JP2001161650A - Device for measuring velocity of transmission of pulse wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reasonably priced device for measuring the velocity of transmission of a pulse wave which measures correctly even when the distance between the two sensors for the pulse wave is short. SOLUTION: Every time the difference ΔT in the timing of sampling is changed by a means 76 for changing the difference in the timing, a cross- correlation value Φp (ΔT) of a first and a second waveforms each represented by a first pulse wave signal SM1 and a second pulse wave signal SM2 of one pulse is calculated by a means 80 for calculating the cross-correlation value. Time DT for transmitting the pulse wave and the velocity PWV of transmission of the pulse wave are calculated by a means 86 for calculating the velocity PWV based on the first and the second waveforms used for calculating maximum of the cross-correlation value Φp (ΔT). The forms of the first and the second waveforms of the pair, whose cross-correlation value Φp (ΔT) is the maximum, are the most alike. The time DT and the velocity PWV are accurately calculated, based on he first and the second waveforms that are the most alike, without using an expensive device for a high-speed processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to pulse wave velocity information relating to a pulse wave velocity in which a pulse wave propagates in an artery of a living body. More particularly, the present invention relates to a pulse wave velocity information measuring apparatus capable of measuring pulse wave velocity information between short portions with high accuracy.

[0002]

2. Description of the Related Art Various pulse wave propagation velocity information measuring devices for measuring pulse wave propagation velocity information have been proposed. This is because the pulse wave propagation velocity information can be used for estimating a blood pressure value, arterial stiffness, peripheral resistance, and the like.

In order to measure the above-mentioned pulse wave propagation velocity information, it is necessary to attach a pulse wave sensor to two predetermined portions of a living body. However, in order to integrally form the two pulse wave sensors, In order to measure the degree of arteriosclerosis, it is desired to measure the pulse wave velocity information by shortening the distance between two pulse wave sensors (for example, about several cm).

[0004]

However, if the distance between the two pulse wave sensors is short, the time required for the pulse wave to propagate between the two pulse wave sensors, that is, the pulse wave propagation time DT, becomes short.
The pulse wave propagation time DT may be shorter than the sampling period T _S for reading the pulse wave detected from the pulse wave sensor. The pulse wave propagation time DT is longer than the sampling period T
If it is shorter than _S , the pulse wave transit time DT cannot be measured. Further, even not shorter than the sampling period T _S, when the pulse-wave propagation time DT is several times the sampling period T _S comparable or sampling period T _S is the accurate pulse-wave propagation time DT It cannot be measured.

FIG. 1 illustrates the difference between the original pulse wave transit time DT 'and the actually measured pulse wave transit time DT when the pulse wave transit time DT is about several times the sampling period T _S. The first pulse wave sensor detected by the first pulse wave sensor.
It is a figure which characteristically shows the rising part of a waveform and the rising part of the 2nd waveform detected by the 2nd pulse wave sensor. FIG. 1A shows an original waveform, that is, a waveform detected when the sampling period T _{S is set} to infinitesimal. The pulse wave propagation time DT ′ is determined by the rising point a ′ of the first pulse wave and the second pulse wave DT ′.
This is the time difference from the rising point b 'of the pulse wave. However, in actuality, the sampling period T _S is a certain period of time, and the first pulse wave and the second pulse wave are a series of points read at each sampling period T _S indicated by ●. FIG. 1B shows a measured pulse wave composed of a series of points read at every sampling period T _S. As shown in FIG. 1B, the sampling period T
_{Since S} has a certain size, even if the first pulse wave and the second pulse wave originally have the same shape as shown in FIG. In some cases. Therefore, the reference points (the rising point a of the first pulse wave and the rising point b of the second pulse wave in FIG. 1) for calculating the pulse wave propagation time DT are different from the original reference points, and are measured. The pulse wave transit time DT is different from the original pulse wave transit time DT ′.

[0006] In order to accurately measure the pulse wave propagation time DT, it is conceivable to shorten the sampling period T _S, the shortened sampling period T _S, that much large amount of waveform data is read Therefore, there is a problem that high-speed processing is required and the apparatus becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to measure accurate pulse wave propagation velocity information even when the distance between two pulse wave sensors is short. Another object of the present invention is to provide an inexpensive pulse wave propagation velocity information measuring device.

[0008]

Means for Solving the Problems The present inventor has conducted various studies on the background of the above circumstances and found that the measured pulse wave differs from the original pulse wave due to the long sampling period T _S. Also, if the waveforms of the first pulse wave and the second pulse wave match each other, an accurate pulse wave transit time DT can be calculated. Further, the waveform of the first pulse wave and the waveform of the second pulse wave can be compared with each other. It was found that the sampling timing should be relatively shifted in order to match with the above.

That is, the gist of the present invention to achieve the above object is to provide a first pulse wave sensor and a second pulse wave sensor which are respectively attached to predetermined portions of a living body, A pulse wave propagation speed related to a pulse wave propagation speed at which a pulse wave propagates in a living body based on a first pulse wave signal output from the sensor and a second pulse wave signal output from the second pulse wave sensor A pulse wave velocity information measuring device for measuring information, comprising: (a) a sampling timing for capturing a first pulse wave signal output from the first pulse wave sensor;
A timing difference changing unit for changing a sampling timing difference between the sampling timing for capturing the second pulse wave signal output from the pulse wave sensor and a predetermined shift unit, and (b) the timing difference changing unit. A cross-correlation value for calculating a cross-correlation value between a first waveform and a second waveform respectively represented by the first pulse wave signal and the second pulse wave signal for a predetermined period every time the sampling timing difference is changed Calculating means, (c) by the cross-correlation value calculating means, among the cross-correlation values calculated each time the sampling timing difference is changed, maximum value determining means for determining the maximum value, and (d) the maximum value Using the first waveform and the second waveform used for calculating the maximum value determined by the value determining means, a predetermined portion of the first waveform is set as a first reference point, and the second waveform of the second waveform is determined. Pulse wave velocity information calculating means for calculating the pulse wave velocity information based on a time difference between the first reference point and the second reference point, wherein the fixed part is a second reference point. A pulse wave propagation velocity information measuring device, characterized in that:

[0010]

In this way, every time the sampling timing difference is changed by the timing difference changing means, the first pulse wave signal and the second pulse wave signal for a predetermined period are calculated by the cross-correlation value calculating means. A cross-correlation value between the first waveform and the second waveform respectively represented is calculated, and the pulse wave propagation velocity information calculating means calculates the cross-correlation value based on the first waveform and the second waveform used for calculating the maximum value of the cross-correlation value. Pulse wave propagation velocity information is calculated. The combination of the first waveform and the second waveform having the maximum cross-correlation value is a waveform in which the shapes of the first waveform and the second waveform are most similar to each other, and the pulse wave propagation velocity information is the most similar to each other. Since the calculation is based on the approximated first and second waveforms, accurate pulse wave propagation velocity information can be calculated without using an expensive device capable of high-speed processing.

[0011]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram showing a circuit configuration of a pulse wave velocity information measuring apparatus 10 to which the present invention is applied.
In the figure, a pulse wave propagation velocity information measuring device 10 measures pulse wave propagation velocity information based on a pulse wave signal SM supplied from a pressure pulse wave detection probe 12 shown in detail in FIG.

As shown in FIG. 3, the pressure pulse wave detecting probe 12 is attached to a neck 14 of a living body by an attaching band 16.
As shown in detail in FIG. 4, a case 20 for accommodating a sensor housing 18 in the shape of a container, and a screwed to the sensor housing 18 to move the sensor housing 18 in the width direction of the carotid artery 22 and inside the case 20 Screw shaft 2 driven to rotate by a motor (not shown) provided in
4 is provided. The pressure pulse wave detection probe 12 is attached by the mounting band 16 so that the open end of the sensor housing 18 faces the body surface 26 of the neck 14 of the living body.

Inside the sensor housing 18, a pressure pulse wave sensor 30 is provided via a diaphragm 28 so as to be relatively movable and protrudable from an open end of the sensor housing 18. The sensor housing 18, the diaphragm 28 and the like are provided. Thereby, a pressure chamber 32 is formed. As shown in FIG. 2, pressure air is supplied from the air pump 34 through the pressure regulating valve 36 into the pressure chamber 32, so that the pressure pulse wave sensor 30 The body surface 26 is pressed with a pressing force corresponding to the pressure (Pa).

The sensor housing 18 and the diaphragm 28 constitute a pressing device 38 for pressing the pressure pulse wave sensor 30 toward the carotid artery 22, and the screw shaft 24
A motor (not shown) constitutes a pressing position changing device that changes the pressing position where the pressure pulse wave sensor 30 is pressed in the width direction of the carotid artery 22, that is, a width direction moving device 40.

On the pressing surface 40 of the pressure pulse wave sensor 30,
As shown in FIG. 5, a large number of semiconductor pressure-sensitive elements (hereinafter, referred to as pressure-sensitive elements) E are arranged in two parallel rows, and a first pressure-sensitive element row E1 and a second pressure-sensitive element row E2 are respectively provided. Has formed. The first pressure-sensitive element row E1 is composed of a plurality of first pressure-sensitive elements E1 (m) (m: an integer), and the length thereof is the pressure pulse wave parallel to the width direction of the carotid artery 22, that is, the screw axis 24. In the moving direction of the sensor 30, it is set to, for example, 2 cm so as to be longer than the diameter of the carotid artery 22, and the first pressure-sensitive elements E1 (m) are arranged at regular intervals. Similarly to the first pressure-sensitive element row E1, the second pressure-sensitive element row E2 is also composed of a plurality of second pressure-sensitive elements E2 (n) (n: integer), and the length and each pressure-sensitive element E2
The arrangement interval of (n) is the same as that of the first pressure-sensitive element row E1. Further, the first pressure-sensitive element row E1 and the second pressure-sensitive element row E2
Is set to a relatively short distance, for example, about 1 cm.

In the pressure pulse wave detecting probe 12 configured as described above, the first pressure-sensitive element row E1 is located on the upstream side,
The row of pressure-sensitive elements E2 is pressed onto the carotid artery 22 on the body surface 26 of the neck 14 so that the row E2 is on the downstream side. When the pressure pulse wave detection probe 12 is mounted on the carotid artery 22 on the opposite surface 26, each pressure sensing element E detects a pressure vibration wave, that is, a pressure pulse wave generated from the carotid artery 22 and transmitted to the body surface 26. Then, the pressure pulse wave signal SM representing the pressure pulse wave is supplied to a sample hold circuit 44 provided for each pressure sensing element E. The sample-and-hold circuit 44 periodically and time-selects the pressure pulse wave signal SM input from the pressure-sensitive element E according to the sampling pulse from the arithmetic and control unit 46, and sequentially outputs the selected pressure pulse wave signal SM to the multiplexer 48. I do.

The multiplexer 48 includes a pressure pulse wave signal SM sequentially supplied from the plurality of sample and hold circuits 44.
Is output to the A / D converter 50 in a time-sharing manner. The A / D converter 50 A / D converts the pressure pulse wave signal SM input from the multiplexer 48 and supplies the signal to the arithmetic and control unit 46.

The arithmetic and control unit 46 includes a CPU 52, a ROM
54, a RAM 56, and a so-called microcomputer having an I / O port (not shown) and the like.
The CPU 52 executes signal processing while utilizing the storage function of the RAM 56 in accordance with a program stored in the ROM 54 in advance, so that the air pump 34 and the pressure regulating valve 36
A drive signal is output through a drive circuit (not shown) to adjust the pressure in the pressure chamber 32, a pressure pulse wave signal SM is read from the pressure pulse wave sensor 30, and a pulse is generated based on the pressure pulse wave signal SM. The wave propagation velocity information is calculated, and the calculated pulse wave propagation velocity information is displayed on the display 58. Note that the CPU 52
In order to measure a sampling timing difference ΔT changed by a shift unit T _U, which will be described later, a unit having a clock number equal to or less than the shift unit T _U is used.

FIG. 6 shows the pulse wave velocity information measuring device 1 described above.
FIG. 3 is a functional block diagram illustrating a main part of a control function of the arithmetic and control unit 46 at 0. In FIG. 6, the sampling pulse output means 70 is provided to each sample and hold circuit 44 provided for each pressure-sensitive element E at the same time or with a predetermined sampling timing difference ΔT set by a timing difference changing means 76 described later. A sampling pulse having a preset sampling period T _S is output. The sampling cycle T _S is set, for example, to several milliseconds to several tens of milliseconds. The above sampling period T _S
By sampling pulse is output for each, because pressure-pulse-wave signal SM is read from the pressure-sensitive elements E for respective sampling period T _s, the sampling pulse output means, signal reading means for reading the pressure-pulse-wave signal SM Functioning as

The pulse pressure calculating means 72 controls each sample and hold circuit 44 at every predetermined sampling period T _S.
Detected by the plurality of pressure-sensitive elements E arranged in the first pressure-sensitive element row E1 and the second pressure-sensitive element row E2 on the pressing surface 42 of the pressure pulse wave sensor 30 based on the pressure pulse wave signal SM supplied from the pressure pulse wave sensor SM. the pulse pressure P _M of the pressure pulse wave, respectively calculated for each sensitive element E. Figure 7 is a diagram showing an example of a pressure pulse wave signal SM is sequentially detected by the pressure-sensitive elements E, the pulse pressure P _M,
As shown in FIG. 7, it is the difference between the pressure at the peak c of the pressure pulse wave for each beat and the pressure at the rising point d (or the minimum point).

The sensor determining means 74 includes a first pressure-sensitive element row E
1 among the first pressure-sensitive elements E1 (m) constituting
Pulse pressure P calculated by the means 72_MIs the largest element
Optimal pressure sensitive element E1_OAnd the second pressure-sensitive element row E2 is configured.
Among the second pressure-sensitive elements E2 (n) to be formed, the pulse pressure calculating means 7
Pressure P calculated by 2_MIs the 2nd optimum feeling for the largest element
Pressure element E2_OTo decide. Determined as above
First optimal pressure sensitive element E1 _OAnd second optimal pressure-sensitive element E2_O
Is a pressure-sensitive element E located immediately above the carotid artery 22,
In the pulse wave propagation velocity information calculating means 86 described below, the first
Suitable pressure sensing element E1 _OPressure pulse wave signal SM output from₁
And the second optimum pressure-sensitive element E2_OThe second output from
Pressure pulse signal SM_TwoPulse wave velocity information is calculated based on the
It is. Therefore, in this embodiment, the first optimum pressure-sensitive element E1_O
And second optimal pressure-sensitive element E2_OPulse wave sensor 3 provided with
0 functions as the first pulse wave sensor and the second pulse wave sensor
In particular, one of the pressure-sensitive elements E is the first optimum pressure-sensitive element E.
1_OThe first pressure-sensitive element row E1 side determined by
Functioning as one of the pressure-sensitive elements E
Element E2_OThe second pressure-sensitive element row E2 side determined as
Functions as a wave sensor.

The timing difference changing means 76 outputs the first pressure pulse wave signal SM ₁ output from the first optimum pressure sensing element E1 _O.
And a sampling timing sample and hold circuit 44 takes in every sampling period T _S, the second pressure-pulse-wave signal SM ₂ output from the second optimum pressure sensitive element E2 _O sample-and-hold circuit 44 for each sampling period T _S The sampling timing difference ΔT with respect to the sampling timing to be taken is set to the maximum timing difference ΔT for each predetermined shift unit T _U.
Change until _Tmax .

FIG. 8 shows the sampling timing difference Δ
FIG. 3 is a diagram illustrating T, wherein the upper part shows sampling pulses output by the sampling pulse output means 70 to the sample and hold circuit 44 connected to the first optimum pressure sensing element E1 _O , and the lower part shows sampling pulse output. the means 70, the sampling pulse outputted to the sample hold circuit 44 connected to the second optimum pressure sensitive element E2 _O. As shown in FIG. 8, the time difference between the output of the sampling pulse to one sample and hold circuit 44 and the output of the sampling pulse to the other sample and hold circuit 44 is the sampling timing difference ΔT.

The shift unit T _U is a period shorter than the sampling period T _S , and is the sensitivity required by the later-described pulse wave propagation velocity information calculation means 86 and the first optimum pressure-sensitive element E1 _O. It is determined based on the inter-element distance L between the second optimal pressure sensitive element E2 _O. Note that the sensitivity is the minimum unit to be calculated, that is, the resolution.
Further, the pulse wave propagation velocity PWV is calculated by Expression 1. (Equation 1) PWV = L / DT Therefore, for example, the sensitivity of the pulse wave propagation velocity PWV is 10 (m
/ s) is required, and the first pressure-sensitive element E1 _O
When the distance L between the first and second pressure-sensitive elements E2 _O is 2 cm, the pulse wave propagation time DT when the pulse wave propagation velocity PWV is 600 (m / s) is 3.33 (msec) according to Equation 1. And the pulse wave propagation velocity P
Pulse wave propagation time DT when WV is 610 (m / s) is 3.28 (msec)
Becomes The difference between the two pulse wave transit times DT is 3.33-3.28 = 0.
05 (msec). That is, when the sensitivity is 10 (m / s) and the distance between the two pulse wave sensors is 2 cm, the pulse wave propagation time DT
Requires a sensitivity of 0.05 (msec). Therefore, 0.05 (mse
c) is the shift unit T _U. The range in which the sampling timing difference ΔT is shifted for each shifting unit T _U is from the timing difference ΔT of 0 to the maximum timing difference ΔT _max , and the maximum timing difference ΔT _max is determined from the sampling period T _S by the shifting unit T T. _U minus the value (ΔT
_max is a = T _S -1T _U).

Each time the sampling difference ΔT is changed by the timing difference changing unit 76, the waveform storage unit 78 stores the first pulse wave signal SM ₁ read in accordance with the sampling pulse output shifted by the sampling timing difference ΔT. and a second predetermined period of the pulse wave signal SM ₂ stores in a predetermined storage area in the RAM 56. The predetermined period is a period including a part serving as a reference point in the pulse wave propagation velocity information calculation means 86 described later, and is, for example, one beat or several beats.

The cross-correlation value calculating means 80 stores the waveform
The sampling timing difference ΔT is changed by the means 78
Each time the first pulse wave signal SM is stored for a predetermined period of time₁
And the second pulse wave signal SM_TwoFor a given period of time
First pulse wave signal SM₁The first waveform represented by
Two pulse wave signal SM_TwoThe cross-correlation function Φ with the second waveform represented by _p
(t) is changed every time the sampling timing difference ΔT is changed.
Each is calculated, and the sampling timing difference
Cross-correlation function Φ calculated every time ΔT is changed _p(t)
To which the sampling timing difference ΔT is substituted
Correlation value Φ_P(ΔT) is calculated. Note that the subscript p
Is T_S/ T_UIt is the following integer. Also, each other
Correlation function Φ_p(t) is the sampling timing difference ΔT
, The cross-correlation value Φ_P(ΔT)
Is a phase calculated for each sampling timing difference ΔT.
Cross-correlation coefficient Φ_p(t) represents the maximum value.

The maximum value determining means 82 determines the maximum value of the cross-correlation values Φ _P (ΔT) calculated by the cross-correlation value calculating means 80 each time the sampling timing difference ΔT is changed. The cross-correlation value Φ _P (ΔT) is the first
Since the degree of correlation (approximation) between the shape of the waveform and the shape of the second waveform is represented, the cross-correlation value Φ _P (ΔT) becomes the maximum value because
This is a case where the correlation is calculated based on the waveform having the largest correlation between the first waveform and the second waveform stored every time the sampling timing difference ΔT is changed. FIG. 9 is a diagram characteristically showing a rising portion of the first pulse wave and a rising portion of the second pulse wave used for calculating the maximum value. In order to compare with FIG. The waveform has the same shape as the first pulse wave shown in FIG. The portion indicated by the broken line in the figure is the rising portion of the original pulse wave, and the measured first pulse wave and second pulse wave are different from the original pulse wave, but only the sampling timing difference ΔT By delaying the sampling timing of the second pressure pulse wave signal SM2, a _second pulse wave having a high correlation with the first pulse wave is detected.

The inter-sensor distance calculating means 84 calculates the inter-element distance (ie, inter-sensor distance) L between the first optimum pressure sensing element E1 _O and the second optimum pressure sensing element E2 _O determined by the sensor determining means 74. It is determined based on a relationship stored in advance. FIG. 10 illustrates the relationship between the first optimum pressure-sensitive element E1 _O and the second optimum pressure-sensitive element E2 _O and the distance L between the elements.

Based on the first and second waveforms for which the maximum value determined by the maximum value determining means 82 has been calculated, the pulse wave propagation speed information calculating means 86 determines a predetermined portion of the first waveform (for example, a rising edge). Point or peak) as a first reference point s _1, and a portion corresponding to the first reference point in the second waveform as a second reference point s ₂ , from the first reference point s ₁ to the second reference point s _2. Is calculated as the pulse wave transit time DT, and the pulse wave transit speed PWV is calculated from the pulse wave transit time DT based on the equation (1).

For example, when the first reference point s ₁ and the second reference point s ₂ used for calculating the pulse wave propagation time DT are the rising point of the first waveform and the rising point of the second waveform shown in FIG. time difference between the rising point s ₂ rising point of the first pulse wave s ₁ and the second pulse wave is a pulse wave propagation time DT. As shown in FIG. 9, the rising point s ₁ of the first pulse wave is determined at a time Δc before the rising point s ₁ ′ of the original first pulse wave, but the second pressure pulse signal SM sampling timing difference ΔT than ₂ sampling timing first sampling timing of the pressure pulse wave signal SM ₁
The rising point s ₂ of the second pulse wave is also delayed by Δ from the original rising point s ₂ ′ of the second pulse wave.
Since the time is determined by the time before c, the accurate pulse wave transit time DT is calculated. Further, the pulse wave propagation time PWV is calculated by substituting the pulse wave propagation time DT calculated by the pulse wave propagation time calculating means and the inter-element distance L determined by the inter-sensor distance determining means 84 into the equation (1). I do. The pulse wave propagation velocity PWV calculated in this manner is smaller than the distance between two independent pulse wave sensors at two predetermined portions of the living body as in the related art, in terms of the inter-element distance (inter-sensor distance). Can be accurately determined, so that an accurate pulse wave propagation velocity PWV can be calculated.

FIG. 11 is a flowchart for explaining more specifically the main part of the control operation of the arithmetic and control unit 46 shown in the functional block diagram of FIG. Note that this flowchart is executed in a state where the mounting position and the pressing force of the pressure pulse wave sensor 30 are maintained in the optimum state by the width direction moving device 40 and the pressing device 38.

In FIG. 11, in step S1 (hereinafter, the steps are omitted), the arithmetic and control unit 46 applies a predetermined period T of about several milliseconds to each sample and hold circuit 44.
_{When the} sampling pulse is output in _S , the pulse wave signal SM is read from each pressure-sensitive element E.

At S2, whether or not the pressure pulse wave signal SM for one beat has been read from each pressure sensing element E is determined, for example, based on the rising point of the pressure pulse wave represented by any of the pressure pulse wave signals SM. Is determined. While the determination in S2 is denied, S1 is repeatedly executed, and the reading of the pressure pulse wave signal SM is continued. When the pressure pulse wave for one beat is read, the determination in S2 is affirmed, and S3 corresponding to the pulse pressure calculating means 72 is executed.

At S3, the pressure pulse wave signal SM read for each pressure sensing element E by repeating the above S1 and S2.
, The rising point d and the peak c of the pressure pulse wave represented by each pressure pulse signal SM are determined, and the peak c
Of the pulse pressure P _{M for} each pressure sensitive element E from the difference between
Are calculated respectively.

At S4 corresponding to the sensor determining means 74, the pulse pressure P calculated for each pressure-sensitive element E at S3 is obtained.
_M is compared respectively for the first pressure sensitive element column E1 and the second pressure sensitive element column E2, most pulse pressure P _M of the first pressure sensitive element E1 (m) has a larger element first optimal pressure sensitive element E1 _O
And the pulse pressure P of the second pressure-sensitive element E2 (n)
_M is larger elements are determined in the second optimal pressure sensitive element E2 _O.

At S5 corresponding to the inter-sensor distance calculating means 84, the inter-element distance L between the first optimum pressure-sensitive element E1 _O and the second optimum pressure-sensitive element E2 _O determined at S4 is calculated. Is done.

At S6 corresponding to the sampling pulse output means 70, the sample and hold circuit 44 connected to the first optimum pressure sensing element E1 _O determined at S4 is supplied to the sampling and holding circuit 44 at every predetermined sampling period T _S. A sampling pulse is output, and the second optimum pressure sensing element E2 _{O is} delayed by a predetermined sampling timing difference ΔT from the timing at which the sampling pulse is output.
To the sample and hold circuit 44 connected to the sampling pulse is outputted for each of the predetermined sampling period T _S. The initial value of the sampling timing difference ΔT is set to 0, and is added by a shift unit T _U in S11 described later.

Subsequently, S7 corresponding to the waveform storage means 78
Steps S8 to S8 are executed. First, in S7, the above-mentioned S6
And a predetermined sampling period T_SThe sampling pulse
First pressure pulse wave signal SM read by being output
₁And the second pressure pulse signal SM _TwoShows the RAM 56
Not stored in a predetermined storage area. And in the following S8
Is the first pressure pulse wave signal SM in S7.₁And the first
2 pressure pulse wave signal SM_TwoWhether or not one beat was memorized,
That is, whether the first pulse wave and the second pulse wave have been stored for one beat
Is determined. If this determination is denied, the above-mentioned S6
Thereafter, the first pressure pulse wave signal SM is repeatedly executed.₁,
2 pressure pulse wave signal SM_TwoReading and remembering continue
You.

On the other hand, if the judgment in S8 is affirmative, in S9 corresponding to the subsequent cross-correlation value calculating means 80, the 1 stored in S6 to S8 is repeated.
The first pulse wave and the second pulse wave for the beat are made into a first waveform and a second waveform, and a cross-correlation function Φ _p (t) between the first waveform and the second waveform is calculated. Correlation function Φ
_p (t) is the sampling timing difference Δ in S6.
By substituting T, its cross-correlation function Φ _p (t)
Are calculated. The cross-correlation value Φ _p (ΔT) representing the maximum value of is calculated.

Subsequently, S10 to S11 corresponding to the timing difference changing means 76 are executed. First, in S10,
It is determined whether or not the change of the sampling timing difference ΔT has been completed. That is, the sampling timing difference Δ
It is determined whether or not T exceeds a maximum timing difference ΔT _max which is a value obtained by subtracting one shift unit T _U from the sampling period T _S. While the judgment in S10 is denied,
In subsequent S11, the sampling timing difference ΔT is updated by adding one shift unit T _U to the sampling timing difference ΔT, and then the above-mentioned S6 and subsequent steps are repeatedly executed. Note that S6 to S11 are T _S /
It is repeated T _U times (if T _S / T _U is not an integer, the maximum integer value less than it).

On the other hand, if the determination in S10 is affirmative, in S12 corresponding to the following maximum value determining means 82, the cross-correlation calculated every time the sampling timing difference ΔT is changed in the repetition of S6 to S11. The maximum value of the values Φ _p (ΔT) is determined.

Subsequently, S13 to S14 corresponding to the pulse wave propagation velocity information calculating means 86 are executed. First, in S13, based on the first waveform and the second waveform used for calculating the maximum value of the cross-correlation value Φ _p (ΔT) determined in S12, the rising point of the first waveform is defined as the first waveform. 1 as a reference point s _1, a rising point of the second waveform as the second reference point s _2, the time difference between the first reference point s ₁ to the second reference point s ₂ is calculated as the pulse wave propagation time DT. And
In S14, the pulse wave propagation velocity PWV is calculated by substituting the inter-element distance L determined in S5 and the pulse wave propagation time DT calculated in S13 into the above equation (1).

At S15, the pulse wave velocity PWV calculated at S14 is displayed on the display 58. Then, in S16, it is determined whether or not a measurement end operation has been performed based on whether or not a measurement end signal has been supplied from a stop switch (not shown). If the determination in S16 is denied, S1 and subsequent steps are repeatedly executed. If the determination is affirmed, this routine is terminated. If the determination in S16 is denied, the processing is not performed after S6,
The reason that S1 and the subsequent steps are repeatedly executed is that the position of the pressure pulse wave sensor 30 with respect to the carotid artery 22 may have changed due to body motion or the like. In that case, the first pressure-sensitive element array and the second
Element for detecting the maximum pulse pressure P _M in the sensitive element row is because there is a possibility that changes.

As described above, according to the present embodiment, each time the sampling timing difference ΔT is changed by the timing difference changing means 76 (S10 to S11), the cross-correlation value calculating means 80 (S9) outputs one beat. The cross-correlation value Φ _P (ΔT) between the first waveform and the second waveform respectively represented by the first pulse wave signal SM ₁ and the second pulse wave signal SM ₂ is calculated, and the pulse wave propagation velocity information calculation means 86 In (S13 to S14), the pulse wave propagation time DT and the pulse wave propagation velocity PWV are calculated based on the first waveform and the second waveform used for calculating the maximum value of the cross-correlation value Φ _P (ΔT). . The combination of the first waveform and the second waveform having the maximum cross-correlation value Φ _P (ΔT) is a waveform in which the shapes of the first waveform and the second waveform are most similar to each other, and the pulse wave transit time DT and Since the pulse wave propagation velocity PWV is calculated based on the first waveform and the second waveform that are closest to each other, the pulse wave propagation time DT and the pulse wave propagation time DT can be accurately calculated without using an expensive device capable of high-speed processing. The wave propagation velocity PWV is calculated.

While the embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be applied to other embodiments.

For example, in the above-described embodiment, the pressure pulse wave sensor 30 has the first pressure-sensitive element row E1 and the second pressure-sensitive element row E2.
Is provided, the pressure pulse wave sensor 30 functions as both the first pulse wave sensor and the second pulse wave sensor. However, the first pulse wave sensor and the second pulse wave sensor are independently configured. You may.

In the above embodiment, the pulse wave sensor is
The pressure pulse wave sensor 30, which is a sensor of a type that detects a pressure vibration wave transmitted to the body surface 26 of the living body, is used. At least one of the sensors irradiates the living tissue with light of a predetermined wavelength, A photoelectric pulse wave sensor that detects a pulse wave from a change in the amount of reflected light, or an impedance pulse wave sensor that detects a change in impedance via an electrode attached to a finger may be used. In addition, as the pulse wave sensor mounted on the upstream side, a heart sound microphone or an electrocardiographic lead device that detects an electrocardiogram or an electrocardiographic lead signal that can be considered as a pulse wave in the most upstream part, that is, the heart, may be used. .

In the above-described embodiment, the pressure pulse wave sensor 3
The reference numeral 0 indicates that the carotid artery wave is detected by being attached to the neck 14 of the living body, but may be a pulse wave sensor attached to other parts such as the wrist, the thigh, and the fingertip.

The present invention can be modified in various other ways without departing from the gist thereof.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a difference between an original pulse wave transit time DT ′ and an actually measured pulse wave transit time DT when the pulse wave transit time DT is about several times the sampling period T _S. is there.

FIG. 2 is a block diagram illustrating a circuit configuration of a pulse wave velocity information measuring apparatus according to an embodiment of the present invention.

FIG. 3 is a diagram showing a state in which the pressure pulse wave detection probe of FIG. 2 is attached to a neck.

FIG. 4 is an enlarged view illustrating a pressure pulse wave detection probe of FIG. 2 with a part cut away.

FIG. 5 is a view for explaining an arrangement state of pressure-sensitive elements arranged on a pressing surface of the pressure pulse wave sensor of FIG. 2;

6 is a functional block diagram illustrating a main part of a control function of an arithmetic and control unit in the pulse wave propagation velocity information measuring device in FIG. 2;

FIG. 7 is a diagram exemplifying a pressure pulse wave signal SM output from a pressure-sensitive element of the pressure pulse wave sensor of FIG. 2;

FIG. 8 is a diagram showing a sampling timing difference ΔT.

9 is a diagram characteristically showing a rising portion of a first pulse wave and a rising portion of a second pulse wave determined by the maximum value determining means of FIG. 6;

FIG. 10 is a diagram showing a relationship between a first optimum pressure-sensitive element E1 _O , a second optimum pressure-sensitive element E2 _O, and a distance L between elements.

11 is a flowchart for further specifically explaining a main part of the control operation of the arithmetic and control unit shown in the functional block diagram of FIG. 6;

[Explanation of symbols]

10: pulse wave propagation velocity information measuring device 30: pressure pulse wave sensor (first pulse wave sensor, second pulse wave sensor) 76: timing difference changing means 80: cross-correlation value calculating means 82: maximum value determining means 86: pulse Wave propagation velocity information calculation means

Claims (1)

[Claims] 1. A first pulse wave sensor and a second pulse wave output from the first pulse wave sensor, comprising a first pulse wave sensor and a second pulse wave sensor respectively attached to predetermined portions of a living body. A pulse wave velocity information measurement device that measures pulse wave velocity information related to a pulse wave velocity at which a pulse wave propagates in a living body based on a second pulse wave signal output from a sensor, A sampling timing difference between a sampling timing for capturing the first pulse wave signal output from the first pulse wave sensor and a sampling timing for capturing the second pulse wave signal output from the second pulse wave sensor is set in advance. A timing difference changing means for changing each of the shifted units; each time the sampling timing difference is changed by the timing difference changing means, the first pulse wave signal and the second pulse wave signal for a predetermined period 2 but a first waveform representing each of the first
A cross-correlation value calculating unit that calculates a cross-correlation value with the waveform, and a cross-correlation value calculated by the cross-correlation value calculating unit each time the sampling timing difference is changed.
A maximum value determining means for determining a maximum value, and the first waveform and the second waveform used for calculating the maximum value determined by the maximum value determining means, and a predetermined portion of the first waveform is defined as a first reference. A pulse wave propagation velocity for calculating the pulse wave propagation velocity information based on a time difference between the first reference point and the second reference point. A pulse wave velocity information measuring device, comprising: information calculating means.