WO2023032120A1 - Heartbeat detection method and heartbeat detection device - Google Patents

Abstract

This heartbeat detection device comprises: an R wave detection unit (3) that detects R waves from an electrocardiogram; an R-R interval calculation unit (4) that calculates an R-R interval, which is the time interval between an R wave and the preceding R wave that were detected by the R wave detection unit (3); and a heart rate calculation unit (5) that calculates a heart rate on the basis of the R-R interval. The R-R interval calculation unit (4) pauses R wave detection during a period in which the elapsed time since the time of the most recent R wave is less than or equal to a skip width. The skip width is set as a value that is shorter than 60000/HRmax, where HRmax is the maximum value of the heart rate to be measured.

Description

Heartbeat detection method and heartbeat detection device

The present invention relates to a heartbeat detection method and a heartbeat detection device for detecting a heartbeat from an electrocardiogram waveform.

The ECG (Electrocardiogram) waveform is an observation of the electrical activity of the heart and consists of a continuous heartbeat waveform. One heartbeat waveform consists of components such as P wave, Q wave, R wave, S wave, T wave, etc., which reflect the activity of the atria and ventricles. Of these waves, the R wave accompanies the contraction of the ventricle and has a large amplitude. Therefore, detection of the heartbeat is often performed based on the peak derived from the R wave.

As a conventional heartbeat detection method, there is a method disclosed in Patent Document 1. The method disclosed in Patent Document 1 uses an index value that focuses on the relationship between the peak of the time difference value of the ECG waveform and the value in a certain time region before and after the peak, and uses a determination logic based on a threshold. to detect the R wave. This method has the advantage that it is sensitive not only to the amplitude of the ECG waveform but also to the shape (time width of the peak), and can emphasize peaks that are likely to be R waves.

On the other hand, when the R wave is detected using the determination logic based on the threshold, it is normal for the index value to continue to exceed the threshold for a while after exceeding the threshold once. In addition, since the human heart rate has an upper limit, it is reasonable to assume that the next R wave will not arrive immediately after the R wave. Therefore, after the detection of the R wave, a process of stopping the operation of detecting the R wave for a certain period of time is routinely performed.

In addition, if the RR interval (RRI), which is the time interval between the detected R wave and the previous R wave, is too short than the standard, it is determined that noise, etc. other than the R wave was erroneously detected. Therefore, the process of rejecting R-wave detection also has rationality. Also, in R-wave detection, the value of the instantaneous heart rate (=60000/RRI) may deviate from the normal value due to an error due to noise mixed into the ECG waveform. Therefore, it is common to output a stabilized average heart rate by temporally averaging the instantaneous heart rate.

However, there are individual differences in the ECG waveform, and depending on the shape of the Q wave, R wave, and S wave, the peak of the index value as described above may be gentle, or the index value may have multiple peaks. Sometimes it happens. For this reason, the timing at which it is determined that the index value exceeds the threshold may fluctuate back and forth by about 20 ms at maximum. This timing fluctuation, setting of the lower limit value of RRI, and skipping of R-wave detection may cause errors in R-wave detection and heart rate measurement.

Below, we will explain the reasons why R-wave detection and heart rate measurement are incorrect. 8 and 9 are diagrams showing examples of index values calculated by a conventional heartbeat detection method. However, the index values are shown only in the vicinity of the threshold TH. Here, it is assumed that the upper limit of the heart rate to be measured is 300 bpm and the heart rate obtained from the observed ECG waveform is also 300 bpm. Two consecutive peaks P1 and P2 appear in the index value. The center points of the peaks P1 and P2 are separated by RRI=200 ms, which corresponds to a heart rate of 300 bpm. Each of the peaks P1 and P2 has a gently wavy shape instead of a sharp shape.

In the example of FIG. 8, time T1 is detected as the time of the R wave because the index value exceeds the threshold TH at time T1. The index value next exceeds the threshold TH at time T2, and the interval between times T1 and T2 is 186 ms. However, the skip width tskip after the R wave detection is set to 200 ms, and the R wave detection is suspended during the period up to 200 ms elapsed from the time T1, so the time T2 is detected as the time of the R wave. I can't.

In the example of FIG. 9, the skip width tskip is changed to 180ms. As in the example of FIG. 8, the index value exceeds the threshold TH at time T1, so time T1 is detected as the time of the R wave. Furthermore, after the elapsed time from time T1 exceeds tskip=180 ms, the index value exceeds the threshold TH at time T2, and time T2 is detected as the time of the R wave. However, since the lower limit RRI _LOW of RRI is set to 200 ms and the interval between times T1 and T2 is 186 ms, 186 ms is not adopted as RRI and is excluded from the calculation of the instantaneous heart rate. Also, the index value next exceeds the threshold TH at time T3, but since the R-wave detection is suspended during the period up to 180 ms elapsed from time T2, time T3 is detected as the time of the R-wave. pass without doing so.

Even if there is fluctuation in the timing at which the index value exceeds the threshold TH as in the examples of FIGS. If the RRI is averaged, it becomes a constant value, and an appropriate average heart rate can be obtained. However, if the lower limit of the RRI is set in accordance with the upper limit of the heart rate to be measured without a margin, cases in which the RRI swings to the short side as shown in the example of FIG. 9 are excluded. The numbers are calculated biased towards the smaller side.

Japanese Patent No. 6527286

The present invention has been made to solve the above problems, and an object of the present invention is to provide a heartbeat detection method and a heartbeat detection device capable of accurately measuring the heart rate.

The heartbeat detection method of the present invention comprises a first step of detecting an R wave from an electrocardiogram waveform of a living body; and a third step of calculating a heart rate based on the RR interval, wherein the second step is the most recent R-wave detected in the first step. including the step of stopping R-wave detection during a period in which the elapsed time from the time is equal to or less than the skip width, wherein the skip width is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heart rate to be measured. It is characterized by being set.
In one configuration example of the heartbeat detection method of the present invention, in the second step, the time obtained by subtracting the time of the previous R wave from the time of the latest R wave detected in the first step is the lower limit. The lower limit is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heart rate to be measured. It is characterized by being

In one configuration example of the heartbeat detection method of the present invention, the skip width is set to a value shorter than (60000/HRmax)-20.
In one configuration example of the heartbeat detection method of the present invention, the lower limit is set to a value shorter than (60000/HRmax)-20.
In one configuration example of the heartbeat detection method of the present invention, the skip width is equal to or less than the lower limit.

Further, the heartbeat detection apparatus of the present invention includes an R wave detection section configured to detect an R wave from an electrocardiogram waveform of a living body, and an R wave detected by the R wave detection section and an R wave immediately before the R wave. An RR interval calculation unit configured to calculate an RR interval, which is a time interval, and a heart rate calculation unit configured to calculate a heart rate based on the RR interval, The RR interval calculation unit stops R wave detection during a period in which the elapsed time from the time of the latest R wave detected by the R wave detection unit is equal to or less than the skip width, and the skip width is measured. It is characterized in that it is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heart rate to be applied.
Further, in one configuration example of the heartbeat detection device of the present invention, the RR interval calculation unit subtracts the time of the previous R wave from the time of the latest R wave detected by the R wave detection unit. If the time is shorter than the lower limit, the calculated time is not adopted as the RR interval, and the lower limit is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heart rate to be measured. It is characterized by being set.

According to the present invention, by setting the skip width to a value shorter than 60000/HRmax with respect to the upper limit value HRmax of the heart rate to be measured, it is possible to detect the R wave without failing to detect the heart rate. It can be measured accurately.

FIG. 1 is a block diagram showing the configuration of a heartbeat detection device according to an embodiment of the present invention. FIG. 2 is a flow chart illustrating the operation of the heartbeat detection device according to the embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of the R-wave detector of the heartbeat detector according to the embodiment of the present invention. FIG. 4 is a flow chart for explaining the operation of the R-wave detector of the heartbeat detector according to the embodiment of the present invention. FIG. 5 is a diagram for explaining an operation example of the heartbeat detection device according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an example of operation of the heartbeat detection device according to the embodiment of the present invention. FIG. 7 is a block diagram showing a configuration example of a computer that implements the heartbeat detection device according to the embodiment of the present invention. FIG. 8 is a diagram for explaining a conventional heartbeat detection method. FIG. 9 is a diagram for explaining a conventional heartbeat detection method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a heartbeat detection device according to an embodiment of the present invention. The heart rate detection device includes an electrocardiograph 1 that outputs an ECG waveform sampling data string, a storage unit 2 that stores an ECG waveform sampling data string and sampling time information, and R An R-wave detector 3 that detects waves, an RR interval calculator 4 that calculates RR intervals from time-series data of R-wave times, and a heart rate that calculates heart rates based on RR intervals. and a calculator 5 .

Next, the operation of the heartbeat detection device of this embodiment will be explained using FIG. In this embodiment, D(i) is a data string obtained by sampling an ECG waveform. i (i=1, 2, . . . ) is a number given to data of one sampling. Needless to say, the larger the number i, the later the sampling time.

The electrocardiograph 1 measures an ECG waveform of a living body (human body) (not shown) and outputs a sampling data string D(i) of the ECG waveform (step S1 in FIG. 2). At this time, the electrocardiograph 1 adds sampling time information to each sampling data and outputs the data. Since the specific method of measuring the ECG waveform is a well-known technique, detailed description thereof will be omitted. The storage unit 2 stores the sampling data sequence D(i) of the ECG waveform output from the electrocardiograph 1 and the information on the sampling time.

The R-wave detection unit 3 detects R-waves from the ECG waveform sampling data sequence D(i) stored in the storage unit 2 (step S2 in FIG. 2).

3 is a block diagram showing the configuration of the R-wave detector 3. As shown in FIG. The R-wave detection unit 3 includes a positive/negative inversion value calculation unit 30 that calculates the positive/negative inversion value of the time difference of the sampling data from the sampled data string of the ECG waveform at each sampling time, and a time range A before the sampling time to be processed. and the time difference positive/negative reversed value in the time range B after the sampling time to be processed. An index value calculation unit 32 that calculates an index value obtained by subtracting the maximum value from the time difference positive/negative inversion value at each sampling time, and sets the sampling time to be processed to the time of the R wave when the index value exceeds a predetermined threshold. and a time determination unit 33 .

The maximum value detection unit 31 includes a FIFO buffer (First In, First Out) 310 to which the time difference positive/negative inversion value calculated by the positive/negative inversion value calculation unit 30 is input, and a FIFO buffer to which the output value of the FIFO buffer 310 is input. 311, a FIFO buffer 312 that receives the output value of the FIFO buffer 311, and the maximum value M of the positive/negative inverted value of the time difference stored in the FIFO buffer 310 and the inverted positive/negative value of the time difference stored in the FIFO buffer 312. and a detection processing unit 313 that performs detection at each sampling time.

The index value calculation unit 32 calculates the maximum value detected by the maximum value detection unit 31 from the FIFO buffer 320 to which the time difference positive/negative inversion value calculated by the positive/negative value calculation unit 30 is input, and the output value of the FIFO buffer 320. and a subtraction processing unit 321 that calculates an index value x obtained by subtracting M at each sampling time.

The operation of the R-wave detector 3 of this embodiment will be described below with reference to FIG. In order to calculate the time difference positive/negative inversion value Y(i) of the sampling data D(i), the positive/negative inversion value calculation unit 30 calculates the data D(i+1) after one sampling of the sampling data D(i) and the data D(i+1) one sampling before. Data D(i-1) are obtained from the storage unit 2 (step S100 in FIG. 4). Then, the positive/negative inversion value calculator 30 calculates the time difference positive/negative inversion value Y(i) of the sampling data D(i) for each sampling time as shown in the following equation (step S101 in FIG. 4).
Y(i)=-{D(i+1)-D(i-1)} (1)

The positive/negative inversion value calculation unit 30 inputs the calculated time difference positive/negative inversion value Y(i) to the FIFO buffer 320 at each sampling time (step S102 in FIG. 4).

In addition, the positive/negative inversion value calculation unit 30 inputs the calculated time difference positive/negative inversion value Y(i) to the FIFO buffer 310 at each sampling time (step S103 in FIG. 4). The output of FIFO buffer 310 is input to FIFO buffer 311 (step S104 in FIG. 4), and the output of FIFO buffer 311 is input to FIFO buffer 312 (step S105 in FIG. 4). The FIFO buffers 310 to 312 are for obtaining the maximum value M of the time difference positive/negative inversion values in the time ranges A and B. FIG.

The time interval L3 corresponding to the length of the FIFO buffer 311 (the delay time from when the time difference positive/negative inversion value is input to the FIFO buffer 311 until it is output) is the width of the peak derived from the R wave (approximately 10 ms). ), preferably about 50 ms. This interval L3 is the interval between the time ranges A and B. Also, a time interval L2 corresponding to the length of the FIFO buffer 310 (a delay time from when the time difference positive/negative inversion value is input to the FIFO buffer 310 until it is output), and a time interval corresponding to the length of the FIFO buffer 312 L4 (the delay time from when the time difference positive/negative inversion value is input to the FIFO buffer 312 until it is output, L2=L4) is appropriately about 100 ms.

Also, the time interval L1 corresponding to the length of the FIFO buffer 320 should be L1=L2+L3/2. Therefore, in the above numerical example, L1 is 125 ms. By setting L1=L2+L3/2 and L2=L4, the range of -(L2+L3/2) to -(L3/2) is obtained for the time (sampling time to be processed) of the output value a of the FIFO buffer 320. The maximum value M can be obtained for the range from (L3/2) to (L2+L3/2), and the maximum value M can be subtracted from the output value a.

The detection processing unit 313 detects the maximum value M of the time difference positive/negative inversion value stored in the FIFO buffer 310 and the time difference positive/negative inversion value stored in the FIFO buffer 312 at each sampling time (step S106 in FIG. 4). .
The subtraction processing unit 321 calculates an index value x(i)=a−M by subtracting the maximum value M from the output value a of the FIFO buffer 320 at each sampling time (step S107 in FIG. 4).

When the index value x(i) exceeds the predetermined threshold value TH (YES in step S108 in FIG. 4), the time determining unit 33 determines that the sampling time of the index value x(i) is appropriate as the time of the R wave. Determine if there is, and fix the time of the R wave. Specifically, the time determination unit 33 determines whether the time difference ΔT between the sampling time of the index value x(i) exceeding the threshold TH and the time of the immediately preceding R wave is longer than a preset skip width tskip. (step S109 in FIG. 4), and if the time difference ΔT is equal to or less than the skip width tskip (NO in step S109), the sampling time of the index value x(i) exceeding the threshold TH is adopted as the time of the R wave. do not. Through such processing of step S109, skip processing of R-wave detection can be realized. If the sampling time of the index value x(i) is not adopted as the time of the R wave, the processing target is shifted to the sampling data D(i) at the next sampling time, and the processing after step S100 is performed again. .

Further, when the time difference ΔT is longer than the skip width tskip (YES in step S109), the time determining unit 33 sets the sampling time of the index value x(i) exceeding the threshold TH as the time of the R wave (Fig. 4 step S110).

As described above, the time difference positive/negative inversion value Y(i) is calculated from the sampling data D(i), and the index value x(i) is calculated from the time difference positive/negative inversion value Y(i). Therefore, the sampling time of the index value x(i) is the sampling time of the time difference positive/negative inversion value Y(i) (the sampling time of the data D(i)), which can be obtained from the storage unit 2. is.

In this way, by repeatedly executing the processing of steps S100 to S110 for each sampling period, time-series data of the time of the R wave can be obtained. The time-series data of the time of the detected R wave is stored in the storage unit 2 .
Note that the above R-wave detection method is an example, and the R-wave may be detected by other methods.

Here, in this embodiment, the skip width tskip is set to be equal to or less than the lower limit value of the RR interval (RRI). When the upper limit of the instantaneous heart rate to be measured is HRmax [bpm], the lower limit of RRI RRI _LOW is greater than 0 and less than (60000/HRmax) [ms]. More specifically, the lower limit value RRI _LOW of RRI is set to a value greater than 0 and less than ((60000/HRmax)-20) [ms]. The assumed instantaneous heart rate upper limit HRmax is, for example, 300 bpm.

Therefore, the skip width tskip is greater than 0 and less than (60000/HRmax) [ms]. More specifically, the skip width tskip is set to a value greater than 0 and less than ((60000/HRmax)-20) [ms].

Next, the RR interval calculator 4 calculates the time d by subtracting the time of the previous R wave from the time of the latest R wave detected by the R wave detector 3 (step S3 in FIG. 2). . If the calculated time d is shorter than the preset lower limit value RRI _LOW of RRI (NO in step S4 in FIG. 2), the RR interval calculator 4 discards the time d as the RRI without adopting it. If the time d is equal to or greater than the lower limit value RRI _LOW (YES in step S4), the RR interval calculator 4 determines the time d as RRI [ms] (step S5 in FIG. 2).

The heart rate calculator 5 calculates the instantaneous heart rate HR(i) [bpm] for each RRI based on the RRI [ms] calculated by the RR interval calculator 4 (step S6 in FIG. 2).
HR(i)=60000/RRI (2)

The heart rate calculator 5 also calculates the average heart rate HRave(i) [bpm] for each RRI (step S7 in FIG. 2). Let HR(i) be the instantaneous heart rate obtained from the i-th RRI(i) before averaging, as described above, and HRave(i-1) is the value obtained by averaging the instantaneous heart rates up to the i-1th, and a predetermined If the averaging coefficient of is r, the value HRave(i) obtained by averaging up to the i-th instantaneous heart rate can be obtained by equation (3).
HRave(i)=r×HR(i)+(1−r)×HRave(i−1)
... (3)

In this way, by repeating the processing of steps S1 to S7, time-series data of the instantaneous heart rate HR(i) and the average heart rate HRave(i) are obtained. The calculated time-series data are stored in the storage unit 2 .

FIG. 5 shows an example in which the heartbeat detection method according to this embodiment is applied to the example of FIG. Here, the skip width tskip is set to 180 ms. In the example of FIG. 5, the index value x exceeds the threshold TH at time T1, so the R-wave detector 3 detects time T1 as the time of the R-wave. The R-wave detection unit 3 suspends R-wave detection during the period from time T1 to tskip=180 ms. Detect as wave time. Thus, in this embodiment, the time T2 at which the index value x exceeds the threshold TH can be detected appropriately.

FIG. 6 shows an example in which the heartbeat detection method according to this embodiment is applied to the example of FIG. Here, both the skip width tskip and the lower limit value RRI _LOW of RRI are set to 180 ms. Since the index value exceeds the threshold value TH at time T1 as in the example of FIG. 5, the R wave detector 3 detects time T1 as the time of the R wave. Further, after the elapsed time from time T1 exceeds tskip=180 ms, the index value exceeds the threshold TH at time T2, so that the R wave detector 3 detects time T2 as the time of the R wave.

Since the time d=186 ms obtained by subtracting the time T1 from the time T2 is equal to or greater than the RRI lower limit value RRI _LOW =180 ms, the RR interval calculator 4 adopts the time d as the RRI. Thus, in this embodiment, RRI can be detected appropriately. Moreover, since the peak of the index value x can be detected without missing, the average heart rate can also be calculated appropriately.

The storage unit 2, the R wave detection unit 3, the RR interval calculation unit 4, and the heart rate calculation unit 5 of the heartbeat detection device described in the present embodiment include a CPU (Central Processing Unit), a storage device, and an interface. It can be realized by a computer and a program that controls these hardware resources. A configuration example of this computer is shown in FIG.

The computer includes a CPU 100, a storage device 101, and an interface device (I/F) 102. The I/F 102 is connected with the electrocardiograph 1 and the like. A program for implementing the heartbeat detection method of the present invention is stored in the storage device 101 . The CPU 100 executes the processing described in this embodiment according to the programs stored in the storage device 101 .

The present invention can be applied to technology for detecting the heartbeat of a living body.

DESCRIPTION OF SYMBOLS 1... Electrocardiograph, 2... Storage part, 3... R wave detection part, 4... RR interval calculation part, 5... Heart rate calculation part, 30... Positive/negative inversion value calculation part, 31... Maximum value detection part, 32 ... index value calculation section, 33 ... time determination section, 310 to 312, 320 ... FIFO buffer, 313 ... detection processing section, 321 ... subtraction processing section.

Claims (8)

a first step of detecting R waves from a biological electrocardiogram waveform;
A second step of calculating an RR interval, which is the time interval between the R wave detected in the first step and the previous R wave;
and a third step of calculating a heart rate based on the RR interval;
The second step includes stopping R-wave detection during a period in which the elapsed time from the time of the latest R wave detected in the first step is equal to or less than the skip width;
A heartbeat detection method, wherein the skip width is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heartbeat rate to be measured. The heart rate detection method of claim 1, wherein
In the second step, if the time obtained by subtracting the time of the previous R wave from the time of the latest R wave detected in the first step is shorter than the lower limit, the calculated time RR including steps not taken as intervals,
A heartbeat detection method, wherein the lower limit value is set to a value shorter than 60000/HRmax, where HRmax is the upper limit value of the heartbeat rate to be measured. The heartbeat detection method according to claim 1 or 2,
The heartbeat detection method, wherein the skip width is set to a value shorter than (60000/HRmax)-20. The heartbeat detection method of claim 2,
The heartbeat detection method, wherein the lower limit value is set to a value shorter than (60000/HRmax)-20. The heartbeat detection method according to claim 2 or 4,
The heartbeat detection method, wherein the skip width is equal to or less than the lower limit. an R-wave detector configured to detect R-waves from an electrocardiogram waveform of a living body;
an RR interval calculator configured to calculate an RR interval, which is the time interval between the R wave detected by the R wave detector and the immediately preceding R wave;
a heart rate calculator configured to calculate a heart rate based on the RR interval;
The RR interval calculation unit stops R wave detection during a period in which the elapsed time from the time of the latest R wave detected by the R wave detection unit is equal to or less than the skip width,
The heartbeat detecting device, wherein the skip width is set to a value shorter than 60000/HRmax, where HRmax is the upper limit of the heartbeat rate to be measured. The heartbeat detection device of claim 6,
The RR interval calculation unit calculates the calculated time when the time obtained by subtracting the time of the previous R wave from the time of the latest R wave detected by the R wave detection unit is shorter than the lower limit value. Not adopted as RR interval,
The heart rate detecting device, wherein the lower limit value is set to a value shorter than 60000/HRmax, where HRmax is the upper limit value of the heart rate to be measured. A heartbeat detection device according to claim 7, wherein
The heartbeat detection device, wherein the skip width is equal to or less than the lower limit.

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