Method for estimating vascular function

Abstract

The present invention accurately infers peripheral vascular function. This method comprises: acquiring a photoelectric pulse signal of a peripheral capillary or peripheral arteriole of a user; estimating the user's peripheral blood pressure index on the basis of the acquired photoelectric pulse signal; and inferring peripheral vascular function at the peripheral on the basis of the peripheral blood pressure index.

Description

Technical Field

[0001] The present invention relates to a method for estimating a user's vascular function.

Background Art

[0002] A pulse wave propagating in a user's artery is used as an index for estimating the user's health condition. The pulse wave changes according to the change in the user's blood pressure at the measurement site. Patent Document 1 shows a pulse wave measuring device for measuring blood pressure with a small burden on a living body. In the pulse wave measuring device described in Patent Document 1, blood pressure information is calculated based on pulse wave information, and vascular function is estimated. In Patent Document 1, for example, as an example of estimating vascular function, arteriosclerosis is estimated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the estimation of arteriosclerosis in the pulse wave measuring device described in Patent Document 1, based on the fact that hypertension often occurs when arteriosclerosis develops, arteriosclerosis is estimated. However, there are cases of hypertension even when arteriosclerosis has not progressed, and there are also cases of not having hypertension even when arteriosclerosis has progressed. As described above, when estimating vascular function based on a general relationship, the estimation accuracy of vascular function, particularly peripheral vascular function in the periphery of a living body, may not be sufficient.

[0005] The present invention has been made in view of such circumstances, and an object thereof is to accurately estimate peripheral vascular function.

Means for Solving the Problems

[0006] To solve the above problems, a method executed by a biological information measurement system according to the present invention includes acquiring a photoplethysmogram signal of a capillary or arteriole in the user's periphery, estimating a peripheral blood pressure index of the user based on the photoplethysmogram signal, and estimating the peripheral vascular function of the periphery based on the peripheral blood pressure index.

Advantages of the Invention

[0007] According to the present invention, it becomes possible to accurately estimate the vascular function of the periphery.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the respective drawings. Here, the same reference numerals denote the same components, and overlapping descriptions will be omitted.

[0010] FIG. 1 is an explanatory diagram showing the configuration of a biological information measurement system 10 according to an embodiment of the present invention. The biological information measurement system 10 includes a sensing device 20 that measures biological information of a user (subject), and a computer 30 configured to be communicable with the sensing device 20.

[0011] The sensing device 20 is, for example, a wearable device having a structure that can be worn on a peripheral part (for example, a finger) of a user. The sensing device 20 includes a biological sensor 21 that measures biological information from a peripheral part (for example, a finger) of the user, a control circuit 22 that controls the operation of the biological sensor 21, a communication module 23 that transmits the measurement result of the sensing device 20 to the computer 30 through a wireless line or a wired line, and an acceleration sensor 24 that measures the movement acceleration of the sensing device 20.

[0012] The biological sensor 21 includes, for example, photoelectric plethysmogram sensors 211 and 212 that measure index values indicating the peripheral blood pressure of the user. The peripheral blood pressure in the present invention is defined as the blood pressure of peripheral capillaries and arterioles. Here, an arteriole is a thin artery having a diameter of about 20 to 200 μm, for example, and is a blood vessel existing between an artery and a capillary. Further, a capillary is a thin blood vessel having a diameter of about 10 μm, for example, and is a blood vessel connecting an artery and a vein.

[0013] For example, a reflective photoplethysmography sensor has a light-emitting element and a light-receiving element. Infrared light, red light, or light with a green wavelength is irradiated from the light-emitting element toward the user's body surface, and a photodiode or a phototransistor, which is the light-receiving element, measures the light reflected from the user's body surface. Since oxyhemoglobin exists in the blood of arteries and has the property of absorbing incident light, a photoplethysmogram signal can be measured by sensing the blood flow rate (change in blood vessel volume) that changes with the pulsation of the heart in a time series.

[0014] The communication module 23 transmits the measurement results of the sensing device 20 (for example, the photoplethysmogram signals measured by the photoplethysmography sensors 211 and 212, and the acceleration of the sensing device 20 measured by the acceleration sensor 24) to the computer 30 through a wireless line or a wired line.

[0015] The acceleration sensor 24 measures the moving acceleration of the sensing device 20 when the user changes their posture to measure the pulse wave signal. The acceleration sensor 24 is a three-axis acceleration sensor that detects the direction in which the gravitational acceleration acts, and its detection signal can be used for estimating the height at which the user attaches the sensing device 20 and the position where the user attaches the sensing device 20 (for example, the position of the user's heart), and for estimating the user's posture, such as a standing posture (standing position), a sitting posture (sitting position), or a lying-on-back posture (supine position).

[0016] The computer 30 is, for example, a multifunctional mobile phone called a smartphone or a general-purpose computer (for example, a notebook computer, a desktop computer, a tablet terminal, a server computer, etc.). The computer 30 includes a communication module 31 that receives the measurement results of the biosensor 21 from the sensing device 20 through a wireless line or a wired line, and a signal processing device 32 that performs processing for estimating the user's biological information from the measurement results of the biosensor 21. The signal processing device 32 includes a processor 321, a memory 322, and an input / output interface 323.

[0017] The signal processing device 32 can calculate pulse feature quantities from the photoelectric pulse wave signals measured by the photoelectric pulse wave sensors 211 and 212, and can estimate peripheral blood pressure indexes based on the pulse feature quantities. Further, the signal processing device 32 can estimate the height of the part where the user attaches the sensing device 20 and the posture of the user based on the signal from the acceleration sensor 24.

[0018] FIG. 2 is an explanatory diagram showing the external configuration of the sensing device 20 according to an embodiment of the present invention. The sensing device 20 includes an annular housing 25 configured to be attachable to a finger of a user. For example, in the example shown in FIG. 2, the housing 25 has a hollow cylindrical shape. The biological sensor 21 is attached to the inner peripheral surface (the inner surface of the hollow cylinder) of the housing 25 so that the belly of the user's finger faces the biological sensor 21 when the sensing device 20 is attached to the user's finger. Note that the shape of the housing 25 is not limited to a hollow cylindrical shape, and may be, for example, a cylindrical shape (e.g., a finger sack shape) that fits on the user's finger, and the bottom of the cylinder (the portion where the fingertip abuts) may or may not be present. Further, the sensing device 20 may be provided as, for example, a portable electronic device or an installation-type electronic device, and may be configured to measure a photoelectric pulse wave signal when the user places a finger on the biological sensor 21.

[0019] FIG. 3 shows an example of the posture of the user 40 when measuring biological information. In this example, the user 40 is in a state where the finger wearing the sensing device 20 is stationary at the position of the heart 41, and the sensing device 20 is measuring biological information from the finger of the user 40. Note that the position (measurement position) of the sensing device 20 when measuring biological information is not limited to the position of the heart 41 of the user 40, and may be, for example, the position of the face or the abdomen of the user 40. Further, the posture of the user 40 when measuring biological information may be a sitting posture or a supine posture.

[0020] Referring to FIG. 4, the acquisition of the photoplethysmogram signal by the biosensor 21 will be described. FIG. 4 is a schematic cross-sectional view of the state where the biosensor 21 is attached close to the body surface S of the user.

[0021] The biosensor 21 includes light emitting elements 2111, 2121, and a light receiving element 213. The biosensor irradiates light onto the body surface S and receives the light absorbed or reflected by the user's epidermal region EP, a plurality of capillaries CA, and the arteriole AR which is the branching origin of each capillary. In the present embodiment, the case where one light receiving element 213 is provided for the light emitting elements 2111, 2121 will be described. In this case, the light emitting element 2111 and the light receiving element 213 are the photoplethysmogram sensor 211, and the light emitting element 2121 and the light receiving element 213 are the photoplethysmogram sensor 212. Note that light receiving elements may be provided for the light emitting elements 2111, 2121 respectively.

[0022] The light emitting element 2111 is, for example, an LED or a laser having a wavelength in the vicinity of blue to yellow-green (preferably a wavelength in the vicinity of 500 to 550 nm). The light emitting element 2121 is, for example, an LED or a laser having a wavelength in the vicinity of red to near infrared (preferably a wavelength in the vicinity of 750 to 950 nm). The light emitting element 2111 irradiates light in a wavelength range that is strongly absorbed in the living body, and the light emitting element 2121 irradiates light in a wavelength range that is relatively weakly absorbed in the living body. The light receiving element 213 is a photodiode or a phototransistor. The signal generated when the light from the light emitting element 2111 is received by the light receiving element 213 is the first photoplethysmogram signal, and the signal generated when the light from the light emitting element 2121 is received by the light receiving element 213 is the second photoplethysmogram signal.

[0023] The light-emitting element 2111 is provided at a position closer to the light-receiving element 213 than the light-emitting element 2121. For example, it is preferable that the distance between the light-emitting element 2111 and the light-receiving element 213 is about 1 to 3 mm, and the distance between the light-emitting element 2121 and the light-receiving element 213 is about 5 to 20 mm. By providing the light-emitting element 2111 at a position closer to the light-receiving element 213 than the light-emitting element 2121, the received light signal based on the light from the light-emitting element 2111 can contain more information on the shallow region of the skin than the received light signal based on the light from the light-emitting element 2121.

[0024] The light emitted from the light-emitting element 2111 is absorbed by the user's epidermal region EP and the capillary CA on the side of the epidermal region EP, and the transmitted light or reflected light is detected by the light-receiving element 213. The light emitted from the light-emitting element 2121 is absorbed by the user's epidermal region EP, capillary CA, and arteriole AR inside the body from the epidermal region EP, and is detected by the light-receiving element 213. In FIG. 4, the light from the light-emitting elements 2111 and 2121 is schematically shown as the light along the optical path P1 from the light-emitting element 2111 and the light along the optical path P2 from the light-emitting element 2121, respectively.

[0025] Note that the photoplethysmogram sensor used by the signal processing device 32 to estimate the peripheral blood pressure index does not necessarily have a plurality of photoplethysmogram sensors. For example, the signal processing device 32 may estimate the peripheral blood pressure index based on the photoplethysmogram signal acquired by a set of the light-emitting element 2111 and the light-receiving element 213. Alternatively, the signal processing device 32 may estimate the peripheral blood pressure index based on the photoplethysmogram signal acquired by a set of the light-emitting element 2121 and the light-receiving element 213. That is, the photoplethysmogram sensor in the biological sensor 21 may be one.

[0026] In the biological information measurement system 10, the blood pressure of the user can be estimated based on the photoplethysmogram signal measured by the biological sensor 21. Alternatively, in the biological information measurement system 10, through the computer 30, an input of the blood pressure measured by another sphygmomanometer can be received.

[0027] Next, while referring to FIG. 5, the pulse wave characteristic quantities will be described. In the following description, data measured by the finger-mounted sensing device 20 using an LED with a green wavelength (about 525 nm) as the light-emitting element 2111, an LED with a near-infrared wavelength (about 940 nm) as the light-emitting element 2121, and a silicon photodiode as the light-receiving element 213 will be shown and described.

[0028] Reference numeral 51 indicates a velocity pulse wave signal obtained by differentiating the photoelectric pulse wave (photoplethysmogram) signal by the first order. Reference numeral 52 indicates an acceleration pulse wave signal obtained by differentiating the photoelectric pulse wave signal by the second order. The peaks (maximum peak and minimum peak) of the acceleration pulse wave signal 52 are called a wave, b wave, c wave, d wave, and e wave, respectively, as shown in the same figure. Reference numeral 53 indicates the photoelectric pulse wave signal. As the pulse wave characteristic quantities, for example, the peak time difference between each peak (a wave, b wave, c wave, d wave, and e wave), the height of each peak, the ratio of each peak time difference to the pulse interval, the peak half-value width, the ratio of the positive-side area to the negative-side area of the a to e wave portions of the acceleration pulse wave signal 52, the degree of coincidence between the measured pulse wave waveform and the template of the pulse wave waveform, etc. can be used. Also, as the pulse wave characteristic quantities, not only the pulse wave characteristic quantities per beat, but also the average value and standard deviation of the pulse wave characteristic quantities of several beats to several tens of beats can be used.

[0029] Among the pulse wave characteristic quantities, those that are easily affected by the contact state and pressure between the biosensor 21 and the skin are, for example, the pulse wave height and the heights of the a wave, b wave, c wave, d wave, and e wave of the acceleration pulse wave, etc., characteristic quantities related to the signal intensity. Compared with such pulse wave characteristic quantities, those that are less affected by the contact state and pressure between the biosensor 21 and the skin are pulse wave characteristic quantities related to time such as the peak times of the a wave, b wave, c wave, d wave, and e wave. By calculating a peripheral blood pressure index, which is an index value indicating the degree of peripheral blood flow or the degree of peripheral blood pressure of the user, from such pulse wave characteristic quantities related to time, it is possible to make it less affected by the contact state and pressure between the biosensor 21 and the skin. Also, unless otherwise specified, blood flow means peripheral blood flow.

[0030] Generally, for the systolic blood pressure measured at the wrist, the blood pressure drops due to the vascular resistance between the wrist and the periphery. When only the height of the measurement site from the heart is changed, since the vascular resistance between the wrist and the periphery can be regarded as almost constant, the peripheral blood pressure is proportional to the systolic blood pressure at the wrist. When only the height of the measurement site from the heart is changed, it is considered that the peripheral blood pressure index is almost proportional to the systolic blood pressure.

[0031] FIG. 6 is a graph in which the peripheral blood pressure index estimated by the biological information measurement system 10 is plotted against the systolic blood pressure of the subject. Each point on the graph corresponds to the data of one subject, and the number of data is 21. In FIG. 6 and each subsequent figure, diabetic patients are plotted as black circles and healthy subjects are plotted as white circles.

[0032] The biological information measurement system 10 measures the first photoplethysmogram signal and the second photoplethysmogram signal for 30 seconds while the subject (user) holds the sensing device 20 at the height of the chest (heart). The biological information measurement system 10 calculates the peripheral blood pressure index at each measurement time based on the first photoplethysmogram signal and the second photoplethysmogram signal at each measurement time. The systolic blood pressure is the blood pressure measured by a cuff-type blood pressure monitor attached to the subject's wrist.

[0033] As shown in FIG. 6, there is a relationship that as the systolic blood pressure increases, the peripheral blood pressure index decreases. In diabetes, due to the decrease in glucose metabolism ability and the continuation of hyperglycemia, blood vessels are damaged, vascular endothelial function decreases, and arteriosclerosis and peripheral vascular disorders often progress. That is, diabetic patients have poor peripheral vascular function.

[0034] Diabetic patients tend to have high blood pressure, and also in FIG. 6, the higher the systolic blood pressure, the higher the proportion of diabetic patients. However, there are also diabetic patients whose systolic blood pressure is at the same level as that of healthy subjects, and the above tendency is not significant. Therefore, it is difficult to estimate the deterioration of peripheral vascular function as shown in diabetic patients based only on the systolic blood pressure.

[0035] On the one hand, the peripheral blood pressure index is low in diabetic patients and shows a significantly higher tendency in healthy individuals. That is, based on the peripheral blood pressure index, it is possible to classify actual patients with poor peripheral vascular function. Therefore, it is shown that the determination of peripheral vascular function can be accurately performed using the peripheral blood pressure index.

[0036] Instead of the plotting method in FIG. 6, as shown in FIG. 7, by plotting the value obtained by dividing the peripheral blood pressure index by the systolic blood pressure with respect to the systolic blood pressure, the above tendency becomes more prominent.

[0037] In the biological information measurement system 10, based on the tendency shown in FIG. 6 or FIG. 7, a predetermined threshold value is set for the peripheral blood pressure index, and using the threshold value, the peripheral vascular function of the user can be estimated.

[0038] Next, the variation in the estimation result of the peripheral blood pressure index according to the height position of the sensing device 20 with respect to the user will be described. FIG. 8 is a graph plotting the systolic blood pressure and the peripheral blood pressure index when the sensing device 20 is brought close to the chest, head, and abdomen of the subject in the sitting posture.

[0039] For example, point D1 is the plot when the subject brings the sensing device 20 close to the chest, point D2 is the plot when the subject brings the sensing device 20 close to the head, and point D3 is the plot when the subject brings the sensing device 20 close to the abdomen.

[0040] In FIG. 8, the measurement results at three positions for a certain subject are connected by a line. Since the height of the measurement site relative to the heart changes, the systolic blood pressure and the peripheral blood pressure index change due to the pressure variation (head difference) according to the height.

[0041] For example, the points D1, D2, and D3 of the peripheral blood pressure index measured for a certain healthy subject show a tendency that the peripheral blood pressure index changes proportionally to the systolic blood pressure. This tendency is the same for the data measured for other healthy subjects. In many cases, the systolic blood pressure is the lowest when measured at the height of the "forehead" (head), and the highest when measured at the height of the "navel" (abdomen).

[0042] On the other hand, for diabetic patients, point D4 is a plot for the chest, point D5 is a plot for the head, and point D3 is a plot for the abdomen. From points D4, D5, and D6, no tendency can be seen that the peripheral blood pressure index changes proportionally to the systolic blood pressure. This tendency is the same for the data measured for other diabetic patients.

[0043] As described above, the amount of change in the peripheral blood pressure index when the height of the measurement site by the sensing device 20 changes is significantly different between healthy subjects and diabetic patients. Specifically, healthy subjects with good peripheral vascular function have a larger amount of change in the peripheral blood pressure index than diabetic patients with poor peripheral vascular function. Therefore, based on the amount of change in the peripheral blood pressure index when the height of the measurement site is changed, the peripheral vascular function can be estimated.

[0044] Figure 9 is a graph in which each subject plots the maximum value of the amount of change in the peripheral blood pressure index with respect to the systolic blood pressure when the height of the sensing device 20 relative to the subject is changed. As shown in Figure 9, there is a tendency that the amount of change in the peripheral blood pressure index for diabetic patients with poor peripheral vascular function is smaller than the amount of change in the peripheral blood pressure index for healthy subjects.

[0045] Instead of the plotting method in Figure 9, as shown in Figure 10, by plotting the value obtained by dividing the amount of change in the peripheral blood pressure index with respect to the systolic blood pressure by the systolic blood pressure, the above tendency becomes more prominent.

[0046] In the biological information measurement system 10, based on the tendency shown in FIG. 9 or FIG. 10, a predetermined threshold value is set for the amount of change in the peripheral blood pressure index when the height of the sensing device 20 with respect to the user is changed, and using the threshold value, the peripheral vascular function of the user can be estimated.

[0047] Note that, as the amount indicating the change in the peripheral blood pressure index when the height is varied, the maximum amount of change was used, but the change rate of the peripheral blood pressure index or the maximum value and minimum value of the peripheral blood pressure index may also be used.

[0048] In the above example, the estimation of the peripheral vascular function was performed using the measurement results at three measurement positions of the chest, head, and abdomen. However, for example, the estimation may be performed using the measurement results at two measurement positions of the chest and head. Further, the combination of the two measurement positions may be the chest and abdomen or the head and abdomen.

[0049] Also, for a plurality of postures in which the relative height of the sensing device 20 with respect to the heart is different, there may be a posture in which the user lies supine on a flat surface and the user places the hand on the chest, and a posture in which the user lies supine on a flat surface and the user places the hand on the flat surface. When the hand is placed on the chest, the sensing device 20 attached to the hand is at a position higher than the position of the heart. Also, when the hand is placed on the flat surface, the sensing device 20 is at a position lower than the heart. In this way, the relative height of the sensing device 20 with respect to the heart can also be made different.

[0050] These postures are postures that the user can easily take and are postures that each user can repeatedly take with high reproducibility. Further, for example, by limiting "abdomen" to "umbilicus" and "head" to "forehead", the repeatability can be further increased, and the measurement variation among users is reduced.

[0051] As described above, the peripheral blood pressure index changes according to the relative height of the sensing device 20 with respect to the heart. Therefore, in the biological information measurement system 10, the computer 30 has a function of determining the height of the sensing device 20 from the heart, and the computer 30 may estimate the peripheral vascular function when the sensing device 20 is at the height of the user's heart. Thereby, the relative height of the sensing device 20 with respect to the heart can be restricted, so that the estimation of the peripheral vascular function can be performed while suppressing the influence due to the change in the peripheral blood pressure index caused by the difference in the relative height.

[0052] Further, in the biological information measurement system 10, the computer 30 may have a function of estimating the amount of change in the height of the sensing device 20 based on the information from the acceleration sensor 24 of the sensing device 20. The computer 30 may estimate the peripheral vascular function based on the peripheral blood pressure index and the amount of change in height. The computer 30 can correct the influence on the peripheral blood pressure index due to the height variation of the sensing device 20 that affects the peripheral blood pressure index, based on the amount of change. Thereby, the estimation accuracy of the peripheral vascular function is improved. Note that, in the biological information measurement system 10, the height of the sensing device 20 may be input from the outside through the computer 30.

[0053] In the biological information measurement system 10, the sensing device 20 measures a photoplethysmogram signal continuously or intermittently during sleep from a user who is sleeping while wearing the sensing device 20, and the computer 30 estimates the peripheral blood pressure index, and may estimate the peripheral vascular function from the time change of those estimated values (for example, maximum value, minimum value, change rate, amount of change, variance, coefficient of variation, time when the maximum value or minimum value is taken, etc.).

[0054] Generally, peripheral blood flow increases during sleep, so peripheral blood pressure increases. Despite this tendency, when the peripheral blood pressure during sleep is low, it can be estimated in a simple way that the peripheral vascular function is poor.

[0055] Peripheral blood pressure indicators during sleep change temporarily when the posture (supine position, lateral position, prone position, etc.) or the position of the hand changes due to turning over or the like. However, since such temporary changes do not need to be captured, the need for continuous measurement is low. Furthermore, continuous measurement consumes a large amount of power, but in wearable devices, it is desirable for the battery to be small, so intermittent measurement is more desirable.

[0056] The measurement interval is desirably, for example, to perform measurements of about 5 to 60 seconds at intervals of 1 to 10 minutes. Thereby, in the case of good sleep, it is possible to detect variations due to REM sleep and non-REM sleep, which are said to repeat in a cycle of about 90 minutes, and the effects of intermediate awakenings.

[0057] Also, the peripheral blood pressure indicator varies when the measurement site is moving violently or during exercise. Therefore, in the biological information measurement system 10, the computer 30 may determine whether the user is in a resting state based on information from the acceleration sensor 24 of the sensing device 20, and estimate the peripheral vascular function by using the peripheral blood pressure indicator when the user is in a resting state. Thereby, it is possible to estimate the peripheral vascular function while suppressing the influence of the variation of the peripheral blood pressure indicator when the user is not in a resting state, so that the estimation accuracy is improved.

[0058] Furthermore, in the biological information measurement system 10, the computer 30 can determine the time of falling asleep and waking up by determining the user's sleep state based on information from the acceleration sensor 24 of the sensing device 20. When a change in the peripheral blood pressure indicator occurs, by comparing the timing at which these changes occur with the timing of falling asleep or waking up, for example, it is possible to prevent the change in the peripheral blood pressure indicator at waking up from affecting the estimation of the peripheral vascular function. Thereby, the estimation accuracy of the peripheral vascular function is improved.

[0059] In addition, in the biological information measurement system 10, the sensing device 20 measures a photoplethysmogram signal continuously or intermittently over a period of one day or more, and the computer 30 estimates a peripheral blood pressure index, and estimates the peripheral vascular function from changes in those estimated values (maximum value, minimum value, change rate, change amount, variance, coefficient of variation, time when the maximum value or minimum value is reached, etc.).

[0060] In this case, for the photoplethysmogram signal, the need for continuous measurement is low, similar to the measurement during sleep, and it is preferably measured intermittently. The measurement is preferably performed, for example, such that measurements of about 5 to 60 seconds are taken at intervals of 1 to 10 minutes. Thereby, it is possible to detect the influence of fluctuations in peripheral vascular function due to events such as exercise and meals that affect peripheral vascular function.

[0061] FIG. 11 is a flowchart showing an example of processing in the vascular function estimation method according to an embodiment of the present invention. The processing by the biological information measurement system 10 is performed, for example, when programs stored in non-temporary storage areas of the sensing device 20 and the computer 30, respectively, are executed by the sensing device 20 and the computer 30 each including an information processing device such as a processor.

[0062] In step S1101, the sensing device 20 of the biological information measurement system 10 measures a photoplethysmogram signal from the finger of the user wearing the sensing device 20. Specifically, the photoplethysmogram sensor 211 measures a first photoplethysmogram signal, and the photoplethysmogram sensor 212 measures a second photoplethysmogram signal.

[0063] In step S1102, the sensing device 20 transmits the measurement result to the computer 30 of the biological information measurement system 10.

[0064] In step S1103, the computer 30 receives the measurement result of the sensing device 20.

[0065] In step S1104, computer 30 estimates the user's peripheral blood pressure index. For example, computer 30 calculates a pulse wave feature quantity from the photoelectric pulse wave signal measured by biosensor 21, and calculates the user's peripheral blood pressure index from the calculated pulse wave feature quantity.

[0066] In step S1105, computer 30 estimates the user's peripheral vascular function based on the peripheral blood pressure index. For example, computer 30 estimates the peripheral vascular function based on the threshold value of the peripheral blood pressure index stored in a storage unit such as memory 322.

[0067] The biological information measurement system 10 further determines whether the user is asleep, and repeats the processes from steps S1101 to S1104 over the time when the user is sleeping, and may continuously or intermittently measure the user's first photoelectric pulse wave signal and second photoelectric pulse wave signal a plurality of times, and estimate a plurality of peripheral blood pressure indexes. The biological information measurement system 10 may estimate the peripheral vascular function based on the temporal change of the peripheral blood pressure indexes estimated a plurality of times in step S1105.

[0068] The biological information measurement system 10 repeats the processes from steps S1101 to S1104 over the time when the user is active during a day, and may continuously or intermittently measure the user's first photoelectric pulse wave signal and second photoelectric pulse wave signal a plurality of times, and estimate a plurality of peripheral blood pressure indexes. The biological information measurement system 10 may estimate the peripheral vascular function based on the temporal change of the peripheral blood pressure indexes estimated a plurality of times in step S1105.

[0069] FIG. 12 is a flowchart showing another example of the processing of the vascular function estimation method according to the embodiment of the present invention.

[0070] In step S1201, the sensing device 20 of the biological information measurement system 10 acquires information used for calculating the first height of the finger of the user wearing the sensing device 20. For example, the sensing device 20 acquires information used for calculating the first height from the acceleration sensor 24, taking the relative height of the user's finger with respect to the heart as the first height.

[0071] In step S1202, the sensing device 20 measures a photoplethysmogram signal from the finger of the user wearing the sensing device 20. Specifically, the photoplethysmogram sensor 211 measures the first photoplethysmogram signal, and the photoplethysmogram sensor 212 measures the second photoplethysmogram signal.

[0072] In step S1203, the sensing device 20 transmits information indicating the first height, the first photoplethysmogram signal, and the second photoplethysmogram signal to the computer 30 of the biological information measurement system 10 as measurement results.

[0073] In step S1204, the computer 30 receives the measurement results of the sensing device 20.

[0074] In step S1205, the computer 30 calculates the first height based on the information used for calculating the first height, and estimates the peripheral blood pressure index of the user corresponding to the first height. At this time, the computer 30 estimates the peripheral blood pressure index corresponding to the first height as the first peripheral blood pressure index.

[0075] In step S1206, the sensing device 20 acquires information used for calculating the second height of the finger of the user wearing the sensing device 20. For example, the sensing device 20 acquires information used for calculating the second height from the acceleration sensor 24, taking the relative height of the user's finger with respect to the heart, which is different from the first height, as the second height.

[0076] The processing from step S1207 to step S1209 is the same as the processing from step S1202 to S1204.

[0077] In step S1210, the computer 30 calculates the second height based on the information used for the calculation of the second height, and estimates the peripheral blood pressure index of the user corresponding to the second height. At this time, the computer 30 estimates the peripheral blood pressure index corresponding to the second height as the second peripheral blood pressure index.

[0078] Note that the acquisition of the information used for the calculation of the height in steps S1201 and S1206 does not necessarily have to be performed. For example, the computer 30 may acquire information indicating the first height and the second height of the sensing device 20 from the user or the like, and associate the information with the peripheral blood pressure index.

[0079] In step S1211, the computer 30 estimates the peripheral vascular function of the user based on the first peripheral blood pressure index and the second peripheral blood pressure index. For example, the computer 30 calculates the change amounts of the first peripheral blood pressure index and the second peripheral blood pressure index, and estimates the peripheral vascular function based on the magnitudes of the change amounts.

[0080] As described above, exemplary embodiments of the present invention have been described. The method executed by the biological information measurement system described in the present embodiment is a method executed by the biological information measurement system, including acquiring a photoplethysmogram signal of the capillary or arteriole of the user's periphery, estimating the peripheral blood pressure index of the user based on the photoplethysmogram signal, and estimating the peripheral vascular function of the periphery based on the peripheral blood pressure index.

[0081] The peripheral blood pressure index of the user is an index that appropriately reflects the peripheral vascular function. By using the peripheral blood pressure index, it is possible to accurately estimate the peripheral vascular function.

[0082] The above method further includes estimating the blood pressure of the user based on the photoplethysmogram signal, and estimating the peripheral vascular function of the periphery may include estimating the peripheral vascular function based on the peripheral blood pressure index and the blood pressure.

[0083] Accordingly, the peripheral vascular function can be estimated by combining the peripheral blood pressure index and the blood pressure that affects the peripheral blood pressure index. Therefore, the estimation accuracy of the peripheral vascular function is improved.

[0084] In the above method, estimating the peripheral blood pressure index may further include continuously or intermittently measuring the user's peripheral blood pressure index a plurality of times during the user's sleep, and estimating the peripheral vascular function may further include estimating the user's peripheral vascular function from the changes in the peripheral blood pressure index measured during the user's sleep.

[0085] Accordingly, since the estimation of the peripheral vascular function can be performed based on the changes in the peripheral blood pressure index during sleep, the estimation of the peripheral vascular function can be made simpler.

[0086] The above method may further include determining the user's sleep state. Accordingly, it is possible to prevent the changes in the peripheral blood pressure index during waking from affecting the estimation of the peripheral vascular function. Therefore, the estimation accuracy of the peripheral vascular function is improved.

[0087] In the above method, estimating the peripheral blood pressure index may further include continuously or intermittently measuring the user's peripheral blood pressure index a plurality of times over a period of one day or more, and estimating the peripheral vascular function may further include estimating the user's peripheral vascular function from the changes in the user's peripheral blood pressure index measured over a period of one day or more.

[0088] Accordingly, it is possible to detect the influence of fluctuations in the peripheral vascular function caused by events such as exercise and diet that affect the peripheral vascular function. By correcting this influence, the accuracy of the estimation of the peripheral vascular function can be improved.

[0089] The above method further includes determining whether the user's finger is at the height of the user's heart. Estimating the peripheral blood pressure index includes estimating the peripheral blood pressure index when the finger is at the height of the heart. Estimating the peripheral vascular function may include estimating the peripheral vascular function based on the peripheral blood pressure index when the finger is at the height of the heart. Thereby, it becomes possible to accurately estimate the peripheral vascular function using a threshold value for the peripheral blood pressure index when at the height of the heart.

[0090] In the above method, estimating the peripheral blood pressure index includes estimating a first peripheral blood pressure index when the user's finger is at a first height and a second peripheral blood pressure index when the user's finger is at a second height different from the first height. Estimating the peripheral vascular function may include estimating the peripheral vascular function based on a first peripheral vascular function estimated based on the first peripheral blood pressure index and a second peripheral vascular function estimated based on the second peripheral blood pressure index.

[0091] Thereby, it is possible to estimate the peripheral vascular function while suppressing the influence of fluctuations in the peripheral blood pressure index due to height fluctuations on the estimation of the peripheral vascular function. Thus, the estimation accuracy of the peripheral vascular function is improved.

[0092] In the above method, the first height and the second height may be any one of the height when the user holds the user's hand at the height of the user's chest in a sitting position, the height when the user holds the user's hand at the height of the user's head in a sitting position, or the height when the user holds the user's hand at the height of the user's abdomen in a sitting position.

[0093] In the above method, the first height and the second height may be any one of the height when the user holds the user's hand at the height of the user's chest in a supine position on a flat surface or the height when the user holds the user's hand at the height of the flat surface in a supine position.

[0094] The above postures are postures that the user can easily take and postures that each user can repeatedly take with high reproducibility. Thus, the peripheral vascular function is estimated with good reproducibility.

[0095] The above method further includes obtaining a change amount between a first height and a second height, and estimating the peripheral vascular function may be performed based on the peripheral blood pressure index and the change amount. Thereby, variations in the estimation result of the peripheral blood pressure index due to the physical characteristics of the user and the influence due to fluctuations in the measurement position can be suppressed, and the estimation accuracy of the peripheral vascular function is improved.

[0096] The above method further includes determining whether the user is in a resting state, and estimating the peripheral vascular function may include estimating the peripheral vascular function based on the peripheral blood pressure index when the user is in a resting state.

[0097] Thereby, the peripheral vascular function can be estimated based on the peripheral blood pressure index with stable fluctuations, and the estimation accuracy of the peripheral vascular function is improved.

[0098] It should be noted that each of the above-described embodiments is for facilitating the understanding of the present invention and is not for limiting and interpreting the present invention. The present invention can be changed / improved without departing from its gist, and equivalents thereof are also included in the present invention. That is, as long as what those skilled in the art appropriately adds design changes to each embodiment has the features of the present invention, it is included in the scope of the present invention. For example, each element included in each embodiment and its arrangement, conditions, shape, size, etc. are not limited to those illustrated and can be changed as appropriate. Also, each embodiment is an example, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the features of the present invention.

Explanation of Reference Numerals

[0099] 10... Biological information measurement system, 20... Sensing device, 21... Biological sensor, 211, 212... Photoelectric plethysmogram sensors, 2111, 2121... Light-emitting elements, 213... Light-receiving element, 22... Control circuit, 23... Communication module, 24... Acceleration sensor, 25... Housing, 30... Computer, 31... Communication module, 32... Signal processing device

Claims

1. A method performed by a biological information measurement system, comprising: acquiring a photoplethysmogram signal of a capillary in a user's periphery or an arteriole in the periphery; estimating a peripheral blood pressure index indicating the degree of the user's peripheral blood pressure or blood flow rate using a pulse feature quantity based on the photoplethysmogram signal; estimating the user's blood pressure based on the photoplethysmogram signal; and estimating peripheral vascular function based on the peripheral blood pressure index and the blood pressure.

2. The method according to claim 1, wherein estimating the peripheral blood pressure index includes continuously or intermittently measuring the peripheral blood pressure index of the user a plurality of times during the user's sleep; and estimating the peripheral vascular function further includes estimating the user's peripheral vascular function from changes in the peripheral blood pressure index measured during the user's sleep.

3. The method according to claim 2, further comprising determining the user's sleep state.

4. The method according to claim 1, wherein estimating the peripheral blood pressure index includes continuously or intermittently measuring the peripheral blood pressure index of the user a plurality of times over a period of one day or more; and estimating the user's peripheral vascular function from changes in the peripheral blood pressure index measured over a period of one day or more of the user.

5. The method according to claim 1, further comprising determining whether the user's finger is at the height of the user's heart; estimating the peripheral blood pressure index includes estimating the peripheral blood pressure index when the finger is at the height of the heart; and estimating the peripheral vascular function includes estimating the peripheral vascular function based on the peripheral blood pressure index when the finger is at the height of the heart.

6. The method according to claim 1, wherein estimating the peripheral blood pressure index includes estimating a first peripheral blood pressure index when the user's finger is at a first height and a second peripheral blood pressure index when the user's finger is at a second height different from the first height; and estimating the peripheral vascular function includes estimating the peripheral vascular function based on the first peripheral blood pressure index and the second peripheral blood pressure index.

7. The method according to claim 6, wherein the first height and the second height are the height when the user holds the user's hand at the height of the user's chest while in a seated position, the height when the user holds the user's hand at the height of the user's head while in a seated position, or the method is any one of the heights when the user holds the user's hand at the height of the user's abdomen while in a seated position.

8. The method according to claim 6, wherein the first height and the second height are the height when the user holds the user's hand at the height of the user's chest in a supine position on a flat surface, or the method is any one of the heights when the user holds the user's hand at the height of the flat surface in the supine position.

9. The method according to any one of claims 6 to 8, further comprising obtaining a change amount between the first height and the second height, estimating the peripheral vascular function includes estimating the peripheral vascular function based on the peripheral blood pressure index and the change amount.

10. The method according to claim 1, further comprising determining whether the user is in a resting state, estimating the peripheral vascular function includes estimating the peripheral vascular function based on the peripheral vascular function when the user is in a resting state.

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