing arrest time T1 + breathing adjustment time T2) > follow-up observation time T3

[0109] 9 and 10 are flowcharts showing an example of the flow of a biological information measurement process executed by the CPU 21 when an instruction to start measurement is received from the user via the input unit 27 with the photoelectric sensor 11 attached to the fingertip of the subject.

[0110] A biological information measurement program that defines the biological information measurement process is stored in advance in, for example, the ROM 22 of the biological information measurement device 10. The CPU 21 of the biological information measurement device 10 reads the biological information measurement program stored in the ROM 22 and executes the biological information measurement process.

[0111] When the biological information measurement device 10 receives the instruction to start measurement, it starts measuring the oxygen saturation level and stores the measured oxygen saturation level in the RAM 23, for example.

[0112] Fig. 11 is a graph showing an example of time-dependent changes in the oxygen saturation of the subject obtained by the biological information measurement process. The flow of the biological information measurement process will be described below with reference to the graph in Fig. 11. In the graph in Fig. 11, the biological information measurement device 10 receives an instruction to start measurement from the user via the input unit 27 at time t0.

[0113] First, in step S10 of Fig. 9, the CPU 21 notifies the subject to stop breathing as a preparatory action for the first LFCT measurement. In the graph of Fig. 11, the CPU 21 notifies the subject to stop breathing at time t1. That is, the first LFCT measurement starts at time t1.

[0114] Having notified the subject to stop breathing, in step S20, the CPU 21 starts a timer TM1. The timer TM1 is a timer for measuring a breathing stop time T1. The CPU 21 starts the timer TM1, for example, using a timer function built into the CPU 21. If the CPU 21 does not have a built-in timer function, the CPU 21 may start the timer TM1, for example, using a timer unit (not shown) connected to the I / O 25.

[0115] In step S30, CPU 21 determines whether timer TM1 has reached breathing stop time T1. If timer TM1 has not reached breathing stop time T1, CPU 21 repeatedly executes the determination process of step S30 until timer TM1 reaches breathing stop time T1. Because the subject stops breathing until timer TM1 reaches breathing stop time T1, the subject's oxygen saturation level decreases after time t1, as shown in the graph of FIG. 11. Because there is a distance between the lungs and the fingertip, it takes time for the photoelectric sensor 11 attached to the fingertip to detect a drop in oxygen saturation caused by the subject's cessation of breathing. Therefore, after time t1, the oxygen saturation remains the same as before cessation of breathing, but then begins to drop towards time t2.

[0116] If it is determined in the determination process of step S30 in FIG. 9 that the timer TM1 has reached the breathing pause time T1, the process proceeds to step S40.

[0117] In step S40, the CPU 21 stops the timer TM1. "Stopping" the timer TM1 means stopping the timer TM1 from measuring time and setting the value of the timer TM1 to "0." In other words, stopping the timer TM1 is equivalent to resetting the timer TM1.

[0118] In step S50, CPU 21 notifies the subject to resume breathing. In the graph of Fig. 11, CPU 21 notifies the subject to resume breathing at time t2, when breathing stop time T1 has elapsed since time t1. This causes the subject to resume breathing, which had been stopped. In other words, the subject stops breathing for the entire breathing stop time T1.

[0119] As already explained, there is a distance between the lungs and the fingertip, so even if the subject resumes breathing at time t2, it takes time for the photoelectric sensor 11 attached to the fingertip to detect the increase in oxygen saturation due to the subject's resumption of breathing. Therefore, the oxygen saturation continues to decrease even after time t2 has passed.

[0120] When the subject resumes breathing, CPU 21 starts the first follow-up monitoring of oxygen saturation in step S60. "Starting follow-up monitoring of oxygen saturation" refers to a state in which CPU 21 associates the time when the subject resumes breathing (time t2 in this case) with the oxygen saturation measured at time t2 when the subject resumes breathing, and then detects a change in the oxygen saturation used for measuring the LFCT.

[0121] Therefore, in step S70, the CPU 21 starts a timer TM2 and a timer TM3. The timer TM2 is a timer for measuring a breathing adjustment time T2. The timer TM3 is a timer for measuring a follow-up observation time T3. That is, the CPU 21 continues measuring the oxygen saturation from time t2 until the follow-up observation time T3 has elapsed.

[0122] Meanwhile, the subject who has resumed breathing will regulate his / her breathing in preparation for the second LFCT measurement.

[0123] In step S80, the CPU 21 determines whether the timer TM2 started in step S70 has reached the breathing adjustment time T2. If the timer TM2 has not reached the breathing adjustment time T2, the CPU 21 repeatedly executes the determination process of step S80 until the timer TM2 reaches the breathing adjustment time T2.

[0124] If it is determined in the determination process of step S80 that the timer TM2 has reached the breathing adjustment time T2, the process proceeds to step S90, where the CPU 21 stops the timer TM2.

[0125] In step S100, CPU 21 notifies the subject to stop breathing as a preparatory action for the second LFCT measurement. In the graph of Fig. 11, CPU 21 notifies the subject to stop breathing at time t3. That is, the second LFCT measurement starts at time t3.

[0126] Having notified the subject to stop breathing, CPU 21 starts timer TM1 in step S110.

[0127] As already explained, due to the relationship "breathing adjustment time T2<follow-up observation time T3," the first LFCT measurement continues even after time t3. That is, the CPU 21 repeatedly performs the first LFCT measurement even after time t3, when the subject stops breathing in order to perform the second LFCT measurement. Therefore, even if the second LFCT measurement is started, it is possible to measure the LFCT of the subject whose oxygen saturation inflection point appears after the breathing adjustment time T2 has elapsed.

[0128] In step S120, the CPU 21 determines whether the timer TM3 started in step S70 has reached the elapsed observation time T3. If the timer TM3 has not reached the elapsed observation time T3, the CPU 21 proceeds to step S160 to continue the first LFCT measurement.

[0129] In step S160, CPU 21 determines whether timer TM1 started in step S110 has reached breathing-stop time T1. If timer TM1 has not reached breathing-stop time T1, CPU 21 proceeds to step S120. That is, CPU 21 alternately executes the determination process of step S120 and the determination process of step S160 until timer TM1 reaches follow-up observation time T3.

[0130] If it is determined in the determination process of step S120 that the timer TM3 has reached the elapsed observation time T3, the process proceeds to step S130. In the graph of Fig. 11, the timer TM3 has reached the elapsed observation time T3 at time t4.

[0131] At time t4, the first oxygen saturation follow-up observation ends, and the first LFCT measurement also ends. Therefore, in step S130, the CPU 21 stops the timer TM3.

[0132] In step S140, the CPU 21 acquires the oxygen saturation measured over the follow-up observation time T3 in chronological order from the RAM 23, detects the inflection point of the oxygen saturation, and then measures the time from the time t2 when the subject resumes breathing to the time when the inflection point of the oxygen saturation appears, and sets this as the measurement result of the first LFCT.

[0133] In step S150, the CPU 21 notifies the user of the first LFCT measurement result measured in step S140, for example, by displaying it on the display unit 28. Thereafter, the CPU 21 proceeds to step S160, where it determines whether the timer TM1 has reached the breath-hold time T1.

[0134] If it is determined in the determination process of step S160 that the timer TM1 has reached the breathing pause time T1, the process proceeds to step S170 in FIG.

[0135] Since the measurement of the breath-hold time T1 has ended, in step S170, the CPU 21 stops the timer TM1.

[0136] In step S180, CPU 21 notifies the subject to resume breathing. In the graph of Fig. 11, CPU 21 notifies the subject to resume breathing at time t5, when breathing-pause time T1 has elapsed since time t3. This causes the subject to resume breathing.

[0137] As the subject resumes breathing, in step S190, CPU 21 starts a second oxygen saturation follow-up measurement. Therefore, in step S200, CPU 21 starts timer TM3. In the first oxygen saturation follow-up measurement, in step S70 of FIG. 9, CPU 21 started timer TM2 in addition to timer TM3. However, since the second oxygen saturation follow-up measurement is the final oxygen saturation follow-up measurement, the subject does not need to regulate his or her breathing in preparation for the next LFCT measurement. Therefore, CPU 21 does not need to start timer TM2.

[0138] In step S210, the CPU 21 determines whether the timer TM3 started in step S200 has reached the elapsed observation time T3. If the timer TM3 has not reached the elapsed observation time T3, the CPU 21 repeatedly executes the determination process of step S210.

[0139] On the other hand, if it is determined in the determination process of step S210 that the timer TM3 has reached the elapsed observation time T3, the process proceeds to step S220. In the graph of Fig. 11, the timer TM3 has reached the elapsed observation time T3 at time t6.

[0140] At time t6, the second oxygen saturation observation ends, and the second LFCT measurement also ends. Therefore, in step S220, the CPU 21 stops the timer TM3.

[0141] In step S230, the CPU 21 acquires the oxygen saturation measured over the follow-up observation time T3 from time t5 to time t6 from the RAM 23 in chronological order, and detects the inflection point of the oxygen saturation. Then, the CPU 21 measures the time from time t5 when the subject resumes breathing to the time when the inflection point of the oxygen saturation appears, and sets this as the measurement result of the second LFCT.

[0142] In step S240, the CPU 21 notifies the user of the second LFCT measurement result measured in step S230 by displaying it on the display unit 28, for example.

[0143] In step S250, the CPU 21 substitutes the first LFCT acquired in step S140 and the second LFCT measured in step S230 into a predetermined equation that represents the relationship between the LFCT and cardiac output, for example, to measure the cardiac output for each measurement.

[0144] It should be noted that even if the CPU 21 measures the LFCT of the subject, it is not necessary to measure the subject's cardiac output at the same time, and therefore the CPU 21 does not have to execute the process of step S250.

[0145] With the above, the CPU 21 ends the biological information measurement process shown in FIGS.

[0146] In this way, when the biological information measuring device 10 measures the LFCT of the subject multiple times in response to a single measurement start instruction, it notifies the subject to stop breathing in order to prepare for the next LFCT measurement before the end of the oxygen saturation observation time T3 from the previous measurement.

[0147] On the other hand, Figure 12 is a graph showing an example of the change over time in the oxygen saturation of a subject when the subject is notified to stop breathing in preparation for the second LFCT measurement after the oxygen saturation follow-up observation time T3 in the first LFCT measurement has ended.

[0148] In the graph shown in Fig. 12, the first follow-up observation time T3 from time t2 to time t3 and the second breath-hold time T1 from time t3 to time t5 do not overlap. Therefore, time t6 corresponding to the end of the second LFCT measurement shown in Fig. 12 is longer than time t6 corresponding to the end of the second LFCT measurement shown in Fig. 11 by the time (t4-t3) in Fig. 11. In other words, the biological information measurement device 10 according to this embodiment can reduce the time required to measure the LFCT multiple times compared to starting the next LFCT measurement after the previous LFCT measurement has finished. Furthermore, as the time required to measure the LFCT is reduced, the time required to measure biological information calculated from the LFCT, such as cardiac output, is also reduced.

[0149] 9 and 10, an example has been described in which the LFCT is notified for each LFCT measurement, but the LFCTs measured in each measurement may be notified together after a specified number of LFCT measurements have been completed. Specifically, instead of notifying the LFCT for the first measurement in step S150 in Fig. 9, the LFCT for the first measurement and the LFCT for the second measurement may be notified together in step S240 in Fig. 10.

[0150] Furthermore, the biological information measurement device 10 does not need to measure the LFCT for each LFCT measurement. Specifically, the biological information measurement device 10 stores only the chronological changes in oxygen saturation in the nonvolatile memory 24 without executing steps S140, S150, S230, S240, and S250 of the biological information measurement process shown in FIGS. 9 and 10 . Then, after the biological information measurement process is completed, the biological information measurement device 10 acquires the oxygen saturation from the nonvolatile memory 24 in response to a user instruction and measures the LFCT for each measurement. By storing the oxygen saturation after the start of measurement in the nonvolatile memory 24 in chronological order, the biological information measurement device 10 can acquire the measured oxygen saturation at any time later, thereby measuring the LFCT for each measurement at the timing instructed by the user. This LFCT measurement method is applicable, for example, to a situation in which a subject measures their oxygen saturation at home and a medical professional later checks the subject's oxygen saturation and LFCT at a hospital.

[0151] Second Embodiment In the first embodiment, the follow-up observation time T3 is a fixed value. However, to measure the LFCT of a subject, the oxygen saturation may be measured from the time the subject resumes breathing until an inflection point in the oxygen saturation is detected.

[0152] Therefore, in the second embodiment, a biological information measurement device 10 will be described that performs control to vary the follow-up observation time T3 depending on the detection status of the inflection point of oxygen saturation in the final LFCT measurement.

[0153] FIG. 13 is a flowchart showing an example of the flow of the biological information measurement process executed by the CPU 21 following the biological information measurement process according to the first embodiment shown in FIG.

[0154] When the biological information measurement device 10 receives the instruction to start measurement, it starts measuring the oxygen saturation level and stores the measured oxygen saturation level in the RAM 23, for example.

[0155] Like the biological information measurement device 10 according to the first embodiment, the biological information measurement device 10 according to the second embodiment also performs two consecutive LFCT measurements in response to a single measurement start instruction.

[0156] In step S160 of the biological information measurement process shown in Figure 9, if it is determined that the timer TM1, which was started when the subject stopped breathing for the second time, has reached the breathing stop time T1, the process proceeds to step S300 in Figure 13.

[0157] Since the measurement of the second breath-hold time T1 has ended, in step S300, the CPU 21 stops the timer TM1.

[0158] In step S310, CPU 21 notifies the subject to resume breathing, which causes the subject to resume breathing.

[0159] As the subject has resumed breathing, in step S320, the CPU 21 starts monitoring the progress of oxygen saturation in the second, that is, final, LFCT measurement.

[0160] In step S330, CPU 21 acquires the change in oxygen saturation during follow-up and determines whether an inflection point in the subject's oxygen saturation has been detected. If an inflection point in the oxygen saturation has not been detected, CPU 21 repeats the determination process of step S330 until an inflection point in the oxygen saturation is detected. On the other hand, if an inflection point in the oxygen saturation has been detected, CPU 21 proceeds to step S340.

[0161] In step S340, the CPU 21 calculates the time from the time t5 when the subject resumes breathing to the time t 60 The time until the second LFCT is measured is used as the measurement result.

[0162] In step S350, the CPU 21 notifies the user of the second LFCT measurement result measured in step S340 by displaying it on the display unit 28, for example.

[0163] In step S360, the CPU 21 substitutes the first LFCT acquired in step S140 of FIG. 9 and the second LFCT measured in step S340 into a predetermined arithmetic expression that expresses the relationship between the LFCT and cardiac output, for example, to measure the cardiac output for each measurement.

[0164] With the above, the CPU 21 ends the biological information measurement process according to the second embodiment shown in FIGS.

[0165] That is, the CPU 21 of the biological information measuring device 10 according to the second embodiment performs control so that the period from when the subject resumes breathing until the inflection point of oxygen saturation is detected is set as the follow-up observation time T3 in the final LFCT measurement.

[0166] FIG. 14 is a graph showing an example of the change in the oxygen saturation level of the subject over time when, in the final LFCT measurement, the inflection point in the subject's oxygen saturation level is detected from the time t5 when the subject resumes breathing until the predetermined follow-up observation time T3, i.e., before the pre-change follow-up observation time T3, has elapsed.

[0167] As shown in Figure 14, the inflection point of oxygen saturation appears at time t 60 However, if the time t5 is before the time t6 at which the pre-change follow-up observation time T3 has elapsed, the follow-up observation time T3 is from the time t5 to the time t 60 In the example shown in Fig. 14, the shortened follow-up observation time T3 is indicated by hatching.

[0168] That is, the biological information measuring device 10 according to the second embodiment can shorten the time required from receiving an instruction to start measurement from the user to completing the final LFCT measurement, compared to when the second LFCT measurement is completed after the predetermined follow-up observation time T3 before the change has elapsed.

[0169] On the other hand, Figure 15 is a graph showing an example of the change in the oxygen saturation level of the subject over time in the second LFCT measurement, when the inflection point of the subject's oxygen saturation level is detected after the pre-change follow-up observation time T3 has elapsed from the time t5 when the subject resumed breathing.

[0170] As shown in Figure 15, the inflection point of oxygen saturation appears at time t 60 However, if the time t5 is later than the time t6 at which the follow-up observation time T3 before the change has elapsed, the follow-up observation time T3 is from the time t5 to the time t 60 In the example shown in Fig. 15, the extended follow-up observation time T3 is indicated by hatching.

[0171] If breathing is repeatedly stopped, the inflection point of oxygen saturation may appear later in the latter LFCT measurement than in the earlier LFCT measurement.

[0172] That is, in the biological information measurement device 10 according to the second embodiment, even if an inflection point of oxygen saturation appears after the elapse of the follow-up observation time T3 before the change in the final LFCT measurement, the LFCT measurement does not need to be terminated midway. Therefore, the LFCT of the subject can be measured more accurately than when the length of the follow-up observation time T3 is not adjusted.

[0173] In the second embodiment, a control example has been described in which the period from when the subject resumes breathing until an inflection point in oxygen saturation is detected in the final LFCT measurement is set as the follow-up observation time T3. The CPU 21 of the biological information measurement device 10 may also apply this control of varying the follow-up observation time T3 in accordance with the detection of an inflection point in oxygen saturation to other LFCT measurements other than the final LFCT measurement. In this case, the user may set a measurement in which the follow-up observation time T3 is varied in accordance with the detection of an inflection point in oxygen saturation.

[0174] <Modification> Various modifications of the first and second embodiments will be described.

[0175] The CPU 21 of the biological information measurement device 10 may vary the breathing adjustment time T2 depending on the measurement conditions of the LFCT of the subject, rather than setting the breathing adjustment time T2 to a fixed value.

[0176] For example, if a subject repeatedly stops breathing, even if the duration of each breath stop is the same, the longer the breath stop, the more difficult it tends to be. Therefore, the CPU 21 may perform control to adjust the breathing adjustment time T2 so that it becomes longer as the LFCT measurement for the same subject approaches the final measurement.

[0177] As the subject's breathing becomes more labored, the oxygen saturation at the end of the fixed breathing control time T2, i.e., the oxygen saturation before breathing stops, may decrease. Therefore, for each LFCT measurement, the CPU 21 may set the extension rate of the breathing control time T2 using the rate of decrease in oxygen saturation before breathing stops in the immediately preceding LFCT measurement. For example, the CPU 21 may use the rate of decrease in oxygen saturation before breathing stops in the immediately preceding LFCT measurement as the extension rate of the breathing control time T2 in the next LFCT measurement.

[0178] It is not necessary for the CPU 21 to make the breathing adjustment time T2 in each measurement of the LFCT longer than the breathing adjustment time T2 in the measurement of the immediately preceding LFCT. For example, the breathing adjustment time T2 in each measurement up to a predetermined intermediate measurement of the LFCT (referred to as an "intermediate measurement") may be the same, and the breathing adjustment time T2 in each measurement of the LFCT after the intermediate measurement may be made longer than the breathing adjustment time T2 in each measurement of the LFCT before the intermediate measurement.

[0179] Furthermore, the CPU 21 may vary the breath-hold time T1 depending on the measurement conditions of the LFCT of the subject, rather than setting the breath-hold time T1 to a fixed value.

[0180] As already explained, it is observed that the subject tends to have difficulty holding his / her breath as the final LFCT measurement approaches. In response to this, the length of the breathing adjustment time T2 is adjusted in the above example, but the CPU 21 may also perform control to adjust the breathing-holding time T1 so that it is shorter as the LFCT measurement for the same subject approaches the final measurement.

[0181] In this case, the CPU 21 may set the reduction rate of the breathing hold time T1 for each LFCT measurement using the decrease rate of the oxygen saturation level in normal conditions in the immediately preceding LFCT measurement. For example, the CPU 21 may use the decrease rate of the oxygen saturation level before breathing hold in the immediately preceding LFCT measurement as the reduction rate of the breathing hold time T1 in the next LFCT measurement.

[0182] As mentioned above, there are individual differences in the time from when a subject resumes breathing until the oxygen saturation inflection point appears, and there are also individual differences in the oxygen saturation value at the inflection point, causing variations. Therefore, the breathing-hold time T1 is set to a length that will cause the oxygen saturation value at the inflection point to fall below the reference oxygen saturation value H for as many subjects as possible.

[0183] However, some subjects may experience changes in their physical condition that prevent the oxygen saturation value at the inflection point from falling below the reference oxygen saturation value H. The accuracy of the LFCT measured for such subjects may be lower than the accuracy of the LFCT measured when the oxygen saturation value at the inflection point falls below the reference oxygen saturation value H.

[0184] On the other hand, there are some subjects whose oxygen saturation inflection point value is lower than the oxygen saturation reference value H by a large amount. The accuracy of the LFCT measured for such subjects may not be different from the accuracy of the LFCT measured when the oxygen saturation inflection point value is the same as the oxygen saturation reference value H.

[0185] The value of the oxygen saturation at the inflection point varies depending on the length of the breathing pause time. Therefore, the CPU 21 may perform control to vary the breathing pause time T1 according to the minimum value of the oxygen saturation of the subject, i.e., the difference between the value at the inflection point of the oxygen saturation and the reference value H of the oxygen saturation.

[0186] Fig. 16 is a diagram showing an example of the difference between the value at an inflection point of oxygen saturation and the oxygen saturation reference value H. Oxygen saturation curve 30 in Fig. 16 shows an example in which the value at the inflection point of oxygen saturation is not below the oxygen saturation reference value H, while oxygen saturation curve 32 shows an example in which the value at the inflection point of oxygen saturation is below the oxygen saturation reference value H. Furthermore, difference e1 represents the difference between the inflection point on oxygen saturation curve 30 and the oxygen saturation reference value H, and difference e2 represents the difference between the inflection point on oxygen saturation curve 32 and the oxygen saturation reference value H.

[0187] For a subject whose oxygen saturation value at the inflection point is not below the oxygen saturation reference value H, as in oxygen saturation curve 30, the CPU 21 lengthens the breath hold time T1 from the preset breath hold time T1 as the difference between the oxygen saturation value at the inflection point and the oxygen saturation reference value H increases, so that the oxygen saturation inflection point falls below the oxygen saturation reference value H. By lengthening the breath hold time T1 from the preset breath hold time T1, the measurement accuracy of the LFCT improves compared to before the breath hold time T1 was extended.

[0188] Furthermore, for a subject whose oxygen saturation value at the inflection point is lower than the oxygen saturation reference value H by an unnecessarily large amount, as in oxygen saturation curve 32, CPU 21 shortens breath hold time T1 from the preset breath hold time T1 so that the oxygen saturation inflection point falls below the oxygen saturation reference value H and approaches the oxygen saturation reference value H as the difference between the oxygen saturation value at the inflection point and the oxygen saturation reference value H increases. By shortening breath hold time T1 from the preset breath hold time T1, the time required to measure the LFCT is shortened compared to before shortening breath hold time T1, while maintaining the measurement accuracy of the LFCT.

[0189] While one aspect of the biological information measurement device 10 has been described above using an embodiment, the disclosed form of the biological information measurement device 10 is merely an example, and the form of the biological information measurement device 10 is not limited to the scope described in the embodiment. Various modifications or improvements can be made to the embodiment without departing from the gist of the present disclosure, and forms incorporating such modifications or improvements are also included in the technical scope of the disclosure. For example, the order of the biological information measurement process shown in the first and second embodiments may be changed without departing from the gist of the present disclosure.

[0190] In the above embodiment, the biological information measurement process is implemented by software. However, the same processes as those shown in Figures 9 and 10 and 9 and 13 may be implemented by hardware. In this case, the processing speed can be increased compared to when the biological information measurement process is implemented by software.

[0191] In the above embodiment, the term "processor" refers to a processor in a broad sense, including a general-purpose processor (e.g., CPU 21) and a dedicated processor (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0192] Furthermore, the operations of the processors in the above embodiments may not only be performed by a single processor, but may also be performed by multiple processors located at physically separate locations working together. Furthermore, the order of the operations of the processors is not limited to the order described in the above embodiments, and may be changed as appropriate.

[0193] In the above embodiment, an example in which the biological information measurement program is stored in the ROM 22 has been described, but the storage location of the biological information measurement program is not limited to the ROM 22. The biological information measurement program of the present disclosure can also be provided in a form recorded on a storage medium readable by the computer 20. For example, the biological information measurement program may be provided in a form recorded on an optical disk such as a CD-ROM (Compact Disk Read Only Memory) or a DVD-ROM (Digital Versatile Disk Read Only Memory). Furthermore, the biological information measurement program may be provided in a form recorded on a portable semiconductor memory such as a USB (Universal Serial Bus) memory or a memory card.

[0194] ROM 22, non-volatile memory 24, CD-ROM, DVD-ROM, USB, and memory cards are examples of non-transitory storage media.

[0195] Furthermore, the biological information measurement device 10 may download a biological information measurement program from an external device connected to the communication unit 29 via a communication line and store the downloaded biological information measurement program in a non-transitory storage medium. In this case, the CPU 21 of the biological information measurement device 10 reads the biological information measurement program downloaded from the external device from the non-transitory storage medium and executes the biological information measurement process. [Explanation of symbols]

[0196] 1, 1A, 1B Light-emitting element 3 Photodetector 4 arteries 5. Veins 6 Capillaries 8 Living organisms 10 Biological information measuring device 11 Photoelectric Sensor 12 Pulse wave processing section 13 Oxygen saturation measurement unit 14 Oxygen circulation time measurement unit 15 Cardiac output measuring section 16 Timer section 17 Notification Department 20 Computer 21 CPU 22 ROM 23 RAM 24 Non-volatile memory 25 I / O 26 Bus 27 Input Unit 28 Display Unit 29 Communication Unit 30, 32 Oxygen saturation curve 94 Arrow 96, 97 Absorption curve 98 Red area 99 Infrared region H standard value S Oxygen saturation T1 Breathing hold time T2 Breathing adjustment time T3 Follow-up time TM1, TM2, TM3 timers e1, e2 difference

Claims

1. a processor; The processor: The oxygen circulation time is the time it takes for oxygen to circulate through the arteries, veins, and capillaries that run throughout the body of the person being measured. The oxygen circulation time is the time from when the person being measured resumes breathing, which was once stopped, until an inflection point at which the oxygen saturation in the person's blood changes from decreasing to increasing is detected. When the oxygen circulation time is measured multiple times in succession, if the time elapsed since the person being measured resumed breathing reaches a breathing adjustment time, which is the time from when the person being measured is instructed to resume breathing until when the person being measured is again instructed to stop breathing, which is a preparatory action for measuring the oxygen circulation time in the next measurement, and which is set to a time shorter than the measurement period of the oxygen circulation time in the person being measured, before the measurement period of the oxygen circulation time, which is set to a predetermined length as a period for observing the oxygen saturation in the person's blood, the person being measured is notified to stop breathing. Biometric information measuring device.

2. The processor varies the breathing adjustment time in accordance with the measurement status of the oxygen circulation time of the subject. The biological information measuring device according to claim 1 .

3. The processor controls the breathing adjustment time so that the breathing adjustment time becomes longer as the measurement of the oxygen circulation time of the subject approaches the final measurement. The biological information measuring device according to claim 2 .

4. The processor performs control to determine the period from when the subject who has stopped breathing is instructed to resume breathing until when the inflection point is detected as the breathing adjustment time. The biological information measuring device according to claim 2 .

5. The processor controls the measurement of the oxygen circulation time so as not to end until the inflection point is detected in the final measurement of the oxygen circulation time for the subject. The biological information measuring device according to claim 4 .

6. The processor controls the breath-holding time, which is the period from when the subject is instructed to stop breathing until when the subject is instructed to resume breathing, so as to shorten the breath-holding time as the measurement of the oxygen circulation time of the subject approaches the final measurement. The biological information measuring device according to any one of claims 1 to 5.

7. The processor varies a breathing stop time, which is a period from when the subject is instructed to stop breathing to when the subject is instructed to resume breathing, according to a difference between the minimum value of the oxygen saturation in the subject's blood and a predetermined reference value of oxygen saturation, which defines the minimum value of oxygen saturation required for measuring oxygen circulation time. The biological information measuring device according to any one of claims 1 to 5.

8. When the minimum value is equal to or less than the reference value, the processor shortens the breath-holding time as the difference increases, and when the minimum value exceeds the reference value, the processor lengthens the breath-holding time as the difference increases. The biological information measuring device according to claim 7 .

9. When oxygen circulation time, which is the time required for oxygen to circulate through the arteries, veins, and capillaries that are distributed throughout the body of a person to be measured, is measured multiple times in succession, the oxygen circulation time being the time from when the person to be measured resumes breathing after having stopped it until an inflection point at which the oxygen saturation in the person's blood changes from decreasing to increasing is detected, the time being the time from when the person to be measured resumes breathing until when the person to be measured is again instructed to stop breathing, which is a preparatory action for measuring the oxygen circulation time in the next measurement, reaches a breathing adjustment time set to a time shorter than the measurement period of the oxygen circulation time in the person to be measured, before the elapsed time from when the person to be measured resumes breathing reaches a measurement period of the oxygen circulation time set to a predetermined length as a period for observing the oxygen saturation in the person's blood. Biometric information measurement program.

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