JP2001145606A - Filter for pulse wave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter for pulse wave sensors capable of outputting accurate pulse waves. SOLUTION: The pass band of a band pass filter 48 for filtering a signal from a pulse wave sensor 40 ranges 1 to 30 Hz. Namely, a low-frequency cut-off is set to 1 Hz and a high-frequency cut-off is set to 30 Hz. Thus, the filter 48 is capable of allowing a signal in a pulse frequency band and a signal expressing a waveform constituting the rising part of a pulse wave, which are included in a signal outputted from the sensor 40, to pass through without attenuation and can effectively attenuate noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a filter connected to a pulse wave sensor and filtering a signal output from the pulse wave sensor.

[0002]

2. Description of the Related Art When measuring the oxygen saturation of blood in an artery or measuring the pulse rate, a pulse wave sensor for detecting an arterial wave representing the pulsation of an artery is used. By the way, the signal output from the pulse wave sensor includes not only a signal representing an arterial wave but also low-frequency noise such as swell close to a DC component, and high-frequency noise such as body motion induction and environmental noise. Therefore, a filter is provided to remove those noises and obtain a signal representing only the target arterial wave.

When measuring the oxygen saturation, light of two different frequencies is alternately irradiated on the surface of a living body, and the ratio of the maximum amplitude intensity of the scattered light of each light is calculated, and based on the ratio of the amplitude intensity. To calculate the oxygen saturation. When measuring a pulse rate, a pulse wave peak is detected, and a pulse cycle and a pulse rate are measured from the peak interval. Thus, the arterial wave detected by the pulse wave sensor often uses information at the peak, such as the maximum amplitude intensity or the peak detection time, and the peak of the arterial wave is a signal having a pulse frequency. From the above, the pass band of the filter is a necessary and sufficient range for suitably removing noise and passing a signal having a pulse frequency, for example, 1 to 1.
The passband of 10 Hz, that is, the low-frequency cutoff frequency was set to 1 Hz and the high-frequency cutoff frequency was set to 10 Hz.

[0004]

However, a conventional general filter set in a pass band necessary and sufficient to pass a signal having a pulse frequency is used, and a pulse represented by the signal passed through the filter is used. The reference point a in the wave is determined by the rising tangent method, and the pulse wave propagation time DT is calculated based on the reference point a.
When the estimated blood pressure value EBP is determined on the basis of the EBP, the estimated blood pressure value EBP is inaccurate and does not always correspond to the true blood pressure value BP. Note that the above-mentioned rising tangent method, as shown in FIG. 1, determines the maximum inclination point a of the pulse wave, the base line L ₂ drawn between the tangent L ₁ and the rising point b at the maximum inclination point a In this method, the intersection point is determined as the reference point. Since the reference point can be determined more accurately than when the rising point b is gentle and the detection time greatly varies, the pulse wave propagation time DT This is a method suitable for determining a reference point for calculating.

Considering the reason why the estimated blood pressure value EBP is inaccurate, the true blood pressure value BP measured by an invasive method or the like is considered.
It has been found that the cause is that the fluctuation of the pulse wave propagation time DT is large with respect to the fluctuation of the pulse wave. The pulse wave transit time DT is
A detection time of a reference point determined based on a heartbeat synchronous wave detected in a predetermined part of a living body, and a detection time of a reference point determined based on a heartbeat synchronous wave detected in a different part from that part Therefore, a large variation in the pulse wave transit time DT means a large variation in the reference point for determining the pulse wave transit time DT.

[0006] Then, when the reason why the above-mentioned reference point fluctuates was further examined, the conventional filter for the pulse wave sensor is as follows.
As described above, the passband is set to a range necessary and sufficient to pass a signal having a pulse frequency, but the shape of the arterial wave is complicated, and the arterial wave is divided into a plurality of sine waves having different frequencies. Considering the synthesis of sine waves, there is a steep part in the rising part of the arterial wave (that is, the part from the rising point to the peak). May be a filter attenuation range. Therefore, they found that the waveform of the signal passed through the filter did not accurately represent the arterial wave.

FIG. 2 is a diagram comparing a pulse wave represented by a signal passed through a conventional filter (in which the frequency of a sine wave constituting the rising portion of the pulse wave is in an attenuation range) with an original pulse wave. The upper side shows a pulse wave represented by a signal passed through a conventional filter, and the lower side shows an original pulse wave. As shown in FIG. 2, the pulse wave represented by the signal passed through the conventional filter tends to be slower in rising than the original pulse wave. If such an inaccurate pulse wave is used, even if the reference point is determined by the rising tangent method, an error occurs by ΔDT.

That is, the object of the present invention is to
An object of the present invention is to provide a pulse wave sensor filter capable of outputting an accurate pulse wave.

[0009]

The gist of the present invention for solving the above-mentioned problems is to detect and output an arterial wave of a living body from a pulse wave sensor attached to the living body. A pulse wave sensor filter that passes a signal of a predetermined frequency band among the signals, wherein the pass band is a band including a pulse frequency band signal and a frequency band of a wave constituting a rising portion of the arterial wave. It is in.

[0010]

According to the above configuration, the filter attenuates the signal in the pulse frequency band and the signal representing the wave constituting the rising portion of the pulse wave included in the signal output from the pulse wave sensor without attenuation. Since the signal is passed, the signal passing through the filter accurately represents the arterial wave.

[0011]

In another embodiment of the present invention, preferably, the passband is:
It includes a frequency band of at least 1 to 30 Hz. In this way, the pulse frequency band is 1 to 10 Hz
And the rising frequency of the pulse wave is 10
In this way, the filter attenuates the signal in the pulse frequency band and the signal representing the rising waveform of the pulse wave, which are included in the signal output from the pulse wave sensor, because the signal is substantially included in the range of 30 Hz. It can be passed without.

Preferably, the pass band has a low cutoff frequency of 1 Hz and a high cutoff frequency of 30 Hz.
With this configuration, the filter can pass the signal in the pulse frequency band and the signal representing the waveform constituting the rising portion of the pulse wave included in the signal output from the pulse wave sensor without attenuation. In addition, noise can be effectively attenuated.

Preferably, a tangent at the maximum slope point of the pulse wave represented by the signal output from the pulse wave sensor attached to the living body, and a base line connecting the periodically rising points of the pulse wave. Is defined as one reference point, a predetermined portion of the heartbeat synchronous wave detected by the heartbeat synchronous wave sensor attached to a part of the living body is defined as the other reference point, and the time of occurrence of one reference point and the other reference point In a pulse wave propagation velocity information calculation device that calculates pulse wave propagation velocity information related to the velocity at which a pulse wave propagates in the artery of the living body based on the time difference from the point generation time, the pulse wave velocity is output from the pulse wave sensor. The pulse wave sensor filter is provided for filtering a signal which is transmitted through the pulse wave sensor, and the one reference point is determined based on a waveform represented by a signal passed through the pulse wave sensor filter. With this configuration, since the signal output from the pulse wave sensor and passed through the pulse wave sensor filter represents an accurate pulse wave, the one reference point is accurately determined. The pulse wave velocity information calculated based on the point becomes accurate.

[0014]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 3 is a block diagram illustrating the configuration of the blood pressure monitoring device 8 having the function of calculating the pulse wave propagation speed information and also functioning as the device for calculating the pulse wave propagation speed.

In FIG. 3, a blood pressure monitoring device 8 includes a cuff 10 having a rubber bag in a cloth band-shaped bag and wound around, for example, an upper arm 12 of a patient, and a cuff 10 connected to the cuff 10 via a pipe 20. It has a pressure sensor 14, a switching valve 16, and an air pump 18 connected thereto. This switching valve 16
Switches between three states: a pressure supply state in which the supply of pressure into the cuff 10 is permitted, a slow discharge state in which the cuff 10 is gradually discharged, and a rapid discharge state in which the cuff 10 is rapidly discharged. It is configured to be.

The pressure sensor 14 detects the pressure in the cuff 10 and outputs a pressure signal SP representing the pressure to the static pressure discriminating circuit 22.
And the pulse wave discrimination circuit 24. Static pressure filter circuit 22 includes a low pass filter, steady pressure or cuff pressure P _C to discriminate the cuff pressure signal SK representative of the in the cuff pressure signal SK to the A / D converter 2 is included in the pressure signal SP
6 to the electronic control unit 28.

The pulse wave discrimination circuit 24 includes a band-pass filter, and a pulse wave signal SM which is a vibration component of the pressure signal SP.
₁ is discriminated in frequency and the pulse wave signal SM ₁ is supplied to the electronic control unit 28 via the A / D converter 29. The cuff pulse wave represented by the pulse wave signal SM ₁ is a pressure vibration wave, that is, a cuff pulse wave generated from a brachial artery (not shown) and transmitted to the cuff 10 in synchronization with the heartbeat of the patient. 14 and the pulse wave discrimination circuit 24 function as a cuff pulse wave sensor.

The electronic control unit 28 includes a CPU 30, R
The microcomputer 30 includes a so-called microcomputer having an OM 32, a RAM 34, an I / O port (not shown), and the like. The CPU 30 executes signal processing using a storage function of the RAM 34 according to a program stored in the ROM 32 in advance. Thus, a drive signal is output from the I / O port to control the switching valve 16 and the air pump 18 and to control the display contents of the display 36.

The electrocardiograph 38 continuously detects an electrocardiogram, which is a so-called electrocardiogram, showing an action potential of the myocardium through a plurality of electrodes 39 attached to a predetermined portion of a living body. A signal SM ₂ indicating an electrocardiographic wave is supplied to the electronic control unit 28. It should be noted that the electrocardiographic guiding device 38
Is for detecting the Q wave or the R wave of the electrocardiographic wave corresponding to the time when the blood in the heart starts to be pumped toward the aorta. I have.

The pulse wave sensor 40 is a peripheral pulse wave sensor that non-invasively detects and outputs a pulse wave of a peripheral arteriole including capillaries, and is part of a living body (for example, the cuff 10 is not wound). Side fingertips). This pulse wave sensor 40
Is a photoelectric pulse wave sensor of the type that detects a photoelectric pulse wave,
The housing 42 of the pulse wave sensor 40 is configured to be able to accommodate a part of a living body. Inside the housing 42, red light or infrared light in a wavelength band that can be reflected by hemoglobin,
800n preferably unaffected by oxygen saturation
a light emitting element 44 as a light source for irradiating a wavelength of about m toward the epidermis of a living body, and a light detecting element 46 for detecting scattered light from inside the epidermis. Output to the pass filter 48.

The band pass filter 48 (that is, the filter for the pulse wave sensor) connected to the pulse wave sensor 40 is
It is composed of an analog signal processing circuit having a capacitor and a coil or a resistor (not shown). Of the signals output from the pulse wave sensor 40, the signal representing the peripheral arteriole is passed without attenuation, and other noise is blocked ( In order to attenuate the frequency, a high frequency side is set wider than a pass band of a conventional filter for a pulse wave sensor. For example, the pass band is 1 Hz to 30 Hz (that is, a low cutoff frequency is 1 Hz, and a high cutoff frequency is Is set to 30 Hz). The band-pass filter 48 has an advantage that there is no delay of an output signal or variation in the delay as compared with a digital filter that performs a digital filter process according to a program stored in advance. Then, the photoelectric pulse wave signal SM ₃ , which is an analog signal output from the band-pass filter 48, is supplied to the electronic control device 28 via the A / D converter 49.

FIG. 4 shows an electronic device in the blood pressure monitoring device 8.
Functional block for explaining a main part of the control function of control device 28
FIG. The blood pressure measurement means 50 includes a cuff pressure control means 52
For example, the pressure of the cuff 10 wound around the upper arm of a living body
The compression pressure is set to a predetermined target pressure value P. _cm(For example, 180mmHg
About 3mmHg / sec after rapidly increasing the pressure to about
During the slow pressure decay period in which the pressure is gradually decreased at the speed of
Pulse wave signal SM to be sampled₁ Changes in the amplitude of the pulse wave
Systolic blood pressure using a well-known oscillometric method
Value BP_SYS, Mean blood pressure value BP_MEAN, And diastolic blood pressure B
P_DIAEtc., and the determined systolic blood pressure value B
P_SYS, Mean blood pressure value BP_MEAN, And diastolic blood pressure BP
_DIAAre displayed on the display 36.

The pulse wave propagation velocity information calculating means 54 determines a predetermined portion generated in each cycle of the electrocardiographic lead waveform sequentially detected by the electrocardiographic lead device 38 functioning as a heartbeat synchronous wave sensor as a first reference point s _1. and then, is sequentially outputted from the pulse wave sensor 40, further, a band-pass filter 48 a second reference point s ₂ a predetermined site occurring every period of the pulse wave represented by the photoelectric pulse-wave signal SM ₃ which is passed through a, There is provided a time difference calculating means for sequentially calculating a time difference between the detection time of the first reference point s _{1 and} the detection time of the second reference point s ₂ , that is, the pulse wave propagation time DT. For example, as shown in FIG. using R-wave as a reference point s _1, point determined by the rising tangent method as the second reference point s _2, i.e., the tangent L ₁ and the photoelectric pulse wave at the maximum inclination point a at the rising of the photoelectric pulse wave baseline ( Base line) L Using the intersection with ₂ , the time from the R wave to the intersection is sequentially calculated as the pulse wave propagation time DT. Further, based on the time difference DT sequentially calculated by the time difference calculating means, the pulse wave propagation speed information calculating means 54 calculates the propagation speed V of the pulse wave propagating in the artery of the subject from the equation 1 stored in advance. Calculate _M (m / sec) sequentially. still,
In Equation 1, L (m) is the distance from the left ventricle via the aorta to the site where the pulse wave sensor 40 is attached,
_PEP (sec) is the pre-ejection period from the R wave of the electrocardiographic lead waveform to the rising point of the aortic root pulse waveform. The distance L and the pre-ejection period T _PEP are constants, and values obtained based on experiments in advance are used.

[0024] (Formula _{1) V M = L / (} DT-T PEP)

The correspondence determining means 56 includes a blood pressure measuring means 5
Systolic blood pressure value BP measured by 0 _SYSAnd its blood pressure measurement
Based on the pulse wave velocity information during the fixed period,
If the pulse wave transit time DT during the blood pressure measurement period or
Pulse wave velocity V_M2 or 3 based on the average of
Determine the coefficient of the correspondence equation set in advance
You. The method of determining the coefficient in this case is, for example,
When a staff is used, the blood pressure is measured by the blood pressure measuring means 50.
Systolic blood pressure BP_SYSCalculated within the above blood pressure measurement period
The set pulse wave propagation time DT is used as a set, and
Obtained systolic blood pressure BP_SYSAnd pulse wave transit time DT
As a set, the coefficients α and
And β are determined in advance. Or, by the blood pressure measuring means 50
Measured systolic blood pressure BP_SYSAnd within the above blood pressure measurement period
Using the calculated pulse wave transit time DT, the coefficient α
And β are determined (changed) in advance. In addition,
Above systolic blood pressure BP_SYSInstead of the blood pressure measuring means 50
Average blood pressure value BP measured_MEANOr diastolic blood pressure B
P_DIAMay be used. In short, the estimated blood pressure value EBP
Is the systolic, mean, or diastolic blood pressure
It is selected depending on the value.

(Equation 2) EBP = α (1 / DT) + β (where α is a positive constant, β is a positive constant)

(Equation 3) EBP = α (V _M ) + β (where α is a positive constant and β is a positive constant)

The estimated blood pressure value determining means 58, blood pressure values of the biological BP and pulse wave propagation time of the living DT or the propagation velocity V _M
The correspondence between the (Formula 2 or Formula 3), the actual pulse wave propagation time DT or propagation velocity V _M estimated BP value EBP based on the living body successively calculated by the pulse wave propagation velocity information calculation means 54 between the Are sequentially determined, and the determined estimated blood pressure value EBP is trend-displayed on the display 36 as shown in FIG.

The estimated blood pressure value abnormality judging means 60 performs the blood pressure measurement by the blood pressure measuring means 50 based on the fact that the estimated blood pressure value EBP determined by the estimated blood pressure value determining means 58 exceeds a predetermined judgment reference value. Start. That is, the estimated blood pressure value abnormality judging means 60 also functions as a blood pressure measurement starting means, and the estimated blood pressure value EBP determined by the estimated blood pressure value determining means 58 is set to a predetermined reference value, for example, the previous blood pressure measured by the blood pressure measuring means 50. When the blood pressure is measured by the cuff 10 as a reference, the estimated blood pressure value EBP is determined to be abnormal based on a change from the blood pressure by a predetermined value or a predetermined ratio, and the blood pressure measurement by the blood pressure measurement means 50 is started.

FIG. 7 is a flow chart for explaining a main part of the control operation in the electronic control unit 28 of the blood pressure monitoring device 8. The estimated blood pressure value EBP is sequentially determined from the pulse wave propagation time DT using the above equation (2). An example in which the blood pressure is monitored by using the method will be described.

In FIG. 7, in step S1 (hereinafter, the steps are omitted), an initial process for clearing a counter, a register, and the like (not shown) is executed. The maximum slope of the photoelectric pulse wave represented by the photoelectric pulse wave signal SM _{3 which} is sequentially output from the pulse wave sensor 40 from the point of occurrence of the R-shaped wave (first reference point s ₁ ) and is filtered by the band-pass filter 48 Point a
, The pulse wave transit time DT from the time of occurrence of the intersection (second reference point s ₂ ) of the tangent line L ₁ and the base line L ₂ at
Is calculated.

Next, in S3 and S4 corresponding to the cuff pressure control means 52, the switching valve 16 is switched to the pressure supply state and the air pump 18 is driven, so that the cuff 10 is rapidly pressurized for blood pressure measurement. There together is started, the cuff pressure P _C is whether a preset target pressing pressure P _CM than about 180mmHg is determined. If the determination in S4 is denied, increase the cuff pressure P _C by the signal line S2 below is repeatedly executed is continued.

[0033] However, the S4 by increasing the cuff pressure P _C
Is affirmed, the blood pressure measurement algorithm is executed in S5 corresponding to the blood pressure measurement means 50.
That is, the air pump 18 is stopped and the switching valve 16 is switched to the slow exhaust pressure state to lower the pressure in the cuff 10 at a predetermined gentle speed of about 3 mmHg / sec. Pulse signal SM sequentially obtained by
Based on the change in the amplitude of the pulse wave represented by _1, the systolic blood pressure value BP _SYS , the average blood pressure value BP _MEAN , and the diastolic blood pressure value BP _DIA are measured according to a well-known oscillometric blood pressure value determining algorithm, The pulse rate and the like are determined based on the pulse wave interval. Then, the measured blood pressure value BP, the pulse rate, and the like are displayed on the display 36, and the switching valve 16 is switched to the rapid pressure release state, so that the pressure in the cuff 10 is rapidly discharged.

Next, in S6 corresponding to the correspondence relationship determining means 56, the pulse wave transit time DT calculated in S2 in this routine and the systolic blood pressure value BP _SYS determined in S5 are set as a set in this routine. The pulse wave transit time DT and the estimated blood pressure value E are set as another set using the pulse wave transit time DT and the systolic blood pressure value BP _SYS determined in the previous routine.
The coefficients α and β of the correspondence (Equation 2) with BP are determined.

When the pulse wave transit time blood pressure correspondence is determined as described above, it is determined in S7 whether the R wave of the electrocardiographic waveform and one beat of the photoelectric pulse wave have been input.
If the determination in S7 is denied, S7 is repeatedly executed. If the determination is affirmed, in S8 corresponding to the pulse wave propagation velocity information calculation means 54, the R wave of the newly input electrocardiographic waveform is obtained. And the pulse wave propagation time DT for the photoelectric pulse wave is calculated in the same manner as in S2.

In step S9 corresponding to the estimated blood pressure value determining means 58, the pulse wave propagation time DT obtained in step S8 is substituted into the pulse wave transit time blood pressure correspondence relationship obtained in step S6, that is, equation 2. , Estimated blood pressure value E
BP (systolic blood pressure EBP _SYS , mean blood pressure EBP _MEAN ,
Alternatively, the diastolic blood pressure value EBP _DIA ) is determined, and the estimated blood pressure value EBP for each beat is displayed on the display 36 in a trend format, for example, as shown in FIG.

Next, the above-mentioned estimated blood pressure value or more determination means 60
In S10 corresponding to the above, it is determined whether or not the estimated blood pressure value EBP calculated in S9 has exceeded a predetermined reference value. If the determination in S10 is denied, in S11 that follows, the elapsed time since the blood pressure measurement was performed by the cuff 10 in S5 has passed the preset cycle of about 15 to 20 minutes, that is, the calibration cycle. Is determined.

If the determination in S11 is negative,
The blood pressure monitoring routine after S7 is repeatedly executed,
The estimated blood pressure value EBP is determined continuously for each beat, and the determined estimated blood pressure value EBP is displayed on the display 36 in a time-series trend display. However, if the determination in S13 is affirmative, the cuff calibration routine of S2 and subsequent steps is executed again to determine the correspondence again.

If the determination in S10 is affirmative, S12 is executed and an abnormal display of the estimated blood pressure value EBP is displayed on the display 36. Then, S2 and subsequent steps are repeated to re-determine the correspondence. When executed, cuff 1
A blood pressure measurement with 0 is activated.

As described above, according to the present embodiment, the band-pass filter 48 has a passband of 1 to 30 Hz, that is, a low-frequency cutoff frequency of 1 Hz and a high-frequency cutoff frequency of 30 Hz.
z, the bandpass filter 48
Is included in the signal output from the pulse wave sensor 40,
The signal of the pulse frequency band and the signal representing the waveform constituting the rising portion of the pulse wave can be passed without attenuation,
In addition, noise can be effectively attenuated.

Further, according to the present embodiment, the blood pressure monitoring device 8
Has a band-pass filter 48 for filtering a signal output from the pulse wave sensor 40,
The second reference point s ₂ is determined on the basis of 8 the waveform represented by the photoelectric pulse-wave signal SM ₃ which is passed through a. Since the photoplethysmographic signal SM ₃ passed through the band-pass filter 48 represents an accurate pulse wave, the second reference point s ₂ is accurately determined, and is calculated based on the second reference point s _2. The pulse wave propagation time DT to be obtained becomes accurate. Further, since the estimated blood pressure value EBP corresponds one-to-one with the pulse wave transit time DT, the estimated blood pressure value EBP
BP is also accurately determined.

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

For example, in the above-described embodiment, the band-pass filter 48 has a low cut-off frequency of 1 Hz, but the low cut-off frequency is within a range that hardly attenuates the pulse frequency component contained in the pulse wave. It is set for the purpose of removing low-frequency noise such as undulations close to the DC component.
Hz need not be 1 Hz or less (for example, 0.08
Hz or 0.1 Hz).

In the above-described embodiment, the band-pass filter 50 has a high cut-off frequency of 30 Hz. However, the high cut-off frequency is within a range in which the sine wave forming the rising portion of the pulse wave is hardly attenuated. Since it is set for the purpose of removing high-frequency noise such as body motion guidance and environmental noise, the frequency need not be 30 Hz if the purpose can be suitably achieved, and is 30 Hz or more (for example, 35 Hz or 40 Hz) or 30 Hz or less (for example, 25 Hz or 28H).
z) may be set.

In the above-described embodiment, the pulse wave represented by the photoelectric pulse wave signal SM ₃ passed through the band-pass filter 48 determines the reference point s ₂ for calculating the pulse wave propagation time DT. Information obtained based on the pulse wave represented by the photoelectric pulse wave signal SM ₃ passed through the band-pass filter 48 and based on the waveform from the rising point to the peak of the pulse wave exemplified below. May be calculated. The information obtained from the waveform from the rising point to the peak of the pulse wave includes, for example, U-time defined as the time from the rising point b to the peak c of the pulse wave and the maximum slope point a in FIG. The slope γ of the tangent, the first half time from the rising point b to the maximum slope point a, the second half time from the maximum slope point a to the peak c, or the ratio of the first half time to the second half time. Since the information obtained based on the waveform from the rising point to the peak of the pulse wave is information including a steep portion of the pulse wave, it is determined based on the signal passed through the band-pass filter 48. Then, it becomes accurate information.

In the above-described embodiment, the band-pass filter 48 is a circuit including a capacitor and the like.
The electronic control device 28 in which a predetermined program is stored in advance at 32 may function as a bandpass filter. That is, the bandpass filter may be a digital filter.

In the above-described embodiment, the electrocardiographic lead-in device 38 is used as the heartbeat synchronous wave sensor. However, since the heart sound is also a heartbeat synchronous wave, a heart sound microphone may be used as the heartbeat synchronous wave sensor. . In addition, since the pulse synchronization wave is a heartbeat synchronization wave, impedance change is detected via a pulse wave sensor attached to a predetermined part of the living body, for example, a photoelectric pulse wave detection probe for an oximeter, and an electrode attached to a finger. An impedance pulse wave sensor for detecting, a pressure pulse wave sensor pressed by a carotid artery or a radial artery to detect its internal pressure, and a type for detecting a change in pressure in a compression band attached to a predetermined portion (for example, an upper arm) of a living body A pulse wave sensor such as a pressure pulse wave sensor described above may be used as a heartbeat synchronous wave sensor.

In the above-described embodiment, the pulse wave sensor 40
Was a sensor of the type that detects a photoelectric pulse wave, but an impedance pulse wave sensor that detects an impedance change through an electrode attached to a finger, and detects an internal pressure of the pulse wave when pressed by a carotid artery or a radial artery. Other types of pulse wave sensors, such as a pressure pulse wave sensor and a pressure pulse wave sensor that detects a change in pressure in a compression band attached to a predetermined portion (for example, an upper arm) of a living body, may be used.

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 illustrating a reference point s determined by a rising tangent method.

FIG. 2 is a diagram showing a comparison between a pulse wave represented by a signal passed through a conventional filter and an original pulse wave.

FIG. 3 is a block diagram illustrating a circuit configuration of a blood pressure monitoring device according to an embodiment of the present invention.

FIG. 4 is a functional block diagram for explaining a main part of a control function of the electronic control device in the embodiment of FIG. 1;

FIG. 5 is a diagram illustrating a time difference DT obtained by a control operation of the electronic control device in the embodiment of FIG. 1;

FIG. 6 is an estimated blood pressure value E obtained in the embodiment of FIG. 1;
FIG. 7 is a diagram illustrating an example in which a BP is trend-displayed on a display.

FIG. 7 is a flowchart illustrating a main part of a control operation of the electronic control device in the embodiment of FIG. 1;

FIG. 8 is a diagram illustrating information obtained from a waveform from a rising point to a peak of a pulse wave.

[Explanation of symbols]

 8: blood pressure monitoring device (pulse wave velocity information calculation device) 40: pulse wave sensor 48: band pass filter (filter for pulse wave sensor)

Claims (2)

[Claims] 1. A filter for a pulse wave sensor that passes a signal of a predetermined frequency band among signals output from a pulse wave sensor attached to a living body in order to detect and output an arterial wave of the living body. A filter for a pulse wave sensor, wherein the pass band is a band including a pulse frequency band signal and a frequency band of a wave constituting a rising portion of the arterial wave. 2. The pass band is at least 1 to 30 Hz.
2. The pulse wave sensor filter according to claim 1, wherein the filter includes the following frequency band.