JP2024063672A - Arterial endothelial function testing device - Google Patents

Abstract

[Problem] To provide a highly reliable arterial endothelial function testing device that can efficiently apply a sufficient amount of shear stress to the endothelium of the arterial blood vessel of a living body under compression by a compression cuff. [Solution] The device includes a shear stress application control unit 36 that controls a compression pressure control unit 32 so as to generate blood flow vibrations that can be detected by a blood flow vibration determination unit 38. As a result, the shear stress application control unit 36 controls the compression pressure control unit 32 so as to generate blood flow vibrations that can be detected by the blood flow vibration determination unit 38, so that a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessel 14a of the living body under compression by a compression cuff 12, thereby improving the reliability of the arterial blood vessel 14a endothelial function testing device. [Selected Figure] Figure 2

Description

The present invention relates to an arterial endothelial function testing device that can test the endothelial function of blood vessels by applying shear stress to the endothelium of the artery of a living body from a pressure cuff wrapped around a part of the living body.

There is research showing that a decline in endothelial function of arterial blood vessels occurs prior to arteriosclerosis in the body, and various devices for evaluating such endothelial function have been proposed. This endothelial function refers to a vasodilatory response that occurs when the endothelium, located at the innermost periphery of the exothelium, mesothelium, and endothelium that make up the arterial vascular wall, produces NO based on the shear stress of the blood flow that acts on the endothelium, which relaxes the smooth muscle.

For example, Patent Document 1 proposes an endothelial function testing device. These endothelial function testing devices use a pressure band to compress the subject's arm to stop bleeding in the artery, maintaining the condition for, for example, five minutes, and then measure the change in the cross-sectional shape of the artery, as determined using ultrasound images, when the bleeding is released, for example the maximum rate of change in the vascular lumen diameter compared to the endothelial diameter before bleeding was stopped, and evaluate the endothelial function of the arterial blood vessel based on the maximum rate of change in the vascular lumen diameter. With the above-mentioned endothelial function testing device, after five minutes of bleeding stoppage with a pressure band, the bleeding is suddenly released, applying shear stress to the endothelium of the arterial blood vessel within a short period of time.

However, when a pressure band in a tourniquet state is suddenly released to cause blood flow in the arterial blood vessel and apply shear stress to the endothelium of the arterial blood vessel, not only does this cause pain to the subject, but because blood is forced to pass through the open arterial blood vessel, it is not always possible to apply a sufficient amount of shear stress for a sufficient period of time.

In response to this, an endothelial function testing device for an arterial blood vessel has been proposed, which includes a compression band (cuff) wrapped around a part of the living body, a compression pressure control unit that controls the compression pressure of the compression band, and a pressure sensor connected to the compression band and detects the compression pressure of the compression band, a shear stress applying unit that applies shear stress to the endothelium of the arterial blood vessel by blood flow for each of a plurality of pulse waves, which are pressure vibrations that are superimposed on the compression pressure controlled by the compression pressure control unit in synchronization with the heartbeat of the living body, and a vasodilation response evaluation unit that starts the continuation of the dilation-related value of the arterial blood vessel after the shear stress is applied by the shear stress applying unit, and calculates an evaluation value that evaluates the endothelial function of the arterial blood vessel based on the dilation-related value. For example, the endothelial function evaluation device for an arterial blood vessel using a pulse wave extracted from the compression band cuff pressure described in Patent Document 2 is one such device. According to this type of device for evaluating endothelial function of arterial blood vessels, the compression pressure controlled by the compression pressure control unit applies shear stress to the endothelium of the arterial blood vessels by blood flow for each of multiple pulse waves, which are pressure vibrations that are superimposed on the compression pressure in synchronization with the heartbeat of the living body. Since blood flows through the arterial blood vessels that have been narrowed by the compression of the compression band, the device has the characteristic that sufficient shear stress can be applied to the endothelium of the arterial blood vessels in a relatively short period of time.

JP 2007-061182 A JP 2018-192234 A

In the above-mentioned conventional arterial vascular endothelial function evaluation device, during the compression pressure reduction process in which the compression pressure of the compression band is increased above the systolic blood pressure of the living body and then decreased to atmospheric pressure, the blood flow that passes through the arterial blood vessel narrowed by the compression of the compression band, which occurs repeatedly in synchronization with the pulse wave, is used to apply shear stress to the endothelium of the arterial blood vessel. However, when blood is simply passed through the arterial blood vessel narrowed by the compression of the compression band in synchronization with the pulse wave, the application of shear stress needs to be completed within a relatively short vasodilation reaction time of about 18 to 20 seconds from the start of the application of shear stress to the start of the vasodilation reaction, so that a sufficient amount of shear stress is not necessarily applied to the endothelium of the arterial blood vessel, and sufficient accuracy in evaluating endothelial function cannot be obtained.

The present invention was made against the background of the above circumstances, and its purpose is to provide a highly reliable device for testing the endothelial function of arterial blood vessels that can efficiently apply a sufficient amount of shear stress to the endothelium of the arterial blood vessels of a living body under pressure from a pressure band.

In light of the above circumstances, the inventors have conducted various studies to generate a sufficient amount of shear stress by passing a blood flow synchronized with the pulse through an arterial blood vessel narrowed under the pressure of a compression band wrapped around a part of the living body, for example the upper arm, a limited number of times within a relatively short time until the onset of a vasodilation reaction. As a result, based on the assumption that the shear stress applied to the endothelium of the arterial blood vessel is greater when the blood flow passing through the arterial blood vessel compressed by the compression band is a vortex flow than when it is a laminar flow, the inventors have noticed that, in addition to the fundamental frequency of the pulse wave, a fundamental frequency component of another vibration higher than that is generated when the cuff pressure signal, which is the pressure of the compression band, is collected and frequency analyzed in a state in which blood flows through a part of the arterial blood vessel narrowed by the compression band while decreasing from a compression pressure higher than the systolic blood pressure of the living body. And, it was estimated that the other vibration of the fundamental frequency component with a higher fundamental frequency of the pulse wave is a vibration (blood flow vibration) caused by a vortex flow of blood generated when blood flows through an arterial blood vessel narrowed under the compression pressure of the compression band.

Then, it was found that when shear stress is applied to the endothelium of an artery using a pulse wave that is generated in the process of increasing the pressure to a level sufficient to collapse the artery, performing avascularization, and then decreasing the compression pressure, and that the blood flow associated with the pulse wave accompanied by blood flow vibrations (blood flow sounds) caused by blood vortices is greater than when a pulse wave (a pulse wave in which the blood flow passing through the artery is laminar) that is not accompanied by blood vortex vibrations (blood flow sounds) generated when compressed by a compression band is used, and that it is possible to efficiently apply sufficient shear stress to the endothelium of an artery in a limited number of times within the relatively short time from the start of the application of shear stress to the start of the vasodilation reaction, thereby obtaining a highly reliable device for testing the endothelial function of an artery. The present invention was made based on such findings.

That is, the gist of the first invention is an endothelial function testing device for an arterial blood vessel, which includes (a) a pressure band that wraps around a part of a living body, a pressure sensor that detects the pressure of the pressure band, a blood flow vibration determination unit that detects blood flow vibration generated from an arterial blood vessel in the living body compressed by the pressure band, and a pressure control unit that controls the pressure of the pressure band, and after blood flow is blocked by the pressure band, the pressure band gradually releases the arterial blood vessel in the living body by lowering the pressure to apply shear stress to the endothelium of the arterial blood vessel, and then evaluates the endothelial function of the arterial blood vessel based on changes in the pressure pulse wave, which is the fluctuation of the pressure in the pressure band, while maintaining the pressure of the pressure band at a predetermined pressure pulse wave collection pressure, and (b) a shear stress application control unit that controls the pressure control unit so that the blood flow vibration detected by the blood flow vibration determination unit occurs.

According to the first invention, the endothelial function testing device for arterial blood vessels includes: (a) a pressure sensor for wrapping a part of a living body; a pressure sensor for detecting the pressure of the pressure sensor; a blood flow vibration determination unit for detecting blood flow vibrations generated from the arterial blood vessels in the living body compressed by the pressure sensor; and a pressure control unit for controlling the pressure of the pressure sensor. After the part of the living body is blocked by the pressure sensor, the pressure of the pressure sensor is gradually released by lowering the pressure sensor to apply shear stress to the endothelium of the arterial blood vessels. After that, the pressure sensor evaluates the endothelial function of the arterial blood vessels based on the pressure pulse wave, which is the fluctuation of the pressure in the pressure sensor, while maintaining the pressure sensor at a predetermined pressure pulse wave collection pressure. (b) A shear stress application control unit for controlling the pressure sensor to generate the blood flow vibrations detected by the blood flow vibration determination unit. As a result, the shear stress application control unit controls the compression pressure control unit so that the blood flow vibration detected by the blood flow vibration determination unit occurs, so that a sufficient amount of shear stress can be efficiently applied to the endothelium of the living body's arterial blood vessels under compression by the compression band, thereby improving the reliability of the arterial blood vessel endothelial function testing device.

Preferably, the blood flow vibration determination unit extracts pressure vibrations that are superimposed on the compression pressure signal in synchronization with the pulse of the living body from the compression pressure signal representing the compression pressure detected by the pressure sensor, and determines the blood flow vibrations based on the magnitude of the frequency components of the blood flow vibrations contained in the pressure vibrations. As a result, the blood flow vibrations are determined based on the magnitude of the frequency components of the blood flow vibrations contained in the pressure vibrations that are superimposed on the cuff pressure signal in synchronization with the pulse of the living body, and therefore a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessels of the living body under compression by the compression band.

Moreover, preferably, the blood flow vibration determination unit determines blood flow vibration based on whether the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration to the magnitude of the fundamental frequency component of the pulse wave contained in the pressure vibration is equal to or greater than a predetermined threshold value. As a result, the blood flow vibration is determined based on a relative comparison between the magnitude of the fundamental frequency component of the pulse wave contained in the pressure vibration and the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration, so that the influence of gain changes and individual differences is reduced, and a sufficient magnitude of shear stress can be efficiently and reliably applied to the endothelium of the arterial blood vessels of the living body under compression by a pressure band.

Preferably, the blood flow vibration determination unit includes a microphone that is attached to the pressure band to detect blood flow sounds generated in the arterial blood vessel, and determines the blood flow vibration based on the magnitude of the blood flow sounds detected by the microphone. In this way, blood flow vibration can be obtained without using a bandpass filter and frequency analysis, and a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessel of the living body under pressure from the pressure band.

Preferably, the endothelial function testing device further includes a blood flow blocking control unit that blocks blood flow to a part of the living body for 30 seconds or more by applying pressure to the compression band before the compression band is lowered. This releases the blood flow blocking effect of the compression band when the pressure in the arterial blood vessel downstream of the compression band and the venous blood vessel connected to the arterial blood vessel via the capillary vessel are sufficiently equalized, ensuring the flow of blood into the arterial blood vessel downstream of the compression band and enhancing the effect of applying shear stress.

Preferably, the compression pressure control unit decreases the compression pressure of the compression band when the blood flow vibration determination unit determines that the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration obtained in the section where the compression pressure of the compression band is constant is below a predetermined threshold, and maintains the compression pressure of the compression band for a predetermined pulse rate when the blood flow vibration determination unit determines that the ratio of the magnitude of the fundamental frequency component of the blood flow vibration is equal to or greater than a predetermined threshold. As a result, blood flows in which the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration is equal to or greater than a predetermined threshold are used more frequently for applying shear stress, thereby enhancing the effect of applying shear stress.

Moreover, preferably, the predetermined threshold value is set to a smaller value as it deviates from the mean blood pressure value of the living body. This allows a blood flow with a high shear stress application effect to be used, further enhancing the effect of applying shear stress.

Preferably, the compression pressure control unit gradually decreases the compression pressure, and the blood flow vibration determination unit determines the blood flow vibration based on whether the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration obtained in a section where the compression pressure by the compression band is constant is equal to or greater than a predetermined threshold value. In this way, the pressure vibration can be obtained accurately without being affected by the frequency component of the compression pressure, compared to when using pressure vibration obtained in a section where the compression pressure changes continuously.

Preferably, the shear stress application control unit causes the compression pressure control unit to release the compression by the compression band when a preset shear stress application time has elapsed since the first blood flow occurs due to a decrease in the compression pressure of the compression band. In this way, it is possible to avoid overlapping between the application of shear stress and the start of a vasodilation reaction, and the reliability of the arterial endothelial function testing device can be improved. The preset shear stress application time is set to be as long as possible within a range that is shorter than the vasodilation reaction start time from the first blood flow to the start of a vasodilation reaction, for example, 18 seconds.

Preferably, the endothelial function testing device includes a compression pressure holding control unit that holds the compression pressure of the compression band at a predetermined pressure pulse wave collection pressure for a predetermined time after the shear stress application control unit applies shear stress to the arterial blood vessel directly below the compression band, a pressure pulse wave collection control unit that continuously collects pressure pulse waves for a predetermined period of time while the compression pressure of the compression band is held at the pressure pulse wave collection pressure, and a vascular dilation rate calculation unit that calculates the dilation rate of the arterial blood vessel in terms of equivalent blood vessel diameter by volumetrically converting the pressure pulse waves continuously collected for a predetermined period by the pressure pulse wave collection control unit. This makes it unnecessary to use an ultrasonic probe and a probe support device that supports it and searches for an optimal position, an ultrasonic image generation device that processes signals from the ultrasonic probe to generate ultrasonic images, etc., making the device simple and small. Furthermore, the vascular dilation rate calculation unit converts the pressure pulse waves collected continuously for a predetermined period by the pressure pulse wave collection control unit into a volumetric value to calculate the arterial vascular dilation rate using an equivalent vascular diameter conversion. This means that the timing at which the vascular diameter (vascular volume) becomes maximum due to the vasodilation reaction caused by the shear stress acting on the arterial blood vessel almost coincides with the detection timing of any of the pressure pulse waves collected continuously for a predetermined period, enabling highly reliable vascular endothelial function testing.

1 is a diagram for illustrating an example of an endothelial function testing device for arterial blood vessels to which the present invention is preferably applied; 2 is a functional block diagram illustrating a main part of a control function of an electronic control device provided in the endothelial function testing device of FIG. 1 . 3 is a time chart illustrating a change in compression pressure of the compression band controlled by the compression pressure control unit of FIG. 2 . 3 is a diagram for explaining the detection operation of blood flow vibration by the blood flow vibration determination unit in FIG. 2, showing a case where the magnitude of the fundamental wave component of the blood flow vibration falls below a threshold value. FIG. 3 is a diagram for explaining the detection operation of blood flow vibration by the blood flow vibration determination unit in FIG. 2, showing a case where the magnitude of the fundamental wave component of the blood flow vibration is equal to or greater than a threshold value. FIG. 2 is a flowchart illustrating a main part of the control operation of an electronic control device provided in the endothelial function testing device of FIG. 1 . 7, 8, and 9 are diagrams showing the smallest first judgment threshold among the three judgment thresholds used in another embodiment of the present invention. The blood flow vibration judgment unit 38 judges whether the fundamental frequency component of the blood flow vibration has been exceeded by the judgment threshold Th. The first judgment threshold is a smallest first judgment threshold among the three judgment thresholds used in another embodiment of the present invention ... FIG. 8 is a diagram showing a second determination threshold value, which is the largest of the three determination threshold values used in the embodiment of FIG. 7; FIG. 8 is a diagram showing a third determination threshold, which is greater than the first determination threshold and smaller than the second determination threshold, of the three determination thresholds used in the embodiment of FIG. 7; In another embodiment of the present invention, a microphone is provided in the pressure cuff 12 so that the blood flow vibration determining unit can determine the presence or absence of blood flow vibration generated from an arterial blood vessel under pressure by the pressure cuff. FIG. 5 is a diagram corresponding to FIG. 3 and showing changes in compression pressure Pc of a compression cuff 12 in another embodiment of the present invention. FIG. 5 is a diagram corresponding to FIG. 3 and showing changes in compression pressure Pc of a compression cuff 12 in another embodiment of the present invention.

An embodiment of the present invention will be described in detail below with reference to the drawings. Note that in the following embodiment, the drawings have been appropriately simplified or modified, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Figure 1 is a schematic diagram illustrating an endothelial function testing device 10 for an arterial blood vessel, which is an example of the present invention. In Figure 1, a pressure cuff 12 has an inflatable bag similar to a cuff used in blood pressure measurement, and is wrapped around a part of a living body, such as an upper arm 14. A piping 20 is connected to the pressure cuff 12, and a control valve 16 and an air pump 18 are connected in series via the piping 20 to adjust the pressure or exhaust flow rate in the pressure cuff 12 by supplying air to the pressure cuff 12 and exhausting air from the pressure cuff 12. A pressure sensor 22 is also connected to the pressure cuff 12 via the piping 20, and the pressure sensor 22 is adapted to detect the pressure Pc applied to the arterial blood vessel 14a directly below the pressure cuff 12.

The cuff pressure signal SPc, which indicates the compression pressure Pc of the compression cuff 12 detected by the pressure sensor 22, is supplied to the low-pass filter 24 and the band-pass filter 26. The low-pass filter 24 separates the static pressure component from the cuff pressure signal SPc and outputs the cuff pressure signal SPc. The band-pass filter 26 separates the vibration component that is superimposed on the cuff pressure signal SPc in synchronization with the heartbeat of the living body from the cuff pressure signal SPc and outputs the pulse wave signal SPm. The cuff pressure signal SPc and the pulse wave signal SPm are supplied to the electronic control device 30 via the A/D converter 28. The electronic control device 30 is composed of a so-called microcomputer that includes a CPU 30a, a RAM 30c, a ROM 30b, etc., processes input signals according to a pre-stored program, and outputs the processing results to a display 30d.

Figure 2 is a functional block diagram explaining the control functions of the electronic control device 30. In Figure 2, the compression pressure control unit 32 controls the compression pressure Pc of the compression cuff 12 by controlling the control valve 16 or the air pump 18 according to commands from the blood flow obstruction control unit 34, the shear stress application control unit 36, or the compression pressure maintenance control unit 42.

In response to the start of the endothelial function testing device 10, the blood flow control unit 34 controls the compression pressure control unit 32 to increase the compression pressure Pc of the compression cuff 12 to a target pressure increase value P1, which is a blood flow pressure preset to, for example, about 180 mmHg, higher than the systolic blood pressure of the living body, and maintain the target pressure value P1 for a predetermined blood flow period T1, for example, about 30 seconds or more, in order to block the blood flow in the arterial blood vessel 14a immediately below the compression cuff 12 wrapped around the upper arm 14. This blood flow period T1 is a preset pressure equalization time during which the arterial blood vessel 14a downstream of the compression cuff 12 and the venous blood vessel connected thereto via the capillary blood vessel are sufficiently equalized with each other. If the above-mentioned blood flow pressure is maintained for a period shorter than the blood flow period Ts, the amount of blood flowing into the arterial blood vessel 14a downstream of the compression cuff 12 after the blood flow is released is reduced. If the occlusion pressure is maintained for longer than the occlusion period Ts, the amount of blood flowing into the arterial blood vessel 14a downstream of the compression cuff 12 after the occlusion is released will be saturated, unnecessarily lengthening the measurement time.

When the maintenance of the occlusion pressure exceeds the occlusion period T1, the shear stress application control unit 36 causes the compression pressure control unit 32 to decrease the compression pressure Pc of the compression band 12 at a predetermined decreasing speed so that the blood flow vibration is detected by the blood flow vibration determination unit 38. The blood flow vibration determination unit 38 performs frequency analysis using a Fourier transform FFT on the pulse wave signal SPm output from the bandpass filter 26, extracts the fundamental frequency component of the pulse wave and the fundamental frequency component of the blood flow vibration contained in the pulse wave signal SPm, which is a vibration component superimposed on the cuff pressure signal SPc, and detects the occurrence of blood flow vibration based on the fundamental frequency component of the blood flow vibration exceeding a determination threshold Th set at a predetermined ratio to the magnitude of the fundamental frequency component of the extracted pulse wave. This blood flow vibration (blood flow sound) is generated due to a vortex generated when blood passes through a portion of the arterial blood vessel 14a narrowed by the compression of the compression band 12.

Figure 3 shows an example in which the shear stress application control unit 36 controls the compression pressure applied by the compression belt 12 to gradually lower the cuff pressure signal SPc, and Figure 4 shows an example of the frequency analysis result of the pulse wave signal SPm obtained when the cuff pressure signal SPc is constant during the process of the cuff pressure signal SPc decreasing. In Figure 4, the peak waveform in which the relative value of the signal magnitude is 1 and is centered around 1 Hz is the fundamental wave of the pulse wave, and the peak waveform in which the relative value of the signal magnitude is less than 1 and is centered around 6 Hz is the fundamental wave of the frequency blood flow vibration.

In Fig. 3, the blood flow obstruction control unit 34 causes the compression pressure control unit 32 to increase the pressure to a target pressure increase value P1 set higher than the systolic blood pressure (at time t0) and maintain the pressure during the blood flow obstruction period T1. The shear stress application control unit 36 causes the compression pressure control unit 32 to gradually decrease the cuff pressure signal SPc indicating the compression pressure by the compression cuff 12 by a constant pressure decrease amount of, for example, about 3 to 4 mmHg after the start point of the decrease (at time t1), and even if blood flow vibration occurs during this process (at time t2), if the magnitude of the fundamental wave of the blood flow vibration falls below the judgment threshold value Th (Fig. 4), the cuff pressure signal SPc is decreased for each pulse beat, and if the magnitude of the fundamental wave of the blood flow vibration is equal to or greater than the judgment threshold value Th (Fig. 5, at time t3), the cuff pressure signal SPc is maintained constant until the predetermined pulse rate (3 beats in Fig. 3) is reached. The shear stress application control unit 36 then starts a rapid decrease in the compression pressure applied by the compression band 12 when the rapid drop start point (time t4) is reached before the vasodilation reaction start time (e.g., 18 to 20 seconds) between the occurrence of the first blood flow and the start of the vasodilation reaction has elapsed, or when the magnitude of the fundamental wave of the blood flow vibration falls below the judgment threshold value Th (time t4). The shear stress application time Tz shown in FIG. 3 is, in the case of , a period set slightly shorter than the vasodilation reaction start time (e.g., 18-20 seconds) between the occurrence of the first blood flow and the start of the vasodilation reaction.

This rapid reduction in the compression pressure by the compression belt 12 may be achieved by directly releasing the compression pressure by the compression belt 12, but in the case of FIG. 3, the cuff pressure signal SPc is rapidly reduced in stages by a constant pressure reduction range of about 6 to 8 mmHg after time t4. The shear stress application time in the shear stress application control unit 36 is set to be as long as possible within the range of the vasodilation reaction start time from the occurrence of the initial blood flow to the start of the vasodilation reaction, for example, 18 seconds.

In FIG. 3, blood flow vibrations that occur while the cuff pressure signal SPc is kept constant are assigned symbols indicating the order of occurrence, and the pressure represented by the cuff pressure signal SPc at time t2 when the first blood flow vibration occurs indicates the systolic blood pressure value, and the pressure represented by the cuff pressure signal SPc at time t4 when the final 12th blood flow vibration occurs indicates the diastolic blood pressure value. During the downward process of compression by the compression cuff 12 shown in FIG. 3, the blood pressure measurement unit 40 determines the pressure represented by the cuff pressure signal SPc at time t2 when the first blood flow vibration occurs as the systolic blood pressure value SBP, and determines the pressure represented by the cuff pressure signal SPc at time t4 when the final blood flow vibration occurs as the diastolic blood pressure value DBP. The embodiment in FIG. 3 shows an example of applying shear stress while measuring the blood pressure value of a living body.

When the shear stress application control unit 36 ends application of shear stress and the compression pressure of the compression belt 12 is quickly reduced, the compression pressure maintenance control unit 42 maintains the compression pressure Pc of the compression belt 12 at the maintenance pressure P2 for collecting the pressure pulse wave. This maintenance pressure P2 of the compression pressure Pc is continued until the measurement of the endothelial function ends (time t4). The maintenance pressure P2 is a value lower than the mean blood pressure value, preferably a value lower than the diastolic blood pressure value, and more preferably a value similar to the venous blood pressure value, for example a value of about 30 mmHg, or a value greater than the venous blood pressure value and less than the diastolic blood pressure value.

The pressure pulse wave acquisition control unit 44 continuously acquires pressure pulse waves superimposed on the compression pressure Pc of the compression belt 12 during a predetermined holding period T2 while the compression pressure Pc of the compression belt 12 is held at the holding pressure P2. This holding period T2 starts at time t5 when the compression of the upper arm 14 is released after compressing the upper arm 14 with the compression belt 12 and avascularizing the upper arm 14 for a predetermined time H, and ends at time t6 when a period of, for example, 250 to 300 seconds, sufficiently covers the timing when the volume of the arterial blood vessel 14a reaches its maximum due to the vasodilation reaction caused by the shear stress caused by the release of the avascularization.

The pulse wave processing control unit 46 converts the pressure pulse waves collected continuously for a predetermined period T2 by the pressure pulse wave collection control unit 44 into a volume (volume) to calculate the expansion rate of the arterial blood vessel in terms of the equivalent blood vessel diameter. This will be explained in detail below.

The compression pressure of the compression belt 12 is Pc, the internal volume (capacity) of the compression belt 12 is Vc, the volume change of the measurement site (site wrapped by the compression belt 12) under compression by the compression belt 12 is ΔVc, and the change in compression pressure accompanying this volume change is ΔPc. However, assuming that the medium volume does not change due to deformation of the compression belt 12 and that the temperature is also constant, formula (1) is established according to Boyle's law.
Pc × Vc = constant ... (1)

In this case, when the volume of the compression belt 12 decreases by ΔVc due to deformation of the compression belt 12 caused by the expansion of the upper arm 14 due to the generation of a pulse wave in the arterial blood vessel 14a, and the pressure increase within the compression belt 12 is ΔPc, the following equation (2) is obtained.
Pc × Vc = (Pc + ΔPc) × (Vc - ΔVc)
= Pc × Vc + Vc × ΔPc - Pc × ΔVc - ΔPc × ΔVc ... (2)
Here, since ΔPc × ΔVc is a small amount, it can be omitted as follows:
Vc × ΔPc − Pc × ΔVc = 0 (3)
Therefore, Vc × ΔPc = Pc × ΔVc ... (4)
Therefore, ΔVc=(Vc/Pc)×ΔPc (5)
In equation (5), if the compression pressure Pc in the compression cuff 12 is constantly being measured, then if Vc is known, then ΔPc can be measured to obtain ΔVc, which is the change in capacitance of the measurement object.

On the other hand, the rate of change ΔVc/Vc obtained by comparing the above-mentioned change in capacitance ΔVc with the original volume Vc of the upper arm 14 that is the target of compression by the compression cuff 12 is expressed as follows, assuming that the composite blood vessel diameter in the region compressed by the compression cuff 12 is D and the length of the target region is L, and that the change in capacitance is considered to be a change in blood vessel volume: Here, the composite blood vessel diameter D is the cross-sectional area of a cylinder having the composite volume of the arterial blood vessel that is thought to cause a change in capacitance in the region compressed.
ΔVc/V=π((D+ΔD) ² −D ^{2 )} L/πD ² L (6)
Equation (7) is obtained by modifying equation (6). Equation (7) is used to convert the pressure change ratio, which is the amplitude ratio of the pressure pulse wave, into the vascular diameter change ratio.
ΔVc/Vc=(2DΔD+ ^ΔD2 )/ ^D2≈ (2DΔD)/ ^D2
= 2ΔD / D ... (7)

Now, substituting equation (5) into equation (7), we get
ΔD/D=(Vc×ΔPc)/(2×Vc×Pc) (8)

At this time, the relationship between the increase in the volume V of the measurement target (upper arm 14) compressed by the compression cuff 12 and the increase in the compression pressure Pc has been experimentally demonstrated, so the volume Vc of the compression cuff 12 is given by equation (9), where Vhold is the capacity (volume) of the compression cuff 12 when measuring the change in volume, and Vo is the capacity (volume) of the compression cuff 12 that does not contribute to the compression pressure.
Vc=Vhold-Vo

The relationship between the compression pressure Pc (mmHg) in the compression cuff 12 and the volume V of the compression cuff 12 is experimentally shown in Figure 5 when the flow rate into the compression cuff 12 is measured using a flow meter. This relationship is expressed by the following multidimensional approximation formula (9). The constant c in formula (9) corresponds to the above-mentioned Vo.
V = _a1 x ^Pc2 + _b1 x Pc + _c1 ... (9)

The relationship of the above formula (9) is used when decreasing the compression pressure Pc of the compression cuff 12. When formula (9) is differentiated with respect to time,
dV/dt = 2a x Pc x dPc/dt + b x dPc/dt
= (2a × Pc + b) × dPc / dt ... (10)
Here, exhaust flow rate Q=dV/dt (11)
Pressure drop rate K=dPc/dt (12)
Therefore, the relationship between the exhaust flow rate Q and the pressure drop speed K is expressed by the following equation (13).
Q = K × ( _2a1 × Pc + _b1 ) ... (13)
From equation (13), the exhaust flow rate Q is determined by the set pressure reduction rate K and the compression pressure Pc (measured value) in the compression cuff 12. The pressure reduction rate K is set as follows from the pressure Pcs at the start of pressure reduction, the pressure Pce at the end of pressure reduction, and the pressure reduction time ΔT.
K = (Pcs - Pce) / ΔT ... (14)

The vascular dilation rate calculation unit 48 determines the maximum amplitude pressure pulse wave among the multiple pressure pulse waves collected continuously, for example, every beat, during a predetermined holding period T2 by the pressure pulse wave collection control unit 44, calculates the amplitude ratio ΔPc/Pc between the amplitude (mmHg or mV) of the maximum amplitude pressure pulse wave and, for example, the amplitude (mmHg or mV) of the initial pressure pulse wave, the terminal pressure pulse wave, or the minimum amplitude pressure pulse wave during the ischemia period T1, and calculates the vascular diameter change ratio, i.e., the arterial vascular diameter dilation rate ΔD/D, from the amplitude ratio ΔPc/Pc using the relationship in equation (7), and displays it on the display 30d to evaluate the endothelial function of the living body.

Figure 6 is a flow chart explaining the main control operations of the electronic control device 30, showing a vasodilation rate measurement routine that is started by starting up the arterial endothelial function testing device 10. In Figure 6, in step S1 (hereinafter, steps are omitted), the air pump 18 is driven and the control valve 16 is controlled to increase the compression pressure Pc, which is the internal pressure of the compression cuff 12 wrapped around a part of the living body, i.e., the upper arm 14. Next, in S2, it is determined whether the compression pressure Pc, which is the internal pressure of the compression cuff 12, has reached a preset target pressure increase value P1. If the determination in S2 is negative, S1 and subsequent steps are repeatedly executed, but if the determination is positive, S3, which corresponds to the blood flow obstruction control unit 34, is started. Time t0 in Figure 3 shows this state.

In S3, the compression pressure Pc, which is the internal pressure of the compression cuff 12, is maintained at the target pressure increase value P1, and the portion of the upper arm 14 around which the compression cuff 12 is wrapped is occluded for a preset occlusion period T1. In the following S4, after the end of occlusion, i.e., the start of the descent (time t1), the compression pressure Pc begins to decrease stepwise for each pulse by a constant pressure drop of, for example, about 3 to 4 mmHg. Time t1 in Figure 3 shows this state.

Next, in S4, which corresponds to the shear stress application control section, when the magnitude of the fundamental wave of the blood flow vibration is equal to or greater than the judgment threshold Th (time t3 in FIG. 5), the compression pressure Pc is controlled so that as many blood flow vibrations as possible occur, and shear stress is applied to the endothelium of the arterial blood vessel 14a. The application of shear stress to the endothelium of the arterial blood vessel 14a continues until the point at which a rapid drop begins (time t4) is reached that exceeds the shear stress application time Tz, which is set slightly shorter than the vasodilation reaction start time (for example, 18 to 20 seconds) from the occurrence of the first blood flow to the start of the vasodilation reaction, or until the point at which the magnitude of the fundamental wave of the blood flow vibration falls below the judgment threshold Th (time t4), at which point the compression pressure by the compression band 12 begins to decrease rapidly.

In S6, it is determined whether the compression pressure Pc by the compression cuff 12 has fallen below the holding pressure P2. As long as the determination in S6 is negative, S4 and subsequent steps are repeatedly executed. If the determination is positive, in S7 corresponding to the blood pressure measurement unit 40, for example, in the process of decreasing the compression by the compression cuff 12 shown in FIG. 3, the pressure represented by the cuff pressure signal SPc at time t2 when the first blood flow vibration occurs is determined as the systolic blood pressure value SBP, and the pressure represented by the cuff pressure signal SPc at time t4 when the final blood flow vibration occurs is determined as the diastolic blood pressure value DBP.

Next, in S8 corresponding to the compression pressure holding control unit 42, the compression pressure Pc of the compression band 12 is held at a preset holding pressure P2. Next, in S9 corresponding to the pressure pulse wave collection control unit 44, during the holding period T2 during which the compression pressure Pc of the compression band 12 is held at the relatively low value of holding pressure P2, pressure pulse waves, which are pressure vibrations that are superimposed on the compression pressure Pc of the compression band 12 detected by the pressure sensor 22 for each beat, are collected sequentially. This collection is performed for a period that sufficiently covers the timing at which the arterial blood vessel volume is maximized due to the vasodilatory response caused by the application of shear stress at time t3, for example, a period between 250 and 300 seconds.

Next, in S9, which corresponds to the vascular dilation rate calculation unit 48, the maximum amplitude pressure pulse wave is determined from among the multiple pressure pulse waves collected continuously, for example, every beat, during the specified period T2, and the amplitude ratio ΔPc/Pc between the amplitude (mmHg or mV) of the maximum amplitude pressure pulse wave and, for example, the amplitude (mmHg or mV) of the first pressure pulse wave, the last pressure pulse wave, or the minimum amplitude pressure pulse wave during the specified period T2 is calculated. The vascular diameter dilation rate (vascular diameter change ratio) ΔD/D is calculated from the amplitude ratio ΔPc/Pc using the relationship in equation (7), and is displayed on the display 30d. This vascular diameter dilation rate ΔD/D is used to evaluate the endothelial function of the living body.

Then, in S11, the compression of the compression belt 12 is released, and termination processing such as resetting each register is performed, after which this routine is terminated.

As described above, the endothelial function testing device 10 of this embodiment includes a compression cuff 12 that wraps around a part of the living body, a pressure sensor 22 that detects the compression pressure Pc of the compression cuff 12, a blood flow vibration determination unit 38 that detects blood flow vibration generated from the arterial blood vessel 14a in the living body compressed by the compression cuff 12, and a compression pressure control unit 32 that controls the compression pressure Pc of the compression cuff 12. After a part of the living body is blocked by the compression pressure Pc of the compression cuff 12, the compression pressure Pc is gradually released in the living body by lowering the compression pressure Pc to apply shear stress to the endothelium of the arterial blood vessel 14a, and the compression pressure Pc of the compression cuff 12 is maintained at a predetermined holding pressure P2. The endothelial function testing device 10 for the arterial blood vessel 14a evaluates the endothelial function of the arterial blood vessel 14a based on the pressure pulse wave, which is the fluctuation of the compression pressure Pc in the compression cuff 12, and includes a shear stress application control unit 36 that controls the compression pressure control unit 32 so that blood flow vibration detected by the blood flow vibration determination unit 38 is generated.

As a result, the shear stress application control unit 36 controls the compression pressure control unit 32 so that blood flow vibrations are generated that are detected by the blood flow vibration determination unit 38, so that a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessel 14a of the living body under compression by the compression band 12, thereby improving the reliability of the endothelial function testing device for the arterial blood vessel 14a.

According to the arterial vascular endothelial function testing device 10 of this embodiment, a blood flow vibration determination unit 38 is provided that extracts pressure vibrations superimposed on the cuff pressure signal SPc in synchronization with the pulse of the living body from the cuff pressure signal SPc corresponding to the compression pressure Pc detected by the pressure sensor 22, and determines the blood flow vibration based on the magnitude of the frequency component of the blood flow vibration contained in the pressure vibrations. In this way, the blood flow vibration determination unit 38 determines the blood flow vibration based on the magnitude of the frequency component of the blood flow vibration contained in the pressure vibrations superimposed on the cuff pressure signal SPc in synchronization with the pulse of the living body, so that a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessel 14a of the living body under compression by the compression cuff 12.

According to the arterial blood vessel endothelial function testing device 10 of this embodiment, the blood flow vibration judgment unit 38 judges the blood flow vibration based on whether the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration to the magnitude of the fundamental frequency component of the pulse wave contained in the pressure vibration is equal to or greater than a predetermined judgment threshold Th, so that the influence of gain changes and individual differences is reduced, and a sufficient amount of shear stress can be efficiently and reliably applied to the endothelium of the living body's arterial blood vessel 14a under compression by the compression cuff 12.

According to the arterial endothelial function testing device 10 of this embodiment, the compression pressure control unit 32 is provided with a blood flow obstruction control unit 34 that obstructs the blood flow in the upper arm 14 for 30 seconds or more by compressing the compression belt 12 prior to the reduction of the compression pressure by the compression belt 12. As a result, the blood flow obstruction by the compression belt 12 is released in a state where the arterial blood vessel 14a downstream of the compression belt 12 and the venous blood vessel connected thereto via the capillary vessel are sufficiently equalized, so that the amount of blood flowing into the arterial blood vessel 14a downstream of the compression belt 12 is secured, and the effect of applying shear stress is enhanced.

According to the arterial endothelial function testing device 10 of this embodiment, the compression pressure control unit 32 lowers the compression pressure by the compression belt 12 when the blood flow vibration judgment unit 38 judges that the ratio of the magnitude of the fundamental frequency component of the blood flow vibration falls below a predetermined threshold, and maintains the compression pressure by the compression belt 12 for a predetermined pulse rate when the blood flow vibration judgment unit 38 judges that the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration obtained in the section where the compression pressure by the compression belt 12 is constant is equal to or greater than a predetermined judgment threshold Th. As a result, blood flows in which the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the cuff pressure signal SPc is equal to or greater than the predetermined judgment threshold Th are used more frequently for applying shear stress, thereby enhancing the effect of applying shear stress.

According to the arterial vascular endothelial function testing device 10 of this embodiment, the compression pressure control unit 32 gradually lowers the compression pressure, and the blood flow vibration determination unit 38 determines the blood flow vibration based on whether the ratio of the magnitude of the fundamental frequency component of the blood flow vibration contained in the pressure vibration obtained in the section where the compression pressure by the compression cuff 12 is constant is equal to or greater than a predetermined determination threshold value Th. In this way, the pressure vibration can be obtained accurately without being affected by the frequency component of the decreasing compression pressure, compared to the case where the pressure vibration obtained in the section where the compression pressure changes continuously is used.

According to the arterial blood vessel endothelial function testing device 10 of this embodiment, the shear stress application control unit 36 causes the compression pressure control unit 32 to release the compression by the compression belt 12 when a preset shear stress application time Tz has elapsed since the first blood flow occurs due to the decrease in compression pressure of the compression belt 12. This makes it possible to avoid overlapping of the application of shear stress and the start of the vasodilation reaction, thereby improving the reliability of the arterial blood vessel 14a endothelial function testing device. The preset shear stress application time Tz is set to be as long as possible within a range that is shorter than the vasodilation reaction start time, for example, 18 seconds, from the first blood flow to the start of the vasodilation reaction.

The arterial vascular endothelial function testing device 10 of this embodiment includes a compression pressure holding control unit 42 that holds the compression pressure of the compression belt 12 at a predetermined holding pressure P2 for a predetermined holding period T2 after the shear stress application control unit 36 applies shear stress to the arterial blood vessel 14a directly below the compression belt 12, a pressure pulse wave acquisition control unit 44 that continuously collects pressure pulse waves for a predetermined period while the compression pressure of the compression belt 12 is held at the holding pressure P2, and a vascular dilation rate calculation unit 48 that converts the pressure pulse waves continuously collected for the predetermined period by the pressure pulse wave acquisition control unit 44 into a volumetric value to calculate the dilation rate of the arterial blood vessel 14a in terms of an equivalent blood vessel diameter.

This eliminates the need for an ultrasonic probe, a probe support device that supports it and searches for the optimal position, and an ultrasonic image generating device that processes signals from the ultrasonic probe to generate ultrasonic images, making the device simple and compact. Furthermore, the vascular expansion rate calculation unit 48 calculates the expansion rate of the arterial blood vessel 14a using equivalent blood vessel diameter conversion by volumetrically converting the pressure pulse waves collected continuously for a predetermined period by the pressure pulse wave collection control unit 44. This means that the timing at which the blood vessel diameter (vascular volume) becomes maximum due to the vasodilation reaction caused by the shear stress acting on the arterial blood vessel 14a almost coincides with the detection timing of any of the pressure pulse waves collected continuously for a predetermined period, enabling highly reliable vascular endothelial function testing.

Next, another embodiment of the present invention will be described. In the following description, parts common to the previous embodiment will be given the same reference numerals and will not be described.

7, 8, and 9 show three types of first, second, and third thresholds Th1, Th2, and Th3 as the judgment thresholds Th used by the blood flow vibration judgment unit 38 to judge whether the fundamental frequency component of the blood flow vibration has been exceeded. In the above-mentioned embodiment, the judgment threshold Th was a constant value, but in this embodiment, it is changed to three levels: the first judgment threshold Th1 used to judge blood flow vibration in the early stage of the compression pressure drop period, the second judgment threshold Th2 used to judge blood flow vibration in the middle stage of the compression pressure drop period, and the third judgment threshold Th3 used to judge blood flow vibration in the later stage of the compression pressure drop period.

The first judgment threshold Th1 is smaller than the second judgment threshold Th2 and the third judgment threshold Th3, and is set to, for example, about 20% of the magnitude of the fundamental frequency component of the pulse wave. The third judgment threshold Th3 is smaller than the second judgment threshold Th2, and is set to, for example, about 40% of the magnitude of the fundamental frequency component of the pulse wave. The third judgment threshold Th3 is larger than the first judgment threshold Th1 and the third judgment threshold Th3, and is set to, for example, about 60% of the magnitude of the fundamental frequency component of the pulse wave. In this embodiment, the judgment threshold Th is set to a smaller value as the compression pressure applied by the compression cuff 12 deviates from the mean blood pressure value.

According to this embodiment, in order to minimize the effect of the compression pressure by the compression band 12 on the action of applying shear stress based on the judgment of blood flow vibration, a relatively small first judgment threshold Th1 is used to judge blood flow vibration in the early stage of the compression pressure drop period when the effect of applying shear stress due to the passage of blood flow is relatively large. However, a relatively large second judgment threshold Th2 is used to judge blood flow vibration in the middle stage of the compression pressure drop period when the effect of shear stress due to the passage of blood flow is relatively small.

Figure 10 shows an example in which the blood flow vibration determination unit 38 determines the presence or absence of blood flow vibration generated from the arterial blood vessel 14a under compression by the compression belt 112 based on a signal from a microphone 150 provided on the compression belt 12. The blood flow sound is generated by vortexes of blood flow passing through a portion of the arterial blood vessel 14a that has been narrowed by compression.

According to the arterial blood vessel endothelial function testing device 10 of this embodiment, a microphone 150 is provided in the compression cuff 112 to detect blood flow sounds generated in the arterial blood vessel 14a, and blood flow vibration is determined based on the magnitude of the frequency components of the blood flow vibration detected by the microphone 150. According to this embodiment, blood flow vibration can be obtained without using the bandpass filter 26 and frequency analysis, and a sufficient amount of shear stress can be efficiently applied to the endothelium of the arterial blood vessel 14a under compression by the compression cuff 112.

Figure 11 shows an example of another embodiment of the present invention in which the shear stress application control unit 36 controls the compression pressure of the compression belt 12 to continuously lower the cuff pressure signal SPc at a speed of about 3 to 6 mmHg/sec, except for the section (time t3 to time t4) in which the compression pressure at which the blood flow vibration is detected by the blood flow vibration detection unit 38 is maintained constant. According to this embodiment, it is easier to control the decrease in the compression pressure Pc of the compression belt 12 compared to the case in which the compression pressure Pc is reduced in stages, and the measurement time is shortened.

Figure 12 shows an example of another embodiment of the present invention in which the shear stress application control unit 36 controls the compression pressure by the compression cuff 12 to continuously lower the cuff pressure signal SPc. However, in the section (time t3 to time t4) in which blood flow vibration is detected by the blood flow vibration detection unit 38, the cuff pressure signal SPc is lowered at a slower speed, for example, of 1 to 3 mmHg/sec, compared to other sections in which the cuff pressure signal SPc is lowered continuously at a speed of, for example, 3 to 6 mmHg/sec. In this embodiment, too, it is easier to control the lowering of the compression pressure Pc of the compression cuff 12, and the measurement time is shortened, compared to when the compression pressure Pc is lowered in stages.

The above describes in detail an embodiment of the present invention based on the drawings, but the present invention can also be applied in other aspects.

For example, in the above-mentioned embodiment, in order to obtain the vascular dilation rate, the compression pressure holding control unit 42 holds the compression pressure of the compression belt 12 at a predetermined holding pressure P2 for a predetermined holding period T2 after the shear stress application control unit 36 applies shear stress to the arterial blood vessel 14a directly below the compression belt 12, the pressure pulse wave acquisition control unit 44 continuously collects pressure pulse waves for a predetermined period while the compression pressure of the compression belt 12 is held at the holding pressure P2, and the vascular dilation rate calculation unit 48 calculates the dilation rate of the arterial blood vessel 14a in terms of the equivalent blood vessel diameter by volumetrically converting the pressure pulse waves continuously collected for a predetermined period by the pressure pulse wave acquisition control unit 44. However, instead of these, when the blood flow is released, the change in the cross-sectional shape of the artery grasped using an ultrasound image obtained using an ultrasound probe, for example, the maximum rate of change in the vascular lumen diameter relative to the endothelial diameter before hemostasis, may be measured, and the endothelial function of the arterial blood vessel may be evaluated based on the maximum rate of change in the vascular lumen diameter.

In addition, in the above-mentioned embodiment, air, which is a compressed fluid, is supplied from the air pump 18 to generate the compression pressure Pc in the compression belt 12. However, instead of this, a cylinder that supplies carbon dioxide gas or nitrogen gas may be used, or a non-compressible fluid such as water or oil may be used.

In addition, in the above-mentioned embodiment, the compression belt 12 is wrapped around the upper arm 14, but it may be wrapped around any part of the body, such as the lower leg.

Note that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

10, 110: endothelial function testing device 12, 112: compression garment 14: upper arm (part of the living body)
14a: Arterial blood vessel 16: Control valve 18: Air pump 20: Pipe 22: Pressure sensor 30: Electronic control device 32: Compression pressure control unit 34: Blood flow obstruction control unit 36: Shear stress application control unit 38: Blood flow vibration determination unit 40: Blood pressure measurement unit 42: Compression pressure maintenance control unit 44: Pressure pulse wave acquisition control unit 46: Pulse wave processing control unit 48: Vascular dilation rate calculation unit 150: Microphone T2: Retention period (predetermined retention period)
Th, Th1 to Th3: Determination thresholds (predetermined determination thresholds)

Claims (10)

an arterial endothelial function testing device comprising a compression band wrapped around a part of a living body, a pressure sensor that detects the compression pressure of the compression band, a blood flow vibration determination unit that detects blood flow vibration generated from an arterial blood vessel in the living body compressed by the compression band, and a compression pressure control unit that controls the compression pressure of the compression band, the device evaluating endothelial function of the arterial blood vessel based on a pulse wave generated in the arterial blood vessel, which is a pressure pulse wave that is a fluctuation in the compression pressure in the compression band, while maintaining the compression pressure of the compression band at a predetermined pressure pulse wave sampling pressure after blood flow is blocked by the compression band and the arterial blood vessel in the living body is gradually released by decreasing the compression pressure to apply shear stress to an endothelium of the arterial blood vessel,
a shear stress application control unit that controls the compression pressure control unit so that the blood flow vibration detected by the blood flow vibration determination unit is generated. 2. The apparatus for testing endothelial function of an arterial blood vessel according to claim 1, wherein the blood flow vibration determination unit extracts pressure vibrations superimposed on the cuff pressure signal in synchronization with the pulse of the living body from the cuff pressure signal representing the compression pressure detected by the pressure sensor, and determines the blood flow vibrations based on the magnitude of frequency components of the blood flow vibrations contained in the pressure vibrations. 3. The apparatus for inspecting endothelial function of an arterial blood vessel according to claim 2, wherein the blood flow vibration determination unit determines the blood flow vibration based on whether a ratio of a magnitude of a fundamental frequency component of the blood flow vibration contained in the pressure vibration to a magnitude of a fundamental frequency component of a pulse wave contained in the pressure vibration is equal to or greater than a predetermined threshold value. 2. The device for testing endothelial function of an arterial blood vessel according to claim 1, wherein the blood flow vibration determining unit includes a microphone provided in the compression garment to detect blood flow sounds generated in the arterial blood vessel, and determines the blood flow vibration based on the magnitude of the frequency components of the blood flow vibration detected by the microphone. The arterial endothelial function testing device of claim 1, characterized in that the compression pressure control unit is provided with a blood flow obstruction control unit that obstructs blood flow to a part of the living body for 30 seconds or more by compression with the compression band prior to the reduction of the compression pressure by the compression band. 4. The device for testing endothelial function of an arterial blood vessel according to claim 3, wherein the compression pressure control unit decreases the compression pressure applied by the compression band when the blood flow vibration determination unit determines that the proportion of the magnitude of the fundamental frequency component of the blood flow vibration included in the pressure vibration obtained in a section where the compression pressure applied by the compression band is constant is below a predetermined threshold, and maintains the compression pressure applied by the compression band for a predetermined pulse rate when the blood flow vibration determination unit determines that the proportion of the magnitude of the fundamental frequency component of the blood flow vibration is equal to or greater than a predetermined threshold. 7. The apparatus for inspecting endothelial function of an arterial blood vessel according to claim 6, wherein the predetermined threshold value is set to a smaller value as it deviates from a mean blood pressure value of the living body. The compression pressure control unit reduces the compression pressure in stages,
7. The device for testing endothelial function of an arterial blood vessel according to claim 6, wherein the blood flow vibration determination unit determines the blood flow vibration based on whether a ratio of a magnitude of a fundamental frequency component of the blood flow vibration contained in the pressure vibration obtained in a section where the compression pressure by the compression cuff is constant is equal to or greater than a predetermined threshold value. The apparatus for testing endothelial function of an arterial blood vessel according to claim 6, characterized in that the shear stress application control unit causes the compression pressure control unit to release the compression by the compression band when a preset shear stress application time has elapsed since a first pulse wave is generated due to a decrease in the compression pressure of the compression band. a compression pressure holding control unit that holds the compression pressure of the compression band at a predetermined pressure pulse wave collection pressure for a predetermined time after the shear stress application control unit applies shear stress to the arterial blood vessel immediately below the compression band;
a pressure-pulse-wave collection control unit that continuously collects pressure pulse waves for a predetermined period of time while the compression pressure of the compression band is maintained at the pressure-pulse-wave collection pressure;
and a vasodilation rate calculation unit that calculates the dilation rate of the arterial blood vessel in terms of an equivalent blood vessel diameter by volumetrically converting the pressure pulse wave continuously collected for a predetermined period by the pressure pulse wave collection control unit.

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