JP2021041070A - Pulse wave analysis device and pulse wave analysis program - Google Patents

Abstract

To reduce the influence of the noise of a portion between the a wave and the e wave of an acceleration pulse wave signal or a portion corresponding to the portion in a speed pulse wave signal or a volume pulse wave signal when acquiring a pulse wave signal for acquiring biological information.SOLUTION: A microcomputer 35 acquires pulse wave data for plural pulses from an A/D converter 34, differentiates twice to acquire acceleration pulse wave data, detects a feature point (peak of the a wave) of the acceleration pulse wave data to record waveform data for one pulse, acquires an appearance frequency value for each data value for each temporal axis position for one pulse after recording the waveform data for plural pulses, acquires an appearance frequency cumulative value for each signal value for each temporal axis position with the cumulation for plural pulses of the appearance frequency value for one pulse, and acquires acceleration pulse wave data for acquiring biological information on the basis of the most frequent value of the appearance frequency cumulative value.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pulse wave analysis device and a pulse wave analysis program having a function of removing noise due to movement of a living body from a pulse wave signal detected from a living body.

Conventionally, there is a pulse wave analysis device provided with an optical pulse wave sensor that detects a pulse wave of a living body by utilizing the light absorption characteristic of hemoglobin in blood. This pulse wave analyzer irradiates a living body with light having a wavelength that is easily absorbed by blood from a light emitting element such as a light emitting diode, and emits light that has passed through the living body or light that has entered the living body and is reflected by scattering after entering the living body. A volume pulse wave is detected by receiving light with a light receiving element such as a photodiode or a photodiode and converting it into an electric signal (volume pulse wave signal), and this volume pulse wave signal or a velocity pulse wave obtained by differentiating the volume pulse wave signal once. By analyzing the signal or the acceleration pulse wave signal obtained by differentiating the volume pulse wave signal twice, biological information such as blood pressure and heart rate is acquired (Patent Documents 1, 2, and 3).

By the way, these biological information are acquired based on the feature quantities (peak value, peak interval, etc.) obtained from the pulse wave signal (volume pulse wave signal, velocity pulse wave signal, acceleration pulse wave signal), but the pulse wave. Due to its characteristics, it is difficult to obtain the signal stably because noise due to the movement of the human body, including unconscious life activity and fluctuation by the autonomic nerve, is superimposed on the signal. In addition, some noise frequencies overlap with the frequency components of the pulse wave signal features, and it is difficult to completely remove them.

As a pulse wave measurement / analysis device that addresses this problem, there is a pulse wave measurement / analysis device described in Patent Document 4. This pulse wave measuring / analyzing device is a frequency distribution of the a-e interval, which is the interval between the peak of the a wave (early contraction positive wave) and the peak of the e wave (extended initial positive wave) with respect to the acceleration pulse wave signal. Is obtained, and the average waveform of the frequently used acceleration pulse wave signal is used as the acceleration pulse wave signal for acquiring biological information.

Japanese Unexamined Patent Publication No. 2001-61795 Japanese Unexamined Patent Publication No. 2007-61572 Japanese Unexamined Patent Publication No. 2000-225097 Japanese Patent No. 3965435

However, since the noise due to the movement of the living body also exists in the section between the a wave and the e wave, the waveform selection for averaging based on the frequency distribution of the a-e interval is performed without considering the noise. In the pulse wave measuring / analyzing device of the above, the influence of noise may remain on the average waveform of the obtained acceleration pulse wave signal.

The present invention has been made to solve such a problem, and an object of the present invention is to obtain a pulse wave signal (acceleration pulse wave signal or velocity pulse wave signal or volumetric pulse wave signal) for acquiring biological information. At the time of acquisition, it is to reduce the influence of noise in the portion between the a wave and the e wave of the acceleration pulse wave signal, or the portion corresponding to the portion in the velocity pulse wave signal or the volumetric pulse wave signal.

The present invention relates to a pulse wave signal acquisition means for acquiring a plurality of beats of a pulse wave signal and a time axis position for each beat with respect to the pulse wave signals for a plurality of beats acquired by the pulse wave signal acquisition means. The most frequent value acquisition means for accumulating the appearance frequency value for each signal value of the above for a plurality of beats and acquiring the most frequent value having the maximum appearance frequency value, and the most frequent value acquisition means acquired by the most frequent value acquisition means. It is a pulse wave analysis apparatus having the most frequent pulse wave signal acquisition means for acquiring a pulse wave signal for acquiring biological information based on a value.
Further, the present invention is a program for making a computer function as each means of the pulse wave analyzer of the present invention.

According to the present invention, when acquiring a pulse wave signal (acceleration pulse wave signal, velocity pulse wave signal, or volumetric pulse wave signal) for acquiring biological information, the a wave and the e wave of the acceleration pulse wave signal are combined. It is possible to reduce the influence of noise in the intermediate portion, or the portion corresponding to the portion in the velocity pulse wave signal or the volume pulse wave signal.

It is a block diagram which shows the structure of the pulse wave analysis apparatus which concerns on embodiment of this invention. It is a flowchart which shows the operation of the main part of the pulse wave analysis apparatus which concerns on embodiment of this invention. It is a figure which shows 2 beats of the waveform of a volume pulse wave signal, a velocity pulse wave signal, and an acceleration pulse wave signal. It is a figure which shows an example of the appearance frequency value for each data value for each time axis position of the acceleration pulse wave data for one beat. It is a figure which shows an example of the appearance frequency cumulative value for each data value for each time axis position of the acceleration pulse wave data for a plurality of beats. It is a figure which shows the shading image which becomes higher density as the cumulative value of appearance frequency in FIG. 5 becomes higher, and the mode acceleration pulse wave acquired by the spline curve passing through the part of the highest density of the shading image.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<Configuration of pulse wave analyzer>
FIG. 1 is a block diagram showing a configuration of a pulse wave analysis device according to an embodiment of the present invention. The pulse wave analysis device 1 includes a photoelectric pulse wave sensor 2, a signal processing unit 3, an operation unit 4, and a display unit 5.

The photoelectric pulse wave sensor 2 is a sensor that optically detects a positive pulse wave by utilizing the absorption characteristic of hemoglobin in blood, and includes an LED 21 as a light emitting element and a photo sensor 22 as a light receiving element.

The signal processing unit 3 is a signal processing unit that drives the photoelectric pulse wave sensor 2 and acquires and processes the volume pulse wave detected by the photoelectric pulse wave sensor 2. The drive unit 31, the amplification unit 32, and the filter 33. , A / D converter 34, and microcomputer (microcomputer) 35.

The operation unit 4 is a user interface for inputting various instructions and information to the signal processing unit 3, and the display unit 5 is a user interface for displaying a pulse wave or the like processed by the signal processing unit 3.

The LED 21 of the photoelectric pulse wave sensor 2 emits light according to the drive voltage output from the drive unit 31 of the signal processing unit 3. The photosensor 22 outputs a detection signal (volume pulse wave signal) radiated from the LED 21 and transmitted through the human body such as a fingertip, or a detection signal (volume pulse wave signal) according to the intensity of the reflected light reflected by the human body.

The amplification unit 32 of the signal processing unit 3 is composed of, for example, an amplifier using an operational amplifier, and amplifies the volume pulse wave signal. The filter 33 performs filtering for removing noise, which is a component other than the frequency component that characterizes the volume pulse wave, from the volume pulse wave signal amplified by the amplification unit 32. The A / D converter 34 digitizes (converts into a digital value) the volumetric pulse wave signal that has passed through the filter 33 to obtain volumetric pulse wave data.

The microcomputer 35 includes a CPU 35a, a RAM 35b, and a ROM 35c. The CPU 35a executes various arithmetic processes (details will be described later) on the volume pulse wave data. The ROM 35c stores programs and data used when the CPU 35a executes various arithmetic processes, and the RAM 35b is a work area for temporarily storing programs and data when the CPU 35a executes various arithmetic processes.

<Operation of pulse wave analyzer>
FIG. 2 is a flowchart showing the operation of a main part of the pulse wave analysis device according to the embodiment of the present invention. This operation is executed by the microcomputer 35 in the signal processing unit 3. That is, the microcomputer 35 functions as a pulse wave signal acquisition means, a mode acquisition means, a superposition means, a most frequent pulse wave signal acquisition means, a waveform data generation means, and an image data generation means.

First, the microcomputer 35 acquires the volumetric pulse wave data from the A / D converter 34 (step S1), and then filters the volumetric pulse wave data (step S2). This filtering process is a process for removing noise from the volume pulse wave data, and may be configured to execute either one without using it in combination with the filtering process by the filter 33. Next, the microcomputer 35 acquires the acceleration pulse wave data by differentiating the volume pulse wave data twice (step S3).

Here, step S3 is supplemented. FIG. 3 is a diagram showing two beats of waveforms of a volume pulse wave signal, a velocity pulse wave signal, and an acceleration pulse wave signal. The horizontal axis of this figure is time, and the vertical axis is the signal value (pulse wave signal level) of each pulse wave signal.

Next, the microcomputer 35 determines whether or not the acceleration pulse wave is a peak, that is, point a which is the peak of a wave (initial contraction positive wave), point b which is the peak of b wave (initial contraction negative wave), and c wave (contraction). It is determined whether or not it is the c point which is the peak of the mid-term re-rising wave, the d point which is the peak of the d wave (late contraction re-falling wave), or the e point which is the peak of the e wave (extended early positive wave). (Step S4). Then, if it is determined to be a peak (step S4: Yes), it is determined whether or not the peak is a feature point (step S5). Here, it is determined whether or not the point a is easy to determine because the rising edge of the waveform is sharp. Instead of determining whether or not the peak is the a-wave, it may be determined whether or not the a-wave is rising.

Then, when it is determined that it is a feature point (step S5: Yes), recording of a waveform of one beat is started with this feature point as a start point (reference point) (step S6), and whether or not the waveform is being recorded is determined. Judgment (step S7). If it is determined in step S4 that it is not a peak (step S4: No), and if it is determined that it is not a feature point in step S5 (step S5: No), it is determined whether or not the waveform is being recorded as it is.

If it is determined that the waveform is being recorded (step S7: Yes), it is determined whether or not the data is long enough (step S8). Here, when the acceleration pulse wave data for one beat is recorded, it is determined that the data length is sufficient (step S8: Yes), and the waveform recording is terminated (step S9).

Next, the acceleration pulse wave data for one beat recorded this time is superimposed on the acceleration pulse wave data recorded in the past (step S10), and whether or not the number of overlaps is sufficient, that is, the number of overlaps is a predetermined number (for example, 100). Is determined (step S11). At the time of this superposition, the alignment in the time axis direction is performed with the above-mentioned start point as a reference point.

When it is determined that the number of superpositions is sufficient (step S11: Yes), the mode value of the pulse wave data at each position of the acceleration pulse wave data in the time axis direction is calculated (step S12), and the mode of the acceleration pulse wave is calculated. It is acquired, output to the display unit 5 (step S13), and the flow shown in this figure is terminated.

When it is determined in step S7 that the waveform is not being recorded (step S7: No), when it is determined that the step data is not long enough (step S8: No), and when it is determined in step S11 that the number of superpositions is not sufficient (step S7: No). Step S11: No), the process returns to step S1, and the process is repeated from the acquisition of the volume pulse wave data.

<Specific example of steps S10 to S12>
Here, steps S10 to S12 will be specifically described.
FIG. 4 is a diagram showing an example of an appearance frequency value for each data value for each time axis position (every time) of acceleration pulse wave data for one beat. This appearance frequency value is acquired when step S10 is executed using the acceleration pulse wave data for one beat recorded by one execution of steps S6 → S7 → S8 → S9.

The horizontal direction of this figure is time, and the vertical direction is a data value (acceleration pulse wave signal level), which correspond to the horizontal axis and the vertical axis of the acceleration pulse wave signal in FIG. 3, respectively. However, in FIG. 4, for convenience of explanation, the units in both directions are roughly illustrated, the time in the horizontal direction is composed of 22 unit times, and the voltage in the vertical direction is composed of 25 unit voltages. In this figure, "1" and "0" are count values of appearance frequency values for each data value for each time. For convenience, halftone dots are added to the portion where the appearance frequency value is "1" for each time.

FIG. 5 is a diagram showing an example of an appearance frequency cumulative value for each data value for each time axis position of acceleration pulse wave data for a plurality of beats. This figure is an appearance frequency cumulative value obtained by adding (accumulating) the appearance frequency value shown in FIG. 4 for 100 times, and is a time in the horizontal direction and a data value (acceleration pulse wave signal level) in the vertical direction. In this figure, "##" of the cumulative value of appearance frequency represents "100".

FIG. 6 is a diagram showing a shading image in which the density increases as the cumulative value of appearance frequency in FIG. 5 increases, and a mode accelerometer wave acquired by a spline curve passing through a portion of the shading image having the highest density. However, for convenience, the cumulative value of appearance frequency is omitted. The shading image and the waveform of the most frequent acceleration pulse wave are displayed by outputting the image data and the waveform data generated by the microcomputer 35 to the display unit 5. When there are a plurality of data values that are the mode values, for example, the data value in the center is adopted.

As described in detail above, according to the pulse wave analysis device 1 according to the embodiment of the present invention, the most frequent value of the acceleration pulse wave signal is used instead of the average waveform of the acceleration pulse wave signal. It has the effect of being less susceptible to frequency fluctuations and amplitude fluctuations based on the movement of. In addition, there is an effect that a rounding error does not occur when acquiring a pulse wave signal for acquiring biological information.

In the embodiment described above, the mode of the acceleration pulse wave signal is used to obtain the mode of the acceleration pulse wave signal, but the present invention is the most of the volume pulse wave signal or the velocity pulse wave signal. By using the mode, it is also possible to acquire the mode volume pulse wave signal or the mode frequency pulse wave signal. Further, a piezoelectric pulse wave sensor can be used instead of the photoelectric pulse wave sensor.

1 ... pulse wave analyzer, 2 ... photoelectric pulse wave sensor, 3 ... signal processing unit, 35 ... microcomputer, 21 ... LED, 22 ... photo sensor.

Claims (4)

A pulse wave signal acquisition means for acquiring a pulse wave signal for a plurality of beats,
With respect to the pulse wave signals for a plurality of beats acquired by the pulse wave signal acquisition means, the appearance frequency value for each signal value for each time axis position for each beat is accumulated for a plurality of beats, and the appearance frequency value is the maximum. The mode acquisition means for acquiring the mode value, which is the signal value of
Based on the mode acquired by the mode acquisition means, the mode acquisition means for acquiring the pulse wave signal for acquiring biometric information and the mode acquisition means.
A pulse wave analyzer having. In the pulse wave analyzer according to claim 1,
The mode acquisition means is a pulse wave analysis device having a superimposing means for aligning the time axis position of the pulse wave signal for each beat with a feature point of the pulse wave signal as a starting point. In the pulse wave analyzer according to claim 1 or 2.
The image data generation means for generating image data for displaying a high-density grayscale image as the most frequent value acquired by the most frequent value acquisition means is higher, and the highest image data generated by the image data generation means. A pulse wave analyzer comprising a waveform data generation means for generating waveform data of a pulse wave signal for acquiring biological information as a curve passing through a concentration portion. A program for operating a computer as each means of the pulse wave analyzer according to any one of claims 1 to 3.

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