JPH0889487A - Pulse waveform detector - Google Patents

Abstract

PURPOSE: To provide a pulse waveform detector capable of accurately detecting a pulse waveform rising point even if variation by disturbance, etc., overlapped with the pulse wave, by detecting a downward zero crossing point of differential waveform of pulse wave signals and detecting the maximum gradient point of the pulse wave going back from the downward zero crossing point. CONSTITUTION: When this pulse waveform detector is applied to a blood pressure meter, a cuff 1 is pressurized by driving a pump 3 by a controller 13 and an electromagnetic valve 4 is controlled by the controller 13 to reduce pressure in the cuff 1 as time elapses. Blood pressure pulse wave signals S2 from a pressure sensor 2 are smoothdifferentiated by a CPU 13b at every steps of pressure reduction in the cuff 1 and a downward zero crossing point m of the differential wave form is detected. A maximum gradient point P is detected going back from the downward zero crossing point m and is judged to be greater than the threshold value or not. When the judgement is 'yes', the maximum pulse wave point is searched from the signals S2 and the pulse wave rising point is searched from the maximum gradient point, then the pulse wave height is determined by the pulse wave rising point and the maximum pulse wave point.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a blood pressure monitor, a blood flow meter,
The present invention relates to a pulse wave waveform detection device that is used in a pulse oximeter, a pulse wave velocity meter, and the like and detects a waveform peak point and a rising point when measuring a pulse wave.

[0002]

2. Description of the Related Art Conventionally, in blood pressure monitors, the Korotkoff sound recognition method and the oscillometric method are known as blood pressure measuring methods. In the blood pressure measurement by the Korotkoff sound recognition method, the Korotkoff sound may not disappear even when the diastolic pressure is not reached, as well as the influence of noise and the dropout of the Korotkoff sound. In the blood pressure measurement by the oscillometric method that can avoid the decrease in the accuracy of this blood pressure measurement, the pulse wave caused by the pulsation of the artery is captured as vibration in the cuff, and systolic pressure and diastolic pressure are measured based on this vibration. are doing.

In the blood pressure measurement by the oscillometric method, since the systolic pressure and the diastolic pressure are measured from the change in the pulse wave crest value, the waveform peak point and the rising point thereof are measured. In this case, the peak value of the peak value is detected at the peak point of the waveform, and the rising point is detected by capturing the change in the inclination of the pulse waveform.

[0004]

Since the peak point of the waveform of the pulse wave clearly appears, it can be easily and surely detected. on the other hand,
The rising point of the pulse wave is a point where the slope of the waveform changes, and is difficult to detect. Especially when there is a transient pressure fluctuation, drift, noise, etc. when depressurizing the cuff pressure, such a pressure change will be added to the pulse wave waveform and calculation will be performed, so the accuracy in identifying the rising point will deteriorate. . Therefore, there is a drawback that the accuracy of blood pressure measurement of systolic pressure and diastolic pressure deteriorates.

The present invention solves the above drawbacks of the prior art. When measuring the pulse wave to detect the peak point and the rising point of the pulse wave, the rising point of the pulse wave is accurately determined. It is an object of the present invention to provide a pulse wave waveform detection device that can be detected and, for example, improves measurement accuracy of systolic pressure and diastolic pressure when blood pressure is measured by a sphygmomanometer.

[0006]

In order to achieve the above object, the invention according to claim 1 is a pulse wave waveform detecting apparatus for detecting a rising point as well as a waveform peak point of a pulse wave, and detects a pulse wave of a living body. Pulse wave detecting means for detecting, differentiating means for differentiating the pulse wave signal from the pulse wave detecting means, first detecting means for detecting a downward zero cross point of the differential waveform from the differentiating means, and maximum slope point of the differential waveform Second detecting means for detecting upward from the downward zero-cross point, third detecting means for detecting the pulse wave maximum value point from the pulse wave signal output by the pulse wave detecting means, and inclination detected by the second detecting means. A fourth detection means for detecting the rising point of the pulse wave from the maximum point is provided.

In the pulse wave waveform detecting apparatus according to the present invention, the fourth detecting means sets a reference point before the starting point which is the maximum inclination of the pulse wave of the living body detected by the second detecting means, and , Take a predetermined distance vertically from the tangent line of the reference point, and use the line connecting the tip and start point of this predetermined distance as the scope, and if there is no judgment point before the reference point in this scope,
Advance the reference point by one and take a distance vertically from the tangent line of the reference point, and perform processing with the line connecting the tip of this distance and the start point as the scope, and after repeating this processing, the previous judgment point When is inside the scope, the reference point is determined as the pulse wave rising point.

According to another aspect of the pulse wave waveform detecting apparatus of the present invention, the fourth detecting means has a time axis point before the starting point which is the time axis point of the maximum inclination of the pulse wave of the living body detected by the second detecting means. Is set as a reference point, a predetermined time is taken from this reference point in the opposite direction on the time axis, and the line connecting the time elapsed point and the start point is used as a scope, and the time axis point of the reference point is in front of Check if the judgment point of is inside the scope, and if the previous judgment point is inside the scope, advance the time axis of the reference point by one and move from the reference point to the time axis. It takes a predetermined time in the opposite direction, and repeats the process with the line connecting the time elapsed point and the start point as the scope, and when the previous judgment point goes out of the scope after this process is repeated, The reference point is determined as the pulse wave rising point.

[0009]

In the pulse wave waveform detecting device according to the present invention having the above-mentioned structure, the downward zero-cross point in the differential waveform obtained by differentiating the pulse wave signal is detected, and the maximum slope of the differential waveform is determined as the downward zero-cross point. It goes up from and detects. Furthermore, the pulse wave maximum value point is detected, and the rising point of the pulse wave is detected from the detected maximum slope point. Therefore, when the pulse wave is measured and the waveform peak point and the rising point are detected, the rising point of the pulse wave is accurately detected.

Therefore, the accuracy of measuring the systolic pressure and the diastolic pressure when the blood pressure is measured by the sphygmomanometer is improved by applying this pulse waveform detecting device. Further, in the blood flow meter, continuous blood pressure is measured. The rising point of the waveform of the pulse wave in the flow pulse wave is accurately detected, and the integrated accurate stroke volume is measured.
Further, in the pulse oximeter, the respective amplitude values of the AC component of the detection signal for infrared (IR) light and the AC component of the detection signal for red (R) light are accurately measured from the rising point of the waveform of the pulse wave. . Further, the pulse wave propagation velocity meter accurately measures the propagation times of the carotid pulse wave and the hip artery pulse wave from the rising point of the waveform of the pulse wave.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of a pulse wave waveform detecting apparatus of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of a sphygmomanometer to which the pulse wave waveform detection device of the present invention is applied. In FIG. 1, this sphygmomanometer includes a cuff 1 attached to the upper arm or finger of a person to be measured, a pressure sensor 2 for outputting a signal indicating air pressure and a blood pressure pulse wave at the cuff 1, and a control signal C1 for controlling the cuff 1. And a pump 3 for pressurizing to the indicated value. Further, after the cuff 1 is pressurized, the electromagnetic valve 4 for exhausting the pressure for reducing the pressure of the cuff 1 for a while with the indicated value of the control signal C2, and the DC pressure signal S1 from the pressure sensor 2 are supplied to a low-pass filter (LPF) not shown. And a DC amplifier 6 for extracting and amplifying high frequency noise components.

Further, the pressure signal (S
1) is converted into a digital signal, and the blood pressure pulse wave signal (S2) from the pressure sensor 2 is passed through a band pass filter (BPF) or a high pass filter (HPF) in the DC amplifier 6 which is not shown. An AC amplifier 8 for taking out and amplifying the blood pressure pulse wave signal (S2) is provided. In addition, the blood pressure pulse wave signal (S2) from the AC amplifier 8
A / D converter 9 for converting the signal into a digital signal, and pump 3
Pump controller for controlling the delivery of air from the pump 11
And an electromagnetic valve driver 12 that drives the electromagnetic valve 4 to control exhaust.

Further, this blood pressure monitor has a pressure signal (S1) from the A / D converters 7 and 9 and a blood pressure pulse wave signal (S).
2) is taken in to detect the waveform peak point and rising point of the pulse wave, the pump 3 is further controlled through the pump controller 11, and the compressed air in the cuff 1 is exhausted through the solenoid valve driver 12. It has a controller 13 for controlling the pressure to be reduced. Further, a key panel 14 for instructing the start of detection of the pulse peak and rising points of the pulse wave, and for performing various operations, and a liquid crystal display (LCD) 15 for displaying processing contents, processing waveforms, etc. on the screen are provided. It is provided.

The controller 13 takes in the pressure signal (S1) and the blood pressure pulse wave signal (S2) from the A / D converters 7 and 9 and sends the control signals to the pump controller 11 and the solenoid valve driver 12. I / O port 13a for CPU and CPU 13
b, a working RAM 13c, and a ROM 3d storing a control program for this apparatus.

Next, the operation of this embodiment will be described. FIG. 2 is a diagram showing the pressure state of the cuff 1, the blood pressure pulse wave signal (S2), and the rising point mark waveform of the pulse wave.
3 is a flowchart showing a processing procedure of the overall operation (blood pressure measurement) of the sphygmomanometer shown in FIG. 1. 1 to 3, the controller 13 in FIG. 1 controls the pump 3 to a value preset by the key panel 14 to pressurize the cuff 1 as shown in FIG. 2 (a), and The solenoid valve 4 is controlled by the controller 13, and as shown in FIG.
Is depressurized over time. The pressure signal (S1) indicating the reduced pressure state is sent to the pressure sensor 2, the DC amplifier 6 and the A
Through the / D converter 7, the CPU 13b in the controller 13
Captured via the / O port 13a.

At the same time, the blood pressure pulse wave signal (S2) AC amplifier 8
And the CPU 13b of the controller 13 through the A / D converter 9
Is taken in through the I / O port 13a (step (indicated by S in FIG. 3) 10). As shown in FIG. 4A, the CPU 13b performs smoothing differentiation of the blood pressure pulse wave signal (S2) from the pressure sensor 2 at each step of decompression of the cuff 1, and determines the downward zero cross point m of the differential waveform. It is detected (steps 11 and 12). Further, the maximum slope point P shown in FIG. 4B is detected backward from the downward zero-cross point m, and it is checked whether or not the maximum slope point P has noise components other than the pulse wave removed. It is judged whether or not it is equal to or higher than a preset threshold level (threshold value) (steps 13, 1).
4).

If it is less than the threshold level (step 14: No), the process returns to step 10 and the processing up to this point is repeated. If it is higher than the threshold level (step 14: Yes), the highest point (peak point) of the pulse wave is searched for from the blood pressure pulse wave signal S2 shown in FIG. Is determined (step 15,
16). After that, as shown in FIG. 4B, the maximum slope point P is detected backward from the downward zero-cross point m, the pulse wave rising point is searched for from the maximum slope point P, and this pulse wave rising point is determined. (Step 17). Next, the pulse wave height is determined from this pulse wave rising point and the previously obtained pulse wave maximum point. It is determined whether or not the peak value of the blood pressure pulse wave signal (S2) obtained at all stages of the pressure reduction of the cuff 1 satisfies the preset termination condition (steps 18, 1).
9). As the termination condition, in this embodiment, the maximum crest value is 5
The case where a pulse wave peak value of 0% to 70% or less is detected for 1 to 4 beats is set. If not satisfied (step 19: No), the pressure of the next cuff 1 is further reduced (step 20), and the process returns to step 10 to repeat the processing up to this point. That is, the pulse wave height of the blood pressure pulse wave signal (S2) in decompression at all stages of the cuff 1 is determined (step 1
9).

When the pulse wave height of the blood pressure pulse wave signal (S2) at all stages of decompressing the cuff 1 is determined in step 19 (step 19: Yes), the controller 13 causes the solenoid valve driver 12 to operate. Fully open the solenoid valve 4. The data so far are stored in the RAM 13c of the controller 13, and thereafter, the controller 13 calculates and determines the blood pressure values of the systolic pressure and the diastolic pressure (step 21).

In this way, the blood pressure pulse wave signal (S2) detected at each step of decompression of the cuff 1 is differentiated, the pulse wave maximum value point is then detected, and the rising point of the waveform is detected. Is going. Next, the method of determining the pulse wave rising point (step 17 in FIG. 3) will be described in detail.

FIG. 5 is a flow chart (subroutine) of the processing procedure for determining the rising point of the pulse wave by the vertical line.
FIG. 6 is a schematic diagram showing a processing state of determining a pulse wave rising point by a vertical line. 5 and 6, after the pulse wave maximum value point is determined by the process of the controller 13 in step 16 in FIG. 3, the first detection shown in FIG.
The pulse wave rising point is detected with the maximum inclination point (waveform difference peak point) P shown in 1 as the starting point, and the point before the starting point is set as the reference point A (i) (steps 30 and 31).
The distance ε on the graph is taken perpendicularly from the tangent line of the reference point A (i), and the line connecting the start point and the tip of the distance ε is used as the scope, and the determination point A (i-1) before the reference point is inside the scope ( This judgment is made while checking whether or not it is on the opposite side of the reference point A (i) with the scope in between (step 32,
33, 34). Although there are individual differences in the systolic and diastolic movements of the heart, an appropriate distance ε for identifying the rising point from the left ventricular systolic period or the like can be obtained from statistical processing of many presenter data.

When the previous decision point A (i-1) is inside the scope in step 34 (Yes), FIG. 6 (b)
As shown in, the reference point is advanced by one to become the reference point A (i-1) (step 35), and the process of step 32 is repeated.
That is, the processing procedure is repeated from the tangent line of the reference point to obtain the distance ε perpendicularly (step 32). After this repetition, in step 34, the previous judgment point is outside the scope.
In the case shown in (c) (No), this reference point is determined as the rising point (step 36).

FIG. 7 is a flowchart (subroutine) of the processing procedure for determining the pulse wave rising point on the time axis, and FIG. 8 is a schematic diagram of the processing state for determining the pulse wave rising point on the time axis. 7 and 8, after the pulse wave maximum value point is determined by the processing of the controller 13 in step 16 in FIG. 3, the maximum slope point shown in FIG. 4 is detected at the first detection shown in FIG. (Waveform differential maximum value point) The detection of the pulse wave rising point (time axis point) is started with the time axis point of P as the start point, and the time axis before the start point is set to the reference point A (i) (step 40). , 41). Before the reference point (time axis point) A (i), the line connecting the start point and the elapsed point of the predetermined time t is taken as the scope, taking a predetermined time t on the graph from the reference point A (i) in the direction opposite to the time axis. This judgment is made while checking whether or not the judgment point A (i-1) is inside the scope (steps 42, 43, 44).

When the previous judgment point A (i-1) is inside the scope in step 44 (Yes), FIG. 6 (b)
As shown in, the time axis of the reference point is advanced by one and the reference point is set to A
(I-1), and the process of step 42 is repeated. That is, the process is repeated from the processing procedure in which the predetermined time t is set in the direction opposite to the time axis from the reference point (step 45). After this repetition, in step 44, when the previous determination point is outside the scope as shown in FIG. 6C (No), this reference point is determined as the pulse wave rising point (step 46).

In this way, the rising point of the pulse wave is accurately detected, and the blood pressure values of the systolic pressure and the diastolic pressure in the sphygmomanometer are accurately determined. The detection of the rising point of the waveform of the pulse wave is also required in other medical measuring instruments, and for example, the pulse wave waveform detecting device can be applied to a blood flow meter, a pulse oximeter, and a pulse wave velocity meter.

Another embodiment to which this pulse wave waveform detecting apparatus is applied will be described below. First, in the blood flow meter, as shown in FIG.
As shown in, the waveform volume u from the rising point of the pulse wave waveform in the continuous blood flow pulse wave to the rising point of the pulse wave waveform in the next blood flow pulse wave is integrated to detect the blood stroke volume. . Therefore, as in the case of the blood pressure monitor described above, the waveform rising point is accurately detected, and by integrating the waveform between the rising points of this pulse wave waveform, the reliable stroke volume can be measured.

Next, in the pulse oximeter, FIG.
As shown in (a), the amplitude values of the AC component AC1 of the detection signal for infrared (IR) light and the AC component AC2 of the detection signal for red (R) light shown in FIG. 10B are measured. . When this amplitude value is measured, the AC wave components AC1 and AC2 can be reliably measured by accurately detecting the waveform rising point of the pulse wave in the same manner as the blood pressure monitor described above.

The pulse wave velocity meter detects the propagation time T of the carotid pulse wave and the hip artery pulse wave as shown in FIG. Also in this case, the propagation time T can be reliably measured by accurately detecting the rising point of the waveform of the pulse wave in the same manner as the blood pressure monitor described above.

[0028]

As is apparent from the above description, according to the pulse wave waveform detecting device of claims 1 to 3, the downward zero cross point of the differential waveform obtained by differentiating the pulse wave signal is detected, and the downward zero cross point is detected. The maximum point of the slope of the pulse wave is detected by going up from. Furthermore, since the rising point of the pulse wave is detected using the scope from the maximum point of inclination of the detected pulse wave,
Even when a fluctuation due to a disturbance or the like is superimposed on the pulse wave, the waveform rising point of the pulse wave is detected more accurately. Therefore, there is an effect that an accurate detection value of the pulse wave rising point can be obtained in an apparatus that performs various measurements using the waveform of the pulse wave.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a sphygmomanometer to which a pulse wave waveform detection device of the present invention is applied.

FIG. 2 is a diagram showing a pressure state of a cuff, a blood pressure pulse wave, and a rising point of the pulse wave in the embodiment.

FIG. 3 is a flowchart showing a processing procedure of overall operation of the sphygmomanometer shown in FIG.

FIG. 4 is a diagram showing a blood pressure pulse wave signal and its differential waveform in the operation of the embodiment.

FIG. 5 is a flowchart of a processing procedure (subroutine) for determining a pulse wave rising point with a vertical line in the operation of the embodiment.
Is.

FIG. 6 is a schematic diagram showing a processing state of determining a pulse wave rising point by the perpendicular line shown in FIG.

FIG. 7 is a flowchart (subroutine) of a processing procedure for determining the pulse wave rising point on the time axis in the operation of the embodiment.

8 is a schematic diagram of a processing state of determining a pulse wave rising point on the time axis shown in FIG. 7. FIG.

FIG. 9 is a diagram for explaining processing of a pulse wave waveform in the blood flow meter in the embodiment.

FIG. 10 is a diagram for explaining processing of a pulse wave waveform in a pulse oximeter in the embodiment.

FIG. 11 is a diagram for explaining the processing of the pulse wave waveform in the pulse wave velocity meter in the example.

[Explanation of symbols]

 1 Cuff 2 Pressure sensor 3 Pump 4 Solenoid valve 6 DC amplifier 8 AC amplifier 11 Pump controller 12 Solenoid valve driver 13 Controller 14 Key panel 15 Liquid crystal display (LCD) S1 Pressure signal S2 Blood pressure pulse wave signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location A61B 5/14 310 7638-2J 7638-2J A61B 5/02 340 A

Claims (3)

[Claims] 1. A pulse wave waveform detecting device for detecting a rising point as well as a waveform peak point of a pulse wave, wherein a pulse wave detecting means for detecting a pulse wave of a living body, and a pulse wave signal from the pulse wave detecting means are differentiated. Differentiating means, first detecting means for detecting a downward zero-cross point of the differential waveform from the differentiating means, and second detecting means for detecting a maximum slope point of the differential waveform in a backward upward direction from the downward zero-cross point. A third detecting means for detecting a pulse wave maximum value point from a pulse wave signal output by the pulse wave detecting means, and a fourth detecting means for detecting a rising point of the pulse wave from the maximum inclination point detected by the second detecting means. A means for detecting a pulse wave waveform, comprising: 2. The fourth detecting means sets a reference point in front of a starting point which is the maximum inclination of the pulse wave of the living body detected by the second detecting means and which is perpendicular to a tangent line of the reference point. Take a distance and use the line connecting the tip and the starting point of this predetermined distance as the scope, and if the judgment point before the reference point is inside this scope, advance the reference point by one and do the same as above. If a predetermined distance is taken perpendicularly from the tangent line of the reference point and the line connecting the start point and the start point of this distance is used as the scope process, and if the previous judgment point is outside the scope after repeating this process The pulse wave waveform detecting apparatus according to claim 1, wherein the reference point is determined as a pulse wave rising point. 3. The fourth detecting means sets, as a reference point, a time axis point before a start point which is a time axis point of the maximum inclination of the pulse wave of the living body detected by the second detecting means, and A predetermined time is taken in the opposite direction on the time axis from this reference point, and the line connecting the time elapsed point and the start point is used as the scope, and the determination point before the time axis point of the reference point is inside the scope. If the previous judgment point is inside the scope by checking whether it is inside or not, advance the time axis of the reference point by one and take a predetermined time from the reference point in the opposite direction of the time axis as described above. , And, repeat the process that uses the line connecting the time lapse point and the start point as the scope, and if the previous determination point appears outside the scope after repeating this process, use this reference point as the pulse wave rising point. The pulse wave waveform detection device according to claim 1, wherein the pulse wave waveform detection device is determined. Place