Heart rate detection system, heart rate detection method, and program

Abstract

To provide a heart rate detection system capable of accurately detecting a heart rate of a measured person.SOLUTION: The heart rate detection system comprises: a Doppler data acquisition unit 31 which acquires measurement data including waveform components caused by the movement of the heart of a measured person; a band filter unit 32 which applies a band filter of a prescribed passing band to the measurement data; a heart rate estimation unit 33 which estimates the heart rate of the measured person based on the measurement data having the band filter 32 applied thereto; and a band change unit 34 which changes the band of the band filter 32 based on the estimated heart rate.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a heart rate detection system, a heart rate detection method and a program, and more particularly to a technique for detecting the heart rate of a subject from measurement data that includes waveform components caused by cardiac movement. [Background technology]

[0002] Various systems for detecting the heart rate of a person being measured have been considered. One example is a method for detecting the heart rate in a non-contact manner using a microwave Doppler sensor, as described in Patent Document 1 below. With a microwave Doppler sensor, the movement of the chest of the person being measured can be converted into data, from which the heart rate can be detected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-134795 A Summary of the Invention [Problem to be solved by the invention]

[0004] Generally, measurement data obtained from a subject contains many noise components in addition to components caused by the movement of the heart, so it is conceivable to apply a bandpass filter to the measurement data and detect the subject's heart rate based on the measurement data from which noise has been removed. However, since the movement of the subject's heart changes in a complex manner depending on the heart rate, using a filter with a fixed passband may actually reduce the accuracy of heart rate detection.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a heart rate detection system, a heart rate detection method, and a program that can accurately detect the heart rate of a subject from measurement data that includes waveform components due to cardiac movement. [Means for solving the problem]

[0006] (1) In order to solve the above problems, the heart rate detection system of the present invention includes a measurement data acquisition means for acquiring measurement data including waveform components attributable to the movement of the subject's heart, a band pass filter means for applying a band pass filter of a given pass band to the measurement data, a heart rate estimation means for estimating the heart rate of the subject based on the measurement data to which the band pass filter has been applied, and a band changing means for changing the band of the band pass filter based on the estimated heart rate.

[0007] (2) The heart rate detection system according to (1) may further include a band storage unit that stores the value of the heart rate in association with an upper limit value and a lower limit value of the band. The band changing unit may determine the band of the band filter after the change based on the contents stored in the band storage unit.

[0008] (3) In the heart rate detection system described in (2), the band storage means may store a common upper limit value in association with the heart rate that is equal to or less than a predetermined value.

[0009] (4) In the heart rate detection system described in (2) or (3), the band storage means may store a common lower limit value in association with the heart rate equal to or greater than the predetermined value.

[0010] (5) In the heart rate detection system according to any one of (2) to (4), the band storage means may associate a smaller lower limit value with a heart rate value that is less than the predetermined value, and may associate a larger upper limit value with a heart rate value that is greater than the predetermined value.

[0011] (6) In the heart rate detection system described in any one of (1) to (5), the band changing means may change the band of the band filter in accordance with an amount of change in the value of the heart rate estimated based on the measurement data to which the band filter of the same band has been applied.

[0012] (7) In the heart rate detection system according to any one of (1) to (6), the measurement data may be Doppler data acquired by a Doppler sensor.

[0013] (8) A heart rate detection method according to the present invention includes a measurement data acquisition step of acquiring measurement data including waveform components attributable to cardiac movement of a subject, a band pass filter step of applying a band pass filter of a given pass band to the measurement data, a heart rate estimation step of estimating the heart rate of the subject based on the measurement data to which the band pass filter has been applied, and a band changing step of changing the band of the band pass filter based on the estimated heart rate.

[0014] (9) A program according to the present invention is a program for causing a computer to function as measurement data acquiring means for acquiring measurement data including waveform components resulting from cardiac motion of a subject, bandpass filter means for applying a bandpass filter of a given passband to the measurement data, heart rate estimating means for estimating the heart rate of the subject based on the measurement data to which the bandpass filter has been applied, and band changing means for changing the band of the bandpass filter based on the estimated heart rate. This program may be stored in a computer-readable information storage medium such as a semiconductor memory or a magneto-optical disk. Effect of the Invention

[0015] According to the present invention, the band of the band filter is changed based on the estimated heart rate of the subject, so that the heart rate of the subject can be detected with high accuracy. [Brief description of the drawings]

[0016] [Figure 1] 1 is a configuration diagram of a heart rate detection system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram of a data processing device. [Diagram 3] FIG. 4 is a diagram illustrating the contents stored in a band storage unit. [Figure 4]FIG. 1 is a diagram showing an electrocardiogram waveform. [Diagram 5] FIG. 2 is a diagram showing frequency bands corresponding to each part of an electrocardiogram waveform. [Figure 6] 1A and 1B are diagrams illustrating a procedure for determining the upper and lower limits of a passband of a bandpass filter. [Figure 7] 4 is a flowchart showing the operation of the heart rate detection system according to the present embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0018] Fig. 1 is a configuration diagram of a heart rate detection system according to an embodiment of the present invention. As shown in the figure, the heart rate detection system 1 includes a Doppler sensor 2 and a data processing device 3. The heart rate detection system 1 is set up, for example, in a house, and detects the heart rate of a person to be measured, for example, while sleeping. The Doppler sensor 2 is provided, for example, near a bed, facing the chest of the person to be measured.

[0019] Microwaves are emitted from the Doppler sensor 2, and the reflected waves near the subject's heart are received by the Doppler sensor 2. The reflected waves are frequency shifted due to the Doppler effect, and by observing this, the subject's heart rate can be obtained. The reflected waves are detected by quadrature detection as a Doppler signal containing an I signal and its orthogonal component, a Q signal, and are converted into digital Doppler data before being output to a data processing device 3. The Doppler data input to the signal processing device 3 is time-series data, and indicates the amplitude (I component and Q component) at each time.

[0020] The data processing device 3 may be configured by a known computer, for example including a CPU, memory, an input device and a display, and by executing the data processing program of this embodiment, generates the heart rate of the subject based on the Doppler data output from the Doppler sensor 2.

[0021] 2 is a functional block diagram of the data processing device 3. As shown in the figure, the data processing device 3 functionally includes a Doppler data acquisition unit 31, a band filter 32, a heart rate estimation unit 33, a band change unit 34, and a band storage unit 35. The heart rate estimation unit 33 includes an FFT unit 33a and a peak identification unit 33b. These functions are realized by the data processing device 3, which is a computer, executing the data processing program. The data processing program may be read by the data processing device 3 from a computer-readable information storage medium such as a semiconductor memory or a magneto-optical disk. Alternatively, the data processing program may be downloaded to the data processing device 3 from a communication network such as the Internet.

[0022] The Doppler data acquisition unit 31 acquires Doppler data indicating the movement of the subject's chest, acquired by the Doppler sensor 2. The Doppler data includes components attributable to the movement of the subject's heart as well as other components attributable to the subject's body movement and breathing, and is an example of the "measurement data" of the present invention.

[0023] The bandpass filter 32 applies a bandpass filter to the Doppler data acquired by the Doppler data acquisition unit 31. This extracts components resulting from the movement of the subject's heart from the Doppler data. As the passband of the bandpass filter, default upper and lower limit frequencies are stored in advance in the memory. Furthermore, when the upper and lower limit frequencies are written to the memory by the band change unit 34, the bandpass filter is applied using the written values.

[0024] The heart rate estimation unit 33 estimates the heart rate of the subject based on the Doppler data to which the bandpass filter has been applied. As an example of the configuration, the FFT unit 33a may perform FFT (Fast Fourier Transform) on the Doppler data to obtain the frequency spectrum of the Doppler data. Then, the peak identification unit 33b may identify a peak in the frequency spectrum that is the result of the FFT, and the value may be set as the heart rate of the subject.

[0025] The band changing unit 34 changes the band of the band filter based on the heart rate estimated by the heart rate estimating unit 33. Specifically, it writes the upper and lower limit values ​​of the pass band determined based on the heart rate to memory. These values ​​are read by the band filter 32 and used as pass band information. The band changing unit 34 stores the default heart rate of the data processing device 3 (e.g., 60 BPM) in memory. When changing the band of the band filter, it stores the estimated value of the heart rate used to determine the band in memory instead of the default heart rate. The band changing unit 34 changes the band again when the current estimated value of the heart rate has changed by more than the threshold value from the value stored in memory.

[0026] The band change unit 34 may determine the band of the band filter after the change based on the memory contents of the band memory unit 35. FIG. 3 is a diagram showing the memory contents of the band memory unit 35. As shown in the figure, the band memory unit 35 stores, for example, heart rate values ​​20 to 140 (BPM) in 10 degree increments in association with the upper and lower limit values ​​(Hz) of the pass band of the band filter for each heart rate value. Here, the band memory unit 35 stores a common upper limit value of 16.7 (Hz) in association with heart rates of 20 to 60 (BPM) that are equal to or less than the reference heart rate of 60 (BPM). In addition, the band memory unit 35 stores a common lower limit value of 4.0 Hz in association with heart rates of 60 (BPM) or more. Furthermore, for heart rates less than 60 (BPM), the band memory unit 35 associates a lower limit value with a smaller value as the heart rate value decreases. Also, for heart rates higher than 60 (BPM), a higher upper limit value is associated with the higher heart rate value. Based on the memory contents of the band memory unit 35 shown in the figure, the upper and lower limit values ​​of the pass band corresponding to the heart rate estimated by the heart rate estimation unit 33 are read out, and these values ​​are used by the band filter 32. Note that the heart rate values ​​shown in the figure are in increments of 10, but if a value between these is estimated by the heart rate estimation unit 33, the upper and lower limit values ​​of the pass band may be determined by interpolating the upper and lower limit values ​​corresponding to the preceding and following heart rate values, respectively.

[0027] Here, the passband of the bandpass filter is set in consideration of the electrocardiogram waveform of a healthy person. FIG. 4 is a diagram showing an electrocardiogram waveform. The vertical direction indicates the detected potential of the electrocardiograph, and the horizontal direction indicates time. As shown in the figure, the electrocardiogram waveform of a healthy person includes, in chronological order, P waves, QRS waves, T waves, and U waves. The QRS wave specifically includes Q waves, R waves, and S waves. As shown in FIG. 5, the normal value of the time width of the P wave is 60 to 100 (ms). This is converted into a frequency range of 10 to 16.7 (Hz). Similarly, the normal value of the time width of the QRS wave is 60 to 100 (ms), which is converted into a frequency range of 10 to 16.7 (Hz). The normal value of the time width of the T wave is 100 to 250 (ms), which is converted into a frequency range of 4 to 10 (Hz). The normal value of the time width of the U wave is 160 to 250 (ms), which is converted into a frequency range of 4 to 6.25 (Hz). These values ​​are those when the subject's heart rate is a reference heart rate of 60 (BPM).

[0028] FIG. 6 is a diagram for explaining a procedure for determining the upper and lower limits of the passband width of a bandpass filter. It is generally known that the QRS wave and the T wave are affected by the heart rate. Specifically, in the clinical field, a corrected QT time is calculated by dividing the QT time, which is the time from the start of the Q wave to the end of the T wave, by the square root of the RR time (the time from the peak of the R wave to the peak of the next R wave), which is the reciprocal of the heart rate. Then, the corrected QT time is compared with the standard QT time to determine an abnormality in the electrocardiogram waveform.

[0029] Considering this, the normal values ​​of the time width of the QRS wave and the T wave shown in FIG. 4 can be corrected as follows. That is, as shown in FIG. 4, when the reference heart rate is 60 (BPM), the normal value of the time width of the QRS wave is 60 to 100 (ms). Therefore, when the RR time, which is the reciprocal of the heart rate, is α (s), the normal value of the time width of the QRS wave is 60×√α to 100√α (ms). The range of the normal value of this time width can be converted into a frequency range. For example, FIG. 6 shows that when the heart rate is 20, the RR time is 3.00 (the reciprocal of the heart rate), and the normal value of the time width of the QRS wave is 104 (=60×√3) to 173 (=100√3) (ms). It is also shown that the corresponding frequency range is 5.8 to 9.6 (Hz).

[0030] Similarly, when the reference heart rate is 60 (BPM), the normal value of the time width of the T wave is 100 to 250 (ms). Therefore, when the RR time, which is the reciprocal of the heart rate, is α (s), the normal value of the time width of the T wave is 100 × √α to 250 √α (ms). The range of the normal value of this time width can also be converted into a frequency range. For example, FIG. 6 shows that when the heart rate is 20, the RR time is 3.00 (the reciprocal of the heart rate), and the normal value of the time width of the T wave is 173 (= 100 × √3) to 433 (= 250 √3) (ms). It also shows that the corresponding frequency range is 2.3 to 5.8 (Hz).

[0031] Also shown in Figure 6 are the frequency ranges for P and U waves transcribed from Figure 5. Since P and U waves are not affected by heart rate, common values ​​are set for all heart rates.

[0032] In this embodiment, the passband of the band filter is set so as to reliably pass all the components of partial waves such as P waves, QRS waves, T waves, and U waves that constitute the electrocardiogram waveform. For this reason, the maximum value of the upper limit frequency and the lower limit frequency of each partial wave is set as the upper limit of the passband, and the minimum value is set as the lower limit. For example, in FIG. 6, in the case of a heart rate of 20 (BPM), the maximum value is 16.7 (Hz), which is the upper limit frequency of the P wave, and the minimum value is 2.3 (Hz), which is the lower limit frequency of the T wave. These values ​​are stored in the band storage unit 35 as shown in FIG. 3. The same applies to the case of a heart rate of 30 to 50 (BPM).

[0033] Moreover, when the heart rate is 140 BPM, the maximum value is 25.5 Hz, which is the upper limit frequency of the QRS wave, and the minimum value is 4.0 Hz, which is the lower limit frequency of the U wave. These values ​​are stored in the band storage unit 35 as shown in Fig. 3. The same is true for heart rates of 70 to 130 BPM.

[0034] In the case of the reference heart rate (60), the maximum value is 16.7 (Hz), which is the upper limit frequency of the QRS wave and also the upper limit frequency of the P wave, and the minimum value is 4.0, which is the lower limit frequency of the T wave and also the lower limit frequency of the U wave. These values ​​are stored in the band storage unit 35 as shown in FIG.

[0035] In this embodiment, the values ​​stored in the band storage unit 35 are determined based on the electrocardiogram waveform as described above, so that when the heart rate is high (60 to 140), the lower limit of the frequency is the upper limit of the U wave, and is constant regardless of the heart rate. On the other hand, the upper limit of the frequency is the upper limit of the QRS wave, and its value increases according to the heart rate. When the heart rate is low (20 to 60), the upper limit of the frequency is the upper limit of the P wave. Also, the lower limit of the frequency is the lower limit of the T wave, and its value increases according to the heart rate. In this way, the pass band of the band filter can be appropriately set for each heart rate. That is, it is possible to cut out only unnecessary frequency components and reliably pass necessary frequency components, thereby improving the accuracy of estimating the heart rate.

[0036] 7 is a flow diagram showing the operation of the heart rate detection system 1 according to this embodiment. As shown in the figure, in the heart rate detection system 1, first, the Doppler data acquisition unit 31 acquires Doppler data output from the Doppler sensor 2 (S701). Next, the band filter 32 reads the upper and lower limit values ​​of the pass band stored in the memory (S702). At this time, if there are no upper and lower limit values ​​written by the band change unit 34 (S703), the band filter 32 reads the default upper and lower limit values ​​separately stored in the memory (S704). Then, the heart rate estimation unit 33 estimates the heart rate of the subject using the read upper and lower limit values ​​(S705). At this time, if the estimated heart rate value is different from the heart rate value stored in memory by the band changing unit 34 by more than a predetermined threshold (S706), the band changing unit 34 calculates the upper and lower limits of the pass band based on the latest heart rate value estimated by the heart rate estimation unit 33, stores these values ​​in memory, and also stores the latest estimated heart rate value in memory (S707), and returns to the processing of S701.

[0037] According to the above-described heart rate detection system 1, the pass band of the band filter 32 is changed according to the estimated value of the heart rate, so that the processing of the band filter 32 can be optimized, and the accuracy of the estimation of the heart rate can be improved. In particular, the band set in the band filter 32 is determined based on the electrocardiogram waveform, so that the band filter 32 can appropriately pass the waveform components related to the movement of the subject's heart. In addition, the estimated value of the heart rate at the time of band change is stored in memory by the band change unit 34, and the timing of the next band change is determined based on this estimated value, so that excessive repetition of band changes can be prevented.

[0038] The present invention is not limited to the above embodiment, and various modifications are possible, and such modifications also fall within the scope of the present invention. For example, in the above description, Doppler data has been taken as measurement data containing waveform components due to the movement of the subject's heart, but the present invention can be similarly applied to data obtained by other measurement methods. For example, a microdisplacement sensor including a piezoelectric element may be brought into contact with the subject to obtain measurement data showing the subject's minute movements. Alternatively, measurement data showing the subject's blood flow rate may be obtained by contact or non-contact using a photoelectric volumetric pulse wave recording method or the like. Such measurement data also contains components due to the movement of the subject's heart, and the subject's heart rate can be detected by applying the present invention. [Explanation of symbols]

[0039] 1 heart rate detection system, 2 Doppler sensor, 3 data processing device, 31 Doppler data acquisition unit, 32 band filter, 33 heart rate estimation unit, 33a FFT unit, 33b peak identification unit, 34 band change unit, 35 band storage unit.

Claims

1. A measurement data acquisition means for acquiring measurement data including a waveform component caused by the movement of the subject's heart; a bandpass filter means for applying a bandpass filter of a given passband to the measurement data; a heart rate estimation means for estimating a heart rate of the subject based on the measurement data to which the band pass filter has been applied; a band changing means for changing the band of the band filter based on the estimated heart rate; A heart rate detection system comprising:

2. 2. The heart rate detection system according to claim 1, The apparatus further includes a band storage means for storing the value of the heart rate and the upper and lower limits of the band in association with each other, The heart rate detection system according to claim 1, wherein the band changing means determines the band of the band filter after the change based on the contents stored in the band storage means.

3. 3. The heart rate detection system according to claim 2, The heart rate detection system according to claim 1, wherein the band storage means stores a common upper limit value in association with the heart rate that is equal to or lower than a predetermined value.

4. 4. The heart rate detection system according to claim 3, The heart rate detection system according to claim 1, wherein the band storage means stores a common lower limit value in association with the heart rate equal to or greater than the predetermined value.

5. 5. The heart rate detection system according to claim 4, The heart rate detection system is characterized in that, for a heart rate below the predetermined value, the smaller the heart rate value, the smaller the lower limit value associated with the heart rate, and, for a heart rate higher than the predetermined value, the larger the heart rate value, the larger the upper limit value associated with the heart rate.

6. 2. The heart rate detection system according to claim 1, The heart rate detection system, characterized in that the band changing means changes the band of the band filter in accordance with an amount of change in the value of the heart rate estimated based on the measurement data to which the band filter of the same band has been applied.

7. 2. The heart rate detection system according to claim 1, A heart rate detection system, wherein the measurement data is Doppler data acquired by a Doppler sensor.

8. a measurement data acquiring step of acquiring measurement data including a waveform component caused by a movement of the subject's heart; a bandpass filtering step of applying a bandpass filter of a given passband to the measurement data; a heart rate estimating step of estimating a heart rate of the subject based on the measurement data to which the band filter has been applied; a band changing step of changing the band of the band filter based on the estimated heart rate; A method for detecting a heart rate comprising:

9. A measurement data acquiring means for acquiring measurement data including a waveform component caused by the movement of the subject's heart; a bandpass filter means for applying a bandpass filter of a given passband to the measurement data; a heart rate estimation means for estimating a heart rate of the subject based on the measurement data to which the band pass filter has been applied; and A band changing means for changing the band of the band filter based on the estimated heart rate. A program that makes a computer function as a

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