Blood flow dynamics estimation method

Abstract

The present invention accurately estimates peripheral hemodynamics. This hemodynamics estimation method includes: obtaining first photelectric pulse wave signals of the peripheral capillaries of a user; obtaining second photoelectric pulse wave signals of the peripheral arterioles; estimating the pulse wave propagation time on the basis of the first photoelectric pulse wave signals and the second photoelectric pulse wave signals; and estimating the peripheral hemodynamics on the basis of the pulse wave propagation time. The first photoelectric pulse wave signals and the second photoelectric pulse wave signals are obtained from a specific finger of the user.

Description

[Technical field]

[0001] The present invention relates to a method for estimating the hemodynamic status of a user. [Background technology]

[0002] The pulse wave transit time, which is the time it takes for a pulse wave to propagate through a user's artery, is used as an index used to estimate a user's health condition. The pulse wave transit time changes according to changes in the user's blood pressure at the measurement site. Patent Document 1 shows a blood pressure condition measuring device for accurately measuring circulatory dynamics including the blood pressure condition of arterioles or capillaries, which are thinner than arteries, in order to estimate the risk of cardiovascular disease. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 030380 Summary of the Invention [Problem to be solved by the invention]

[0004] The estimation of circulatory dynamics (hemodynamics) described in Patent Document 1 uses a photoelectric pulse wave signal of an arteriole or capillary and a reference biosignal for measuring the propagation time. Here, the reference biosignal is a signal used to estimate the pulse wave propagation time from the heart to an artery that supplies blood to the arteriole or capillary. In Patent Document 1, the estimation of circulatory dynamics is performed based on the pulse wave propagation time.

[0005] When the blood pressure status measuring device described in Patent Document 1 is used to estimate hemodynamics (peripheral hemodynamics) at the site of the peripheral blood vessels of a user, the pulse wave propagation time varies greatly because the length of the arterioles and capillaries, which are the paths through which the pulse wave propagates, varies greatly depending on the individual differences between users and the position where the device is attached. Therefore, in the blood pressure status measuring device, it becomes difficult to estimate the peripheral hemodynamics from the value of the pulse wave propagation time, and a problem may arise in that the estimation accuracy of the peripheral hemodynamics becomes low.

[0006] The present invention has been made in view of the above circumstances, and has an object to accurately estimate peripheral hemodynamics. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, a method executed by the bioinformation measuring system according to the present invention includes acquiring a first photoelectric pulse wave signal of a user's peripheral capillaries, acquiring a second photoelectric pulse wave signal of a capillary arteriole, estimating a pulse wave transit time based on the first photoelectric pulse wave signal and the second photoelectric pulse wave signal, and estimating peripheral hemodynamics based on the pulse wave transit time, wherein the first photoelectric pulse wave signal and the second photoelectric pulse wave signal are acquired from a specified finger of the user. Effect of the Invention

[0008] According to the present invention, it is possible to estimate peripheral hemodynamics with high accuracy. [Brief description of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram showing a configuration of a biological information measuring system according to an embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram illustrating an external configuration of a sensing device according to an embodiment of the present invention. [Diagram 3] 1 is an explanatory diagram showing an example of a posture of a user when measuring biological information; [Figure 4]FIG. 2 is an explanatory diagram illustrating the acquisition of a photoplethysmographic signal by a sensing device according to an embodiment of the present invention. [Diagram 5] FIG. 11 is an explanatory diagram of pulse wave feature amounts. [Figure 6] 5A to 5C are diagrams illustrating estimation of a pulse wave transit time based on a first photoelectric pulse wave signal and a second photoelectric pulse wave signal. [Figure 7] 13 is a graph showing the correlation between pulse wave transit time and a first photoplethysmographic signal. [Figure 8] 1 is a graph showing the correlation between pulse wave transit time and systolic blood pressure. [Figure 9] 1 is a graph showing the correlation between pulse wave transit time and peripheral blood pressure index. [Figure 10] 1 is a graph showing the correlation between the inverse of the pulse wave transit time and a peripheral blood pressure index. [Figure 11] 1 is a graph showing the correlation between pulse wave transit time and peripheral blood pressure index, differentiated according to whether the subject is ill or not. [Figure 12] 1 is a graph showing the correlation between the inverse of the pulse wave transit time and a peripheral blood pressure index, differentiated according to whether the subject is ill or not. [Figure 13] 13 is another graph showing the correlation between pulse wave transit time and peripheral blood pressure index. [Figure 14] 13 is another graph showing the correlation between the inverse of the pulse wave transit time and a peripheral blood pressure index. [Figure 15] 13 is another graph showing the correlation between pulse wave transit time and peripheral blood pressure index. [Figure 16] 13 is another graph showing the correlation between the inverse of the pulse wave transit time and a peripheral blood pressure index. [Figure 17] 1 is a flowchart showing a process flow of a peripheral hemodynamics estimation method according to an embodiment of the present invention. [Figure 18] 10 is a flowchart showing another example of the processing flow of the peripheral hemodynamics estimation method according to the embodiment of the present invention. [Figure 19] 10 is a flowchart showing another example of the processing flow of the peripheral hemodynamics estimation method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, the same reference numerals denote the same components, and duplicated explanations will be omitted.

[0011] 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 that is configured to be able to communicate with the sensing device 20.

[0012] The sensing device 20 is, for example, a wearable device having a structure that can be attached to a peripheral part (for example, a finger) of a user. The sensing device 20 includes a biosensor 21 that measures bioinformation from the peripheral part (for example, a finger) of the user, a control circuit 22 that controls the operation of the biosensor 21, a communication module 23 that transmits the measurement results of the sensing device 20 to a computer 30 via a wireless line or a wired line, and an acceleration sensor 24 that measures the movement acceleration of the sensing device 20.

[0013] The biosensor 21 includes, for example, photoelectric pulse wave sensors 211, 212 that measure an index value indicating the peripheral blood pressure of the user. In the present invention, peripheral blood pressure is defined as the blood pressure of peripheral capillaries and arterioles. Here, an arteriole is a thin artery with a diameter of, for example, about 20 to 200 μm, and is a blood vessel that exists between an artery and a capillary. Moreover, a capillary is a thin blood vessel with a diameter of, for example, about 10 μm, and is a blood vessel that connects an artery and a vein.

[0014] For example, a reflective photoplethysmographic sensor has a light-emitting element and a light-receiving element, and irradiates the user's body surface with infrared light, red light, or light of a green wavelength from the light-emitting element, and measures the light reflected from the user's body surface with a light-receiving element such as a photodiode or phototransistor. Since oxyhemoglobin is present in arterial blood and has the property of absorbing incident light, a photoplethysmographic 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 manner.

[0015] The communication module 23 transmits the measurement results of the sensing device 20 (e.g., the photoplethysmographic signals measured by the photoplethysmographic sensors 211, 212, and the acceleration of the sensing device 20 measured by the acceleration sensor 24) to the computer 30 via a wireless or wired line.

[0016] The acceleration sensor 24 measures the movement acceleration of the sensing device 20 when the user changes his / her posture to measure the pulse wave signal. The acceleration sensor 24 is a three-axis acceleration sensor that detects the direction of gravitational acceleration, and the detection signal can be used to estimate the height at which the user wears the sensing device 20 and the position at which the user wears the sensing device 20 (e.g., the position of the user's heart), and to estimate the user's posture, such as a standing posture, a sitting posture, or a posture lying on one's back (supine position).

[0017] The computer 30 is, for example, a multi-function 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 result of the biosensor 21 from the sensing device 20 via a wireless line or a wired line, and a signal processing device 32 that performs processing to estimate the user's bioinformation from the measurement result of the biosensor 21. The signal processing device 32 includes a processor 321, a memory 322, and an input / output interface 323.

[0018] The signal processing device 32 can, for example, calculate the pulse wave transit time from the photoelectric pulse wave signals measured by the photoelectric pulse wave sensors 211, 212, and estimate the peripheral hemodynamics of the user based on the pulse wave transit time.

[0019] Here, the term pulse wave transit time is generally used to mean the time difference between the peak of an electrocardiogram and the peak of a pulse wave at a measurement site, or the time difference between the peak of a large artery and the peak of a pulse wave at a measurement site. Meanwhile, in this specification, the time difference between the peak of a pulse wave of a capillary in a shallow region of the skin and an arteriole from which the capillary branches is called the pulse wave transit time (peripheral pulse wave transit time). Hereinafter, unless otherwise specified, the pulse wave transit time means the peripheral pulse wave transit time.

[0020] Furthermore, the signal processing device 32 can calculate pulse wave feature amounts from the photoelectric pulse wave signals measured by the photoelectric pulse wave sensors 211, 212, and estimate a peripheral blood pressure index based on the pulse wave feature amounts. Furthermore, the signal processing device 32 can estimate the height of the part of the body where the user is wearing the sensing device 20 and the user's posture, based on the signal from the acceleration sensor 24.

[0021] FIG. 2 is an explanatory diagram showing an external configuration of a sensing device 20 according to an embodiment of the present invention. The sensing device 20 includes a ring-shaped housing 25 configured to be wearable on a user's finger. For example, in the example shown in FIG. 2, the housing 25 has a hollow cylindrical shape. When the sensing device 20 is worn on a user's finger, the biosensor 21 is attached to the inner peripheral surface of the housing 25 (the inner surface of the hollow cylinder) so that the pad of the user's finger faces the biosensor 21. The shape of the housing 25 is not limited to a hollow cylindrical shape, and may be, for example, a cylindrical shape (for example, a finger cot shape) that fits on the user's finger, and may or may not have a bottom of the cylinder (a part that the fingertip abuts against). The sensing device 20 may be provided as, for example, a portable electronic device or a stationary electronic device, and may be configured to measure a photoelectric pulse wave signal by a user placing his or her finger on the biosensor 21.

[0022] 3 is an example of the posture of the user 40 when the biometric information is measured. In this example, the user 40 has the finger on which the sensing device 20 is attached resting at the position of the heart 41, and the sensing device 20 measures the biometric information from the finger of the user 40. Note that the position (measurement position) of the sensing device 20 when measuring the biometric 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 position of the abdomen of the user 40. Furthermore, the posture of the user 40 when measuring the biometric information may be a sitting position or a supine position.

[0023] Fig. 4 explains how the photoplethysmographic signal is acquired by the biosensor 21. Fig. 4 is a schematic cross-sectional view of the biosensor 21 attached adjacent to the body surface S of the user.

[0024] The biosensor 21 has light-emitting elements 2111, 2121 and a light-receiving element 213. The biosensor irradiates light onto the body surface S and receives light absorbed or reflected by the user's epidermal area EP, a plurality of capillaries CA, and arterioles AR from which the capillaries branch. In this embodiment, a case will be described in which one light-receiving element 213 is provided for the light-emitting elements 2111, 2121. In this case, the light-emitting element 2111 and the light-receiving element 213 are the photoplethysmographic sensor 211, and the light-emitting element 2121 and the light-receiving element 213 are the photoplethysmographic sensor 212. Note that a light-receiving element may be provided for each of the light-emitting elements 2111, 2121.

[0025] The light emitting element 2111 is, for example, an LED or 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 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 a living body, and the light emitting element 2121 irradiates light in a wavelength range that is relatively weakly absorbed in a living body. The light receiving element 213 is a photodiode or a phototransistor. A signal generated when the light from the light emitting element 2111 is received by the light receiving element 213 is a first photoplethysmographic signal, and a signal generated when the light from the light emitting element 2121 is received by the light receiving element 213 is a second photoplethysmographic signal.

[0026] 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 light receiving signal based on the light from the light emitting element 2111 can include more information on the shallow region of the skin than the light receiving signal based on the light from the light emitting element 2121.

[0027] Light emitted from the light-emitting element 2111 is absorbed by the user's epidermal area EP and the capillaries CA on the epidermal area EP side, and the transmitted light or reflected light is detected by the light-receiving element 213. Light emitted from the light-emitting element 2121 is absorbed by the user's epidermal area EP, the capillaries CA, and the arterioles AR located inside the body from the epidermal area EP, and is detected by the light-receiving element 213. In Fig. 4, the light from the light-emitting element 2111 is diagrammatically shown as light along an optical path P1, and the light from the light-emitting element 2121 is diagrammatically shown as light along an optical path P2.

[0028] Next, the pulse wave feature amount will be described with reference to Fig. 5. In the following description, data measured by a finger-worn sensing device 20 using a green wavelength (approximately 525 nm) LED as the light-emitting element 2111, a near-infrared wavelength (approximately 940 nm) LED as the light-emitting element 2121, and a silicon photodiode as the light-receiving element 213 will be shown and described.

[0029] Reference numeral 51 denotes a velocity pulse wave signal obtained by first-order differentiation of a photoelectric pulse wave (photoelectric volume pulse wave) signal. Reference numeral 52 denotes an acceleration pulse wave signal obtained by second-order differentiation of the photoelectric pulse wave signal. 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 figure. Reference numeral 53 denotes a photoelectric pulse wave signal. As the pulse wave feature amount, for example, the peak time difference of 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-width, the ratio of the positive side area to the negative side area of ​​the a-e wave portion of the acceleration pulse wave signal 52, the degree of agreement between the measured pulse wave waveform and a template of the pulse wave waveform, and the like can be used. In addition, as the pulse wave feature amount, not only the pulse wave feature amount for each beat but also the average value and standard deviation of the pulse wave feature amount for several beats to several tens of beats can be used.

[0030] Among the pulse wave features, features that are easily affected by the contact state between the biosensor 21 and the skin and pressure, for example, are features related to signal strength, such as the pulse wave height and the heights of the a, b, c, d, and e waves of the accelerated pulse wave. Compared to such pulse wave features, features that are less affected by the contact state between the biosensor 21 and the skin and pressure, are pulse wave features related to time, such as the peak times of the a, b, c, d, and e waves. By calculating an index value indicating the degree of the peripheral blood flow rate or the degree of the peripheral blood pressure of the user from such time-related pulse wave features, it is possible to make it less affected by the contact state between the biosensor 21 and the skin and pressure. In this specification, an index indicating the degree of the peripheral blood flow rate or the degree of the peripheral blood pressure is called a peripheral hemodynamic index. In addition, unless otherwise specified, blood flow rate means peripheral blood flow rate.

[0031] Generally, peripheral blood pressure drops due to vascular resistance between the wrist and the periphery compared to systolic blood pressure measured at the wrist. When the height of the measurement site from the heart is changed only, the vascular resistance between the wrist and the periphery can be considered to be almost constant, so the peripheral blood pressure is proportional to the systolic blood pressure at the wrist. When the height of the measurement site from the heart is changed only, the peripheral blood pressure index is considered to be almost proportional to the systolic blood pressure.

[0032] 6 shows an acceleration pulse wave signal 61 generated based on the first photoelectric pulse wave signal and an acceleration pulse wave signal 62 generated based on the second photoelectric pulse wave signal. The difference between the time when the a-wave of acceleration pulse wave signal 61 reaches its peak and the time when the a-wave of acceleration pulse wave signal 62 reaches its peak is the pulse wave propagation time T. The difference in the times when the peaks occur is for the following reason. First, the pulse wave sent out from the heart passes through an artery and reaches an arteriole, then branches off and reaches the capillaries. As a result, there is a time difference between the time when the pulse wave from the heart reaches the arteriole and the capillaries, and a difference occurs in the time when the acceleration pulse wave signal reaches its peak.

[0033] FIG. 7 is a graph comparing the pulse wave propagation time and the DC component of the first photoelectric pulse wave in the case of FIG. 6. A curve 71 showing the change in the pulse wave propagation time and a curve 72 showing the change in the DC component of the first photoelectric pulse wave show that there is a correlation between the pulse wave propagation time and the DC component of the first photoelectric pulse wave. Here, a large DC component of the first photoelectric pulse wave means that the light is absorbed by the blood less. In this example, a decrease in peripheral blood volume due to a temporary decrease in cardiac output is shown as an increase in the DC component of the first photoelectric pulse wave. When the DC component of the first photoelectric pulse wave showing the peripheral blood volume increases, the correlated pulse wave propagation time also increases, so an increase in the pulse wave propagation time shows a decrease in peripheral blood volume, that is, a deterioration in blood circulation. The DC component of the first photoelectric pulse wave itself changes depending on the contact state and the pressing state between the sensing device 20 and the skin, so it varies for each measurement. Therefore, it is difficult to directly use the DC component of the first photoelectric pulse wave to estimate peripheral hemodynamics. On the other hand, the pulse wave transit time, which is measured with little variance, can be used to estimate peripheral hemodynamics.

[0034] 8 is a graph in which the pulse wave transit time of a subject measured by the biological information measuring system 10 is plotted against the systolic blood pressure of the subject. Each point on the graph corresponds to data for one subject, and there are 21 pieces of data.

[0035] The biological information measurement system 10 measures the first photoelectric pulse wave signal and the second photoelectric pulse wave signal for 30 seconds while the subject (user) holds the sensing device 20 at chest (heart) height. The biological information measurement system 10 calculates the pulse wave transit time at each measurement time based on the first photoelectric pulse wave signal and the second photoelectric pulse wave signal at each measurement time. The biological information measurement system 10 calculates the average value of the pulse wave transit time at each measurement time as the subject's pulse wave transit time. In addition, the systolic blood pressure is the systolic blood pressure measured by a cuff-type blood pressure monitor attached to the subject's wrist. As shown in FIG. 8, there is no clear correlation between the pulse wave transit time and the systolic blood pressure. In other words, it is difficult to estimate peripheral hemodynamics based on the pulse wave transit time from the measurement of blood pressure at the wrist.

[0036] On the other hand, as shown in Fig. 9, the peripheral hemodynamics can be estimated by comparing the pulse wave transit time with the peripheral blood pressure index, which is an index value indicating the degree of the user's peripheral blood pressure calculated from the peripheral pulse wave feature amount. Fig. 9 is a graph in which the pulse wave transit time is plotted against the peripheral blood pressure index when the subject holds the sensing device 20 at chest height. The value of the peripheral blood pressure index changes in conjunction with the peripheral blood pressure.

[0037] Figure 9 shows that the pulse wave transit time increases rapidly when the peripheral blood pressure index is equal to or less than about 7. This suggests that a decrease in the peripheral blood pressure index, i.e., a drop in peripheral blood pressure, causes a decrease in pulse wave velocity, which in turn causes an increase in pulse wave transit time.

[0038] In the bioinformation measuring system 10, a threshold value for the pulse wave propagation time is set based on the variation of the pulse wave propagation time relative to the peripheral blood pressure index, and the peripheral hemodynamics of the user can be estimated based on the threshold value. For example, since the pulse wave propagation time is about 0.02 sec or less when the peripheral blood pressure index is in a range greater than about 7, the threshold value for the pulse wave propagation time can be set to 0.02 sec. When the pulse wave propagation time measured in the bioinformation measuring system 10 exceeds this threshold value, the peripheral hemodynamics of the user can be estimated to be poor. In this case, in the example of FIG. 9, it is estimated that the peripheral hemodynamics of 9 out of 21 people is poor.

[0039] It is possible to determine the peripheral hemodynamics of a user based only on the pulse wave transit time. However, the pulse wave transit time varies depending on the length of the path along which the pulse wave propagates. The length of the path varies depending on the position at which the user wears the sensing device 20 and the user's biological characteristics, such as the cross-sectional area of ​​the finger.

[0040] To eliminate the variation according to the path length, it is desirable to determine the pulse wave velocity obtained by dividing the path length by the pulse wave transit time. However, it is very difficult to measure the length of the arterioles and capillaries (pulse wave transit path) through which the pulse wave is propagated. Therefore, by setting a condition using a peripheral blood pressure index in addition to the pulse wave transit time, it is possible to estimate peripheral hemodynamics with greater accuracy while suppressing the influence of the variation in the pulse wave transit time as described above.

[0041] A graph in which the inverse of the pulse wave transit time is plotted against the peripheral blood pressure index is shown in Fig. 10. As shown in Fig. 10, the data points of each subject are distributed on the plot plane of Fig. 10 so that they can be approximated by a linear equation.

[0042] As an example, the condition using the pulse wave transit time and the peripheral blood pressure index can be determined based on the area defined by a linear conditional expression that connects the points (12,0) and (0,100) of (peripheral blood pressure index, inverse of pulse wave transit time). In other words, whether the peripheral hemodynamics is good or bad is estimated depending on which area of ​​the plot plane defined by the conditional expression the point on the plot plane determined by the peripheral blood pressure index and the inverse of the pulse wave transit time of the user is located. For example, in the case of FIG. 10, if the point is closer to the origin of the plot plane than the line C1 of the conditional expression, the peripheral hemodynamics is estimated to be bad, and if not, the peripheral hemodynamics is estimated to be good. In the example of FIG. 10, the peripheral hemodynamics of 9 out of 21 people is estimated to be bad.

[0043] The advantages of considering the peripheral blood pressure index in this way will be described below. For example, the virtual data point P in Fig. 10 can be estimated to have poor peripheral hemodynamics when a threshold value (line C2) in which the pulse wave transit time is greater than 0.02 sec (the reciprocal is less than 50) is used as in Fig. 9.

[0044] However, as described above, the pulse wave transit time varies among users. Even if the pulse wave transit time is large like data point P, for example, the cause may be a misalignment in the position where the sensing device 20 is worn, and it may be estimated that the actual user has a high peripheral blood pressure index and good peripheral hemodynamics. On the other hand, when estimating peripheral hemodynamics using conditions based on the pulse wave transit time and peripheral blood pressure index, the user corresponding to data point P is estimated to have good peripheral hemodynamics.

[0045] The validity of the above-mentioned method for estimating peripheral hemodynamics will be explained with reference to Figures 11 and 12. Figure 11 is a graph plotting the same data as in Figure 9 with diabetic patients as black circles and healthy subjects as white circles. Figure 12 is a graph plotting the same data as in Figure 10 with diabetic patients as black circles and healthy subjects as white circles.

[0046] In diabetes, blood vessels are damaged and vascular endothelial function is reduced due to a prolonged hyperglycemic state, which often leads to the progression of arteriosclerosis and peripheral vascular disorders. Peripheral vascular disorders include the deterioration of peripheral hemodynamics. In both cases of Figures 11 and 12, data that are estimated to have poor peripheral hemodynamics based on thresholds or conditions are almost all diabetic patients. In other words, both the estimation of peripheral hemodynamics based on the thresholds of pulse wave transit time shown in Figure 11 and the estimation of peripheral hemodynamics based on conditions related to pulse wave transit time and peripheral blood pressure index shown in Figure 12 were successful in estimating actual patients, which shows the validity of this method.

[0047] Next, a description will be given of fluctuations in the estimation results of peripheral hemodynamics depending on the height position of the sensing device 20 relative to the user.

[0048] Fig. 13 is a graph plotting the pulse wave transit time and peripheral blood pressure index when the subject is in a sitting position and the sensing device 20 is brought close to the subject's head. Fig. 14 is a graph plotting the inverse of the pulse wave transit time and peripheral blood pressure index in the same case.

[0049] Fig. 15 is a graph plotting the pulse wave transit time and peripheral blood pressure index when the subject is in a sitting position and the sensing device 20 is brought close to the subject's abdomen. Fig. 16 is a graph plotting the inverse of the pulse wave transit time and peripheral blood pressure index in the same case.

[0050] Comparing Figures 9, 13, and 15 or Figures 10, 14, and 16, respectively, as the relative height of the sensing device 20 to the subject's heart increases, the data with a high peripheral blood pressure index decreases and the data with a high pulse wave transit time increases. This indicates that as the height of the finger, which is the measurement site to which the sensing device 20 is attached, increases, the peripheral blood pressure decreases due to the pressure caused by the difference in height to the heart, and the pulse wave transit time increases. On the other hand, regardless of the height, the peripheral blood pressure index value at which the pulse wave transit time increases sharply is about 7, and remains almost unchanged. In other words, the fluctuation in the threshold value of the pulse wave transit time for estimating peripheral hemodynamics is small.

[0051] The accuracy of estimating peripheral hemodynamics can be improved by measuring the photoplethysmographic signal in a plurality of positions with different relative heights of the sensing device 20 with respect to the heart. For example, (a) the pulse wave propagation time (first pulse wave propagation time) and peripheral hemodynamics (first peripheral hemodynamics) can be estimated based on the photoplethysmographic signal measured at chest height, (b) the pulse wave propagation time (second pulse wave propagation time) and peripheral hemodynamics (second peripheral hemodynamics) can be estimated based on the photoplethysmographic signal measured at head height, and (c) the final peripheral hemodynamics can be estimated based on the first peripheral hemodynamics and the second peripheral hemodynamics.

[0052] By estimating the peripheral hemodynamics in this way, it becomes possible to estimate the peripheral hemodynamics in a more stepwise manner. For example, in both of the above estimations (a) and (b), there is a first case in which the peripheral hemodynamics is estimated to be good, in either of the above estimations (a) or (b), there is a second case in which the peripheral hemodynamics is estimated to be poor, and in both of the above estimations (a) and (b), there is a third case in which the peripheral hemodynamics is estimated to be poor. In this case, (c) the final estimation of the peripheral hemodynamics is performed so that in the first case, the peripheral hemodynamics is estimated to be good, in the second case, the peripheral hemodynamics is estimated to be relatively poor, and in the third case, the peripheral hemodynamics is estimated to be poor.

[0053] In the above example, the peripheral hemodynamics was estimated using the measurement results of two measurement positions, the chest and the head, but the estimation may be performed using the measurement results of three measurement positions, for example, the chest, the head, and the abdomen. Also, the combination of two measurement positions may be the chest and the abdomen, or the head and the abdomen.

[0054] Furthermore, the multiple postures with different relative heights of the sensing device 20 with respect to the heart may include a posture in which the user lies supine on a flat surface and places the hand on the chest, and a posture in which the user lies supine on a flat surface and 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 higher position than the position of the heart. When the hand is placed on the flat surface, the sensing device 20 is at a lower position than the heart. In this manner, the relative height of the sensing device 20 with respect to the heart can also be varied.

[0055] These postures are easy for users to adopt and can be repeatedly adopted by each user with high reproducibility. Furthermore, by limiting the "abdomen" to the "navel" and the head to the "forehead", for example, the reproducibility can be further improved and the measurement variability for each user can be reduced.

[0056] As described above, the pulse wave transit time and the peripheral blood pressure index change depending on the relative height of the sensing device 20 with respect to the heart. Therefore, in the biological information measurement system 10, the computer 30 may have a function of determining the height of the sensing device 20 from the heart, and the computer 30 may estimate the peripheral hemodynamics when the sensing device 20 is at the height of the user's heart. This makes it possible to limit the relative height of the sensing device 20 with respect to the heart, so that the peripheral hemodynamics can be estimated while suppressing the influence of changes in the pulse wave transit time and the peripheral blood pressure index caused by differences in relative height.

[0057] In addition, in the biological information measurement system 10, the computer 30 may have a function of estimating the amount of change in height of the sensing device 20 based on information from the acceleration sensor 24 of the sensing device 20. The computer 30 may estimate peripheral hemodynamics based on the pulse wave transit time and the amount of change in height. The computer 30 can correct the influence of the height change on the pulse wave transit time based on the amount of change in the height of the sensing device 20 that affects the pulse wave transit time. This improves the estimation accuracy of the peripheral hemodynamics. The computer 30 may estimate peripheral hemodynamics based on the pulse wave transit time, the peripheral blood pressure index, and the amount of change in height.

[0058] In the bioinformation measurement system 10, the sensing device 20 continuously or intermittently measures photoplethysmographic signals from a user who sleeps while wearing the sensing device 20, and the computer 30 estimates only the pulse wave transit time, or the pulse wave transit time and peripheral blood pressure index, and may estimate peripheral hemodynamics and sleep quality from changes over time in these estimated values ​​(e.g., maximum value, frequency of increase, rate of change, amount of change, variance, coefficient of variation, time of maximum or minimum value, etc.).

[0059] During sleep, peripheral blood flow generally increases, shortening the peripheral pulse wave transit time and increasing peripheral blood pressure. If the pulse wave transit time increases or peripheral blood pressure decreases during sleep despite this tendency, it can be inferred that peripheral hemodynamics is poor and sleep quality is poor.

[0060] Peripheral hemodynamics during sleep changes temporarily when posture (supine, lateral, prone, etc.) or hand position changes due to turning over in bed, but such temporary changes do not need to be captured, so there is little need for continuous measurement. Furthermore, continuous measurement consumes more power, but small batteries are desirable for wearable devices, so intermittent measurement is preferable.

[0061] It is desirable to measure at intervals of, for example, 5 to 60 seconds at intervals of 1 to 10 minutes. This makes it possible to detect the effects of fluctuations in REM and non-REM sleep, which are said to repeat in approximately 90-minute cycles in good sleep, as well as midnight awakenings.

[0062] In addition, the pulse wave propagation time varies when the measurement site is moving vigorously or during exercise. Therefore, in the biological information measurement system 10, the computer 30 may determine whether the user is at rest from information based on the acceleration sensor 24 of the sensing device 20, and estimate peripheral hemodynamics by using the pulse wave propagation time when the user is at rest. This allows the peripheral hemodynamics to be estimated while suppressing the influence of fluctuations in the pulse wave propagation time when the user is not at rest, improving the estimation accuracy.

[0063] Furthermore, in the biological information measurement system 10, the computer 30 can determine the user's sleep state from information based on the acceleration sensor 24 of the sensing device 20, thereby determining when the user falls asleep or wakes up. When changes in the pulse wave transit time or peripheral blood pressure index occur, the timing of these changes can be compared with the timing of falling asleep or waking up, so that, for example, changes in the pulse wave transit time or peripheral blood pressure index during wakefulness do not affect the estimation of sleep quality. This improves the accuracy of estimating sleep quality.

[0064] In addition, in the bioinformation measuring system 10, the sensing device 20 measures the photoelectric pulse wave signal continuously or intermittently over a period of one day or more, and the computer 30 estimates only the pulse wave transit time, or the pulse wave transit time and peripheral blood pressure index, and estimates the peripheral hemodynamics and the state of peripheral circulatory disorder (the degree of disorder or signs of disorder) from changes in these estimated values ​​(maximum value, frequency of increase, rate of change, amount of change, variance, coefficient of variation, time of maximum or minimum value, etc.).

[0065] If poor peripheral hemodynamics continues for a long period of time, it may lead to peripheral circulatory disorders. Therefore, the biological information measurement system 10 can estimate the signs of peripheral circulatory disorders by measuring the user's photoelectric pulse wave signal for a long period of time and estimating the peripheral hemodynamics.

[0066] In this case, as with measurements during sleep, there is little need to continuously measure the photoplethysmographic signal, and it is preferable to measure it intermittently. It is preferable to measure for about 5 to 60 seconds at intervals of 1 to 10 minutes. This makes it possible to detect the effects of fluctuations in peripheral hemodynamics due to events such as exercise and meals that affect peripheral hemodynamics.

[0067] 17 is a flowchart showing an example of processing in a hemodynamics estimation method according to an embodiment of the present invention. The processing by the biological information measurement system 10 is performed, for example, by the sensing device 20 and the computer 30 each having an information processing device such as a processor, executing a program stored in a non-temporary storage area of ​​the sensing device 20 and the computer 30.

[0068] In step S1701, sensing device 20 of biological information measurement system 10 measures a photoelectric pulse wave signal from the finger of a user wearing sensing device 20. Specifically, photoelectric pulse wave sensor 211 measures a first photoelectric pulse wave signal, and photoelectric pulse wave sensor 212 measures a second photoelectric pulse wave signal.

[0069] In step S1702, the sensing device 20 transmits the measurement result to the computer 30 of the biological information measurement system 10.

[0070] In step S1703, the computer 30 receives the measurement results of the sensing device 20.

[0071] In step S1704, computer 30 estimates the user's pulse wave transit time. For example, computer 30 calculates a pulse wave feature amount from the photoelectric pulse wave signal measured by biosensor 21, and calculates the user's pulse wave transit time from the calculated pulse wave feature amount.

[0072] In step S1705, the computer 30 estimates the peripheral hemodynamics of the user based on the pulse wave transit time. For example, the computer 30 estimates the peripheral hemodynamics based on a threshold value of the pulse wave transit time stored in a storage unit such as the memory 322.

[0073] FIG. 18 is a flowchart showing another example of the process of the hemodynamics estimation method according to the embodiment of the present invention.

[0074] The processing from steps S1801 to S1804 is the same as the processing from steps S1701 to S1704.

[0075] In step S1805, the computer 30 estimates the user's peripheral blood pressure index. For example, the computer 30 calculates a pulse wave feature amount from the photoelectric pulse wave signal measured by the biosensor 21, and calculates the user's peripheral blood pressure index from the calculated pulse wave feature amount.

[0076] In step S1806, the computer 30 estimates the peripheral hemodynamics of the user based on the pulse wave transit time and the peripheral blood pressure index. For example, the computer 30 estimates the peripheral hemodynamics based on conditions for the pulse wave transit time and the peripheral blood pressure index stored in a storage unit such as the memory 322.

[0077] The biological information measuring system 10 may further determine whether the user is asleep, and may repeat the processes in steps S1701 to S1704 or steps S1801 to S1805 while the user is asleep, continuously or intermittently measure the first photoelectric pulse wave signal and the second photoelectric pulse wave signal of the user multiple times, and estimate the pulse wave transit time or the peripheral blood pressure index multiple times. The biological information measuring system 10 may estimate peripheral hemodynamics and further estimate sleep quality based on the time change of the pulse wave transit time or the peripheral blood pressure index estimated multiple times in step S1705 or step S1806.

[0078] The biological information measuring system 10 may repeat the process of steps S1701 to S1704 or steps S1801 to S1805 throughout the time the user is active throughout the day, continuously or intermittently measure the first photoelectric pulse wave signal and the second photoelectric pulse wave signal of the user multiple times, and estimate the pulse wave transit time or the peripheral blood pressure index multiple times. The biological information measuring system 10 may estimate peripheral hemodynamics and further estimate the state of peripheral circulatory disorder based on the time change of the pulse wave transit time or the peripheral blood pressure index estimated multiple times in step S1705 or step S1806.

[0079] FIG. 19 is a flowchart showing another example of the process of the hemodynamics estimation method according to the embodiment of the present invention.

[0080] In step S1901, the sensing device 20 of the biological information measuring system 10 acquires information used to calculate a first height of a finger of a user wearing the sensing device 20. For example, the sensing device 20 acquires information used to calculate 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.

[0081] In step S1902, sensing device 20 measures a photoplethysmographic signal from the finger of a user wearing sensing device 20. Specifically, photoplethysmographic sensor 211 measures a first photoplethysmographic signal, and photoplethysmographic sensor 212 measures a second photoplethysmographic signal.

[0082] In step S1903, sensing device 20 transmits information indicating the first height, the first photoelectric pulse wave signal, and the second photoelectric pulse wave signal to computer 30 of biological information measuring system 10 as measurement results.

[0083] In step S1904, the computer 30 receives the measurement results of the sensing device 20.

[0084] In step S1905, the computer 30 calculates the first height based on the information used to calculate the first height, and estimates the user's pulse wave transit time corresponding to the first height. At this time, the computer 30 estimates the pulse wave transit time corresponding to the first height as the first pulse wave transit time.

[0085] In step S1906, the computer 30 estimates the peripheral hemodynamics corresponding to the first height as the first peripheral hemodynamics based on the first pulse wave transit time. The estimation result is temporarily stored in the memory 322, for example.

[0086] In step S1907, the sensing device 20 acquires information used to calculate a second height of the finger of the user wearing the sensing device 20. For example, the sensing device 20 acquires information from the acceleration sensor 24 to be used to calculate the second height, which is a height of the user's finger relative to the heart and is different from the first height.

[0087] The processing from step S1908 to step S1910 is the same as the processing from step S1902 to S1904.

[0088] In step S1911, the computer 30 calculates the second height based on the information used to calculate the second height, and estimates the user's pulse wave transit time corresponding to the second height. At this time, the computer 30 estimates the pulse wave transit time corresponding to the second height as the second pulse wave transit time.

[0089] Note that the acquisition of information used to calculate the height in steps S1901 and S1907 is not necessarily required. For example, the computer 30 may acquire information indicating the first height and the second height of the sensing device 20 from a user or the like, and associate the information with the pulse wave transit time and peripheral hemodynamics.

[0090] In step S1912, the computer 30 estimates the peripheral hemodynamic state corresponding to the second height as the second peripheral hemodynamic state based on the second pulse wave transit time.

[0091] In step S1913, the computer 30 estimates the peripheral hemodynamics of the user based on the first peripheral hemodynamics and the second peripheral hemodynamics.

[0092] An exemplary embodiment of the present invention has been described above. The method executed by the bioinformation measuring system described in this embodiment includes acquiring a first photoelectric pulse wave signal of a capillary in a user's periphery, acquiring a second photoelectric pulse wave signal of the arteriole in the periphery, estimating a pulse wave transit time based on the first photoelectric pulse wave signal and the second photoelectric pulse wave signal, and estimating peripheral hemodynamics of the periphery based on the pulse wave transit time, and the first photoelectric pulse wave signal and the second photoelectric pulse wave signal are acquired from a predetermined finger of the user.

[0093] By estimating the pulse wave propagation time based on a plurality of photoelectric pulse wave signals acquired from a specific finger of a user, it is possible to estimate the pulse wave propagation time while suppressing the variation in the estimated pulse wave propagation time caused by the variation in the length of the arterioles and capillaries, which are the paths through which the pulse wave propagates, due to individual differences between users and the variation in the position at which the device is attached. This allows the pulse wave propagation time to be measured with high accuracy, and peripheral hemodynamics to be estimated based on the pulse wave propagation time, improving the accuracy of estimating peripheral hemodynamics.

[0094] The method may further include estimating a peripheral blood pressure index of the user, and estimating the peripheral hemodynamics may comprise estimating the peripheral hemodynamics based on the pulse wave transit time and the peripheral blood pressure index.

[0095] This makes it possible to estimate peripheral hemodynamics by combining the pulse wave transit time and peripheral blood pressure index, which are correlated with each other, thereby improving the accuracy of estimating peripheral hemodynamics.

[0096] In the above method, estimating the pulse wave transit time may include continuously or intermittently measuring the user's pulse wave transit time multiple times while the user is sleeping, and may further include estimating the user's peripheral hemodynamics and sleep quality from changes in the pulse wave transit time measured while the user is sleeping.

[0097] This allows the quality of sleep to be estimated in addition to peripheral hemodynamics, making it possible to easily estimate the quality of sleep.

[0098] The method may further include determining the sleep state of the user, thereby preventing changes in pulse wave transit time and peripheral blood pressure index during wakefulness from affecting the estimation of sleep quality, thereby improving the accuracy of the estimation of sleep quality.

[0099] In the above method, estimating the pulse wave transit time may include continuously or intermittently measuring the user's pulse wave transit time multiple times over a period of one day or more, and may further include estimating the user's peripheral hemodynamics and peripheral circulatory disorder state from changes in the user's pulse wave transit time measured over a period of one day or more.

[0100] This makes it possible to estimate the state of peripheral circulatory disorder in addition to peripheral hemodynamics, making it possible to easily estimate the state of peripheral circulatory disorder.

[0101] The method may further include determining whether the user's finger is at the height of the user's heart, estimating the pulse wave transit time may include estimating the pulse wave transit time when the finger is at the height of the heart, and estimating the peripheral hemodynamics may include estimating the peripheral vascular function based on the pulse wave transit time when the finger is at the height of the heart. This enables accurate estimation of peripheral hemodynamics using only the pulse wave transit time when the user's finger is at the height of the heart, or using the pulse wave transit time and a threshold value for the peripheral blood pressure index.

[0102] In the above method, estimating the pulse wave transit time includes estimating a first pulse wave transit time when the user's finger is at a first height and a second pulse wave transit time when the user's finger is at a second height different from the first height, and estimating the peripheral hemodynamics may include estimating the peripheral hemodynamics based on a first peripheral hemodynamics estimated based on the first pulse wave transit time and a second peripheral hemodynamics estimated based on the second pulse wave transit time.

[0103] This makes it possible to estimate peripheral hemodynamics while suppressing the effect of fluctuations in pulse wave transit time due to fluctuations in height on the estimation of peripheral hemodynamics, thereby improving the accuracy of the estimation of peripheral hemodynamics.

[0104] In the above method, the first height and the second height may be either a height when the user is in a seated position and holds the user's hands at the height of the user's chest, a height when the user is in a seated position and holds the user's hands at the height of the user's head, or a height when the user is in a seated position and holds the user's hands at the height of the user's abdomen.

[0105] In the above method, the first height and the second height may be either a height when the user is in a supine position on a flat surface and holds the user's hands at the height of the user's chest, or a height when the user is in a supine position and holds the user's hands at the height of the flat surface.

[0106] The above postures are postures that the user can easily assume and that each user can repeatedly assume with high reproducibility, so that peripheral hemodynamics can be estimated with high reproducibility.

[0107] The method may further include acquiring a change amount between the first height and the second height, and estimating the peripheral hemodynamics may estimate the peripheral hemodynamics based on the pulse wave transit time and the change amount. This makes it possible to suppress the influence of the variation in the estimation result of the pulse wave transit time due to the user's physical characteristics and the fluctuation of the measurement position, thereby improving the estimation accuracy of the peripheral hemodynamics.

[0108] The method may further include determining whether the user is in a resting state, and estimating the peripheral hemodynamics may include estimating the peripheral hemodynamics based on a pulse wave transit time when the user is in a resting state.

[0109] This makes it possible to estimate peripheral hemodynamics based on the pulse wave transit time, the fluctuation of which is stable, thereby improving the accuracy of estimating peripheral hemodynamics.

[0110] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified / improved without departing from the spirit thereof, and equivalents are also included in the present invention. That is, those in which a person skilled in the art appropriately changes the design of each embodiment are also included in the scope of the present invention as long as they have the characteristics of the present invention. For example, the elements and their arrangements, conditions, shapes, sizes, etc. of each embodiment are not limited to those exemplified, and can be appropriately changed. In addition, each embodiment is an example, and it goes without saying that partial replacement 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 characteristics of the present invention. [Explanation of symbols]

[0111] 10... Biometric information measuring system, 20... Sensing device, 21... Biometric sensor, 211, 212... Photoelectric pulse wave sensor, 2111, 2121... Light emitting element, 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 vital sign measurement system, Obtaining a first photoplethysmogram signal of a peripheral capillary of a user; obtaining a second photoplethysmographic signal of the peripheral arteriole; estimating a pulse wave transit time based on the first photoelectric pulse wave signal and the second photoelectric pulse wave signal; and estimating peripheral hemodynamics of the periphery based on the pulse wave transit time; The method, wherein the first photoplethysmogram signal and the second photoplethysmogram signal are obtained from a given finger of the user.

2. 2. The method of claim 1 , estimating a peripheral blood pressure index of the user, The method, wherein estimating the peripheral hemodynamics comprises estimating the peripheral hemodynamics based on the pulse wave transit time and the peripheral blood pressure index.

3. 3. The method according to claim 1 or 2, estimating the pulse wave transit time includes continuously or intermittently measuring the pulse wave transit time of the user a plurality of times while the user is sleeping; The method further includes estimating the peripheral hemodynamics and sleep quality of the user from changes in the pulse wave transit time measured during the user's sleep.

4. 4. The method of claim 3, The method further comprising determining a sleep state of the user.

5. 2. The method of claim 1 , estimating the pulse wave transit time includes continuously or intermittently measuring the pulse wave transit time of the user a plurality of times over a period of one day or more; The method further includes estimating the peripheral hemodynamics and peripheral circulatory disorder state of the user from changes in the pulse wave transit time measured over a period of one day or more of the user.

6. 2. The method of claim 1 , determining whether the user's finger is at heart level of the user; estimating the pulse wave transit time includes estimating the pulse wave transit time when the finger is at heart level; The method, wherein estimating the peripheral hemodynamics includes estimating the peripheral hemodynamics based on the pulse wave transit time when the finger is at heart level.

7. 2. The method of claim 1 , estimating the pulse wave transit time includes estimating a first pulse wave transit time when the user's finger is at a first height and a second pulse wave transit time when the user's finger is at a second height different from the first height, the estimating the peripheral hemodynamics includes estimating the peripheral hemodynamics based on first peripheral hemodynamics estimated based on the first pulse wave transit time and second peripheral hemodynamics estimated based on the second pulse wave transit time.

8. 8. The method of claim 7, The first height and the second height are the height when the user is in a sitting position and holds the user's hands at the height of the user's chest; the height of the user when seated and holding the user's hands at the height of the user's head; or when the user is in a seated position with the user's hands at the height of the user's abdomen.

9. 8. The method of claim 7, The first height and the second height are the height of the user when lying on his / her back on a flat surface with the user's hands held at the height of the user's chest; or when the user is in the supine position and holds the user's hands at the same height as the flat surface.

10. 8. The method of claim 7, obtaining an amount of change between the first height and the second height; The method, wherein estimating the peripheral hemodynamics includes estimating the peripheral hemodynamics based on the pulse wave transit time and the amount of change.

11. 2. The method of claim 1 , determining whether the user is in a resting state; The method, wherein estimating the peripheral hemodynamics includes estimating the peripheral hemodynamics based on the pulse wave transit time when the user is in a resting state.

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