Endothelium function examination device for arterial vessels

Abstract

To provide an endothelium function examination device for arterial vessels that achieves high measurement accuracy without being affected by reflected waves superimposed on the volume pulse wave.SOLUTION: A volume pulse wave amplitude calculation unit 58 defines a section in which no reflected waves are superimposed for the volume pulse wave SM2 within a rising section Ar of the volume pulse wave SM as a fixed no-reflected wave section Am, and calculates the maximum value within the fixed no-reflected wave section Am as the maximum amplitude F2m of volume pulse wave SM2 and the maximum amplitude F3m of the volume pulse wave SM3. An amplitude increase rate calculation unit 64 calculates the amplitude increase rate FRm between the maximum amplitude F2m of the volume pulse wave SM2 immediately before or after the avascularization and the maximum amplitude F3m of the volume pulse wave SM3 indicating the maximum amplitude after release of the avascularization. An arterial vessel dilation function examination unit 66 evaluates the endothelial function of the arterial vessel 14a on the basis of the amplitude increase rate FRm. This configuration enables evaluation of the endothelial function of the arterial vessel 14a without being affected by the reflected waves superimposed on the volume pulse wave SM.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an arterial vascular endothelial function testing apparatus capable of testing the endothelial function of blood vessels based on a volume pulse wave included in the pressure of a compression band wound around a part of a living body.

Background Art

[0002] It is known that a decrease in the endothelial function of arterial blood vessels occurs prior to arteriosclerosis of a living body, and various apparatuses for evaluating such endothelial function have been proposed. The apparatuses described in Patent Document 1 and Patent Document 2 are examples thereof. The above-mentioned endothelial function refers to a vasodilation reaction generated by the production of NO (nitric oxide) from endothelial cells constituting the intima based on the shear stress of blood flow acting on the endothelium located at the innermost circumference among the adventitia, media, and intima that constitute the arterial vessel wall, and the relaxation of smooth muscle by the NO.

[0003] In the endothelial function testing apparatus of Patent Document 1, a compression band (cuff) attached to the upper arm of a living body is rapidly decompressed after maintaining a predetermined blood expulsion period of about 5 minutes at a pressure higher than the maximum blood pressure, and is maintained at a pressure below the maximum blood pressure. Among the cuff pulse waves obtained, the ratio between the peak value of the first pulse wave that appears first and the peak value of the second pulse wave having the maximum amplitude thereafter is used to evaluate the vascular endothelial function of the living body. According to this, it is said that a small and inexpensive vascular endothelial function evaluation apparatus can be obtained.

[0004] Since the compression band (cuff) attached to the upper arm of a living body also serves as a compression device for expelling blood from the upper arm of the living body and a volume pulse wave detection device for detecting a volume pulse wave generated from the artery of the upper arm while maintaining the compression band at a pressure lower than the blood expulsion pressure, there is a drawback that a smooth muscle dilation reaction generated by stress due to applying the blood expulsion pressure to the artery under compression is mixed into the waveform (amplitude) of the volume pulse wave detected while maintaining the compression band at a pressure lower than the blood expulsion pressure.

[0005] In contrast, in the endothelial function examination apparatus of Patent Document 2, a first cuff wound around a first site (forearm) of a living body, a second cuff wound around a second site (upper arm) of the living body, a cuff pressure control unit that controls pressurization and depressurization of the cuff, a pressure sensor connected to the second cuff that detects the cuff pressure of the second cuff, a pulse wave sensor that detects a pulse wave from the cuff pressure of the second cuff, and an analysis unit that analyzes the detected pulse wave. The first cuff pressurizes the first site of the living body in a predetermined blood drive section to stimulate the endothelium of the arterial blood vessel with blood flow, and compares the amplitude of the volume pulse wave before the pressurization stimulus obtained by the second cuff with the amplitude of the volume pulse wave after the pressurization stimulus, and calculates the increase rate, whereby the vascular endothelial function is evaluated. According to this, the first cuff wound around the forearm of the living body is exclusively used for blood drive of the forearm, and the second cuff wound around the second site (upper arm) of the living body is used for detection of the volume pulse wave. Therefore, there is an advantage that the smooth muscle dilation reaction of the artery under compression does not mix into the waveform (amplitude) of the volume pulse wave.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, it is known that reflected waves from the cuff release side are superimposed on the volume pulse wave obtained as the pressure vibration of the cuff. In the endothelial function testing device of Patent Document 1 and the endothelial function testing device of Patent Document 2, the amplitude of the volume pulse wave after the pressurization stimulus is used. However, since the volume pulse wave with the reflected wave superimposed is used, when calculating the amplitude from the minimum value to the maximum value of such a volume pulse wave and examining the endothelial function of the arterial blood vessels of a living body based on the increase ratio between the amplitude of the volume pulse wave immediately before or after blood ejection and the maximum amplitude of the volume pulse wave after blood ejection, the generation timing and magnitude vary depending on the heart rate and blood flow, and the amplitude of the volume pulse wave with the reflected wave superimposed, which has no relation to the vasodilation reaction due to NO production based on the shear stress of the endothelium, changes after ischemia release as shown in, for example, Fig. 8, making it difficult to examine the endothelial function in some cases.

[0008] The present invention has been made against the background of the above circumstances, and an object thereof is to provide an endothelial function testing device for arterial blood vessels with high measurement accuracy that is not affected by the influence of reflected waves superimposed on the volume pulse wave.

[0009] Based on the above circumstances, the inventors of the present invention have conducted various studies and found that reflected waves are not superimposed on the entire volume pulse wave shape, and there is a section (section without reflected waves) where reflected waves are not superimposed from the rise of the volume pulse wave shape. When observing the change in the maximum amplitude within a certain rising section from the rising point of the volume pulse wave shape set within the section without reflected waves, it was found that, unlike the change in the amplitude from the minimum value to the maximum value of the volume pulse wave after blood ejection, it shows the same change as the arterial lumen diameter after blood ejection. The present invention has been made based on such findings.

Means for Solving the Problems

[0010] That is, the gist of the present invention is as follows: (a) a compression device having an inflatable bag for compressing a part of a living body, and a volume pulse wave detection device for detecting a volume pulse wave generated based on a volume change of an arterial blood vessel in a part of the living body different from the compression site by the compression device, and after blood ejection of a part of the living body using the compression device for a predetermined time and then releasing the blood ejection, an endothelial function inspection device for inspecting the endothelial function of the arterial blood vessels of the living body based on the change in the volume pulse wave detected by the volume pulse wave detection device, (b) a volume pulse wave amplitude calculation unit that sequentially calculates, as the amplitude of the volume pulse wave, the maximum value within a preset constant rising section within a reflection wave-free section where no reflection wave is superimposed in the volume pulse wave, (c) an amplitude increase rate calculation unit that calculates an increase rate of the amplitude of the volume pulse wave calculated by the amplitude calculation unit with respect to the amplitude of the volume pulse wave immediately before or after the blood ejection and the maximum amplitude after the blood ejection release, and (d) an arterial vasodilation function inspection unit that evaluates the endothelial function of the arterial blood vessels based on the increase rate calculated by the amplitude increase rate calculation unit.

Advantages of the Invention

[0011] According to the endothelial function inspection device for arterial blood vessels of the present invention, the volume pulse wave amplitude calculation unit calculates, as the amplitude of the volume pulse wave, the maximum value within a preset constant rising section within a reflection wave-free section where no reflection wave is superimposed in the volume pulse wave, the amplitude increase rate calculation unit calculates an increase rate of the amplitude of the volume pulse wave with respect to the amplitude of the volume pulse wave immediately before or after the blood ejection and the maximum amplitude after the blood ejection release, and the arterial vasodilation function inspection unit evaluates the endothelial function of the arterial blood vessels based on the increase rate. Thereby, the endothelial function of the arterial blood vessels is evaluated from the amplitude of the volume pulse wave sequentially obtained within a range not affected by the reflection wave superimposed on the volume pulse wave, so that an endothelial function inspection device for arterial blood vessels with high measurement accuracy can be obtained.

[0012] Preferably, the volume pulse amplitude calculation unit includes a reflected wave-free interval calculation unit that calculates a reflected wave-free interval in which no reflected wave overlaps in the waveforms of the volume pulses sequentially obtained after a blood pumping section in which a part of the living body is blood-pumped for a predetermined time using the compression device, and a reflected wave-free interval amplitude calculation unit that calculates the maximum amplitude within the reflected wave-free interval in the waveform of the volume pulse. As a result, a pulse wave within a reflected wave-free interval in which no reflected wave overlaps in the pulse wave can be obtained, and it becomes possible to evaluate the endothelial function of the arterial blood vessel that is not affected by the reflected wave.

[0013] Preferably, the reflected wave-free interval calculation unit sets, as a reflected wave-free interval in which no reflected wave overlaps in the volume pulse, an interval from the maximum value of the second derivative waveform of the volume amplitude waveform immediately before or immediately after the end of the blood pumping section to the maximum value of the first derivative waveform of the volume amplitude waveform. Since a reflected wave overlaps after the maximum value of the first derivative waveform in the volume pulse, a pulse wave within a reflected wave-free interval in which no reflected wave overlaps in the pulse wave can be obtained as described above.

[0014] Preferably, the blood pumping of a part of the living body for a predetermined time is blood pumping for 5 minutes. As a result, since the blood flow is restarted in a state where the side closer to the distal end than the part of the living body blood-pumped by the compression device is sufficiently in an ischemic state, shear stress is applied to the endothelial cells of the arterial blood vessel due to the blood flow, and thus a flow-dependent dilation response of the arterial blood vessel can be obtained.

[0015] Preferably, the amplitude increase rate calculation unit calculates an increase ratio of the amplitude of the volume pulse calculated by the reflected wave-free interval amplitude calculation unit to the amplitude of the volume pulse immediately after the blood pumping and the maximum amplitude after the release of the blood pumping. As a result, the endothelial function of the arterial blood vessel is evaluated from the amplitude of the volume pulse sequentially obtained within a range not affected by the influence of the reflected wave overlapping the volume pulse.

[0016] Preferably, the compression device has a blood pumping inflation bag that compresses the compression site by the compression device at a pressure higher than the maximum blood pressure value of the living body, and pumps blood from the compression site by the compression device and the peripheral side site of the compression site in the living body. As a result, after the blood pumping is released, the blood flow rate through the artery is sufficiently increased, so that the endothelium in the arterial blood vessel can be sufficiently stimulated by the shear stress generated by the blood flow.

[0017] Preferably, the volume pulse detection device has a sensor inflation bag that compresses a portion of the living body located proximal to the compression site by the compression device at a pressure lower than the minimum blood pressure value of the living body, and detects a volume pulse generated in the inflation bag based on the volume change of the arterial blood vessel. Thereby, the stress applied to the smooth muscle is reduced, and the mixing of the dilation reaction by the smooth muscle is suppressed.

[0018] Preferably, the blood pumping inflation bag and the sensor inflation bag are housed in a single strip-shaped bag wound around the living body, and are positioned at a predetermined interval in the longitudinal direction of the arterial blood vessel. Thereby, it becomes easy to attach the blood pumping inflation bag and the sensor inflation bag to a part of the living body. An endothelial function inspection apparatus for an arterial blood vessel according to claim 7, characterized in that.

Brief Description of Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of each part are not necessarily drawn accurately.

Embodiment

[0021] FIG. 1 is a schematic diagram for explaining an arterial blood vessel endothelial function inspection device 10 which is an example of the present invention. In FIG. 1, the upper arm cuff 12 functioning as a compression device for a part of the living body is an inflation bag wound around a part of the living body, for example, the upper arm 14, which is the same as that used in blood pressure measurement, and functions as an inflation bag for a sensor for detecting a volume pulse wave. A pipe 20 is connected to the upper arm cuff 12, and an upper arm cuff pressure control valve 16 for adjusting the pressure or discharge flow rate in the upper arm cuff 12 by supplying air to the upper arm cuff 12 and discharging air from the upper arm cuff 12 through the pipe 20, and an air pump 18 are connected. Further, an upper arm cuff pressure sensor 22 is connected to the upper arm cuff 12 through the pipe 20, and an upper arm cuff pressure signal SPuc indicating the compression pressure on the arterial blood vessel 14a directly below the upper arm cuff 12 wound around the upper arm 14 is detected.

[0022] The upper arm cuff pressure signal SPuc detected by the upper arm cuff pressure sensor 22 is supplied to a low-pass filter 24 and a band-pass filter 26. The low-pass filter 24 separates the static pressure component from the upper arm cuff pressure signal SPuc and outputs a signal representing the compression pressure Puc (mmHg). The band-pass filter 26 separates the volume pulse wave SM, which is a pressure vibration component superimposed on the compression pressure Pc in synchronization with the heartbeat of the living body, from the upper arm cuff pressure signal SPuc and outputs a signal representing the volume pulse wave SM. The signals representing the compression pressure Puc and the volume pulse wave SM are input to the electronic control device 50 via the A / D converter 28.

[0023] On a compression site different from the upper arm cuff 12 of the living body, for example, on the forearm 30, a forearm cuff 32 composed of an inflatable bag similar to the upper arm 14 is wound. The forearm cuff 32 functions as a blood drive inflatable bag, that is, a compression device, which drives blood on the winding site of the forearm cuff 32 and the peripheral side of the winding site to make it in an ischemic state. A pipe 40 is connected to the forearm cuff 32, and a forearm cuff pressure control valve 36 and an air pump 38 for adjusting the pressure or discharge flow rate in the forearm cuff 32 by supplying air to the forearm cuff 32 and discharging air from the forearm cuff 32 through the pipe 40 are connected. Further, a forearm cuff pressure sensor 42 is connected to the forearm cuff 32 through the pipe 40, and a forearm cuff pressure signal SPfc indicating the compression pressure on the arterial blood vessel 14b directly below the forearm cuff 32 wound around the forearm 32 is detected.

[0024] The forearm cuff pressure signal SPfc detected by the forearm cuff pressure sensor 42 is supplied to a low-pass filter 44. The low-pass filter 44 separates the static pressure component from the forearm cuff pressure signal SPfc and outputs a signal representing the compression pressure Pfc (mmHg). The signal representing the compression pressure Pfc is input to the electronic control device 50 via the A / D converter 48.

[0025] FIG. 2 is an enlarged view schematically showing the multilayer structure of the arterial blood vessel 14a in the upper arm 14 which is the measurement target of the endothelial function inspection device 10 for arterial blood vessels. This arterial blood vessel 14a has a three-layer structure including an intima L1 having a single layer of endothelial cells on the inner peripheral surface, a media L2 composed of smooth muscle and elastic fibers and having elasticity and elasticity, and an adventitia L3 composed of connective tissue.

[0026] Returning to FIG. 1, the electronic control device 50 is composed of a so-called microcomputer, processes input signals according to a program stored in advance, and outputs the processing results to the display 52. The electronic control device 50 functionally includes a forearm cuff pressure control unit 54, an upper arm cuff pressure control unit 56, a volume pulse wave amplitude calculation unit 58, an amplitude increase rate calculation unit 64, and an arterial blood vessel dilation function inspection unit 66.

[0027] When inspecting the endothelial function of the arterial blood vessel 14a, the forearm cuff pressure control unit 54 uses the forearm cuff pressure control valve 36 to increase the pressure of the forearm cuff 32 to a preset blood expulsion pressure Pc1 which is a predetermined value, for example, 50 mmHg higher than the maximum blood pressure value, simultaneously with the start operation (time point t0) of the endothelial function inspection device 10, and expels blood from the forearm cuff 32 of the forearm 30 to the peripheral side for a certain blood expulsion period T1, for example, 5 minutes, to make it in an ischemic state as shown in FIG. 3. Further, as shown in FIG. 3 for example, the upper arm cuff pressure control unit 56 increases the cuff pressure Pc to a preset pulse wave detection pressure Pc2 which is a predetermined value, for example, 10 to 20 mmHg lower than the minimum blood pressure, from the end point (time point t3) of the blood expulsion period T1, or from a time point about 30 seconds before the end of the blood expulsion period T1 (time point t2), maintains the pulse wave detection pressure Pc2 for a preset volume pulse wave collection period T3, for example, about 2 minutes, and when the volume pulse wave collection period T3 elapses (time point t4), returns the cuff pressure Pc to 0 mmHg (atmospheric pressure).

[0028] The above-described blood drive pressure Pc1 is a pressure that sufficiently drives blood in a part of the living body, which is the site where the forearm cuff 32 is wound and the peripheral part thereof, into an ischemic state. For example, it is set to a pressure obtained by adding a predetermined pressure of about 50 mmHg to the maximum blood pressure value Psys of the living body measured in advance. The above-described pulse wave detection pressure Pc2 is a pressure at which a volume pulse wave SM without distortion can be obtained. For example, it is set to a pressure obtained by subtracting a predetermined pressure of about 10 to 20 mmHg from the minimum blood pressure value Pdia of the living body measured in advance. The above-described blood drive section T1 is set to a section (time) that generates a flow-dependent dilation response derived from NO production from endothelial cells due to shear stress application in the arterial blood vessel 14a in a part of the living body where the forearm cuff 32 is wound. For example, it is set to a value within 5 minutes. The length of the above-described volume pulse wave acquisition section T3 is experimentally set in advance so that it sufficiently includes the time point when the volume pulse wave SM3, in which the amplitude of the volume pulse wave SM shows the maximum value due to NO produced from endothelial cells, is generated among the volume pulse waves SM sequentially obtained after the blood drive section T1.

[0029] The volume pulse wave SM, which is a pressure vibration component superimposed on the compression pressure Pc represented by the upper arm cuff pressure signal SPuc detected by the upper arm cuff pressure sensor 22, corresponds to the volume change of the arterial blood vessel 14a. However, generally, a reflected wave component from a portion where the cross-sectional area of the arterial blood vessel 14a, such as a branch, decreases is superimposed on the waveform of this volume pulse wave SM. The amplitude from the minimum value to the maximum value of one volume pulse wave SM may change as shown in FIG. 9, for example, after the elapse of the blood drive section T1. Therefore, it has been difficult to examine the endothelial function of the arterial blood vessel 14a.

[0030] For this reason, as shown in FIG. 1, the volume pulse wave amplitude calculation unit 58 is provided with a reflected wave-free section calculation unit 60 that calculates a reflected wave-free section Am in which no reflected wave is superimposed on the waveform of the volume pulse wave SM sequentially obtained after the blood drive section T1, for example, the volume pulse wave SM2, and a reflected wave-free section amplitude calculation unit 62 that calculates the amplitude Fm (mmHg) in the reflected wave-free section Am in the waveform of the volume pulse wave SM2.

[0031] The reflected wave-free interval calculation unit 60 determines, from the waveform of the volume pulse wave SM2 obtained immediately after the expiration of the blood ejection interval T1, i.e., at the start of the volume pulse wave acquisition interval T3, the portion corresponding to the maximum value of the first derivative waveform of the volume pulse wave SM2 (time point t11 in FIG. 4) as shown in FIG. 4. This portion is the inflection point of the volume pulse wave SM2, and there may be a reflected wave component superimposed after this inflection point. Next, the reflected wave-free interval calculation unit 60 determines the portion corresponding to the maximum value of the second derivative waveform of the volume pulse wave SM2 (time point t10 in FIG. 4) from the waveform of the volume pulse wave SM2. This portion is the rising point of the volume pulse wave SM2. The reflected wave-free interval calculation unit 60 determines that from the rising point (time point t10) to the inflection point (time point t11) of the volume pulse wave SM2 is both the rising interval Ar of the volume pulse wave SM2 and the reflected wave-free interval Am from which the influence of the reflected wave is excluded. The reflected wave-free interval Am of the volume pulse wave SM2 is also applied to the determination of the amplitudes F2m and F3m for the volume pulse wave SM2 and the volume pulse wave SM3.

[0032] For the volume pulse wave SM2, the reflected wave-free interval amplitude calculation unit 62 determines the increase amount of the volume pulse wave SM2 within the above-described reflected wave-free interval Am as the amplitude F2m (mmHg) of the volume pulse wave SM2. Also, for the volume pulse wave SM3 showing the maximum amplitude, as shown in FIG. 5, the reflected wave-free interval amplitude calculation unit 62 determines the rising point (time point t20 in FIG. 5) corresponding to the maximum value of the second derivative waveform of the volume pulse wave SM3 from the volume pulse wave SM3, and determines the increase amount of the volume pulse wave SM3 from that rising point to the end of the reflected wave-free interval Am (time point t21 in FIG. 5) as the amplitude F3m (mmHg) of the volume pulse wave SM3. In FIG. 5, the inflection point corresponding to the maximum value of the first derivative waveform of the volume pulse wave SM3, i.e., the end point of the rising interval Ar of the volume pulse wave SM3, is shown by a broken line. The inflection point of the waveform of the volume pulse wave SM3 showing the maximum amplitude, which is the end point of the rising interval Ar of the volume pulse wave SM3, indicates that it exceeds the end of the reflected wave-free interval Am (time point t21).

[0033] The amplitude increase rate calculation unit 64 calculates and stores the amplitude increase rate FRm (%) of the amplitude F3m of the volume pulse wave SM3 with respect to the amplitude F2m of the volume pulse wave SM2 from formula (1) using the amplitude F2m of the volume pulse wave SM2 and the amplitude F3m of the volume pulse wave SM3. FRm (%) = 〔(F3m - F2m) / F2m〕× 100 ···(1)

[0034] Here, the vasodilation rate AR can be obtained for the following reasons. That is, according to Boyle's law, the product of the compression pressure Pc in the upper arm cuff 12 and the volume CV of the upper arm cuff 12 is constant (Pc × CV = constant). Therefore, when the volume ΔV of the arterial blood vessel 14a changes, as shown in formula (2), the volume CV of the upper arm cuff 12 changes by -ΔV, and the compression pressure Pc in the upper arm cuff 12 changes by ΔP. (Pc + ΔP)×(CV - ΔV)=k ··· (2)

[0035] Ignoring ΔP × ΔV as it is negligible, formula (2) is expressed by formula (3), and substituting Pc × CV = k into formula (3) results in formula (4). Pc × CV + CV × ΔP - Pc × ΔV = k ··· (3) ΔV = ΔP × (CV / Pc) ··· (4)

[0036] Therefore, from formula (4), if the volume CV of the upper arm cuff 12 is constant and the compression pressure Pc of the cuff 12 is constant, then ΔP, which is the magnitude (amplitude Fm) of the volume pulse wave SM, is proportional to the volume change ΔV of the arterial blood vessel 14a. From this, assuming that the cross-section of the arterial blood vessel 14a is circular, since the amplitude increase rate FRm of formula (1) indicating the amplitude change rate of the volume pulse wave SM is in terms of volume, it is possible to measure the vasodilation rate AR of the arterial blood vessel 14a by using the square root of the amplitude increase rate FRm.

[0037] The arterial vasodilation function examination unit 66 performs an examination of the endothelial function of a living body based on whether the amplitude increase rate FRm (%) calculated by the amplitude increase rate calculation unit 64 exceeds a determination threshold value HFRm that has been experimentally determined and set in advance. For example, if the amplitude increase rate FRm (%) is equal to or greater than the determination threshold value HFRm, it is determined that the endothelial function of the living body is normal. However, if the amplitude increase rate FRm (%) is below the determination threshold value HFRm, it is determined that the endothelial function of the living body has declined, and the determination result is displayed on the display 52.

[0038] (Test 1) FIG. 6 shows a case where the change in the amplitude Fm of the region without reflected waves of the volume pulse wave SM superimposed on the compression pressure Pc2 of the upper arm cuff 12 wound around the upper arm 14 after blood release is measured when the forearm 30 of an adult male (55 years old) is blood-driven in the blood-driving section T1 (5 minutes). As shown in FIG. 6, the amplitude Fm of the region without reflected waves of the volume pulse wave SN sequentially increases from the amplitude F2m of the region without reflected waves immediately after the end of the blood-driving section T1, shows the maximum amplitude F3m at the time point t3 after about 85 seconds have elapsed, and passes through a flat state from 70 seconds to 90 seconds. The maximum amplitude F3m may be a saturation value. The amplitude F2m of the region without reflected waves at the time point t2 immediately after the blood-driving section T1 and the maximum amplitude F3m at the time point t3 are preferably the average values of a predetermined number of adjacent data points.

[0039] FIG. 7 is a flowchart for explaining the main part of the control operation of the electronic control device 30. In FIG. 7, in response to the operation of an activation operation body (not shown), first, steps S1 (hereinafter, steps are omitted) to S9 corresponding to the cuff pressure control process executed by the forearm cuff pressure control unit 54 are executed. In step S1 (hereinafter, steps are omitted), pressurization of the forearm cuff 32 wound around the forearm 30 of the living body is started, and the pressure increase of the compression pressure Pfc of the forearm cuff 32 is started (time point t0 in FIG. 3). In the subsequent S2, it is determined whether the compression pressure Pfc of the forearm cuff 32 has reached a blood-driving pressure Pc1 that is set in advance to be higher than, for example, the maximum blood pressure value of the living body. While the determination in S2 is negative, S1 and S2 are repeated. However, when the determination in S2 is affirmative, in S3, the compression pressure Pfc of the forearm cuff 32 is maintained at the blood-driving pressure Pc1 (time point t1 in FIG. 3).

[0040] In the subsequent S4, it is determined whether or not a predetermined period T2, which is, for example, about 30 seconds shorter than the time when the compression pressure Pfc of the forearm cuff 32 is maintained at the preset blood expulsion pressure Pc1, has elapsed at a time t2, for example, from the end point t3 of the blood expulsion period T1. While the determination in this S4 is negative, S3 and S4 are repeated. When the determination in S4 is affirmative, in S5, the pressure increase of the compression pressure Puc of the upper arm cuff 12 is started (at the time t2 in FIG. 3). In the subsequent S6, it is determined whether or not the compression pressure Puc of the upper arm cuff 12 has reached a pulse wave detection pressure Pc2 that is set in advance to be lower than, for example, the minimum blood pressure value of the living body. While the determination in this S6 is negative, S5 and S6 are repeated. When the determination in S6 is affirmative, in S7, the compression pressure Puc of the upper arm cuff 12 is maintained at the pulse wave detection pressure Pc2.

[0041] Next, in S8, it is determined whether or not the time during which the cuff pressure Pfc of the forearm cuff 32 is maintained at the preset blood expulsion pressure Pc1 has elapsed through a blood expulsion period T1 that is set in advance to be about 5 minutes. While the determination in this S8 is negative, S7 and S8 are repeated. When the determination in S8 is affirmative, in S9, the compression pressure Pfc of the forearm cuff 32 is released (at the time t3 in FIG. 3).

[0042] In the subsequent S10, a volume pulse wave SM is continuously collected from the upper arm cuff 12 maintained at the pulse wave detection pressure Pc2. Then, in S11, it is determined whether or not the elapsed time since the upper arm cuff 12 was maintained at the pulse wave detection pressure Pc2 has reached the end of a volume pulse wave collection period T3 that is set in advance to be about 2 minutes and 30 seconds. While the determination in this S11 is negative, S10 and S11 are repeated. When the determination in S11 is affirmative, in S12, the compression pressure Pfc of the upper arm cuff 12 is released (at the time t4 in FIG. 3).

[0043] Next, in S13 corresponding to the volume pulse amplitude calculation unit 58 and the amplitude increase rate calculation unit 64, analysis of the continuously collected volume pulse SM is performed, the amplitude F2m of the volume pulse SM2 and the amplitude F3m of the volume pulse SM3 are calculated, and using the amplitude F2m of the volume pulse SM2 and the amplitude F3m of the volume pulse SM3, from equation (1), the amplitude increase rate FRm (%) of the amplitude F3m of the volume pulse SM3 with respect to the amplitude F2m of the volume pulse SM2 is calculated, and the diameter change of the arterial blood vessel 14a, that is, the vasodilation rate AR, is calculated and displayed on the display 52.

[0044] As described above, according to the endothelial function testing device 10 of the present embodiment, the volume pulse amplitude calculation unit 58 determines, as a constant reflection wave-free section Am, a section in the rising section Ar of the volume pulse SM where the reflection wave does not overlap for the volume pulse SM2, and the maximum value within the constant reflection wave-free section Am is calculated as the maximum amplitude F2m of the volume pulse SM2 and the maximum amplitude F3m of the volume pulse SM3. The amplitude increase rate calculation unit 64 calculates the amplitude increase rate FRm between the maximum amplitude F2m of the volume pulse SM2 immediately before or after blood ejection and the maximum amplitude F3m of the volume pulse SM3 indicating the maximum amplitude after blood ejection release. The arterial blood vessel dilation function inspection unit 66 evaluates the endothelial function of the arterial blood vessel 14a based on the amplitude increase rate FRm. Thereby, the endothelial function of the arterial blood vessel 14a is evaluated from the maximum amplitude F2m of the volume pulse SM2 and the maximum amplitude F3m of the volume pulse SM3 sequentially obtained within the range of the reflection wave-free section Am that is not affected by the reflection wave overlapping the volume pulse SM, so that an endothelial function testing device 10 for arterial blood vessels with high measurement accuracy is obtained.

[0045] Further, according to the endothelial function inspection apparatus 10 of the present embodiment, the volume pulse wave amplitude calculation unit 58 includes a reflected wave-free section calculation unit that calculates a reflected wave-free section Am in which no reflected wave is superimposed on the waveform of the volume pulse wave SM sequentially obtained immediately before or immediately after the end of the blood pumping section T1 in which a part of the living body is blood-pumped for a predetermined time using the forearm cuff 32 compression device, and a reflected wave-free section amplitude calculation unit that calculates the maximum amplitude within the reflected wave-free section Am in the waveform of the volume pulse wave SM. As a result, a pulse wave within the reflected wave-free section Am in which no reflected wave is superimposed on the pulse wave SM can be obtained, and based on this pulse wave, it becomes possible to evaluate the endothelial function of the arterial blood vessel that is not affected by the reflected wave.

[0046] Further, according to the endothelial function inspection apparatus 10 of the present embodiment, the reflected wave-free section calculation unit 60 sets the section from the maximum value of the second differential waveform of the volume amplitude waveform immediately before or immediately after the end of the blood pumping section T1 (time point t10 in FIG. 4) to the maximum value of the first differential waveform of the volume amplitude SM waveform (time point t11 in FIG. 4) as the reflected wave-free section Am in which no reflected wave is superimposed on the volume pulse wave SM. Since the reflected wave is superimposed after the maximum value of the first differential waveform in the volume pulse wave SM, as described above, it is possible to obtain a pulse wave within the reflected wave-free section Am in which no reflected wave is superimposed on the pulse wave.

[0047] Further, according to the endothelial function inspection apparatus 10 of the present embodiment, the blood pumping of a part of the living body for a predetermined time, that is, the blood pumping section T1, is blood pumping for 5 minutes. As a result, since the blood flow is restarted in a state where a part of the living body blood-pumped by the forearm cuff 32 (compression device) and the part on the distal side thereof are sufficiently in an ischemic state, shear stress is applied to the endothelial cells of the arterial blood vessel 14a due to the blood flow, and thus a flow-dependent dilation response of the arterial blood vessel 14a can be obtained.

[0048] Also, according to the endothelial function testing apparatus 10 of the present embodiment, the amplitude increase rate calculation unit 64 calculates the increase rate of the amplitude of the volume pulse wave calculated by the reflected wave-free interval amplitude calculation unit 62 with respect to the amplitude F2m of the volume pulse wave SM2 immediately before or immediately after the end of blood ejection in the blood ejection interval T1 and the amplitude F3m of the volume pulse wave SM3 indicating the maximum amplitude after blood ejection release in the blood ejection interval T1. Thereby, the endothelial function of the arterial blood vessel 14a is evaluated from the amplitude of the volume pulse wave SM sequentially obtained within the range of the reflected wave-free interval Am that is not affected by the reflected wave superimposed on the volume pulse wave SM.

[0049] Also, according to the endothelial function testing apparatus 10 of the present embodiment, the compression device has a forearm cuff 32 (blood ejection inflatable bag) that compresses the compression site by the compression device at a pressure higher than the maximum blood pressure value of the living body, and ejects blood from the compression site by the compression device and the peripheral side site of the compression site in the living body to create an ischemic state. Thereby, since a sufficient blood flow rate is ensured through the arterial blood vessel 14a after blood ejection release, the endothelium in the arterial blood vessel 14a can be sufficiently stimulated by the shear stress generated by the blood flow.

[0050] Also, according to the endothelial function testing apparatus 10 of the present embodiment, the volume pulse wave detection device has an upper arm cuff (sensor inflatable bag) 12 that compresses a portion of the living body located proximal to the compression site by the compression device at a pressure lower than the minimum blood pressure value of the living body, and detects the volume pulse wave SM generated in the upper arm cuff 12 based on the volume change of the arterial blood vessel 14a. Thereby, the stress applied to the smooth muscle of the arterial blood vessel 14a is reduced, and it is suppressed that the dilation reaction by the smooth muscle is mixed in.

[0051] Incidentally, FIG. 8 is a time chart showing the change in the amplitude F between the minimum value and the maximum value of the volume pulse wave SM obtained from the compression pressure Pc2 of the upper arm cuff 12 wound around the upper arm 14 after blood expulsion, when the forearm 30 of an adult male (55 years old) was blood expelled in the blood expulsion section T1 (5 minutes) under the same conditions as in FIG. 6. The amplitude F in this case is the difference between the minimum value and the maximum value of the volume pulse wave SM superimposed with the reflected wave. In this case, the timing and magnitude vary depending on the heart rate and blood flow, and it is the amplitude of the volume pulse wave superimposed with the reflected wave that has nothing to do with the vasodilation reaction due to NO production based on the shear stress of the endothelium. For example, as shown in FIG. 9, it changes continuously and decreases after blood expulsion, so it was difficult to perform endothelial function tests.

Example

[0052] Hereinafter, examples of other compression devices will be described. Note that the same reference numerals are given to the parts common to the above-described examples, and the description thereof will be omitted.

[0053] FIG. 9 is a schematic diagram for explaining a cross section of a compression device that replaces the upper arm cuff 12 and the forearm cuff 32. In FIG. 8, inside a band-shaped armband cover 70 configured in a longitudinal glove shape, which has a length wound around the forearm 30 or the upper arm 14 of the living body and has a width dimension of about 12 cm, for example, an inflation bag 68 for blood expulsion and an inflation bag 69 for a sensor are accommodated in a state of being separated by a predetermined interval D of about 2 cm in the longitudinal direction of the arterial blood vessel 14a. The armband cover 70 is composed of, for example, a highly elastic PVC sheet of about 0.2 to 0.3 mm. On the outer peripheral side inside the armband cover 70, a relatively hard and flexible outer peripheral side inner cover 72 is arranged. On the inner peripheral surface and the outer peripheral surface of the forearm cuff 32 and the upper arm cuff 12, polyester films 74 are respectively interposed. On the inner peripheral side inside the armband cover 70, nylon pile 76 is arranged. And between the nylon pile 76 and the forearm cuff 32 and the upper arm cuff 12, an inflation bag 78 for blood pressure measurement is inserted.

[0054] According to the endothelial function testing apparatus 10 of this embodiment, the blood drive inflation bag 68 and the sensor inflation bag 69 are accommodated in a single belt-shaped armband cover 70 wound around the living body, and are positioned at a predetermined interval in the longitudinal direction of the arterial blood vessel 14a. Thereby, it becomes easy to attach the forearm cuff 32 and the upper arm cuff 12 to a part of the living body. Also, by using the blood pressure measurement inflation bag 78, blood pressure measurement is also possible.

[0055] As described above, an embodiment of the present invention has been described with reference to the drawings, but the present invention is also applicable to other aspects.

[0056] For example, in the above-described embodiment, the cuff 12 is wound around the upper arm 14 as a part of the living body, but it may be wound around other parts such as the forearm or the lower limb.

[0057] Also, in the above-described embodiment, air, which is a compressed fluid, is supplied to generate the compression pressure Pc in the cuff 12, but instead, an incompressible fluid such as water or oil may be used.

[0058] Also, in the above-described embodiment, the upper arm cuff 12 that functions as a sensor inflation bag is used as the compression device that compresses the upper arm 14, but a belt wound around the upper arm 14 may be used. In this case, the belt preferably includes an actuator that adjusts the belt tension. In this case, the pressure sensor is inserted between the belt and the upper arm 14.

[0059] As described above, the preferred embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited to this, and various modifications can be made and implemented without departing from the spirit of the present invention.

Explanation of Reference Numerals

[0060] 10: Endothelial function testing apparatus for arterial blood vessels 12: Upper arm cuff 14: Upper arm 14a: Arterial blood vessel 16: Upper arm cuff pressure control valve 18: Air pump 20: Pipe 22: Upper arm cuff pressure sensor 24: Low-pass filter 26: Band-pass filter 28: A / D converter 30: Forearm 32: Forearm cuff (compression device) 36: Forearm cuff pressure control valve 38: Air pump 40: Pipe 42: Forearm cuff pressure sensor 44: Low-pass filter 48: A / D converter 50: Electronic control device 52: Display 54: Forearm cuff pressure control section 56: Upper arm cuff pressure control section 58: Volume pulse amplitude calculation section 60: Reflected wave-free interval calculation section 62: Reflected wave-free interval amplitude calculation section 64: Amplitude increase rate calculation section 66: Arterial vasodilation function examination section 68: Inflatable bag for blood expulsion 69: Inflatable bag for sensor 70: Wristband cover 72: Outer cover on the peripheral side 74: Polyester film 76: Nylon pile 78: Inflatable bag for blood pressure measurement L1: Intima L2: Media (smooth muscle) L3: Adventitia SM: Volume pulse SM2: Volume pulse obtained at time t2 F2: Amplitude of the volume pulse obtained at time t2 SM3: Volume pulse obtained at time t3 F3: Amplitude of the volume pulse obtained at time t3 T1: Blood expulsion interval T2: Predetermined period T3: Volume pulse acquisition interval Am: Reflected wave-free interval Fm: Amplitude of the reflected wave-free interval of the volume pulse F2m: Amplitude of the interval without reflected waves of the volume pulse wave SM2 obtained at time t2 F3m: Amplitude of the interval without reflected waves of the volume pulse wave SM3 obtained at time t3 FRm: Amplitude increase rate HFRm: Judgment threshold value

Claims

1. A compression device having an inflatable bag for compressing a part of a living body, and a volume pulse wave detection device for detecting a volume pulse wave generated based on a change in the volume of an arterial blood vessel in a part of the living body different from the compression site by the compression device, wherein after blood is driven out of a part of the living body for a predetermined time using the compression device and then the blood drive is released, an endothelial function inspection device for inspecting the endothelial function of the arterial blood vessels of the living body based on a change in the volume pulse wave detected by the volume pulse wave detection device, a volume pulse wave amplitude calculation unit that sequentially calculates, as the amplitude of the volume pulse wave, a maximum value within a preset non-reflected wave section where no reflected wave is superimposed among the volume pulse waves, an amplitude increase rate calculation unit that calculates an increase rate between the amplitude of the volume pulse wave immediately before or after blood drive and the maximum amplitude after blood drive release, which is calculated by the amplitude calculation unit, and an arterial vasodilation function inspection unit that evaluates the endothelial function of the arterial blood vessels based on the increase rate calculated by the amplitude increase rate calculation unit. An endothelial function inspection device for arterial blood vessels, characterized in that.

2. The volume pulse wave amplitude calculation unit, a non-reflected wave section calculation unit that calculates a non-reflected wave section where no reflected wave is superimposed among the waveforms of the volume pulse waves sequentially obtained after a blood drive section in which a part of the living body is blood-driven for a predetermined time using the compression device, and a non-reflected wave section amplitude calculation unit that calculates a maximum amplitude within the non-reflected wave section of the waveform of the volume pulse wave. The endothelial function inspection device for arterial blood vessels according to Claim 1, characterized in that.

3. The non-reflected wave section calculation unit, sets, as a non-reflected wave section where no reflected wave is superimposed on the volume pulse wave, a section from the maximum value of the second derivative waveform of the volume amplitude waveform immediately before or after the end of the blood drive section to the maximum value of the first derivative waveform of the volume amplitude waveform. The endothelial function inspection device for arterial blood vessels according to Claim 2, characterized in that.

4. The blood drive of a part of the living body for a predetermined time is a blood drive for 5 minutes. The endothelial function inspection device for arterial blood vessels according to Claim 1, characterized in that.

5. The amplitude increase rate calculation unit calculates an increase rate between the amplitude of the volume pulse wave calculated by the non-reflected wave section amplitude calculation unit, the amplitude of the volume pulse wave immediately after blood drive, and the maximum amplitude after blood drive release. The endothelial function inspection device for arterial blood vessels according to Claim 1, characterized in that.

6. The compression device has an inflation bag for blood pumping that compresses the compression site by the compression device at a pressure higher than the maximum blood pressure value of the living body, and pumps blood from the compression site by the compression device and the peripheral side site of the compression site in the living body. The arterial vascular endothelial function inspection device according to claim 1, characterized in that.

7. The volume pulse detection device has an inflation bag for a sensor that compresses a portion of the living body located proximal to the compression site by the compression device at a pressure lower than the minimum blood pressure value of the living body, and detects a volume pulse generated in the inflation bag based on a volume change of the arterial blood vessel. The arterial vascular endothelial function inspection device according to claim 6, characterized in that.

8. The inflation bag for blood pumping and the inflation bag for the sensor are accommodated in a belt-shaped bag wound around the living body in a state of being positioned at a predetermined interval in the longitudinal direction of the arterial blood vessel. The arterial vascular endothelial function inspection device according to claim 7, characterized in that.

Images