Vascular endothelial function evaluation system and vascular endothelial function evaluation device

Abstract

In the present invention, a pulse wave measurement unit generates a pulse wave signal from the result of measurement by a pulse wave sensor attached to a site that is further from the heart than a pressure application site at which a pressure is applied in order to tourniquet blood flow. A peripheral blood pressure index calculation unit calculates a peripheral blood pressure index relating to the steepness of the rise, in each beat, of the pulse wave signal generated by the pulse wave measurement unit. A vascular endothelial function evaluation unit evaluates vascular endothelial function on the basis of a value calculated for the peripheral blood pressure index applicable from the point in time at which the tourniquet is released to when the evaluation time has elapsed.

Description

[Technical Field]

[0001] The present invention provides a vascular endothelial function evaluation system, and Vascular endothelial function evaluation device Place Regarding. [Background technology]

[0002] Vascular endothelial cells are responsible for contracting and relaxing the blood vessel wall, adhering inflammatory cells to the blood vessel wall, regulating vascular permeability and the coagulation-fibrinolysis system. These functions of vascular endothelial cells (vascular endothelial function) are impaired by various lifestyle-related diseases such as hypertension, diabetes, dyslipidemia, and obesity. Known methods for evaluating vascular endothelial function include the flow-mediated vasodilation test (FMD) and the EndoPAT test.

[0003] Also, a device for evaluating vascular endothelial function using a cuff-type sphygmomanometer is known (Patent Document 1). This evaluation device evaluates vascular endothelial function based on pulse waves detected by a pressure sensor connected to the cuff of the cuff-type sphygmomanometer in any two periods before, during, or after pressure stimulation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-126487 Summary of the Invention [Problem to be solved by the invention]

[0005] A conventional vascular endothelial function evaluation device (Patent Document 1) uses pulse waves acquired by a pressure sensor connected to a cuff to evaluate vascular endothelial function. The pulse waves acquired by this pressure sensor mainly provide information on large blood vessels, but do not provide information on small blood vessels such as arterioles or capillaries.

[0006] The object of the present invention is to provide a vascular endothelial function evaluation system capable of evaluating vascular endothelial function including arterioles and capillaries, and Vascular endothelial function evaluation device Place The purpose is to provide. [Means for solving the problem]

[0007] According to one aspect of the present invention, From the measurement results of the pulse wave sensor attached to a site farther from the heart than the site where pressure is applied for avascularization, , arterioles or capillaries a pulse wave measuring unit that generates a pulse wave signal; a peripheral blood pressure index calculation unit that calculates a peripheral blood pressure index related to the steepness of the rising edge of the pulse wave signal generated by the pulse wave measurement unit for each beat; a vascular endothelial function evaluation unit that evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when avascularization is released until an evaluation time has elapsed; 、 an output unit that outputs the evaluation result of the vascular endothelial function by the vascular endothelial function evaluation unit; Equipped with 、 The peripheral blood pressure index includes information about the width of the first peak that appears within one beat of a velocity pulse wave obtained by first-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measurement unit. A vascular endothelial function evaluation system is provided.

[0008] According to another aspect of the present invention, From the measurement results of a pulse wave sensor attached to a site farther from the heart than the site where pressure is applied for avascularization , arterioles or capillaries a pulse wave measuring device for generating a pulse wave signal; a control terminal that calculates a peripheral blood pressure index related to the steepness of the rise of the pulse wave signal generated by the pulse wave measuring device for each beat, evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when avascularization is released until an evaluation time has elapsed, and outputs the evaluation results; Equipped with 、 The peripheral blood pressure index includes information about the width of the first peak that appears within one beat of a velocity pulse wave obtained by first-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measuring device. A vascular endothelial function evaluation device is provided. [Effects of the Invention]

[0010] Peripheral blood pressure indices include information on blood flow in peripheral blood vessels such as arterioles and capillaries. Vascular endothelial function is evaluated based on the calculated values ​​of peripheral blood pressure indices from the time when avascularization is released until the evaluation time has elapsed, so vascular endothelial function including information on peripheral blood vessels can be evaluated. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram of a vascular endothelial function evaluation system according to a first embodiment. [Figure 2] FIG. 2A is a perspective view of a pulse wave measuring device, and FIG. 2B is a schematic diagram of a photoplethysmographic sensor and biological tissue in a state where the pulse wave measuring device is worn on a finger. [Figure 3] FIG. 3 is a flowchart showing the procedure of the method for evaluating vascular endothelial function according to the first embodiment. [Figure 4] FIG. 4 is a graph showing an example of a pulse wave, a velocity pulse wave, and an acceleration pulse wave. [Figure 5] FIG. 5 is a graph showing an example of a pulse wave and an acceleration pulse wave. [Figure 6] Figures 6A and 6B are graphs showing the relationship between the peripheral blood pressure index "1 / VE0.5" value calculated from the pulse wave measured when the height from the heart to the measurement site (finger) is changed and when the measurement site is adjusted to chest height and the area around the elbow on the side where the measurement site (finger) is located is cooled, and the systolic blood pressure measured at the wrist. [Figure 7] Figures 7A and 7B are graphs showing the relationship between the peripheral blood pressure index "a / S" value calculated from the pulse wave measured when the height from the heart to the measurement site (finger) is changed and when the measurement site is adjusted to chest height and the area around the elbow on the side where the measurement site (finger) is located is cooled, and the systolic blood pressure measured at the wrist. [Figure 8] Figures 8A and 8B are graphs showing the relationship between the peripheral blood pressure index "(ab) / (ad)" value calculated from the pulse wave measured when the height from the heart to the measurement site (finger) is changed and when the measurement site is adjusted to chest height and the area around the elbow on the side where the measurement site (finger) is located is cooled, and the systolic blood pressure measured at the wrist. [Figure 9] FIG. 9 is a graph showing a pulse wave acquired from subject A whose blood pressure is within the normal range. [Figure 10] 10A to 10F are graphs showing the time changes of peripheral blood pressure indices obtained from the pulse wave shown in FIG. [Figure 11] FIG. 11 is a graph showing the pulse wave obtained from another subject B whose blood pressure is within the normal range. [Figure 12] 12A to 12F are graphs showing the time changes of peripheral blood pressure indices obtained from the pulse wave shown in FIG. [Figure 13] FIG. 13 is a graph showing a pulse wave acquired from subject C whose blood pressure is above the normal range. [Figure 14] 14A, 14B, and 14C are graphs showing changes over time in peripheral blood pressure indices determined from the pulse wave shown in FIG. [Figure 15] FIG. 15 is a graph showing the pulse wave measured for subject A whose pulse wave was measured in FIG. 9, with the duration of occlusion of the artery being prolonged. [Figure 16] 16A to 16F are graphs showing the time changes of peripheral blood pressure indices obtained from the pulse wave shown in FIG. [Figure 17] FIG. 17 is a flowchart showing the procedure of the method for evaluating vascular endothelial function according to the second embodiment. [Figure 18] FIG. 18 is a flowchart showing the procedure of a method for evaluating vascular endothelial function according to a modified example of the second embodiment. [Figure 19] 19A and 19B are graphs showing the time changes in amplitude S (FIG. 5) and peripheral blood pressure index "a / S" obtained from the pulse wave of subject A shown in FIG. [Figure 20] FIG. 20 is a block diagram of a vascular endothelial function evaluation system according to the fourth embodiment. [Figure 21] FIG. 21 is a schematic diagram of a user wearing a measuring device when evaluating vascular endothelial function using the vascular endothelial function evaluation system according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] [First Example] A vascular endothelial function evaluation system and a vascular endothelial function evaluation method according to a first embodiment will be described with reference to FIGS. 1 to 14C.

[0013] FIG. 1 is a block diagram of a vascular endothelial function evaluation system according to a first embodiment. The vascular endothelial function evaluation system according to the first embodiment includes a pulse wave measurement device 20, a control terminal 30, a server 40, and a cuff-type sphygmomanometer 50. The pulse wave measurement device 20, the control terminal 30, the server 40, and the cuff-type sphygmomanometer 50 each include communication units 24, 33, 44, and 55, and perform data communication with each other via these communication units. For example, communication between the pulse wave measurement device 20 and the control terminal 30 and communication between the cuff-type sphygmomanometer 50 and the control terminal 30 uses wireless communication conforming to a short-range wireless communication standard such as Bluetooth (registered trademark). Communication between the control terminal 30 and the server 40 uses a wireless LAN or the like.

[0014] The pulse wave measurement device 20 includes a photoplethysmographic sensor 21, a light-emission control unit 22, a pulse wave measurement unit 23, and a communication unit 24. The photoplethysmographic sensor 21 includes a light-emitting element and a light-receiving element. The light-receiving element receives light that is output from the light-emitting element and passes through biological tissue, and measures the intensity of the received light. The light-emission control unit 22 controls the light emission of the light-emitting element. The pulse wave measurement unit 23 generates a pulse wave signal based on the measured value of the light intensity from the photoplethysmographic sensor 21.

[0015] The control terminal 30 includes a control unit 31, an output unit 32, and a communication unit 33. For example, a smartphone can be used as the control terminal 30. The smartphone can be used as the control terminal 30 by installing an application program on the smartphone.

[0016] The control unit 31 receives a pulse wave signal from the pulse wave measurement device 20 and transfers the received pulse wave signal to the server 40. The control unit 31 also receives the evaluation results of the vascular endothelial function from the server 40 and outputs the evaluation results to the output unit 32. The output unit 32 includes, for example, a display device that displays images. The evaluation results of the vascular endothelial function are displayed on the display device as images or text.

[0017] The server 40 includes a pulse wave feature amount calculation unit 41, a peripheral blood pressure index calculation unit 42, a vascular endothelial function evaluation unit 43, and a communication unit 44. The pulse wave feature amount calculation unit 41 calculates various feature amounts of the waveform of the pulse wave signal received from the control terminal 30 (hereinafter, sometimes simply referred to as the "pulse wave"). The peripheral blood pressure index calculation unit 42 calculates a peripheral blood pressure index related to the steepness of the rising edge of the pulse wave for each beat, based on the feature amount of the pulse wave. The peripheral blood pressure index can be used as an index representing the magnitude of peripheral blood pressure. The peripheral blood pressure index will be described in detail later with reference to Figures 4 to 8B.

[0018] The vascular endothelial function evaluation unit 43 evaluates the vascular endothelial function based on the time-dependent change in the peripheral blood pressure index, and transmits the evaluation result to the control terminal 30. Furthermore, the evaluation result is stored.

[0019] The cuff-type sphygmomanometer 50 includes an inflating unit 51, a pulse detection unit 52, a control unit 53, a blood pressure calculation unit 54, and a communication unit 55. For example, an automatic electronic cuff-type sphygmomanometer can be used as the cuff-type sphygmomanometer 50. The control unit 53 receives commands from the control terminal 30 and controls the inflating of the inflating unit 51. The inflating unit 51 includes a cuff. By wrapping the cuff around the user's upper arm and controlling the inflating, avascularization can be started and released. The pulse detection unit 52 detects the pulse at the site where the cuff is wrapped. The blood pressure calculation unit 54 calculates the blood pressure based on the pressure applied to the cuff and the detection result of the pulse detection unit 52.

[0020] FIG. 2A is a perspective view of pulse wave measuring device 20. In the first embodiment, pulse wave measuring device 20 is a ring-shaped device worn on a user's finger. Photoplethysmographic sensor 21 includes two light-emitting elements 21A and 21B and one light-receiving element 21C. The two light-emitting elements 21A and 21B and the one light-receiving element 21C are arranged on the inner surface of ring-shaped wearing member 27. Note that a configuration including only one of light-emitting elements 21A and 21B may also be used.

[0021] With the attachment member 27 attached to the finger, the light-emitting elements 21A and 21B emit light toward the finger. The light-receiving element 21C is attached at a position where light reflected by or transmitted through the living tissue inside the finger is incident.

[0022] The wearing member 27 further incorporates a light emission control unit 22, a pulse wave measurement unit 23, and a communication unit 24. The light emission control unit 22, the pulse wave measurement unit 23, and the communication unit 24 may be configured as a single integrated circuit.

[0023] 2B is a schematic diagram of the photoplethysmographic sensor 21 and biological tissue when the pulse wave measuring device 20 is worn on a finger. Light-emitting elements 21A and 21B and light-receiving element 21C are in contact with a user's body surface 70. Light-emitting elements 21A and 21B irradiate measurement light toward the body surface 70. The irradiated light is absorbed, reflected, or scattered (hereinafter sometimes simply referred to as "reflected") by an epidermal region 71, arterioles 72, and capillaries 73 within the body surface 70. A portion of the light that passes through biological tissue such as the epidermal region 71, arterioles 72, and capillaries 73 is incident on the light-receiving element 21C.

[0024] The arteriole 72 is a thin blood vessel having a diameter of, for example, 20 μm or more and 200 μm or less, and exists between the artery and the capillary 73. Multiple capillaries 73 branch off from the arteriole 72. The capillary 73 is a thin blood vessel having a diameter of, for example, about 10 μm, and connects the artery and the vein. Multiple capillaries 73 are distributed in a region shallower than the region in which the arteriole 72 is distributed. The blood in the artery contains hemoglobin, which has the property of absorbing the light used for measurement. The blood flow rate changes with the beating of the heart, and the amount of light absorbed also changes in accordance with the change in blood flow rate. Therefore, the intensity of the light received by the light receiving element 21C changes with the beating of the heart.

[0025] The light-emitting element 21A may be configured to output light in a wavelength range from blue to yellow-green (450 nm to 570 nm), preferably in a wavelength range from 500 nm to 550 nm. The light-emitting element 21B may output light in a wavelength range from red to near-infrared light, preferably in a wavelength range from 750 nm to 950 nm. The light-emitting elements 21A and 21B may be configured, for example, as light-emitting diodes (LEDs) or vertical-cavity surface-emitting lasers (VCSELs). The light-receiving element 21C may be configured, for example, as a photodiode (PD) or phototransistor.

[0026] Light in the blue to yellow-green wavelength range is highly absorbed by biological tissue. Therefore, a pulse wave acquired using light in the blue to yellow-green wavelength range reflects information from a region shallower than the skin surface, particularly a region shallower than the region where arterioles 72 are distributed and primarily containing capillaries 73. The arrow pointing from light-emitting element 21A to light-receiving element 21C in FIG. 2B does not indicate the path of light propagation, but rather indicates that light output from light-emitting element 21A passes through epidermal region 71 and a region primarily containing capillaries 73 and is incident on light-receiving element 21C. To ensure that information from a region shallower than the region where arterioles 72 are distributed and primarily containing capillaries 73 is reflected in the acquired pulse wave, it is preferable to shorten the distance L1 between light-emitting element 21A and light-receiving element 21C. For example, it is preferable to set distance L1 to 1 mm or more and 3 mm or less.

[0027] Light with a wavelength shorter than 450 nm can damage biological tissue. To avoid damaging biological tissue, it is preferable that the wavelength of light used to measure pulse waves be 450 nm or longer.

[0028] Light in the red to near-infrared wavelength range is less absorbed by biological tissue than light in the blue to yellow-green wavelength range, so pulse waves acquired using light in the red to near-infrared wavelength range reflect information from areas deeper below the skin surface.

[0029] For example, information about the region where capillaries 73 and arterioles 72 are distributed is reflected. The arrow pointing from light-emitting element 21B to light-receiving element 21C shown in Fig. 2B does not indicate the path of light propagation, but rather indicates that light output from light-emitting element 21B passes through the region where not only capillaries 73 but also arterioles 72 are distributed and is incident on light-receiving element 21C. In order to ensure that information about the region where arterioles 72 and capillaries 73 are distributed is significantly reflected in the acquired pulse wave, it is preferable that distance L2 between light-emitting element 21B and light-receiving element 21C be 5 mm or more and 20 mm or less.

[0030] The absorbance of hemoglobin decreases in the wavelength range longer than 950 nm, so it is preferable to use light in the wavelength range of 950 nm or less to acquire a pulse wave signal.

[0031] In the example shown in FIG. 2B, one light receiving element 21C is arranged for two light emitting elements 21A and 21B, but it is also possible to arrange one light receiving element for one light emitting element 21A and another light receiving element for the other light emitting element 21B.

[0032] 3 is a flowchart showing the steps of the vascular endothelial function evaluation method according to the first embodiment. Before evaluation, the user wraps the cuff of the cuff-type blood pressure monitor 50 around one upper arm or wrist. Furthermore, the user wears the pulse wave measuring device 20 (FIG. 2A) on the base of the index finger on the same side as the arm around which the cuff is wrapped. The pulse wave measuring device 20 may be worn on a finger other than the index finger, or may be worn on the tip of the finger.

[0033] First, the control terminal 30 (FIG. 1) controls the pulse wave measuring device 20 (FIG. 1) to start measuring the pulse wave (step SA1). The measured pulse wave is transmitted to the server 40 (FIG. 1). Thereafter, the control terminal 30 controls the cuff-type sphygmomanometer 50 (FIG. 1) to start avascularization and release the avascularization after a certain period of time has elapsed (step SA2).

[0034] The pulse wave feature value calculation unit 41 of the server 40 calculates the pulse wave feature value of the pulse wave waveform for each beat from the release of the avascularization until a predetermined evaluation time has elapsed (step SA3). The length of the evaluation time is set in advance. Thereafter, the peripheral blood pressure index calculation unit 42 of the server 40 calculates the peripheral blood pressure index for each beat of the pulse wave based on the calculated values ​​of the pulse wave feature value from the release of the avascularization until the evaluation time has elapsed (step SA4). This allows the time change of the peripheral blood pressure index within the evaluation time to be determined.

[0035] Next, the vascular endothelial function evaluation unit 43 of the server 40 evaluates the vascular endothelial function based on the multiple calculated values ​​of the peripheral blood pressure index (step SA5). The vascular endothelial function evaluation unit 43 transmits the evaluation result to the control terminal 30. The control unit 31 of the control terminal 30 outputs the evaluation result received from the server 40 to the output unit 32 (step SA6). For example, the vascular endothelial function is evaluated on a five-level scale from level 1 to level 5.

[0036] Next, various feature quantities of a pulse wave will be described with reference to FIGS.

[0037] FIG. 4 is a graph showing an example of a pulse wave, a velocity pulse wave, and an acceleration pulse wave. The pulse wave feature calculation unit 41 (FIG. 1) of the server 40 performs first-order and second-order differentiation of the pulse wave. The waveforms obtained by first-order and second-order differentiation of the pulse wave are referred to as the velocity pulse wave and acceleration pulse wave, respectively. For example, the velocity pulse wave is obtained by numerically differentiating the intensity of the pulse wave, which is discretely distributed at time intervals corresponding to the sampling rate, at the time intervals corresponding to the sampling rate. Furthermore, the magnitude of the velocity pulse wave is numerically differentiated to obtain the acceleration pulse wave.

[0038] The horizontal axis in Figure 4 represents time in units of seconds, the left vertical axis represents the magnitude of the velocity pulse wave and acceleration pulse wave normalized so that the maximum value is 1, and the right vertical axis represents the magnitude of the pulse wave in arbitrary units. The solid line, long-dashed line, and short-dashed line in the graph shown in Figure 4 represent the pulse wave, velocity pulse wave, and acceleration pulse wave, respectively. Generally, five peaks appear in an acceleration pulse wave within one beat. The first, second, third, fourth, and fifth peaks within one beat are called the a-wave, b-wave, c-wave, d-wave, and e-wave, respectively.

[0039] The full width at half maximum of the first upward peak of the velocity pulse wave is labeled "VE0.5." The difference between the peak values ​​of the a wave and the b wave is labeled "ab," and the difference between the peak values ​​of the a wave and the d wave is labeled "ad." A depression called the incisor (IC) appears slightly behind the maximum peak of the pulse wave.

[0040] FIG. 5 is a graph showing an example of a pulse wave and an acceleration pulse wave. The horizontal axis represents time, the left vertical axis represents the amplitude of the pulse wave in arbitrary units, and the right vertical axis represents the amplitude of the acceleration pulse wave in arbitrary units. Five divisions on the horizontal axis correspond to 0.2 s. The peak value of the a-wave of the acceleration pulse wave is labeled "a," and the amplitude of the pulse wave is labeled "S." The amplitude S of the pulse wave corresponds to the difference between the minimum and maximum values ​​after waveform correction is performed so that the minimum values ​​of the pulse wave for two consecutive pulse beats are the same.

[0041] Next, peripheral blood pressure indicators will be explained. In this specification, "peripheral blood pressure" is defined as the blood pressure in peripheral arterioles and capillaries. Peripheral blood pressure is sometimes used to mean the blood pressure at the wrist or ankle measured with a cuff-type sphygmomanometer, but the blood pressure at the wrist or ankle is measured in a large artery (such as the radial artery) and is different from the peripheral blood pressure defined in this specification. Blood pressure in blood vessels decreases as one progresses from large arteries to arterioles and capillaries. The degree to which blood pressure decreases varies depending on the measurement site, the individual's vascular condition (presence or absence of arteriosclerosis, etc.), mental state (state of the autonomic nervous system, etc.), environment (temperature, presence or absence of noise, etc.), clothing, etc.

[0042] Among the features of the pulse wave, an index that is effective for determining peripheral blood pressure is adopted as the peripheral blood pressure index. The peripheral blood pressure index is considered to have the following characteristics. First, when blood vessels are healthy and vascular resistance remains unchanged, peripheral blood pressure indices have a positive correlation with blood pressure at the upper arm or wrist. Second, when the area around the measurement site is cooled to constrict blood vessels, peripheral blood pressure indices decrease. When blood vessels constrict, peripheral vascular resistance increases, which can cause blood pressure at the upper arm or wrist to rise.

[0043] The following three features are examples of pulse wave features that reflect the above two features of peripheral blood pressure indices. The reciprocal of the full width at half maximum "VE0.5" (hereinafter referred to as "1 / (VE0.5)") The ratio of the peak value a of the a wave of the accelerated pulse wave to the amplitude S of the pulse wave (hereinafter referred to as "a / S"). The ratio of the difference "ab" between the peak values ​​of the a-wave and the b-wave of the accelerated pulse wave to the difference "ad" between the peak values ​​of the a-wave and the d-wave (hereinafter referred to as "(ab) / (ad)"). In this specification, these characteristic quantities of the pulse wave waveform are referred to as “peripheral blood pressure indices.” These peripheral blood pressure indices are related to the steepness of the rising edge of the pulse wave.

[0044] 6A and 6B are graphs showing the relationship between the peripheral blood pressure index "1 / VE0.5" calculated from pulse waves measured when the height of the measurement site (finger) from the heart is changed and when the measurement site is adjusted to chest height and the area around the elbow on the side where the finger is located is cooled, and the systolic blood pressure measured at the wrist. FIGS. 6A and 6B show the results of pulse wave measurements using green light emitted from light-emitting element 21A (FIG. 2A) and near-infrared light emitted from light-emitting element 21B (FIG. 2A), respectively. The pulse wave measured using green light primarily reflects fluctuations in blood flow in capillaries 73 (FIG. 2B), while the pulse wave measured using near-infrared light reflects fluctuations in blood flow in capillaries 73 and arterioles 72 (FIG. 2B).

[0045] The horizontal axis of the graphs in Figures 6A and 6B represents the systolic blood pressure at the wrist in units of mmHg, and the vertical axis represents the peripheral blood pressure index "1 / (VE0.5)" in units of s -1 ]. In each graph, the results of measurements taken for three subjects A, B, and C are shown using triangle, square, and circle symbols, respectively. The three hollow symbols shown for each subject indicate the peripheral blood pressure index "1 / VE0.5" values ​​obtained from pulse waves acquired when the height of the measurement site (finger) was set at navel, chest, and forehead, respectively. The peripheral blood pressure index "1 / VE0.5" values ​​decrease in the order of navel, chest, and forehead. The solid black symbols shown for each subject indicate the peripheral blood pressure index "1 / VE0.5" values ​​obtained from pulse waves acquired when the height of the measurement site was set at chest height and the area around the elbow was cooled.

[0046] Although the degree of correlation varies depending on the subject, it can be seen that when the height of the measurement site is changed, the peripheral blood pressure index "1 / VE0.5" generally has a positive correlation with the systolic blood pressure at the wrist. Furthermore, although there are some exceptions, it can be seen that when the area near the measurement site is cooled to constrict the blood vessels, the peripheral blood pressure index "1 / VE0.5" decreases. This change matches the expected characteristics of the peripheral blood pressure index. Therefore, the peripheral blood pressure index "1 / VE0.5" is considered to be an effective index for estimating peripheral blood pressure.

[0047] The results shown in Figures 6A and 6B indicate that green light is preferable to near-infrared light for measuring the peripheral blood pressure index "1 / VE0.5." Alternatively, the inverse of a parameter representing the width of the maximum peak of the velocity pulse wave may be used as an index instead of the peripheral blood pressure index "1 / VE0.5." Alternatively, a negative exponent of the parameter representing the width of the maximum peak of the velocity pulse wave may be used. More generally, a function may be used as the peripheral blood pressure index, where the parameter representing the width of the maximum peak of the velocity pulse wave is used as a variable, and the value of the function decreases as the width of the peak increases.

[0048] Figures 7A and 7B are graphs showing the relationship between the peripheral blood pressure index "a / S" obtained from the pulse wave measured when the height from the heart to the measurement site (finger) is changed and when the measurement site is adjusted to chest height and the vicinity of the elbow on the side where the finger is located is cooled, and the systolic blood pressure measured at the wrist. Figures 7A and 7B show the measurement results when green light and near-infrared light are used to measure the pulse wave, respectively.

[0049] The horizontal axis of the graphs in Figures 7A and 7B represents systolic blood pressure at the wrist in units of mmHg, and the vertical axis represents the peripheral blood pressure index "a / S" in arbitrary units. The meanings of the symbols in Figures 7A and 7B are the same as those of the symbols in the graphs shown in Figures 6A and 6B.

[0050] The measurement results shown in Figures 7A and 7B show similar trends to those shown in Figures 6A and 6B. Therefore, the peripheral blood pressure index "a / S" is considered to be an effective index for estimating peripheral blood pressure. Furthermore, the results shown in Figures 7A and 7B indicate that green light is preferable to near-infrared light for measuring the peripheral blood pressure index "a / S."

[0051] Instead of the peripheral blood pressure index "a / S," the peripheral blood pressure index may be the product of the peak value a of the a-wave of the accelerated pulse wave raised to a positive power and the amplitude S of the pulse wave raised to a negative power. Alternatively, the peripheral blood pressure index may be calculated based on information regarding the peak value of the a-wave of the accelerated pulse wave and the amplitude of the pulse wave signal. For example, the peripheral blood pressure index may be a function in which the peak value a and the amplitude S are variables, and the value of the function increases as the peak value a increases and decreases as the amplitude S increases.

[0052] Figures 8A and 8B are graphs showing the relationship between the peripheral blood pressure index "(ab) / (ad)" calculated from the pulse wave measured when the height from the heart to the measurement site (finger) is changed and when the measurement site is adjusted to chest height and the vicinity of the elbow on the side where the finger is located is cooled, and the systolic blood pressure measured at the wrist. Figures 8A and 8B show the measurement results when green light and near-infrared light are used to measure the pulse wave, respectively.

[0053] The horizontal axis of the graphs in Figures 8A and 8B represents the systolic blood pressure at the wrist in units of mmHg, and the vertical axis represents the peripheral blood pressure index "(ab) / (ad)." The symbols in Figures 8A and 8B have the same meaning as those in the graphs shown in Figures 6A and 6B.

[0054] The measurement results shown in Figures 8A and 8B show almost the same tendency as the measurement results shown in Figures 6A and 6B. Therefore, the peripheral blood pressure index "(ab) / (ad)" is considered to be an effective index for estimating peripheral blood pressure.

[0055] Instead of the peripheral blood pressure index "(ab) / (ad)", the peripheral blood pressure index may be calculated based on information regarding the difference between the peak values ​​of the a-wave and the b-wave of the accelerated pulse wave and the difference between the peak values ​​of the a-wave and the d-wave. For example, a function may be used as the peripheral blood pressure index, with the difference (ab) between the peak values ​​of the a-wave and the b-wave and the difference (ad) between the peak values ​​of the a-wave and the d-wave as variables, such that the value of the function increases as the value of the difference (ab) increases and decreases as the value of the difference (ad) increases.

[0056] Next, a method for evaluating vascular endothelial function using peripheral blood pressure indices will be described with reference to FIGS. 9 to 14C.

[0057] FIG. 9 is a graph showing pulse waves acquired from subject A, whose blood pressure is within the normal range. The horizontal axis represents the elapsed time from the start of pulse wave measurement in units of [s], and the vertical axis represents the photoplethysmogram (the inverted output from the photoplethysmogram sensor 21 (FIG. 1)) in arbitrary units. The solid lines Gr and Ir in the graph of FIG. 9 represent the measurement results when green light and near-infrared light were used, respectively. Subject A's systolic blood pressure was 115 mmHg, diastolic blood pressure was 76 mmHg, and pulse rate was 65 bpm.

[0058] Approximately 30 seconds after the start of pulse wave measurement, inflation using the cuff-type blood pressure monitor 50 began. It took about 10 seconds from the start of inflation until avascularization began. Once avascularization began, pulse waves could no longer be obtained. Approximately 60 seconds after the start of pulse wave measurement, the pressure in the cuff decreased and pulse waves could be detected. The period during which avascularization was performed is labeled Pa, and the avascularization period is shaded light gray in Figure 9. Measurement was completed approximately 120 seconds after the start of measurement.

[0059] The graphs in Figures 10A to 10F show the change in peripheral blood pressure index over time, and the horizontal axis of these graphs shows the elapsed time in units of [s]. The vertical axis of the graphs in Figures 10A and 10D shows the peripheral blood pressure index "1 / VE0.5" in units of [s]. -1 The vertical axes of the graphs in Figures 10B and 10E represent the peripheral blood pressure index "a / S" in arbitrary units, and the vertical axes of the graphs in Figures 10C and 10F represent the peripheral blood pressure index "(ab) / (ad)." The graphs in Figures 10A to 10C show peripheral blood pressure indices calculated from pulse waves measured using green light, and the graphs in Figures 10D to 10F show peripheral blood pressure indices calculated from pulse waves measured using near-infrared light.

[0060] FIG. 11 is a graph showing the pulse wave obtained from another subject B, whose blood pressure is within the normal range. The horizontal axis represents the elapsed time from the start of pulse wave measurement in units of [s], and the vertical axis represents the photoplethysmogram (the inverted value of the output from the photoplethysmogram sensor 21 (FIG. 1)) in arbitrary units. The solid lines Gr and Ir in the graph of FIG. 11 represent the measurement results when green light and near-infrared light were used, respectively. Subject B's systolic blood pressure was 104 mmHg, diastolic blood pressure was 76 mmHg, and pulse rate was 66 bpm.

[0061] The period of inflation by cuff-type sphygmomanometer 50 from the start to the end of pulse wave measurement is the same as that shown in Fig. 9. The period during which blood vessels are avascularized is labeled Pa, and the avascularization period is shaded light gray in Fig. 11.

[0062] The graphs in Figures 12A to 12F show the change in peripheral blood pressure index over time, and the horizontal axis of these graphs shows the elapsed time in units of [s]. The vertical axis of the graphs in Figures 12A and 12D shows the peripheral blood pressure index "1 / VE0.5" in units of [s]. -1 The vertical axes of the graphs in Figures 12B and 12E represent the peripheral blood pressure index "a / S" in arbitrary units, and the vertical axes of the graphs in Figures 12C and 12F represent the peripheral blood pressure index "(ab) / (ad)." The graphs in Figures 12A to 12C show peripheral blood pressure indexes calculated from pulse waves measured using green light, and the graphs in Figures 12D to 12F show peripheral blood pressure indexes calculated from pulse waves measured using near-infrared light.

[0063] The peripheral blood pressure indices calculated from pulse waves measured using green light and near-infrared light for subject A (graphs from Figures 10A to 10F) and from pulse waves measured using green light for subject B (graphs from Figures 12A, 12B, and 12C) both decreased immediately after the release of avascularization compared to the values ​​before the avascularization. Approximately 10 seconds after the release of avascularization, the peripheral blood pressure indices returned to the values ​​before the avascularization. The decrease in the peripheral blood pressure indices for subject A was more significant than that for subject B. The peripheral blood pressure indices calculated from pulse waves measured using near-infrared light for subject B did not show a clear decrease immediately after the release of avascularization (graphs from Figures 12D, 12E, and 12F).

[0064] The mechanism by which peripheral blood pressure indexes decrease immediately after avascularization is released can be thought of as follows: When vascular endothelial function is normal, releasing avascularization causes the blood vessels to dilate due to the vascular endothelial function. The blood that flows into the large blood vessels is used to dilate the large blood vessels, suppressing the rapid inflow of blood into the downstream capillaries. As a result, the increase in peripheral blood pressure indexes is suppressed for approximately 10 seconds after avascularization is released.

[0065] FIG. 13 is a graph showing pulse waves acquired from subject C, whose blood pressure is above the normal range. This subject is thought to have impaired vascular endothelial function. The horizontal axis of the graph shown in FIG. 13 represents the elapsed time from the start of pulse wave measurement in units of [s], and the vertical axis represents the photoplethysmogram (the inverted value of the output from the photoplethysmogram sensor 21 (FIG. 1)) in arbitrary units. The solid lines Gr and Ir in the graph of FIG. 13 represent the measurement results when green light and near-infrared light were used, respectively. Subject C's systolic blood pressure was 164 mmHg, diastolic blood pressure was 104 mmHg, and pulse rate was 59 bpm.

[0066] The period of inflation by cuff-type sphygmomanometer 50 from the start to the end of pulse wave measurement is the same as that shown in Fig. 9. The period during which blood vessels are avascularized is labeled Pa, and the avascularization period is shaded light gray in Fig. 13.

[0067] The graphs in Figures 14A, 14B, and 14C show the change over time in the peripheral blood pressure index. The horizontal axis of these graphs represents the elapsed time in units of [s]. The vertical axis of the graph in Figure 14A represents the peripheral blood pressure index "1 / VE0.5" in units of [s]. -1 The vertical axis of the graph in FIG. 14B represents the peripheral blood pressure index "a / S" in arbitrary units, and the vertical axis of the graph in FIG. 14C represents the peripheral blood pressure index "(ab) / (ad)." The graphs in FIGS. 14A to 14C show peripheral blood pressure indices calculated from pulse waves measured using green light. Clear pulse wave features could not be calculated from pulse waves acquired using near-infrared light.

[0068] In both cases, the peripheral blood pressure index rose immediately after avascularization was released compared to before the start of avascularization. Approximately 10 seconds after avascularization was released, the peripheral blood pressure index returned to the value it had before the start of avascularization. The mechanism by which the peripheral blood pressure index rose immediately after avascularization was released can be thought of as follows.

[0069] When vascular endothelial function is impaired, the blood vessels do not dilate sufficiently even when avascularization is released. The blood that flows into the large blood vessels flows directly into the downstream arterioles and capillaries, which is thought to increase peripheral blood pressure indexes.

[0070] As shown in the graphs in Figures 9 to 14C, the changes in peripheral blood pressure indexes over time from the release of avascularization until a certain time has elapsed are different between those with normal vascular endothelial function and those with impaired vascular endothelial function. In the first example, the vascular endothelial function is evaluated by utilizing the difference in the behavior of peripheral blood pressure indexes after the release of avascularization.

[0071] Next, we will explain the method for evaluating vascular endothelial function. Peripheral blood pressure indices are calculated based on the pulse wave from the point of release from avascularization until a certain time (hereinafter referred to as evaluation time ET) has elapsed. Figure 10A shows an example of the evaluation time ET. The evaluation time is divided into an anterior period ET1 and a posterior period ET2, and the average value M1 of the peripheral blood pressure indices for the anterior period ET1 and the average value M2 of the peripheral blood pressure indices for the posterior period are calculated.

[0072] Vascular endothelial function is evaluated based on the average peripheral blood pressure index M1 for the anterior period ET1 and the average peripheral blood pressure index M2 for the posterior period ET2. For example, the greater the value obtained by dividing the average peripheral blood pressure index M1 for the anterior period ET1 by the average peripheral blood pressure index M2 for the posterior period ET2 (M1 / M2 is referred to as the vascular endothelial function evaluation index in this specification), the more impaired the vascular endothelial function is considered to be. Furthermore, vascular endothelial function may be evaluated on a five-point scale based on the magnitude of the vascular endothelial function evaluation index M1 / M2. Alternatively, vascular endothelial function may be evaluated based on the difference between the average values ​​M1 and M2.

[0073] Comparing the peripheral blood pressure index before avascularization for subjects A, B, and C, subject A's peripheral blood pressure index was the highest and subject C's peripheral blood pressure index was the lowest. Comparing the magnitude of the vascular endothelial function evaluation index M1 / M2, subject A's vascular endothelial function evaluation index M1 / M2 was the smallest and subject C's vascular endothelial function evaluation index M1 / M2 was the largest. It is thought that subjects with lower vascular endothelial function tend to have lower peripheral blood pressure indexes before avascularization.

[0074] As an example, the evaluation time ET may be set to 40 seconds, and the time point at which 10 seconds have elapsed since the release of avascularization may be divided into an anterior period ET1 and a posterior period ET2. The evaluation time ET and the time point at which the anterior period ET1 and the posterior period ET2 are divided may be determined with reference to data obtained from many subjects.

[0075] For people whose blood pressure is higher than the normal range, it may not be possible to calculate pulse wave feature values ​​from a pulse wave acquired using near-infrared light, as described with reference to Fig. 13. In order to stably calculate pulse wave feature values ​​even for people whose blood pressure is higher than the normal range, it is preferable to acquire the pulse wave using light in the wavelength range from blue to yellow-green.

[0076] Next, the excellent effects of the first embodiment will be described. In the first embodiment, the vascular endothelial function is evaluated by applying pressure to the avascularization site of the upstream artery and measuring the peripheral blood pressure of the downstream arterioles and capillaries, thereby enabling evaluation of the vascular endothelial function from the avascularization site to the arterioles and capillaries.

[0077] Next, a modification of the first embodiment will be described. In the first embodiment, the photoplethysmogram measured by the photoplethysmogram sensor 21 (FIG. 1) was used as the pulse wave for calculating the peripheral blood pressure index, but pulse waves measured by other sensors may also be used, such as pressure pulse waves.

[0078] In the first embodiment, the evaluation time ET (FIG. 10A) is divided into an earlier period ET1 and a later period ET2, and the vascular endothelial function is evaluated based on the ratio of the average values ​​of the peripheral blood pressure indexes in the two periods. However, other methods may be used to evaluate the vascular endothelial function. For example, the vascular endothelial function may be evaluated based on multiple calculated values ​​of the peripheral blood pressure indexes within the evaluation time ET. For example, the vascular endothelial function may be evaluated based on the trend of time-dependent changes in the multiple calculated values ​​of the peripheral blood pressure indexes within the evaluation time ET.

[0079] In the first embodiment, a ring-shaped device worn on a finger is used as pulse wave measuring device 20 (FIG. 2A), but devices of other shapes may also be used. For example, a clip-type device worn on the tip of a finger may also be used. Furthermore, as pulse wave measuring device 20, in addition to a device worn on a finger, a watch-type or wristband-type device worn on the wrist may also be used.

[0080] In the first embodiment, pressure is applied to the upper arm to ablate the blood vessels and the pulse wave is measured at a finger, but the ablation site and the site for measuring the pulse wave are not limited to these. It is also possible to ablate a part of the body by applying pressure and measure the pulse wave at a site farther from the heart than the applied site.

[0081] In the first embodiment, the control terminal 30 (FIG. 1) controls the avascularization and release of the cuff-type sphygmomanometer 50. However, an independent device that does not communicate with the control terminal 30 may be used as the avascularization and release device. For example, a cuff-type sphygmomanometer that does not communicate with the control terminal 30 may be used, or an aneroid sphygmomanometer may be used. In this case, the user or a nearby person may perform the cuff inflation and release operation. The pulse wave feature amount calculation unit 41 (FIG. 1) can detect the start and release points of avascularization from the acquired pulse wave.

[0082] In the first embodiment, as shown in Fig. 1, various functions are shared among the pulse wave measurement device 20, the control terminal 30, and the server 40, but other function sharing arrangements may also be adopted. For example, the function of the pulse wave feature amount calculation unit 41 may be realized by the control terminal 30. Furthermore, all of the functions of the server 40 may be realized by the control terminal 30. Conversely, all of the functions of the control terminal 30 may be realized by the server 40.

[0083] In the first embodiment, vascular endothelial function is evaluated using a peripheral blood pressure index calculated from a pulse wave after release from avascularization. However, instead of a peripheral blood pressure index calculated from a pulse wave during a period ET2 after release from avascularization, a peripheral blood pressure index calculated from a pulse wave for a certain period before avascularization may be used. For example, instead of the average value of the peripheral blood pressure index during a period ET2 after the evaluation time ET shown in FIG. 10A, the average value of the peripheral blood pressure index during a certain period before avascularization may be used. In other words, the average value of the peripheral blood pressure index during a period ET1 may be compared with the average value of the peripheral blood pressure index during a certain period before avascularization.

[0084] Furthermore, vascular endothelial function may be evaluated using both peripheral blood pressure indices calculated from pulse waves during periods ET1 and ET2 after release from avascularization and peripheral blood pressure indices calculated from pulse waves for a certain period before avascularization. For example, vascular endothelial function may be evaluated based on the average values ​​of the peripheral blood pressure indices for the certain period before avascularization and the period ET2, and the average value of the peripheral blood pressure indices for period ET1. The average values ​​of the peripheral blood pressure indices for the certain period before avascularization and the period ET2 may be simple averages, or may be weighted averages depending on the time difference from period ET1.

[0085] Instead of using the peripheral blood pressure index for a certain period before avascularization and the average value of the peripheral blood pressure index for period ET2, the waveforms of the peripheral blood pressure index for a certain period before avascularization and the waveforms of the peripheral blood pressure index for period ET2 may be linearly or curve-approximated, and a representative value of the peripheral blood pressure index for a certain period before avascularization and the peripheral blood pressure index for period ET2 may be calculated based on the approximated line or curve. Vascular endothelial function may be evaluated based on this representative value and the average value of the peripheral blood pressure index for period ET1 after avascularization is released. For example, the value at the midpoint of the approximated line or curve may be used as the representative value.

[0086] Peripheral blood pressure indices fluctuate due to exercise, sudden temperature changes, stress, tension, etc. By evaluating vascular endothelial function with reference to the peripheral blood pressure indices before avascularization, the influence of fluctuations in the peripheral blood pressure indices due to various factors can be reduced, and the evaluation accuracy can be improved. For example, if there is a large difference between the average peripheral blood pressure indices during period ET2 shown in FIG. 10A and the average peripheral blood pressure indices before avascularization, it is recommended to notify the user to measure the pulse wave again.

[0087] In the first embodiment, the control terminal 30 (FIG. 1) controls the pulse wave measuring device 20 (FIG. 1) and the cuff-type sphygmomanometer 50 (FIG. 1). However, the pulse wave measuring device 20 and the cuff-type sphygmomanometer 50 may communicate directly with each other, and the pulse wave measuring device 20 may control the timing of inflation and release by the cuff-type sphygmomanometer 50.

[0088] The pulse wave measuring device 20 preferably measures the pulse wave in synchronization with the timing of inflation and release by the cuff-type sphygmomanometer 50. This allows blood pressure to be measured in parallel with pulse wave measurement. Avascularization begins a certain time after inflation begins, and the control terminal 30 can easily identify the timing of avascularization and release by acquiring inflation and release timing information from the pulse wave measuring device 20.

[0089] [Second Example] Next, a system and method for evaluating vascular endothelial function according to a second embodiment will be described with reference to Figures 15 to 17. Hereinafter, a description of components common to the system and method for evaluating vascular endothelial function according to the first embodiment described with reference to Figures 1 to 14C will be omitted. In the first embodiment, the length (avascularization time) of the avascularization period Pa (Figures 9, 11, and 13) is set to approximately 30 seconds. In the second embodiment, the avascularization time is set to be longer.

[0090] FIG. 15 is a graph showing the pulse waves measured for subject A, whose pulse wave was measured in FIG. 9, with the avascularization time extended. The horizontal axis represents the elapsed time from the start of pulse wave measurement in units of [s], and the vertical axis represents the photoplethysmogram (the inverted output from the photoplethysmogram sensor 21 (FIG. 1)) in arbitrary units. To adjust the avascularization time, pressure was applied to the pressure site using the cuff of an aneroid sphygmomanometer. The solid lines Gr and Ir in the graph of FIG. 15 represent the measurement results when green light and near-infrared light were used, respectively.

[0091] Approximately 30 seconds after the start of pulse wave measurement, inflation using the aneroid sphygmomanometer was initiated. It took approximately 10 seconds from the start of inflation until avascularization began. Once avascularization began, pulse waves could no longer be obtained. Approximately 150 seconds after the start of pulse wave measurement, air was deflated from the cuff. The period during which avascularization was performed is labeled Pa, and the avascularization period is shaded light gray in Figure 15. Measurement was terminated approximately 300 seconds after the start of measurement.

[0092] The graphs in Figures 16A to 16F show the change in peripheral blood pressure index over time, and the horizontal axis of these graphs shows the elapsed time in units of [s]. The vertical axis of the graphs in Figures 16A and 16D shows the peripheral blood pressure index "1 / VE0.5" in units of [s]. -1The vertical axes of the graphs in Figures 16B and 16E represent the peripheral blood pressure index "a / S" in arbitrary units, and the vertical axes of the graphs in Figures 16C and 16F represent the peripheral blood pressure index "(ab) / (ad)." The graphs in Figures 16A to 16C show peripheral blood pressure indexes calculated from pulse waves measured using green light, and the graphs in Figures 16D to 16F show peripheral blood pressure indexes calculated from pulse waves measured using near-infrared light.

[0093] Comparing the graphs in FIGS. 10A to 10F, which were obtained when measurements were taken under conditions in which the avascularization time was relatively short, with the graphs in FIGS. 16A to 16F, which were obtained when measurements were taken under conditions in which the avascularization time was relatively long, the following findings can be obtained.

[0094] The phenomenon of peripheral blood pressure indices decreasing after avascularization and release from avascularization compared to before avascularization occurs regardless of the avascularization time. When measured under relatively short avascularization times, the peripheral blood pressure indices return to their original values ​​in approximately 10 seconds. In contrast, when measured under relatively long avascularization times, it takes longer for the peripheral blood pressure indices to return to their original values. For example, when measured using green light, it takes approximately 30 seconds for the peripheral blood pressure indices to return to their original values, and when measured using near-infrared light, it takes approximately 120 seconds for the peripheral blood pressure indices to return to their original values. Furthermore, when the avascularization time is increased, the decrease in peripheral blood pressure indices becomes more pronounced when measured using near-infrared light compared to when the avascularization time is short.

[0095] The mechanism behind the phenomenon that it takes time for the peripheral blood pressure index to return to its original value when near-infrared light is used can be thought of as follows: When large blood vessels dilate when avascularization is released, the inflow of blood into the capillaries is suppressed, causing the peripheral blood pressure index to decrease. If the avascularization time is long, the blood flow rate in the capillaries and arterioles decreases, and it takes time for the capillaries to fill with blood. It also takes time for the arterioles to fill with blood thereafter.

[0096] When measuring a pulse wave using green light, the pulse wave primarily reflects information about blood flow in the capillaries, while when measuring a pulse wave using near-infrared light, the pulse wave is more likely to reflect information about blood flow in the arterioles as well as the capillaries. Therefore, the peripheral blood pressure index measured using near-infrared light returns to its original value when blood fills not only the capillaries but also the arterioles. Therefore, it takes longer for the peripheral blood pressure index measured using near-infrared light to return to its original value than for the peripheral blood pressure index measured using green light to return to its original value.

[0097] 17 is a flowchart showing the steps of the method for evaluating vascular endothelial function according to the second embodiment. First, the user determines the avascularization time (step SB1). The determined avascularization time is input by the user to the control terminal 30 (FIG. 1), for example. The control unit 31 of the control terminal 30 sets the evaluation time according to the input avascularization time (step SB2). Thereafter, the control unit 31 starts measuring the pulse wave (step SA1), as in the first embodiment (FIG. 3).

[0098] In the first embodiment (FIG. 3), avascularization and release are performed based on a fixed avascularization time (step SA2), but in the second embodiment, avascularization and release are performed based on the avascularization time set in step SB2 (step SB3). The subsequent procedures from step SA3 to step SA5 are the same as those from step SA3 to step SA5 in the first embodiment (FIG. 3).

[0099] Next, the excellent effects of the second embodiment will be described. In the second embodiment, the avascularization time is made longer than in the first embodiment, so that the decrease in the peripheral blood pressure index after release from avascularization becomes more clearly apparent, thereby improving the accuracy of the evaluation of vascular endothelial function. Furthermore, by lengthening the evaluation time in response to the longer avascularization time, the decrease in the peripheral blood pressure index after release from avascularization and the change in recovery can be stably detected.

[0100] Next, a method for evaluating vascular endothelial function according to a modification of the second embodiment will be described with reference to Fig. 18. Fig. 18 is a flowchart showing the steps of the method for evaluating vascular endothelial function according to the modification of the second embodiment.

[0101] In the second embodiment, the user determines the avascularization time (step SB1), but in this modification, the wavelength of light to be used for measuring the pulse wave is determined (step SC1). Then, the evaluation time is set according to the wavelength (step SC2). The subsequent procedures are the same as in the second embodiment.

[0102] As shown in the graphs in Figures 16A to 16F, when near-infrared light is used to measure the pulse wave, it takes longer for the peripheral blood pressure index to recover to its original value than when green light is used. Therefore, when near-infrared light is used, it is preferable to use a longer evaluation time than when green light is used. In this modification, the evaluation time is determined depending on the wavelength of the light used to measure the pulse wave, so that the decrease and recovery of the peripheral blood pressure index after release from avascularization can be stably detected.

[0103] [Third Example] Next, a system and method for evaluating vascular endothelial function according to a third embodiment will be described with reference to Figures 19A and 19B. Hereinafter, a description of components common to the systems and methods for evaluating vascular endothelial function according to the first and second embodiments will be omitted.

[0104] Figures 19A and 19B are graphs showing the changes over time in the amplitude S (Figure 5) and peripheral blood pressure index "a / S" obtained from the pulse wave of subject A shown in Figure 15. The graph in Figure 19A was obtained from the pulse wave measured using green light, and the graph in Figure 19B was obtained from the pulse wave measured using near-infrared light.

[0105] It can be seen that for the period from the time when avascularization was released until 60 seconds had elapsed, the amplitude S of the pulse wave was clearly larger than the amplitude S of the pulse wave before avascularization. This tendency for the amplitude S of the pulse wave to increase is evident both when the measurement light is green light and when the measurement light is near-infrared light. It is presumed that the increase in the amplitude S of the pulse wave is due to an increase in blood flow caused by vasodilation.

[0106] When vascular endothelial function is good, the blood vessels dilate sufficiently after release from avascularization, resulting in a large increase in the amplitude S of the pulse wave. When vascular endothelial function is poor, the blood vessels do not dilate sufficiently, resulting in a small increase in the amplitude S of the pulse wave. In this way, the vascular endothelial function can be evaluated based on the increase in the amplitude S of the pulse wave after release from avascularization. In the third embodiment, the vascular endothelial function is evaluated based on the increase in the amplitude S of the pulse wave in addition to the calculated value of the peripheral blood pressure index from the time when avascularization is released.

[0107] Next, the excellent effects of the third embodiment will be described. In the third embodiment, the accuracy of the evaluation can be improved by evaluating the vascular endothelial function based on the increase in the amplitude S of the pulse wave in addition to the calculated value of the peripheral blood pressure index from the time of release from avascularization.

[0108] [Fourth Example] Next, a system and method for evaluating vascular endothelial function according to a fourth embodiment will be described with reference to Figures 20 and 21. Hereinafter, a description of components common to the system and method for evaluating vascular endothelial function according to the first embodiment will be omitted.

[0109] 20 is a block diagram of a vascular endothelial function evaluation system according to Example 4. The vascular endothelial function evaluation system according to Example 1 includes a pulse wave measuring device 20, a control terminal 30, a server 40, and a cuff-type sphygmomanometer 50. In contrast, the vascular endothelial function evaluation system according to Example 4 further includes a reference pulse wave measuring device 60.

[0110] The reference pulse wave measurement device 60 includes a reference photoplethysmographic sensor 61, a light emission control unit 62, a reference pulse wave measurement unit 63, and a communication unit 64. The configurations and functions of the reference photoplethysmographic sensor 61, the light emission control unit 62, the reference pulse wave measurement unit 63, and the communication unit 64 are the same as the configurations and functions of the photoplethysmographic sensor 21, the light emission control unit 22, the pulse wave measurement unit 23, and the communication unit 24 of the pulse wave measurement device 20 of the first embodiment. The reference pulse wave measurement unit 63 generates a reference pulse wave signal based on the output from the reference photoplethysmographic sensor 61. If a different type of pulse wave sensor is used instead of the photoplethysmographic sensor 21 of the pulse wave measurement device 20, a reference pulse wave sensor that measures the pulse wave using the same method as the photoplethysmographic sensor 21 is used instead of the reference photoplethysmographic sensor 61.

[0111] 21 is a schematic diagram of a user wearing a measuring device when evaluating vascular endothelial function using the vascular endothelial function evaluation system according to the fourth embodiment. The user wraps an inflator 51, such as a cuff, of a cuff-type sphygmomanometer 50 around one upper arm. The user wears a pulse wave measuring device 20 on a finger on the arm wearing the inflator 51. The user wears a reference pulse wave measuring device 60 on a finger on the opposite arm. In this way, the reference pulse wave measuring device 60 is attached to a site on the body that is symmetrical to the site where the pulse wave measuring device 20 is attached.

[0112] When pulse wave measurement begins, the pulse wave is acquired by pulse wave measuring device 20, and a reference pulse wave is acquired by reference pulse wave measuring device 60. The peripheral blood pressure index determined from the pulse wave acquired by pulse wave measuring device 20 is compared with the peripheral blood pressure index determined from the reference pulse wave to evaluate vascular endothelial function.

[0113] The average value of the peripheral blood pressure index obtained from the pulse wave acquired by the pulse wave measurement device 20 during period ET1 (FIG. 10A) is labeled M1, and the average value during period ET2 is labeled M2. The average value of the peripheral blood pressure index obtained from the reference pulse wave during period ET1 (FIG. 10A) is labeled MR1, and the average value during period ET2 is labeled MR2. In the first embodiment, vascular endothelial function is evaluated based on M1 / M2, but in the fourth embodiment, vascular endothelial function is evaluated based on (M1 / M2) / (MR1 / MR2).

[0114] Next, the excellent effects of the fourth embodiment will be described. For the finger from which the reference pulse wave is obtained, avascularization is not performed, so the average values ​​MR1 ​​and MR2 are approximately equal. However, some external factor may cause the average value MR2 to change relative to the average value MR1. In other words, the ratio MR1 / MR2 may deviate from 1. The influence of this external factor is also reflected to a similar extent in the value of M1 / M2. In the fourth embodiment, the vascular endothelial function is evaluated based on (M1 / M2) / (MR1 / MR2), which almost completely eliminates the influence of external factors, thereby improving the accuracy of the evaluation of vascular endothelial function.

[0115] The above-described embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects resulting from similar configurations of multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0116] 20 Pulse wave measuring device 21 Photoplethysmographic sensor 21A, 21B Light emitting element 21C Photodetector 22 Light emission control unit 23 Pulse wave measurement unit 24 Communications Department 27 Mounting material 30 Control Terminal 31 Control Unit 32 Output section 33 Communications Department 40 servers 41 Pulse wave feature calculation unit 42 Peripheral blood pressure index calculation section 43 Vascular Endothelial Function Assessment Division 44 Communications Department 50 Cuff-type blood pressure monitor 51 Pressure section 52 Pulse detector 53 Control Unit 54 Blood pressure calculation unit 55 Communications Department 60 Reference Pulse Wave Measurement Device 61 Reference Photoplethysmographic Sensor 62 Light emission control unit 63 Reference pulse wave measurement unit 64 Communications Department 70 User's body surface 71 Epidermal area 72 Arterioles 73 Capillaries

Claims

1. a pulse wave measuring unit that generates a pulse wave signal of an arteriole or a capillary from the measurement result of a pulse wave sensor attached to a site farther from the heart than the site to be pressurized for avascularization; a peripheral blood pressure index calculation unit that calculates a peripheral blood pressure index related to the steepness of the rising edge of the pulse wave signal generated by the pulse wave measurement unit for each beat; a vascular endothelial function evaluation unit that evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when the avascularization is released until the time when an evaluation time has elapsed; an output unit that outputs the evaluation result of the vascular endothelial function by the vascular endothelial function evaluation unit; Equipped with A vascular endothelial function evaluation system, wherein the peripheral blood pressure index includes information regarding the width of the first peak that appears within one beat of the velocity pulse wave obtained by first-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measurement unit.

2. a pulse wave measuring unit that generates a pulse wave signal of an arteriole or a capillary from the measurement result of a pulse wave sensor attached to a site farther from the heart than the site to be pressurized for avascularization; a peripheral blood pressure index calculation unit that calculates a peripheral blood pressure index related to the steepness of the rising edge of the pulse wave signal generated by the pulse wave measurement unit for each beat; a vascular endothelial function evaluation unit that evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when the avascularization is released until the time when an evaluation time has elapsed; an output unit that outputs the evaluation result of the vascular endothelial function by the vascular endothelial function evaluation unit; Equipped with The peripheral blood pressure index includes information on the difference between the peak value of the a-wave and the peak value of the d-wave of the accelerated pulse wave obtained by second-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measurement unit, and the difference between the peak value of the a-wave and the peak value of the b-wave.

3. 3. The vascular endothelial function evaluation system according to claim 1, wherein the vascular endothelial function evaluation unit evaluates the vascular endothelial function based on both the calculated value of the peripheral blood pressure index before avascularization and the calculated value of the peripheral blood pressure index after avascularization is released.

4. The device further includes a ring-shaped attachment member that is attached to a finger, The vascular endothelial function evaluation system according to claim 1 , wherein the pulse wave sensor is mounted on the attachment member.

5. It is also equipped with a cuff-type blood pressure monitor, The system for evaluating vascular endothelial function according to claim 1 or 2, wherein the pressure applied to the pressure site is applied by the cuff-type sphygmomanometer.

6. the cuff-type blood pressure monitor and the pulse wave measurement unit have a function of wirelessly communicating with each other, 6. The vascular endothelial function evaluation system according to claim 5, wherein the cuff-type sphygmomanometer notifies the pulse wave measurement unit of timings for avascularization and release, and the pulse wave measurement unit calculates the peripheral blood pressure index in synchronization with the timings for avascularization and release of the cuff-type sphygmomanometer.

7. 6. The vascular endothelial function evaluation system according to claim 5, further comprising a control terminal having a function of wirelessly communicating with the cuff-type sphygmomanometer and the pulse wave measurement unit, a function of controlling the avascularization and release operations of the cuff-type sphygmomanometer, and a function of receiving a pulse wave signal from the pulse wave measurement unit and transmitting it to the peripheral blood pressure index calculation unit.

8. 3. The vascular endothelial function evaluation system according to claim 1, wherein the vascular endothelial function evaluation unit further uses, in the evaluation of the vascular endothelial function, a change over time in the amplitude of the pulse wave signal generated by the pulse wave measurement unit from the time when the avascularization is released until a certain time has elapsed.

9. 3. The vascular endothelial function evaluation system according to claim 1, wherein the pulse wave sensor is a photoplethysmographic sensor.

10. 10. The vascular endothelial function evaluation system according to claim 9, wherein the photoplethysmographic sensor uses light within a wavelength range from blue to yellow-green.

11. 11. The vascular endothelial function evaluation system according to claim 10, wherein the photoplethysmographic sensor includes a light-emitting element and a light-receiving element that receives light emitted from the light-emitting element and transmitted through biological tissue, and the distance between the light-emitting element and the light-receiving element is 1 mm or more and 3 mm or less.

12. 3. The vascular endothelial function evaluation system according to claim 1, wherein the vascular endothelial function evaluation unit changes the evaluation time in accordance with a duration of avascularization.

13. the photoplethysmographic sensor has a function of emitting light of at least two different wavelengths; The vascular endothelial function evaluation system according to claim 9 , wherein the vascular endothelial function evaluation unit changes the evaluation time in accordance with the wavelength of light used to acquire the pulse wave signal.

14. The device further includes a reference pulse wave measurement unit that generates a reference pulse wave signal from a measurement result of a reference pulse wave sensor that is attached to a site symmetrical to the site where the pulse wave sensor is attached, 3. The vascular endothelial function evaluation system according to claim 1, wherein the vascular endothelial function evaluation unit further uses the peripheral blood pressure index calculated based on the reference pulse wave signal generated by the reference pulse wave measurement unit when evaluating the vascular endothelial function.

15. a pulse wave measuring device that generates a pulse wave signal of an arteriole or a capillary from the measurement result of a pulse wave sensor attached to a site farther from the heart than the site where pressure is applied for avascularization; a control terminal that calculates a peripheral blood pressure index related to the steepness of the rise of the pulse wave signal generated by the pulse wave measuring device for each beat, evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when avascularization is released until an evaluation time has elapsed, and outputs the evaluation results; Equipped with A vascular endothelial function evaluation device, wherein the peripheral blood pressure index includes information regarding the width of the first peak that appears within one beat of the velocity pulse wave obtained by first-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measurement device.

16. a pulse wave measuring device that generates a pulse wave signal of an arteriole or a capillary from the measurement result of a pulse wave sensor attached to a site farther from the heart than the site where pressure is applied for avascularization; a control terminal that calculates a peripheral blood pressure index related to the steepness of the rise of the pulse wave signal generated by the pulse wave measuring device for each beat, evaluates vascular endothelial function based on the calculated values ​​of the peripheral blood pressure index from the time when avascularization is released until an evaluation time has elapsed, and outputs the evaluation results; Equipped with The peripheral blood pressure index includes information on the difference between the peak value of the a-wave and the peak value of the d-wave of the accelerated pulse wave obtained by second-order differentiation of the waveform of the pulse wave signal generated by the pulse wave measuring device, and the difference between the peak value of the a-wave and the peak value of the b-wave.

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