JP2938238B2 - Atherosclerosis measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arterial stiffness measuring device capable of measuring the stiffness of an artery in a living body.

[0002]

2. Description of the Related Art The state of arteriosclerosis is closely related to the state of the circulatory organs and nerves of a living body and is important medical information. Therefore, it is desired to measure the degree of arteriosclerosis.
However, the degree of arteriosclerosis represents the degree of hardness of the arterial blood vessel wall, and it has been difficult to easily measure it from above the skin.

[0003] The present inventors have conducted various studies on the background of the above circumstances, and as a result, for example, in the process of increasing the compression pressure of a compression device such as a cuff for compressing an artery in a living body to a target compression pressure and then decreasing the pressure. When measuring the blood pressure value based on the sequentially detected pulse wave, the amplitude of the pulse wave gradually decreases after gradually increasing, but the increasing state of the pulse wave amplitude, the height and width of the change curve of the pulse wave amplitude and And the ratio between the maximum value of the pulse wave amplitude and the mean blood pressure value were found to be closely related to the degree of arteriosclerosis of the subject, respectively. The present invention has been made based on such findings.

[0004]

The gist of the first invention is to provide an apparatus for measuring the degree of stiffness of an artery in a living body, comprising: (a) a compression apparatus for compressing the artery; A device, (b) a pressure sensor that detects a compression pressure of the compression device, and outputs a pressure signal representing the compression pressure, and (c) a target compression pressure of the compression device higher than the systolic blood pressure value of the living body. Compression pressure adjusting means for decreasing the pressure at a predetermined rate after increasing the pressure, and (d) pulse wave detecting means for detecting a pulse wave from the artery based on the pressure signal sequentially obtained in the step of decreasing the compression pressure. And (e) arteriosclerosis determining means for determining the degree of arteriosclerosis based on the increasing state of the amplitude of the pulse wave that is generated from the artery and is sequentially detected in the process of lowering the compression pressure. .

[0005]

In the arterial stiffness measuring apparatus according to the first aspect of the present invention, the compression pressure of the compression device for compressing the artery in the living body is higher than the systolic blood pressure value of the living body by the compression pressure adjusting means. In the process of raising the pressure to the target compression pressure and then lowering the pressure at a predetermined rate, the arteriosclerosis determining means determines based on the increasing state of the amplitude of the pulse wave generated from the artery and sequentially detected by the pulse wave detecting means. Thus, the arteriosclerosis degree can be easily measured from above the skin. Thereby, not only can the arteriosclerosis degree, which is an important index representing the state of health of the circulatory organ, be easily measured, for example, it can be used for the measurement of the depth of anesthesia from the relationship between the depth of the anesthesia and the arteriosclerosis degree It can be used to measure mental status from the relationship between sympathetic nerve and arteriosclerosis.

[0006]

A second aspect of the present invention is a device for measuring the degree of stiffness of an artery in a living body, wherein (a) compressing the artery. A compression device, (b) a pressure sensor that detects the compression pressure of the compression device and outputs a pressure signal representing the compression pressure, and (c) a target that sets the compression pressure of the compression device higher than the average blood pressure value of the living body. Compression pressure adjusting means for increasing the compression pressure and then decreasing the pressure at a predetermined rate; and (d) pulse wave detection for detecting a pulse wave from the artery based on the pressure signal sequentially obtained in the step of decreasing the compression pressure. Means, (e) amplitude maximum value determining means for determining the maximum value of the amplitude of the pulse wave sequentially detected in the step of reducing the compression pressure, and (f) pulse wave sequentially detected in the step of reducing the compression pressure Of an amplitude change curve representing the change in amplitude of the amplitude, Curve width determining means for determining the curve width of the portion of the ratio or more, (g) based on the ratio between the maximum value of the amplitude and the curve width, pre-stored between the ratio and the degree of arteriosclerosis And arteriosclerosis determining means for determining the degree of arteriosclerosis of the living body from the determined relationship.

[0007]

In the arterial stiffness measuring apparatus according to the second aspect of the present invention, the compression pressure of the compression device for compressing the artery in the living body is higher than the average blood pressure value of the living body by the compression pressure adjusting means. In the process of increasing the pressure to the target compression pressure and decreasing the pressure at a predetermined speed, the pulse wave is sequentially detected from the artery by the pulse wave detecting means, and the maximum value of the amplitude of the pulse wave is determined by the maximum amplitude value determining means. At the same time, the curve width of the portion of the amplitude change curve representing the change in the amplitude of the pulse wave that is equal to or greater than a predetermined ratio of the maximum value of the amplitude is determined by the curve width determining means. Then, based on the ratio between the maximum value of the amplitude and the curve width, the degree of arteriosclerosis of the living body is determined from the relationship between the ratio and the degree of arteriosclerosis based on the ratio between the maximum value of the amplitude and the curve width. Therefore, the degree of arteriosclerosis can be easily measured from above the skin.

[0008]

A third aspect of the present invention provides a device for measuring the degree of stiffness of an artery in a living body, comprising: (a) a compression device for compressing the artery; Blood pressure measurement means for measuring the average blood pressure value of the living body based on pulse waves sequentially obtained in the process of increasing the compression pressure of the device to a predetermined target compression pressure and then decreasing the pressure at a predetermined speed, (b Based on the ratio between the maximum value of the amplitude of the pulse wave sequentially obtained in the process of lowering the compression pressure and the average blood pressure value, from the relationship stored in advance between the ratio and the degree of arteriosclerosis of the living body And arteriosclerosis determining means for determining the degree of arteriosclerosis.

[0009]

In the arterial stiffness measuring device according to the third aspect of the present invention, the blood pressure measuring means includes:
The average blood pressure value of the living body is measured based on the pulse wave sequentially obtained in the process of increasing the compression pressure of the compression device that compresses the artery in the living body to a predetermined target compression pressure and then decreasing the pressure at a predetermined speed. At the same time, based on the ratio between the maximum value of the amplitude of the pulse wave sequentially obtained in the process of lowering the compression pressure and the average blood pressure value, the arteriosclerosis determining means preliminarily determines the ratio between the ratio and the arteriosclerosis. Since the degree of arteriosclerosis of the living body is determined from the stored relationship, the degree of arteriosclerosis can be easily measured from above the skin.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a diagram showing an example of the configuration of the arteriosclerosis measuring apparatus of the first invention. In FIG. 2, reference numeral 10 denotes a rubber bag-shaped cuff, which is attached, for example, to the upper arm 12 of a human body. The cuff 10 has a pressure sensor 14, a switching valve 16, and an air pump 18 connected to a pipe 20.
Connected through. The switching valve 16 is switched between a pressure supply state in which the supply of pressure into the cuff 10 is allowed, a slow exhaust state in which the cuff 10 is gradually exhausted, and a rapid exhaust state in which the cuff 10 is quickly exhausted. It is configured as follows. The pressure sensor 14 detects the pressure in the cuff 10 and supplies a pressure signal SP representing the pressure to the static pressure discrimination circuit 22 and the pulse wave discrimination circuit 24, respectively. The static pressure discriminating circuit 22 includes a low-pass filter, and a cuff pressure signal S representing a steady pressure (cuff pressure P) included in the pressure signal SP.
K is discriminated and the cuff pressure signal SK is supplied to the control device 28 via the A / D converter 26. The pulse wave discriminating circuit 24 includes a band pass filter, discriminates a pulse wave signal SM representing a pulse wave included in the pressure signal SP, and outputs the pulse wave signal SM.
Is supplied to the control device 28 via the A / D converter 30.
The pulse wave represented by the pulse wave signal SM is a pressure vibration wave generated from the brachial artery and transmitted to the cuff 10 in synchronization with the heartbeat of the subject. In this embodiment, the cuff 10 constitutes a compression device, and the pulse wave discrimination circuit 24 functions as a pulse wave detecting means.

The control device 28 includes a CPU, a ROM, an R
The CPU includes a so-called microcomputer having an AM, an I / O port, and the like. The CPU executes I / O processing by executing signal processing using a storage function of the RAM according to a program stored in the ROM in advance. The cuff pressure P is adjusted by outputting a drive signal from the O port and controlling the switching valve 16 and the air pump 18 via a drive circuit (not shown), so that the cuff pressure P is higher than the expected systolic blood pressure value of the subject. after boosting to a higher predetermined target cuff pressure P _m, based on the pulse wave which is sequentially taken in the process of stepping down the cuff pressure P at a predetermined slow rate, systolic blood pressure, diastolic blood pressure, and mean For example, a systolic blood pressure value SYS, a diastolic blood pressure value DIA, and a well-known oscillometric blood pressure value determining algorithm for determining a blood pressure value such as a blood pressure value. It determines the average blood pressure value MEAN displays the blood pressure value thus determined to the display 32. The amplitudes of the pulse waves sequentially sampled in the slow blood pressure lowering process are obtained and the maximum values of the amplitudes are determined, and the cuff pressure P at the time when the pulse waves of the maximum amplitude are collected is defined as the average blood pressure value MEAN. The cuff pressure P corresponding to the determined inflection point of the pulse wave amplitude on the high pressure side from the mean blood pressure value MEAN is determined as the systolic blood pressure value S
YS and its mean blood pressure value MEA
The cuff pressure P corresponding to the inflection point of the pulse wave amplitude on the lower pressure side than N is determined as the diastolic blood pressure value DIA. In this embodiment, the pressure sensor 14, the switching valve 16,
Air pump 18, static pressure discrimination circuit 22, A / D converter 2
6, the control device 28 and the like constitute a compression pressure adjusting means.

In accordance with a program stored in advance, the control device 28 controls the degree of arterial stiffness of the subject based on the increasing state of the amplitude of the pulse wave sequentially detected from the brachial artery in the process of gradually lowering the cuff pressure P. Is determined, and the determined degree of arteriosclerosis is sequentially displayed on the display device 32. Therefore, in the present embodiment, the control device 28 constitutes arteriosclerosis degree determining means.

[0014] Here, FIG. 3 is a schematic view for explaining the occurrence of the pulse wave at various cuff pressure P at the slow decreasing process from the target cuff pressure P _m in the cuff 10 to compress the brachial artery The figure shown by a solid line represents the inner wall surface of the brachial artery when the heart is expanded, and when the heart is contracted, the brachial artery compressed by the cuff 10 is broken against the cuff pressure P. A pulse wave having a size corresponding to the volume indicated by the diagonal lines is generated by expansion as shown by. That is, as shown in the amplitude change curve of FIG. 4, for example, the cuff pressure P becomes the systolic blood pressure value SY
When the value is larger than S (I in FIG. 4), only a very small pulse wave is generated in a state where the blood flow is blocked, but when the cuff P reaches the systolic blood pressure value SYS (II in FIG. 4), When the flow is resumed and the pulse wave amplitude A gradually increases and the cuff pressure P reaches the mean blood pressure value MEAN (III in FIG. 4), the maximum amplitude A _max
Pulse wave is generated, and the cuff pressure P is changed to the average blood pressure value ME.
When it becomes smaller than AN (IV in FIG. 4), the amplitude A of the pulse wave gradually decreases. In this case, as the blood vessel wall of the brachial artery becomes harder, the elastic deformation of the portion of the brachial artery located on the upstream side of the cuff 10 at the time of cardiac contraction becomes smaller. It is considered that the amplitude of the pulse wave rises sharply as the blood vessel wall of the brachial artery becomes harder. The measurement principle of the arteriosclerosis measuring apparatus of the first invention is based on such a basic principle. Note that the amplitude change curve in FIG. 4 shows an envelope connecting points (not shown) representing the amplitudes of the pulse waves sequentially obtained in the step of decreasing the pressure.

The operation of the arterial stiffness measuring apparatus according to this embodiment will be described below with reference to the flowchart of FIG.

When the power is turned on, an initial process (not shown) is executed, and then step S1 is executed to determine whether or not a start switch (not shown) has been turned ON. If this determination is denied, step S1 is repeatedly executed to be in a standby state, but if affirmed, step S2 is executed to switch the switching valve 16 to the pressure supply state, and After the pump 18 is driven to increase the pressure inside the cuff 10 to a predetermined target cuff pressure Pm (for example, a pressure of about 180 mmHg) higher than the maximum blood pressure value expected by the subject, the air pump 18 is stopped, and S3 is executed and the switching valve 16 is switched to the slow exhaust state, whereby the slow pressure reduction in the cuff 10 is started.

Next, by executing step S4, it is determined whether the pulse wave signal SM has been read and one pulse wave has been detected. If this determination is denied, step S4 is repeatedly executed. If the determination is affirmed, step S5 is executed, and the amplitude A of the detected pulse wave is obtained.
Is calculated and stored together with the cuff pressure P at that time, a blood pressure value determination routine of step S6 is executed.
In this blood pressure value determination routine, the maximum value _Amax of the pulse wave amplitude A sequentially detected is determined, and the cuff pressure P at the time when the pulse wave having the maximum amplitude _Amax is collected is set as the average blood pressure value MEAN. Is determined and the average blood pressure value M
The cuff pressure P corresponding to the inflection point of the pulse wave amplitude on the high pressure side of EAN is determined as the systolic blood pressure value SYS, and the cuff pressure P corresponding to the inflection point of the pulse wave amplitude on the low pressure side of the mean blood pressure value MEAN. Is determined as the diastolic blood pressure value DIA. Next, step S7 is executed to determine whether or not the blood pressure measurement has been completed. If not, steps S4 to S7 are repeatedly executed.

If the blood pressure measurement is completed and the determination in step S7 is affirmative, step S8 is executed, whereby the switching valve 16 is switched to the rapid exhaust state, and the pressure in the cuff 10 is rapidly reduced. Is done. In the following step S9, on the basis of the concept of time constant for example, with 63.2% of the maximum amplitude A _max (0.632A _max) is calculated, in step S10, as shown in FIG. 4, the amplitude The inclination angle θ of the straight line c connecting the inflection point a of the change curve corresponding to the systolic blood pressure value SYS and the point b corresponding to 0.632 A _max is determined. Next, step S11
Is executed, and the arteriosclerosis of the subject is determined on the basis of the actual inclination angle θ determined in step S10 from the relationship stored in advance between the inclination angle θ and the degree of arteriosclerosis as shown in FIG. 5, for example. The degree is determined and step S12
Is executed, and the degree of arterial stiffness is displayed on the display 32 together with the systolic blood pressure value SYS, the diastolic blood pressure value DIA, and the mean blood pressure value MEAN, and the processing is terminated.

As described above, according to the present embodiment, the increasing state of the amplitude of the pulse wave sequentially detected from the brachial artery during the gradual lowering of the pressure in the cuff 10 corresponds to the line c in the change curve of the amplitude.
The actual arterial stiffness is determined from the relationship stored in advance based on the inclination angle θ that is closely related to the arterial stiffness. It can be easily measured from above.

Further, according to the present embodiment, since the conventional oscillometric blood pressure measuring device can be used as it is, there is an advantage that the arteriosclerosis measuring device can be easily configured.

Next, another embodiment of the first invention will be described.

For example, in the above-described embodiment, the arteriosclerosis of the subject is determined based on the actual inclination angle θ from the relationship stored in advance between the inclination angle θ of the straight line c representing the increasing state of the amplitude and the degree of arteriosclerosis. Although the degree is configured to be determined,
This is not always necessary, for example, from the inflection point a corresponding to the systolic blood pressure value SYS in the amplitude change curve to 0.
Arrival time t to reach point b corresponding to 632A _max
(See FIG. 4) to detect an increased state of the pulse wave amplitude,
For example, the arterial stiffness of the subject may be determined based on the actual arrival time t from the relationship between the arrival time t and the degree of arteriosclerosis stored in advance as shown in FIG. 6, for example. Alternatively, an increasing state of the pulse wave amplitude is detected based on an increasing rate of the amplitude of the pulse wave sequentially detected after the slow down of the cuff pressure P is started with respect to the decreasing rate of the cuff pressure P. For example, the arterial stiffness of the subject may be determined based on the actual increase rate from a relationship stored in advance with the arterial stiffness as shown in FIG.

Although the first embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be embodied in other forms.

For example, it is known that the degree of stiffness (flexibility) of the artery changes during anesthesia, and it is known that the artery becomes hard when the sympathetic nerve is excited. If it is configured so that the degree of arteriosclerosis of the subject can be measured at predetermined time intervals, it is possible to monitor the depth of anesthesia of the patient during surgery from the relationship between the degree of anesthesia and the degree of arteriosclerosis, or to stimulate the sympathetic nerve. It is also possible to monitor the mental state of a patient in a ward or the like from the relationship with the degree of arteriosclerosis.

In the above embodiment, the relationship between the inclination angle θ and the degree of arteriosclerosis stored in advance is a linear relationship, but may be a curved or stepped relationship.

Further, in the above-described embodiment, the value of 63.2% of the maximum value of the amplitude change curve is used to obtain the inclination angle θ indicating the increasing state of the pulse wave amplitude. A ratio value other than 63.2% may be used.

In the above-described embodiment, the pulse wave detecting means is constituted by the pulse wave discriminating circuit 24. However, the pulse wave detecting means may be constituted by a digital filter by the microcomputer of the control device 28.

In the above embodiment, only the arterial stiffness may be measured without measuring the blood pressure value.

Next, an embodiment of the second invention will be described. Second
An arterial stiffness measuring apparatus according to an embodiment of the present invention has, for example, a configuration similar to that of the embodiment of the first invention in FIG. 2 and includes step S9 in the flowchart of FIG.
Since steps other than step S11 are configured in the same manner,
Only steps SA9 to SA11 shown in FIG. 8 provided in place of steps S9 to S11 will be described.

First, step SA9 is executed to determine a 90% value (0.9A _max ) of the maximum value A _max of the pulse wave amplitude, and the curve width W () of the portion of the amplitude change curve that is 0.9A _max or more. 9) is determined. Next, step SA1
0 is executed to determine the ratio (A _max / W) between the maximum amplitude value A _max and the curve width W. Next, at step SA1
1 is performed, the ratio (A _max / W) and the actual ratio is determined from a pre-stored relationship shown in FIG. 10 for example between arterial stiffness in step SA10 (A _max /
Based on W), the arterial stiffness of the subject is determined. Thereby, the same effect as that of the embodiment of the first invention can be obtained.
In this case, the control device 28 functions as amplitude maximum value determining means, curve width determining means, and arteriosclerosis degree determining means.

In the embodiment of the second invention,
Target cuff pressure P _m is always possible to obtain the effect of the second invention if I is boosted up to a predetermined amount higher pressure than the mean blood pressure value not necessary to boost up a pressure above the systolic blood pressure value.

Next, an embodiment of the third invention will be described. Third
An arterial stiffness measuring apparatus according to an embodiment of the present invention has, for example, a configuration similar to that of FIG. 2 of the embodiment of the first invention, and has the same configuration except for steps S9 to S11 in the flowchart of FIG. Therefore, only steps SB9 and SB10 shown in FIG. 11 which are provided in place of steps S9 to S11 will be described.

First, step SB9 is executed to determine the ratio ( _Amax / MEAN) between the maximum amplitude value _Amax and the average blood pressure value MEAN determined in step S6. Next, step SB10 is executed, and the ratio (A _max / ME
For example, based on the actual ratio (A _max / MEAN) determined in step SB9 from a pre-stored relationship between AN) and the degree of arteriosclerosis as shown in FIG. It is determined. Thereby, the same effect as that of the embodiment of the first invention can be obtained. In this case, the pressure sensor 14, the switching valve 16, the air pump 18, the static pressure discriminating circuit 22, the pulse wave discriminating circuit 24, the A / D converters 26 and 30,
The control device 28 and the like constitute blood pressure measurement means, and the control device 28 functions as arteriosclerosis degree determination means.

In the third embodiment of the present invention,
The blood pressure measuring means only needs to measure at least the average blood pressure value, and the systolic blood pressure value and the diastolic blood pressure value need not be measured.

The first, second, and third inventions have been described based on one embodiment. However, these are merely examples, and the present invention has various modifications without departing from the spirit thereof. Of course, it can be implemented in an embodiment.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the operation of the apparatus of FIG. 2 according to a first invention.

FIG. 2 is a block diagram showing a configuration example of an arteriosclerosis degree measuring device according to the first invention, the second invention, and the third invention.

FIG. 3 is a schematic diagram for explaining a generation state of a pulse wave at various cuff pressures P in a slow pressure drop process from a target cuff pressure.

FIG. 4 is a diagram illustrating an example of a change curve of the amplitude of a pulse wave sequentially detected in a slow pressure step-down process, and is a diagram illustrating a tilt angle θ and an arrival time t, each of which represents an increase in the amplitude.

FIG. 5 is a diagram showing an example of a relationship stored in advance between an inclination angle θ indicating a pulse wave amplitude increasing state and an arteriosclerosis degree used in step S11 of the flowchart of FIG. 1;

FIG. 6 is a diagram showing an example of a relationship stored in advance between the arrival time t representing the pulse wave amplitude increasing state and the degree of arteriosclerosis.

FIG. 7 is a diagram showing an example of a relationship stored in advance between an increase rate representing a pulse wave amplitude increase state and a degree of arteriosclerosis.

FIG. 8 is a diagram showing a main part of a flowchart for explaining an embodiment of the second invention.

FIG. 9 is a diagram for explaining a curve width and the like determined in step SA9 of FIG. 8;

FIG. 10 is a diagram illustrating an example of a relationship used in step SA11 of FIG. 8;

FIG. 11 is a diagram showing a main part of a flowchart for explaining an embodiment of the third invention.

FIG. 12 is a diagram illustrating an example of a relationship used in step SB10 of FIG. 11;

[Explanation of symbols]

10 cuff (compression device) # 14 pressure sensor, 16 switching valve, 18 air pump, 22 static pressure discriminating circuit, 26 A / D converter, 28
Control device｝ compression pressure adjusting means 24 pulse wave discrimination circuit (pulse wave detecting means) 28 control device (arteriosclerosis determining means, maximum amplitude value determining means, curve width determining means) ｛14 pressure sensor, 16 switching valve, 18 air Pump, 22 static pressure discrimination circuit, 24 pulse wave discrimination circuit, 26,
30 A / D converter, 28 control device｝ blood pressure measuring means

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-305545 (JP, A) JP-A-4-250132 (JP, A) JP-A 1-259836 (JP, A) JP-A-61- 119252 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) A61B 5/00-5/03

Claims (3)

(57) [Claims] 1. A device for measuring the degree of stiffness of an artery in a living body, comprising: a compression device for compressing the artery; a compression pressure of the compression device being detected, and a pressure signal representing the compression pressure being output. A pressure sensor that performs compression pressure control means for increasing the compression pressure of the compression device to a target compression pressure higher than the systolic blood pressure value of the living body and then decreasing the compression pressure at a predetermined rate; and sequentially obtaining the compression pressure in the process of decreasing the compression pressure. Pulse wave detecting means for detecting a pulse wave from the artery on the basis of the pressure signal obtained, and the artery based on the increasing state of the amplitude of the pulse wave generated from the artery and sequentially detected in the process of decreasing the compression pressure. An arterial stiffness measuring device, comprising: an arterial stiffness determining means for determining a stiffness. 2. A device for measuring the degree of stiffness of an artery in a living body, comprising: a compression device for compressing the artery; a compression pressure of the compression device being detected, and a pressure signal representing the compression pressure being output. A pressure sensor, a compression pressure adjusting means for increasing the compression pressure of the compression device to a target compression pressure higher than the average blood pressure value of the living body, and then decreasing the compression pressure at a predetermined speed; and sequentially obtaining the compression pressure in the process of decreasing the compression pressure. Pulse wave detecting means for detecting a pulse wave from the artery based on the pressure signal obtained, and an amplitude maximum value determining means for determining a maximum value of an amplitude of a pulse wave sequentially detected in the step of decreasing the compression pressure; Curve width determining means for determining a curve width of a portion of a predetermined ratio or more of the maximum value of the amplitude of the amplitude change curve representing the change in the amplitude of the pulse wave sequentially detected in the step of decreasing the compression pressure, Maximum value of amplitude Arteriosclerosis determining means for determining the degree of arteriosclerosis of the living body from a pre-stored relationship between the ratio and the degree of arteriosclerosis based on the ratio to the curve width. Curing degree measuring device. 3. A device for measuring the degree of stiffness of an artery in a living body, comprising: increasing a compression pressure of a compression device for compressing the artery to a predetermined target compression pressure, and then increasing the compression pressure at a predetermined speed. Blood pressure measuring means for measuring the average blood pressure value of the living body based on the pulse wave sequentially obtained in the step of lowering the pressure; and a maximum value of the amplitude of the pulse wave sequentially obtained in the step of lowering the compression pressure and the average blood pressure value. An arterial stiffness measuring device for determining an arterial stiffness of the living body from a pre-stored relationship between the ratio and the arterial stiffness based on the ratio.