JPS6234531A - Method for measuring brain wave propagation speed - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a pulse wave velocity measurement method for measuring the propagation velocity of a pulse wave propagating within an artery of a living body.

PRIOR TECHNOLOGY Pressure waves or vibrations of arterial wall that are generated by heart beats and propagate in arteries are generally called pulse waves, but in recent years, the degree of arteriosclerosis has been measured based on the propagation velocity of such pulse waves. The method of determination is attracting attention. This was proposed by focusing on the correlation between pulse wave propagation velocity and degree of arteriosclerosis, etc., but in order to increase the reliability of the determination, pulse wave measurement is performed regardless of noise received by the pulse wave sensor. There is a need for a method that can accurately measure the wave propagation tl speed.

Normally, when measuring the propagation velocity of a pulse wave, pulse waves are detected by pulse wave sensors placed at two points on the artery of a living body, and the time difference between the pulse waves' rise or maximum amplitude point is The propagation time of the pulse wave is determined from the time difference and the distance between the two points.

Problems to be Solved by the Invention However, the waveform of an actual pulse wave is not simple and is noisy. Since the waveform may be distorted depending on the person, the conventional method detects the rise point of the pulse wave and the maximum amplitude point of the pulse wave, calculates the difference in appearance time, and measures the propagation velocity of the pulse wave based on the time difference. In some cases, sufficient measurement accuracy could not be obtained.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist of this method is to detect a single pulse wave propagating within the artery at two points separated by a certain distance on the artery, as shown in the claim correspondence diagram in Figure 1, and While relatively shifting the time axes of the detected first pulse wave and second pulse wave, a cross-correlation coefficient between them is determined, and the amount of shift of the time axes until the cross-correlation coefficient becomes the largest. The purpose of the present invention is to determine the difference in appearance time of the first pulse wave and the second pulse wave based on the above, and determine the pulse wave propagation velocity in the artery based on the difference in appearance time and the certain distance.

Operation and Effects of the Invention In this way, the cross-correlation coefficient accurately represents the degree of similarity between the first pulse wave and the second pulse wave having predetermined characteristics.
While relatively shifting the time axes of the first pulse wave and the second pulse wave, find the cross-correlation coefficient between them, and find the shift meter of the time axes until the cross-correlation coefficient becomes the largest. As a result, even if the pulse wave has a complicated waveform or the waveform is disturbed due to the inclusion of noise, the difference in appearance time of the pulse wave can be determined with high accuracy. Therefore, the reliability of the pulse wave propagation velocity obtained from this difference in appearance time and the distance between the pulse wave sampling positions is increased.

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIG. 2, reference numeral 10 denotes a pulse wave sensor unit 1- which is pressed against an artery appearing near the skin surface of a human body, for example, a carotid artery, and includes a plurality of pulse wave sensors 12a to 12f, six in this embodiment. are arranged in a line at a predetermined distance from each other, and each pulse wave sensor 12a
~N so that 12f is located on the carotid artery? In a state where the 'l' sensor unit 10 is pressed against the neck of the human body,
Each pulse wave sensor 12a to 12f detects a carotid artery wave propagating through its carotid artery, and outputs pulse wave signals S M a -S M f representing the detected carotid artery wave. Note that such a pulse wave sensor unit IO has been proposed, for example, by the applicant of the present application in U.S. Patent Application No. 58-4129, U.S. Pat.
The device proposed as a carotid wave detection device in No. 74 etc. can be used as is or by appropriately changing the dimensions, etc., and FIG. 3 shows an example of its outline. That is, in the figure, the entire pulse wave sensor unit 10
The pulse wave sensors 12a to 12f are arranged in a line at equal intervals within one housing.

Each pulse wave sensor 12a to 12f of the pulse wave sensor unit 10
Each pulse wave signal SMa-3Mf outputted from is amplified by each preamplifier of the preamplifier group 14, and further amplified by each amplifier of the amplifier group 16, and then supplied to each input port of the multiplexer 18. Ru. Note that the amplifier group 16
Each of the amplifiers is equipped with a filter, and the pulse wave signal (SMa' to
SMf') is allowed to pass through, and a type of static bias signal based on the pressing force that presses the pulse wave sensor unit 10 against the carotid artery is prevented from passing through.

The multiplexer 18 periodically selects one pulse wave signal from among the pulse wave signals SMa' to SMf' supplied via the amplifier group 16 according to the content of the boat select signal SP supplied to the boat select terminal. and output the selected pulse wave signal to the A/D converter 20 as the pulse wave signal SM.
supply to. Then, the A/D converter 20 converts the wind wave signal SM into a digital code, outputs it as a pulse wave signal SMD, and supplies this to the I10 boat 22. It should be noted that the pulse wave signal SMD, that is, the pulse wave signal SM, is a pulse wave signal S M a to SM f that is selected according to a predetermined sampling period, as will be clear from the description below. The points representing the magnitude of are arranged in a time division manner to form a composite signal.

In addition, a start push button 24 is connected to the I10 port 22 for instructing the start of all J constant measurement of the pulse wave propagation velocity, and by pressing the start button 24, a start signal SS for instructing the start of measurement is input. There is.

The I10 boat 22 connects to the CPU 26 and R via the data bus.
It is connected to AM28 and ROM30, and CPU2
In accordance with instructions from the CPU 26, various signals including the pulse wave signal SMD and start signal SS are taken in from an external circuit, and in accordance with instructions from the CPU 26, various signals including the port select signal SP are taken in from the external circuit. Output for. The transmission and reception of various signals to and from external circuits via these I10 ports 22 is performed during the process in which the CPU 26 executes signal processing according to a program stored in advance in the ROM 30 while utilizing the temporary storage function of the RAM 28. It has become.

In this embodiment, based on such signal processing, the boat select signal SP is output from the I10 port 22 as described above, and is supplied to the multiplexer 18, and the pulse wave signal input to the multiplexer 18 is S
Pulse wave display signal DMa-DM according to Ma'~SMf'
The pulse wave display signal DM including time division f and the pulse wave velocity display signal DA representing the actual pulse wave velocity are output and supplied to the pulse wave display unit 32 and the display 34, respectively. ing.

Pulse wave display unit 3 to which the pulse wave display signal DM is supplied
2 displays a digital level display 36 in which a plurality of display elements are arranged in a line, and displays the above-mentioned pulse wave display signal DMa-
DMf, that is, the number of pulse wave sensors 12a-12f, each pulse wave display signal DMa-DMf included in the pulse wave display signal DM has a corresponding digital level display 36a-36f. There, as indicated by diagonal lines in FIG. 2, a light emitting display is performed using a number of display elements corresponding to the size and level of each display element. Further, the display device 34 includes a first display section 34a and a second display section 34b, and the actual pulse wave propagation velocity represented by the pulse wave velocity display signal DA is displayed on the first display section 34a. It has become so. Note that this display 34 may be a normal CRT display or L
Various display devices such as an ED display or a dot printer that prints on recording paper can be used, and various display formats including numerical display can be adopted.

Further, an automatic blood pressure measuring device 40 equipped with a cuff 38 is connected to the I10 port 22, and a blood pressure measurement command signal SB is supplied from the I10 port 22 to the automatic blood pressure measuring device 4o. The automatic blood pressure measuring device 4o automatically measures blood pressure when the blood pressure measurement command signal SB is input, and supplies a blood pressure value signal DB representing the blood pressure value that is the measurement result to the I10 boat 22. It has become.

Furthermore, the I10 boat 22 receives a rising blood pressure value signal D.
A standard pulse wave propagation velocity display signal DS representing a standard pulse wave propagation velocity at a standard blood pressure value corrected based on the blood pressure value represented by B is output, and this standard pulse wave propagation velocity display signal DS is the second display section 34b of the display device 34
The pulse wave velocity display signal DA is then displayed in the same manner as the pulse wave velocity display signal DA.

In the device as described above, in this embodiment, C
The PU 26 executes signal processing according to the program flowchart shown in FIG. 4, for example.

The operation of the apparatus of this embodiment will be explained below according to the flowchart shown in FIG.

When the program is started with the pulse wave sensor unit 10 pressed against a predetermined position on the neck of the human body as described above, step S1 is first executed. This step S1 is a step for initial setting, and here, the mutual distances between the pulse wave sensors 12a to 12f, which are stored in advance, are written into the RAM 2B. Note that 117j and 'l'ij between the pulse wave sensors 12a to 12f
;y;[ may be stored in the ROM 30 in advance and ζ may be used.

When the initial setting of step S1 is completed, step S2 is executed continuously, and the contents of the port select signal SP are
For example, the content is set so that all six channels are sequentially switched at a cycle of four cycles. Then, the pulse wave signal SM selected and outputted by the port select signal SP thus set is converted by the A/D converter 20 and converted into a pulse wave signal SMD.
The data is input to the I10 boat 22 as a file and stored.

Further, step S executed subsequent to step S2
3, a pulse wave display signal DM is supplied to the pulse wave display unit 32 based on the stored pulse wave signal SMD. At that time, the pulse wave display signals D M a - D M f representing the magnitude of the pulse waves detected by each pulse wave sensor It is set so that it can be switched sequentially.

That is, these steps S2. In S3, the pulse wave signals SMa"~S detected by the pulse wave sensors 12a~12[
The size of MM is automatically displayed on the digital level displays 36a to 36f of the pulse wave display unit 32 corresponding to the respective pulse wave sensors 12a to 12f.

After step S3 is executed, step S4 is immediately executed, and it is determined whether or not the start signal SS has been input, that is, whether or not the star 1 has been pressed and the i date 24 has been pressed. If the start button 24 has not been pressed yet, steps S2 and subsequent steps are repeated, and if it is determined that the press button 24 has been pressed and an instruction to start measurement of pulse wave propagation velocity has been given, steps S5 and subsequent steps are immediately performed. executed.

Note that, as described above, before giving a measurement instruction, the pulse wave signals SMa' to SMa' detected by each of the pulse wave sensors 12a to 12f are
If the size of SMf'' is displayed, not only can it be determined from the display whether or not the pulse wave sensor unit 10 is properly pressed against the neck, but also the pulse wave sensor unit l-10 can be determined by looking at the display. Since the pressure value iη can be readjusted to the appropriate position, it is possible to readjust the pressure value
Even a person can measure the pulse wave propagation velocity reliably and with high precision.

In step S5, a blood pressure measurement command signal SB is sent to the automatic blood pressure measuring device 40 to cause the automatic blood pressure measuring device 40 to start measuring blood pressure. Note that the automatic blood pressure measurement bag 240 automatically measures the blood pressure value in parallel with the subsequent measurement of the pulse wave velocity based on this blood pressure measurement command signal SB, and sets the blood pressure value to a predetermined blood pressure value (in this embodiment, When the diastolic blood pressure value) is determined, a blood pressure value signal DB representing that blood pressure value is supplied to the I10 boat 22. In other words, in this embodiment, this automatic blood pressure measuring device 40 constitutes blood pressure measuring means.

Next, in step S6, similarly to step S2, the contents of the port select signal SP are set to sequentially switch all input channels at a 4 ms cycle, and the pulse wave signal corresponding to such port select signal SP is set. SMD
is made to write 4g. In the following step S7, similarly to step S3, the pulse wave display and each digital level display 36a to 36f of the unit 32 are set to each pulse wave sensor 12a.
The pulse wave detected at ~12f is displayed.

In step S8, after the input of the start signal SS is confirmed in step S4, a predetermined period, for example, 4
It is determined whether the seconds have passed or not.

Then, the steps from step S6 onward are repeated until the four seconds have elapsed, and after the four seconds have elapsed, the next step S9 is executed.

In step S9, each pulse wave sensor 12a to 12 represented by the pulse wave signal SMD stored in step S8 is
A pair of pulse wave sensors is selected from among the pulse wave sensors 12a to 12f based on the magnitude of the pulse wave (pulse wave signals SMa' to SMM) detected at f. In subsequent steps, the pulse wave propagation velocity is measured based on the pulse wave signals obtained from the pair of pulse wave sensors selected in step S9. Note that in this embodiment, this step S9
The selection of the pulse wave sensor in step S6 is based on the plurality of pulse waves stored in steps S6 to S8 (usually 3 to 3 pulse waves in 4 seconds for adults).
Pulse wave sensors with at least one or more pulse wave sensors arranged in between, based on those with a large average value of the rise angle (6 pulse waves can be obtained) and those with a large average value of maximum amplitude. is selected. In order to detect the pulse wave propagation velocity, two points (1) and (2) of the artery are set, and two pulse wave sensors are selected based on the average value of multiple pulse waves. By doing so, it is possible to more accurately judge which pulse wave sensor is being pressed against the artery more appropriately, and it is also possible to select one or more pulse wave sensors placed with a gap between them. By doing so, the distance between the pulse wave sensors becomes larger, and the measurement accuracy of the pulse wave propagation velocity can be further improved.

Of course, when selecting a pulse wave sensor, it is not necessary to use the average value of multiple pulse waves as the standard as described above.
The selection may be based only on the rise angle of a single pulse wave, or adjacent pulse wave sensors may be selected.

In step SIO, the port select signal SP is set to selectively output only the pulse wave signal detected by the pulse wave sensor selected in step S9, and the switching cycle is set to a sufficiently short cycle, for example, LOOtls. so that each pulse wave data having sufficient resolution to represent each pulse wave detected by the pulse wave sensors is collected.

In step Sll, two channels of pulse wave data obtained from the pulse wave sensor selected in step S9 according to the switching cycle (sampling cycle) set in step SIO are sequentially stored and pulse wave data are stored as the pulse wave display signal DM. The signal is supplied to the wave display unit 32 and displayed on the digital level display 36 corresponding to each pulse wave sensor.

Furthermore, when step S12 is executed following step Sit, it is determined whether a predetermined period has elapsed. Then, steps SIO and subsequent steps are repeatedly executed until the period has elapsed, but when it is determined that the period has elapsed, the pulse wave propagation time determination algorithm A of step S13 is executed. Note that the period is set to a period sufficiently longer than one cycle of one pulse wave obtained through the selected pair of pulse wave sensors, for example, about 2 seconds. That is, in steps SIO to S12, the waveforms of the pulse waves detected by both pulse wave sensors are
The pulse wave data of (.l;'f11) is stored over a time range that includes at least one cycle.

In algorithm A of step S13, the above step 5
Based on the two types of pulse wave data stored in steps 10 to S12, the pulse wave is detected between the two points at the detection positions of the pulse wave sensor selected in step S9, according to the flowchart shown in FIG. The propagation time required for propagation is determined.

That is, when algorithm A in FIG. 5 starts, step SAI is executed first. This step S
In AI, as shown in FIG.
The usage range H of the pulse wave data representing one of the first pulse wave and the second pulse wave respectively represented by the type of pulse wave data, for example, the first pulse wave detected by the upstream pulse wave sensor, is set as the first pulse wave data. A group of partial pulse wave data f(t,) determined to include the maximum peak value of the pulse wave and within the usage range H (where n is the sample data number in the number N of sample data within the usage range H) The length of the partial pulse wave data f(t+s) is determined to sufficiently cover the main part of the first pulse wave. , the time length is the product of the N and the sampling period T.The length of the partial pulse wave data f(ta) is the first
It may be determined based on the rising point of the pulse wave, or may be determined based on the R wave if an electrocardiogram is obtained.

Next, when step SA2 is executed, the partial pulse wave data f(t,) and the partial pulse wave data f of the pulse wave data representing the second pulse wave detected by the pulse wave sensor on the downstream side are
A group of partial pulse wave data g (En
+= ) (However, n+i indicates the sample data number in a series of sample data, n is the number to make the same number of data as the partial pulse wave data f(t,,), and n =0.1.2...NS i is the shift number of partial pulse wave data of the downstream pulse wave, t=o, 1.2
...It is M. ] The cross-correlation coefficient β positive is given by the following formula (1)
It is required according to the following.

Then, in step SA3, it is determined whether the Mth and final cross-correlation coefficient βi has been obtained in step SA2. Initially, the first cross-correlation coefficient β, (+
= 0), the judgment in step SA3 is denied and step SA4 is executed (1), and the partial pulse wave data of the downstream pulse wave used to find the cross-correlation coefficient is only one sample data. shifted (temporally delayed by one sampling period), partial pulse wave data g(t
□, ). The partial pulse wave data g (t++.,) obtained in this way and the partial pulse wave data f (t, ,
) is obtained according to the ff1 equation by executing step SA2 again.

In this way, when steps SA2 to SA4 are repeatedly executed until the judgment in step SA3 is affirmed, a large number of cross-correlation coefficients β are obtained. , β1°...βi are calculated. That is, as shown in Fig. 6, the time axes of the first pulse wave and the second pulse wave detected at two points on the artery are relatively shifted and the cross-correlation coefficient between them is determined. be. Here, in this example, the first data g(to) (n=0.i=0:l of the partial pulse wave data of the downstream pulse wave used to find the cross-correlation coefficient) is as follows.
The first data f (t
o) (n=0). Since there is always a difference in appearance time between the upstream pulse wave and the downstream pulse wave, this ensures that the maximum cross-correlation coefficient is obtained within the range in which the cross-correlation coefficient is calculated. It is.

However, the time point of the first data of the partial pulse wave data on the downstream side may be made to go back in time by a predetermined amount from the time point of the first data of the partial pulse wave data on the upstream side. Furthermore, the maximum value M of the i value corresponding to the shift amount is such that even if the second pulse wave appears due to the expected maximum appearance time difference, its main part is sufficiently included in the partial pulse wave data g(un-i). It is predetermined that the

As a result of the determination in step SA3 being affirmative, when step SA5 is executed, the maximum mutual correlation among the cross-correlation coefficients βi (i=0.1.2...M) obtained in large numbers as described above is calculated. The relationship coefficient β□ is determined using a well-known comparison algorithm. Then, step SA6 is executed to obtain the maximum cross-correlation coefficient β obtained in step SA5. , X (shift ff1), that is, by multiplying the sample data shift number i value by the sampling period T, the pulse wave propagation time is determined. Once the pulse wave propagation time is determined for the first pulse wave and the second pulse wave based on their cross-correlation coefficient β in this manner, the algorithm A ends after step SA6 is completed.

As described above, in this embodiment, since the pulse wave propagation time is calculated based on the amount of shift between the first pulse wave and the second pig wave until the cross-correlation coefficient β becomes maximum, the rise of the pulse wave Compared to the method of calculating the pulse wave propagation time based on points or maximum amplitude points, even if the pulse wave waveform is complex or the pulse wave is disturbed due to noise, etc. The points where the second pulse waves are most similar, in other words, the points where the characteristics of the pulse waves most match are accurately CFed, and high measurement accuracy can be obtained.

Returning to FIG. 4, in step S14 executed after algorithm A in step S13, from the mutual installation distance between the pulse wave sensors 12a to 12f stored in the initial setting in step S1, The distance between the selected pair of pulse wave sensors is determined as the propagation distance of the pulse wave, and the calculation (propagation distance/propagation time) is performed based on this propagation distance and the propagation time obtained in step S13. The actual propagation velocity of the pulse wave can be determined by

Then, in the following step 315, the step S14
A pulse wave propagation velocity display signal DA representing the actual pulse wave propagation velocity determined in is supplied to the display 34, and the first display section 34a
The actual 19 pulse wave propagation velocity is displayed.

Step 7 When step S15 is completed, step S1 continues.
6 is executed, and it is determined whether the blood pressure value signal DB based on the blood pressure measurement command signal SB sent from the automatic surface pressure measuring device 40 in step S5 has been input. This step S16 is repeated while the blood pressure value signal DB is not input, and step S17 is subsequently executed when it is determined that the blood pressure value signal DB has been input.

In step S17, R
The standard pulse wave propagation velocity at a standard blood pressure value, for example 80+n Hg, is determined from the correction data recorded in the OM30.

Note that there is a relationship between the blood pressure value (diastolic blood pressure value) and the pulse wave propagation velocity, as shown in FIG. An appropriate relationship is selected from both the actual pulse wave propagation velocity and the measured blood pressure value at the time of measuring the pulse wave propagation velocity, and the standard pulse wave propagation velocity at the standard blood pressure value is determined from this relationship. In addition, the standard blood pressure value does not necessarily have to be 80 mHg, but as long as it is a value that allows objective judgment of the information obtained from the standard pulse wave velocity.
It can be changed as appropriate.

When the standard pulse wave propagation velocity is determined in step S17, the standard pulse wave propagation velocity display signal DS representing the standard pulse wave propagation velocity is supplied to the display 34 in the following step 818, and the second display section of the display 34 The standard pulse wave propagation velocity is displayed at 34b. In other words, step 318 and the second display section 34b of the display 34 constitute the display means of the second invention of the present application, and the above-described configuration constitutes the second invention of the present application. In this embodiment, after the step 318 is completed, steps S2 and subsequent steps are repeated again.

Although one embodiment of the present invention has been described above, the present invention should not be interpreted as being limited to this embodiment.

For example, in the embodiment described above, the pair of pulse wave sensors were appropriately selected from among the plurality of pulse wave sensors 12a to 12f arranged in the pulse wave sensor unit 10, but the pulse wave sensor unit Alternatively, a pair of pulse wave sensors may be simply provided separated by a predetermined distance.
Alternatively, instead of providing a pair of pulse wave sensors in one pulse wave sensor unit, separate pulse wave sensors may be provided and they may be pressed separately against the carotid artery. However, when pressing the pulse wave sensors individually against the carotid artery in this way, it is necessary to measure the distance between the pulse wave sensors and store it in the RAM 28 in advance.

Furthermore, the artery to which the pair of pulse wave sensors is pressed does not necessarily have to be the carotid artery, but may be the femoral artery or any other artery. Any artery that can be measured with high accuracy is sufficient, and furthermore, if the distance between the pulse wave sensors (substantive length of the artery) can be measured, the pulse wave sensor can be pressed against each of these separate arteries. It is okay to do so.

Further, in the above embodiment, the pulse wave sensor unit 10 is provided which detects a pulse wave based on the pulsation of the artery by being pressed from above the cortical layer toward the artery. Pulse waves propagating through arteries may be detected by disposing a plurality of microphones as pulse wave sensors on the cortical layer, which detect pulse sounds generated at the rising portions and notches of waves. Note that such a microphone is generally selected to be capable of detecting pulse sounds having a frequency of several tens of Iz or more, for example, about 20 Hz or more. In this way, the pulse wave is detected based on the presence or absence of the pulse sound that generates the pulse wave, so the detection can be easily performed, and the pulse wave sensor is placed slightly off the top of the artery to detect the pulse wave. There is an advantage that the propagation time of the pulse wave can be accurately measured even if the size changes.

Furthermore, in the embodiment, the pulse wave (pulse wave signal S) detected by each pulse wave sensor 12a to L2f of the pulse wave sensor unit IO is
The magnitudes of Ma' to SMf") can be individually determined using the digital level indicators 368 to 36f of the pulse wave display unit 32, but such a display function does not necessarily have to be provided. .

In addition, in the embodiment, the automatic blood pressure measuring device 40 has an I
Based on the blood pressure measurement command signal SB from the 10 port 22, the blood pressure value is determined independently of the measurement of the pulse wave propagation velocity, and a conventional automatic blood pressure measurement bag can be used. However, it is also possible to configure the CPU 26, which controls the measurement of the actual pulse wave propagation velocity, to also directly control the operation of the automatic blood pressure measuring device 40.

In addition, the configuration of the hardware circuit and the configuration ring of the flowchart.
Although not enumerated, it goes without saying that the present invention can be implemented with various modifications, improvements, etc. without departing from the spirit thereof.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a perspective view showing an example of the pulse wave sensor UniSoto in FIG. FIG. 4 is a flowchart for explaining the operation of the embodiment shown in FIG. 2, FIG. 5 is a flowchart for explaining algorithm A of the flowchart in FIG. 4, and FIG. It is a figure explaining the pulse wave data when calculating|requiring a cross-correlation coefficient in the algorithm A of a figure. FIG. 7 is a graph showing the relationship between the minimum 1111 pressure value and the pulse wave propagation velocity. Applicant Co., Ltd. [''Korin Figure 1]

Claims (1)

[Claims] One pulse wave propagating within the artery is detected at two points separated by a certain distance on the artery, and the time axes of the first pulse wave and the second pulse wave detected at the two points are compared relative to each other. determining the cross-correlation coefficient between them while shifting them, and determining the difference in appearance time of the first pulse wave and the second pulse wave based on the amount of shift of the time axis until the cross-correlation coefficient becomes the largest; A method for measuring pulse wave propagation velocity, characterized in that the pulse wave propagation velocity in the artery is determined based on the appearance time difference and the certain distance.