JP2014042547A - Atrial fibrillation determination device, and atrial fibrillation determination method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine atrial fibrillation from a signal even if an influence of body motion noises is contained in the signal capable of measuring an RR interval such as a pulse wave signal and a waveform signal of an electrocardiogram.SOLUTION: An atrial fibrillation determination device includes: an acquisition part for acquiring a detection waveform signal that shows a result of electrocardiographic or pulse wave detection; an RR interval calculation part 112 for calculating a parameter corresponding to an RR interval for each frame based on a spectrum of each frame acquired by a frequency analysis of the detection waveform signal that has been acquired, and calculating an RR waveform signal that shows a time change of the parameter; a power calculation part 113 for calculating a time change of the power in a predetermined frequency band in the RR waveform signal; and a determination part 114 for determining whether or not the calculated power satisfies a specified condition, and outputting the information according to the result of the determination.

Description

  The present invention relates to a technique for determining atrial fibrillation.

  There is a technique for determining atrial fibrillation in the medical field related to heart disease. Patent Document 1 discloses a technique for measuring an RR interval obtained from an electrocardiogram for each beat and determining atrial fibrillation based on the standard deviation and frequency distribution. Non-Patent Document 1 describes that atrial fibrillation has an irregular RR interval, and a frequency analysis of the heartbeat of atrial fibrillation has a 1 / fβ component, resulting in white noise due to the fluctuation. ing.

JP 2009-89883 A

Hayano J, Yamasaki F, Sakata S, Okada A, Mukai S, Fujinami T “Spectral characteristics of ventricular response to atrial fibrillation.” Am. J. Physiol. 1997; 273: H2811-H2816

  In Patent Document 1 and Non-Patent Document 1 described above, it is necessary to accurately measure the RR interval for each beat for accurate determination of atrial fibrillation. In measuring the RR interval, it is possible to measure from the waveform signal of the electrocardiogram obtained by measuring the electrocardiogram, but it is also possible to measure from the pulse wave signal obtained by measuring the pulse wave.

However, when measuring a pulse wave, the subject can often move freely during the measurement, so the influence of body motion noise is likely to be included in the pulse wave signal. Even when measuring electrocardiogram, there is a case where the influence of body motion noise is included in the waveform signal of the electrocardiogram, although there is a difference in degree compared with the case where pulse wave is measured. Thus, when affected by body motion noise, it is very difficult to accurately measure the RR interval for each beat.
Therefore, when it is assumed that an accurate RR interval for each beat is measured as in the techniques disclosed in Patent Document 1 and Non-Patent Document 1, a signal including the influence of body motion noise is used. Therefore, atrial fibrillation could not be determined.

  The present invention has been made in view of the above-described circumstances, and one of the purposes thereof includes the influence of body motion noise in a signal capable of measuring an RR interval such as a pulse wave signal and an electrocardiogram waveform signal. However, it is to determine atrial fibrillation from the signal.

In order to solve the above-described problem, the present invention provides an acquisition unit that acquires a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave, and a spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal. An RR interval calculation unit for calculating a parameter corresponding to the average RR interval of the frame for each frame, and a predetermined RR waveform signal indicating a time change of the average RR interval calculated by the RR interval calculation unit. Atrial fibrillation comprising: a power calculation unit that calculates power in a frequency band; and a determination unit that determines whether or not the power satisfies a specific condition and outputs information on the presence or absence of atrial fibrillation according to the determination result A determination device is provided.
According to this atrial fibrillation determination device, even if the influence of body motion noise is included in a signal capable of measuring an RR interval such as a pulse wave signal and an electrocardiogram waveform signal, atrial fibrillation is determined from the signal. Can do.

  In a preferred aspect, the atrial fibrillation determination device includes a variation coefficient calculation unit that calculates a variation coefficient of the average RR interval in the RR waveform signal, and the determination unit includes the combination of the power and the variation coefficient as the value. It may be determined whether a specific condition is satisfied, and information regarding the presence or absence of atrial fibrillation may be output according to the determination result.

In another preferable aspect, the determination unit includes a plurality of sets of the power and the variation coefficient obtained in a plurality of frames, a first cluster having a relatively high power and a high variation coefficient, and a low power and a low variation coefficient. The presence or absence of atrial fibrillation may be determined based on the positional relationship between the first centroid of the first cluster and the second centroid of the second cluster in the variation coefficient-power space.
According to this atrial fibrillation determination device, the presence or absence of atrial fibrillation can be determined using the average RR interval.

In another preferable aspect, when the first centroid and the second centroid are separated by a predetermined first threshold or more, the determination unit is in a state in which atrial fibrillation has developed in the first cluster. May be determined.
According to this atrial fibrillation determination device, the presence or absence of atrial fibrillation can be determined using the result of clustering.

In still another preferred aspect, when the first centroid and the second centroid are not separated by the first threshold or more, an average centroid between the first centroid and the second centroid is determined. When having a power greater than or equal to two thresholds and a coefficient of variation greater than or equal to a third threshold, the determination unit determines that the first cluster and the second cluster are in a state in which atrial fibrillation has developed. May be.
According to this atrial fibrillation determination device, the presence or absence of atrial fibrillation can be determined even when the first cluster and the second cluster are close to each other.

In still another preferred aspect, when the first centroid and the second centroid are not separated by the first threshold or more, an average centroid between the first centroid and the second centroid is determined. When it does not have at least one of a power greater than or equal to two thresholds and a coefficient of variation greater than or equal to a third threshold, the determination unit does not develop atrial fibrillation in the first cluster and the second cluster You may determine with a state.
According to this atrial fibrillation determination device, the presence or absence of atrial fibrillation can be determined even when the first cluster and the second cluster are close to each other.

In another preferred aspect, the lowest frequency of the frequency band is equal to or greater than the reciprocal of the time of the frame.
According to this atrial fibrillation determination device, the accuracy of determination of atrial fibrillation can be improved.

Moreover, in another preferable aspect, the detection unit includes a detection unit that detects the electrocardiogram or the pulse wave of a detection target person, and a notification unit that notifies a user based on information output by the determination unit, and the acquisition The unit acquires a detected waveform signal obtained according to the detected result.
According to this atrial fibrillation determination device, the person to be detected can confirm the determination result of atrial fibrillation in real time.

In another preferred aspect, the acquisition unit includes a noise reduction unit that performs a filtering process to reduce a body movement noise component on the detected waveform signal and outputs the detected waveform signal as the detected waveform signal. .
According to this atrial fibrillation determination device, the detection subject can confirm the determination result of atrial fibrillation in real time while improving the accuracy of determination of atrial fibrillation.

Further, the present invention provides a step of acquiring a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave, and a frame for each frame based on a spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal. Calculating a parameter corresponding to the average RR interval of the frame; calculating a power of a predetermined frequency band in the RR waveform signal indicating a time change of the calculated average RR interval; and There is provided an atrial fibrillation determination method including a step of determining whether or not a condition is satisfied and a step of outputting information on the presence or absence of atrial fibrillation according to the determination result.
According to this atrial fibrillation determination method, even if the influence of body motion noise is included in a signal capable of measuring an RR interval such as a pulse wave signal and an electrocardiogram waveform signal, atrial fibrillation is determined from the signal. Can do.

Further, the present invention provides a computer based on a step of acquiring a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave and a spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal. Calculating a parameter corresponding to the average RR interval of the frame every time, calculating a power of a predetermined frequency band in an RR waveform signal indicating a time change of the calculated average RR interval, and the power Provides a program for executing a step of determining whether or not a specific condition is satisfied and a step of outputting information on the presence or absence of atrial fibrillation according to the determination result.
According to this program, even if the influence of body motion noise is included in a signal capable of measuring an RR interval such as a pulse wave signal and an electrocardiogram waveform signal, atrial fibrillation can be determined from the signal.

The figure explaining the external appearance of the pulse-wave measuring apparatus 1 in embodiment. The figure explaining the structure of the pulse-wave measuring apparatus 1 in embodiment. The figure explaining the functional structure of the atrial fibrillation determination apparatus 100 in embodiment. The figure explaining the frame when performing the frequency analysis of the detection waveform signal L. FIG. The figure explaining the frequency characteristic in the RR space | interval calculation part 112. FIG. The figure explaining the frame when performing the frequency analysis of the RR waveform signal FRR. The figure which shows the determination result by this embodiment. The flowchart of atrial fibrillation determination processing. The figure explaining the determination method of the atrial fibrillation using the electrocardiogram RR interval. The figure explaining the problem of the determination method of atrial fibrillation using the average pulse wave RR interval. The figure which shows the detail of the atrial fibrillation determination process in step S410. The figure which illustrates power waveform signal Pa and variation coefficient signal Sc. The figure which illustrates the power and variation coefficient after a moving average process. The figure which illustrates the relationship between power and a coefficient of variation. The figure which illustrates the result after clustering of the data of FIG.

<Embodiment>
[Overview]

  Conventionally, when determining atrial fibrillation from an electrocardiogram, an RR interval for each beat (referred to as an “electrocardiogram RR interval”) has been used. On the other hand, in this embodiment, atrial fibrillation is determined from the pulse wave. When a pulse wave is used, unlike an electrocardiogram, it may be difficult to accurately specify the RR interval for each beat. Therefore, in the present embodiment, a value indicating the average of RR intervals within a certain period (frame) (referred to as “average pulse wave RR interval”) is used. Here, first, a method for determining atrial fibrillation using the electrocardiogram RR interval will be described. Next, problems when the average pulse wave RR interval is used will be described. Finally, the determination method according to the present embodiment will be described. An outline will be described.

  FIG. 9 is a diagram for explaining a method for determining atrial fibrillation using an electrocardiogram RR interval. FIG. 9 shows a waveform signal indicating fluctuations in the electrocardiogram RR interval. One frame is 480 seconds, and frequency analysis is performed in a band from 0.01 Hz to 0.2 Hz in that frame, and the peak frequency and power are logarithmically converted. It is the graph which expressed. FIG. 9 (a) shows a case where an electrocardiogram RR interval when no atrial fibrillation is developed, and FIG. 9 (b) shows an electrocardiogram RR interval when atrial fibrillation is developed. The case where it is used is shown. The straight line in the figure represents a linear regression line obtained from the plotted data. When the slope β and the correlation coefficient γ of the primary regression line are calculated from these graphs, the following results are obtained.

  In the case where the atrial fibrillation shown in FIG. 9A has not occurred, γ = −0.72 and β = −1.29. In the case where atrial fibrillation shown in FIG. 9B has developed, γ = −0.07 and β = −0.13. Thus, when atrial fibrillation has developed, it becomes clear that the correlation is lost and white noise occurs, and the slope β approaches “0”. Thus, when the electrocardiogram RR interval is used, the presence or absence of atrial fibrillation can be determined from the slope β of the primary regression line and the correlation coefficient γ in the peak frequency and power plot.

  FIG. 10 is a diagram for explaining a problem of the method for determining atrial fibrillation using the average pulse wave RR interval. FIG. 10 shows the waveform signal indicating the fluctuation of the average pulse wave RR interval, with 480 seconds as one frame, in which the frequency analysis is performed in the band from 0.01 Hz to 0.2 Hz, and the peak frequency and power are logarithmically converted. It is a graph expressed as FIG. 10 (a) shows an example in which atrial fibrillation has not developed, and FIG. 10 (b) shows an example in which atrial fibrillation has developed. The straight line in the figure represents a linear regression line obtained from the plotted data.

In the case where atrial fibrillation shown in FIG. 10A has not developed, γ = −0.68 and β = −1.40. In the case where atrial fibrillation shown in FIG. 10B has developed, γ = −0.41 and β = −1.02. Thus, when the average pulse wave RR interval is used, as shown in FIG. 10, there is no significant difference between γ and β depending on the presence or absence of the onset of atrial fibrillation. It is difficult to determine the presence or absence of atrial fibrillation.

  Here, comparing FIGS. 9A and 9B again, it can be seen that the power increases on the high frequency band side when atrial fibrillation occurs. For example, in FIG. 9, when the power is compared in the frequency band near 0.2 Hz, the power when the atrial fibrillation does not develop is “1.59”, and the power when the atrial fibrillation develops is “4”. .97 ". When atrial fibrillation develops, the power in this frequency band increases several times and a significant difference is seen compared to when it does not.

  This increase in power is also observed when the average pulse wave RR interval is used. In FIG. 10, when the power is compared in the frequency band near 0.2 Hz, the power when the atrial fibrillation does not develop is “0.05”, and the power when the atrial fibrillation develops is “0. 30 ". As described above, even when the average pulse wave RR interval is used, the power in this frequency band increases several times when the atrial fibrillation is developed, compared with the case where the atrial fibrillation is not developed, and a significant difference is seen. . In the present embodiment, the presence of atrial fibrillation is determined using this increase in power as one index.

  In this embodiment, a coefficient of variation is used as another indicator of the presence or absence of atrial fibrillation. The variation coefficient is a parameter indicating the degree of variation with respect to the average of the average pulse wave RR interval. When atrial fibrillation develops, irregularities in the RR interval occur. That is, the time interval for each beat becomes irregular. The same applies to the average pulse wave RR interval, and an irregular state (variation with respect to the average) can be used as an index of atrial fibrillation. In the present embodiment, the presence or absence of atrial fibrillation is determined using power and the coefficient of variation as indices. Hereinafter, the apparatus configuration and operation of this embodiment will be described in detail.

[Configuration of Pulse Wave Measuring Device 1]
Drawing 1 is a figure explaining the appearance of pulse wave measuring device 1 in an embodiment. As shown in FIG. 1A, a pulse wave measuring device 1 according to an embodiment of the present invention is a device main body 10 that is worn like a wristwatch on a wrist portion (arm) of a user's 1000 hand to be detected. And a pulse wave detector 20 that is attached to the detection site and detects a pulse wave. The apparatus main body 10 and the pulse wave detection unit 20 are connected by a cable 30. The cable 30 supplies a pulse wave signal (hereinafter referred to as a detection waveform signal L) output from the pulse wave detection unit 20 to the apparatus main body 10, and supplies power from the apparatus main body 10 to the pulse wave detection unit 20.

  A wristband 50 is attached to the apparatus main body 10. The apparatus main body 10 is attached to the arm by the wristband 50 being wound around the user's arm. The apparatus main body 10 is provided with an operation unit 14 and a display unit 15. The operation unit 14 is an operator such as a button switch for the user to input a function selection instruction or the like to the pulse wave measurement device 1. The operation unit 14 may include a touch sensor provided on the display unit 15. The display unit 15 is a display device such as a liquid crystal display or an organic EL display.

  As shown in FIG. 1B, in this example, the detection site where the pulse wave detection unit 20 is worn is a part from the base of the index finger to the second finger joint in the hand 1000. However, any site may be used as long as it can detect a pulse wave. The pulse wave detector 20 is attached to the detection site by being fixed by the fixing band 40. At this time, the fixed band 40 is in a state of covering the pulse wave detection unit 20 and is configured to shield the light from the outside of the fixed band 40 from reaching the light receiving unit of the pulse wave detection unit 20.

  The pulse wave detector 20 detects a pulse wave as follows and outputs a detection waveform signal L indicating the detection result. The pulse wave detection unit 20 includes a light emitting unit (for example, a green LED (Light Emitting Diode)) and a light receiving unit. The pulse wave detection unit 20 emits light corresponding to the power supplied from the apparatus main body 10 via the cable 30 from the light emitting unit. The pulse wave detection unit 20 receives light reflected by hemoglobin in the capillary blood vessel from the light emission unit, and receives a signal corresponding to the received light level as a detection waveform signal L via the cable 30. It is supplied to the apparatus main body 10.

  FIG. 2 is a diagram illustrating the configuration of the pulse wave measurement device 1 according to the embodiment. The pulse wave measuring apparatus 1 includes a CPU (Central Processing Unit) 11, a RAM (Random Access Memory) 12, a ROM (Read Only Memory) 13, an operation unit 14, a display unit 15, an oscillation circuit 16, a timing circuit 17, and an A / D. The apparatus main body 10 having a conversion circuit 18 and an amplification circuit 19 and a pulse wave detection unit 20 are included. The components other than the amplifier circuit 19 and the pulse wave detector 20 are connected via a bus.

  The CPU 11 controls each unit and transfers data according to a control program stored in the ROM 13. The RAM 12 temporarily stores biological information such as the detected waveform signal L and various data generated during execution of the control program in the CPU 11. By executing the control program, the CPU 11 realizes an atrial fibrillation determination function and causes the pulse wave measurement device 1 to function as an atrial fibrillation determination device. The CPU 11 may realize various functions other than the atrial fibrillation determination function by executing a control program. These functions may be realized by, for example, the user operating the operation unit 14.

As described above, the operation unit 14 includes a button switch for inputting a user instruction to the pulse wave measuring device 1. When operated by the user, the operation unit 14 outputs an operation signal indicating the operation content to the CPU 11.
As described above, the display unit 15 includes a display device such as a liquid crystal display or an organic EL display, and the display content is controlled by the CPU 11. The display contents are various images showing time display, various menu screens, pulse wave measurement results, atrial fibrillation determination results, and the like.
The oscillation circuit 16 supplies the CPU 11 with a clock signal that is the basis of control.
The timer circuit 17 measures time under the control of the CPU 11.

The amplification circuit 19 amplifies the detection waveform signal L supplied from the pulse wave detection unit 20 via the cable 30. The gain at the time of amplification is set by the control of the CPU 11.
The A / D conversion circuit 18 converts the detected waveform signal L of the analog signal amplified by the amplification circuit 19 into a digital signal. In this example, the sampling frequency is 100 Hz, which is sufficiently higher than the RR interval obtained from the pulse wave. In this example, quantization is performed with 10 bits. Note that the sampling frequency and the quantization bit may be set to different values depending on the required accuracy.
Subsequently, the functional configuration (atrial fibrillation determination function) of the atrial fibrillation determination apparatus realized by the CPU 11 will be described.

[Function configuration]
FIG. 3 is a diagram illustrating a functional configuration of the atrial fibrillation determination device 100 according to the embodiment. The atrial fibrillation determination device 100 includes a noise reduction unit 111, an RR interval calculation unit 112, a power calculation unit 113, a determination unit 114, a display control unit 115, and a variation coefficient calculation unit 116, and serves as a storage area for various data. This is realized by each functional configuration of the detection waveform signal storage area 121, the RR waveform signal storage area 122, the power waveform signal storage area 123, and the variation coefficient waveform storage area 124.

The detection waveform signal storage area 121 is an area provided on the RAM 12 in which the detection waveform signal L converted into a digital signal by the A / D conversion circuit 18 is stored.
The noise reduction unit 111 performs a filtering process for reducing body motion noise components other than the frequency band corresponding to the RR interval from the detection waveform signal L stored in the detection waveform signal storage area 121 and outputs the result. The filter process is, for example, a process using a high pass filter, a band pass filter, an adaptive filter, or the like. The detected waveform signal L in which the body movement noise component is reduced in the noise reduction unit 111 may be temporarily stored in the RAM 12. The detection waveform signal storage area 121 and the noise reduction unit 111 function as an acquisition unit that acquires the detection waveform signal L used for frequency analysis in the RR interval calculation unit 112.

  In this process, the body motion noise component is reduced, and the influence thereof is reduced from the detected waveform signal L. However, the precise atrium in the technique shown as the background art (Patent Document 1, Non-Patent Document 1). It is not possible to measure an accurate RR interval to the extent that fibrillation can be determined.

  The RR interval calculation unit 112 cuts out a frame for each sampling of the detected waveform signal L from which the body motion noise component has been reduced in the noise reduction unit 111, and performs frequency analysis in a short time (STFT (Short-Time Fourier transform) analysis). To calculate the frequency spectrum. Then, the RR interval calculation unit 112 calculates a parameter corresponding to the RR interval for each frame based on the calculated frequency spectrum, and an RR waveform signal FRR indicating a time change of the parameter is an area provided on the RAM 12. Is stored in the RR waveform signal storage area 122. Note that the RR waveform signal FRR is a set of data indicating changes with time of this parameter.

  In this example, the calculated parameter is a value (average pulse wave RR interval) indicating an average of the RR intervals in the frame, and is, for example, a frequency that is the maximum peak of the frequency spectrum. Therefore, the RR waveform signal FRR indicates a time change of the average pulse wave RR interval. Even if the body motion noise is not completely removed by the noise reduction unit 111, the influence of the body motion noise included in the RR waveform signal FRR can be significantly reduced by the processing in the RR interval calculation unit 112.

  FIG. 4 is a diagram for explaining a frame when performing frequency analysis of the detected waveform signal L. The waveform shown in FIG. 4 is an example of the waveform of the detected waveform signal L. As shown in FIG. 4, the time of each frame is 4 seconds in this example, and sampling is performed every second to perform frequency analysis. That is, each frame is set to be shifted by 1 second and overlaps with the next frame for 3 seconds. Thus, since the sampling timing and the frame are set, the average pulse wave RR interval is an average value for 4 seconds of the RR interval, and the RR waveform signal FRR indicates a change in the average pulse wave RR interval per second. It will be a thing.

  FIG. 5 is a diagram for explaining frequency characteristics in the RR interval calculation unit 112. In the RR interval calculation unit 112, performing the frequency analysis with the frame set as described above is equivalent to superimposing the frequency characteristics in the moving average process. In the frequency characteristics shown in FIG. 5, valleys occur at a frequency of 0.25 Hz corresponding to 4 seconds of the frame time and an integer multiple thereof, and as a general tendency to connect the peaks, the level increases as the frequency increases. The frequency characteristic becomes low, that is, has a negative slope. This slope becomes steeper as the frame time increases. On the other hand, when the frame time is shortened, the inclination approaches “0”, but the body motion noise component remains in the detected waveform signal L. Therefore, the frame time is 1 to 5 seconds, preferably 2 to 4 seconds.

  The power calculation unit 113 performs a short-time frequency analysis (STFT analysis) on the RR waveform signal FRR stored in the RR waveform signal storage area 122, and based on the obtained frequency spectrum, a part of frequency bands (hereinafter referred to as a frequency band). , Calculated frequency band) (hereinafter referred to as band power). The power calculation unit 113 stores the power waveform signal Pa indicating the time variation of the calculated band power in the power waveform signal storage area 123 of the area provided on the RAM 12. Note that the power waveform signal Pa is a collection of data indicating a change in band power with time.

  FIG. 6 is a diagram for explaining a frame when performing frequency analysis of the RR waveform signal FRR. The waveform shown in FIG. 6 is an example of the waveform of the RR waveform signal FRR. As shown in FIG. 6, the time of each frame is 120 seconds in this example, and sampling is performed every 60 seconds for frequency analysis. That is, each frame is set so as to be shifted by 60 seconds and overlaps with the next frame for 60 seconds.

  In addition, the above-described calculated frequency band in which the band power is calculated in the power calculation unit 113 is determined in advance, and in this example, is a band from 0.25 Hz to 0.5 Hz. This is determined as between two valleys (0.25 Hz and 0.5 Hz valleys) of the frequency characteristics shown in FIG. This is because the power in the valley portion is suppressed, so it hardly contributes to the determination of the presence or absence of atrial fibrillation, so the calculated frequency band is determined around the portion that contributes to the determination of the presence or absence of atrial fibrillation. Yes. That is, the range of the calculated frequency band, such as the band from 0.3 Hz to 0.45 Hz, is further narrowed so that only the mountain part is included by excluding the valley part of the frequency characteristics. May be set.

  Here, the lowest frequency (lower limit) and the highest frequency (upper limit) of the calculated frequency band are the frequency characteristics in the RR interval calculation unit 112, that is, the frame time used in the frequency analysis in the RR interval calculation unit 112 in this example. It was decided accordingly. On the other hand, one or both of the upper and lower limit frequencies may not necessarily be determined according to the frame time.

As shown in FIGS. 9 and 10, the lowest frequency in the calculated frequency band is 0.1 Hz or higher, preferably 0.2 Hz or higher, in which the power change becomes clear. At this time, as described above, it is more desirable that the minimum frequency is equal to or greater than the reciprocal of the frame time used in the frequency analysis in the RR interval calculation unit 112.
The maximum frequency in the calculated frequency band is preferably less than or equal to ½ of the sampling frequency of the frequency analysis in the RR interval calculation unit 112 in consideration of the influence of the Nyquist frequency. At this time, as described above, it is more desirable that the maximum frequency is not more than twice the reciprocal of the frame time used in the frequency analysis in the RR interval calculation unit 112.

Returning to FIG. 3, the description will be continued. The variation coefficient calculation unit 116 calculates the variation coefficient CVRR from the RR waveform signal FRR (average pulse wave RR interval) stored in the RR waveform signal storage area 122 according to the following equation (1).
CVRR = σRR / aveRR (1)
Note that σRR and aveRR respectively indicate the standard deviation and average value of the average pulse wave RR interval in one frame period. That is, the variation coefficient CVRR is a parameter indicating the degree of variation with respect to the average. The variation coefficient calculation unit 116 stores the calculated variation coefficient CVRR in the variation coefficient waveform storage area 124. Since the variation coefficient CVRR is calculated for each frame, the variation coefficient waveform storage area 124 stores a signal indicating the time variation of the variation coefficient CVRR (referred to as “variation coefficient signal Sc”). The variation coefficient signal Sc is a set of data indicating the change with time of the variation coefficient CVRR.

  The determination unit 114 determines whether or not a specific determination condition is satisfied with respect to the power waveform signal Pa stored in the power waveform signal storage area 123 and the variation coefficient signal Sc stored in the variation coefficient waveform storage area 124. Output information according to the result. Specific determination conditions will be described later.

If the determination unit 114 determines that it is atrial fibrillation, the determination unit 114 outputs information indicating the determination result to the display control unit 115. The information output from the determination unit 114 may be information regarding the presence or absence of atrial fibrillation, such as information indicating determination of atrial fibrillation, for example. The information display control unit 115 controls the display content of the display unit 15 based on the information output from the determination unit 114, and displays an image indicating that it is determined as atrial fibrillation. The user can confirm whether or not it is atrial fibrillation by viewing this display content. The display content may be a display indicating the determination result of atrial fibrillation in real time or a display indicating a period determined to be atrial fibrillation.
The functional configuration of the atrial fibrillation determination device 100 has been described above. Next, the operation (atrial fibrillation determination process) of the atrial fibrillation determination apparatus 100 will be described with reference to FIG.

[Atrial fibrillation determination processing]
FIG. 8 is a flowchart illustrating atrial fibrillation determination processing in the embodiment. First, when the user operates the operation unit 14 and an instruction to start the determination process of atrial fibrillation is input, the CPU 11 starts the flow shown in FIG. The CPU 11 determines whether or not the user operates the operation unit 14 to input an instruction to end the determination process (step S110). CPU11 complete | finishes the determination process of atrial fibrillation, when the instruction | indication which complete | finishes the determination process is input (step S110; Yes).

  When the instruction to end the determination process is not input (step S110; No), the CPU 11 causes the pulse wave detector 20 to detect the pulse wave and measure the detected waveform signal L (step S120), thereby reducing noise. The body motion noise reduction process is performed by the unit 111 (step S130). At this time, the CPU 11 stores the detection waveform signal L in the detection waveform signal storage area 121 of the RAM 12, but may store the detection waveform signal L subjected to the body movement noise reduction processing.

  The CPU 11 determines whether or not the waveform signal subjected to the body movement noise reduction process is stored in the RAM 12 for one frame (step S140). If one frame has not been accumulated (step S140; No), the CPU 110 returns to step S110 and continues processing. On the other hand, when one frame is accumulated (step S140; Yes), the CPU 11 calculates the average pulse wave RR interval by the RR interval calculation unit 112 (step S210).

The CPU 11 stores the average pulse wave RR interval calculated by the RR interval calculation unit 112 in the RR waveform signal storage area 122 (step S220). The time change of the average pulse wave RR interval stored in this storage area becomes the RR waveform signal FRR.
The CPU 11 determines whether or not one frame of the RR waveform signal FRR stored in the RR waveform signal storage area 122 has been accumulated (step S230). When one frame is not accumulated (step S230; No), the CPU 110 returns to step S110 and continues the process. On the other hand, when one frame is accumulated (step S230; Yes), the CPU 11 calculates the band power by the power calculation unit 113 (step S310).

  The CPU 11 stores the band power calculated by the power calculation unit 113 in the power waveform signal storage area 123 (step S320). The time change of the band power stored in this storage area becomes the power waveform signal Pa.

  The CPU 11 calculates a variation coefficient by the variation coefficient calculation unit 116 (step S330). The CPU 11 stores the variation coefficient calculated by the variation coefficient calculation unit 116 in the variation coefficient waveform storage area 124 (step S340).

  The CPU 11 refers to the stored power waveform signal Pa and variation coefficient signal Sc, and the determination unit 114 determines whether or not the power waveform signal Pa and variation coefficient signal Sc satisfy a predetermined determination condition (step S410). ).

  FIG. 11 is a diagram showing details of the atrial fibrillation determination process in step S410. In step S500, the CPU 11 reads the power waveform signal Pa and the variation coefficient signal Sc from the RAM 12.

FIG. 12 is a diagram illustrating the power waveform signal Pa and the variation coefficient signal Sc. FIG. 12 shows a power waveform signal Pa [msec ² ] and a variation coefficient signal Sc [%] obtained from a pulse wave signal measured for 24 hours for a certain patient. The patient developed atrial fibrillation during the measurement period.

  Refer to FIG. 11 again. In step S501, the CPU 11 performs a moving average process on the power waveform signal Pa and the variation coefficient signal Sc. The moving average process is performed to smooth out fine fluctuations (variations in a short time) for each of the power and the coefficient of variation CVRR. In this example, moving average processing is performed using 20 points of data (that is, data obtained from a 20-minute measurement of a pulse wave).

  FIG. 13 is a diagram illustrating the power waveform signal Pa and the variation coefficient signal Sc after moving average processing. Small fluctuations are smoothed out by moving average processing. Hereinafter, the data after moving average processing is handled as data indicating power and a variation coefficient at a certain time. Since measurement is performed every 60 seconds, data of 1440 points can be obtained by measurement for 24 hours.

  Refer to FIG. 11 again. In step S502, the CPU 11 clusters these data into two clusters by a predetermined algorithm (for example, k-means method widely known as a clustering method).

FIG. 14 is a diagram illustrating the relationship between power and coefficient of variation. The vertical axis represents power [msec ² ], and the horizontal axis represents the coefficient of variation CVRR [%]. As already explained, at the onset of atrial fibrillation, the power and coefficient of variation are relatively high compared to normal. Therefore, the plot near the upper right in FIG. 14 is considered to correspond to the data measured when atrial fibrillation has developed. In this embodiment, data is divided into two clusters by a clustering method, and the presence or absence of atrial fibrillation is determined based on the positional relationship between the two clusters in the coefficient of variation-power space.

  FIG. 15 is a diagram illustrating the result after clustering of the data of FIG. Thus, the data is divided into two clusters by a clustering method (in this example, the k-means method). These two clusters are referred to as cluster C0 and cluster C1, respectively. The cluster C0 is a data group having a relatively high coefficient of variation and high power, and the cluster C1 is a data group having a low coefficient of variation and low power. The data of the cluster C0 is represented by a circle (◯), and the cluster C1 is represented by a triangle (Δ). Further, according to the k-means method, the coordinates of the center of gravity of each cluster in the variation coefficient-power space are calculated. FIG. 15 also shows the positions of the centers of gravity of the clusters C0 and C1.

  Refer to FIG. 11 again. In step S503, the CPU 11 determines whether the position of the center of gravity of the cluster C0 is within a predetermined range, for example, a range of ± 30%, with reference to the position of the center of gravity of the cluster C1. When it is determined that the position of the center of gravity of the cluster C0 is outside the range of ± 30% from the position of the center of gravity of the cluster C1 (step S503; NO), the CPU 11 shifts the processing to step S504. When it is determined that the position of the center of gravity of the cluster C0 is within a range of ± 30% from the position of the center of gravity of the cluster C1 (step S503; YES), the CPU 11 shifts the processing to step S505.

  In step S504, the CPU 11 determines that the cluster C0 is data at the onset of atrial fibrillation.

  When the position of the center of gravity of the cluster C0 is within ± 30% of the position of the center of gravity of the cluster C1, it is determined that the data cannot be separated into two clusters. In this case, as a possibility, a case where atrial fibrillation has not developed during the whole measurement period and a case where atrial fibrillation continues to develop during the whole measurement period can be considered. In this case, the presence or absence of atrial fibrillation is determined based on the values of power and variation coefficient. In step S505 and subsequent steps, a process for this is performed.

  In step S505, the CPU 11 calculates coordinates (hereinafter referred to as “average centroid coordinates”) of an average position (hereinafter referred to as “average centroid coordinates”) between the centroid of the cluster C0 and the centroid of the cluster C1. The average centroid is, for example, a simple average of the centroid of the cluster C0 and the centroid of the cluster C1 (that is, the midpoint between the centroid of the cluster C0 and the centroid of the cluster C1). Alternatively, the average centroid may be a weighted centroid based on the number of data points of the centroid of the cluster C0 and the centroid of the cluster C1 (that is, the centroid of all measurement points).

  In step S506, the CPU 11 determines whether the average barycentric coordinates are within a predetermined range (for example, a variation coefficient of 10.0 or more and power of 0.5 or more). When it is determined that the average barycentric coordinates are within the predetermined range (step S506; YES), the CPU 11 determines that atrial fibrillation has occurred in all measurement periods (step S507). When it is determined that the average barycentric coordinates are not within the predetermined range (step S506; NO), the CPU 11 determines that atrial fibrillation has not occurred in the entire measurement period (step S508).

  Refer to FIG. 8 again. If it is determined that atrial fibrillation has not occurred (step S410; No), the CPU 11 returns to step 110 and continues processing. On the other hand, if it is determined that atrial fibrillation has occurred (step S410; Yes), the CPU 11 causes the display control unit 115 to display a determination result indicating that the atrial fibrillation is occurring (step S420). ), The process returns to step S110 and continues.

Note that the CPU 11 may repeatedly execute the processing from step S110 to step S140 regardless of the determination in step S140. In this case, whenever it becomes Yes in step S140, you may make it perform the process after step S210 in parallel with the process of step S110 to step S140. At this time, in the case of No in step S230 or in the case of No in step S410, the processes after step S210 executed in parallel may be terminated.
The above is the description of the atrial fibrillation determination process.

  FIG. 7 is a diagram illustrating a determination result according to the present embodiment. FIG. 7 shows the result of analyzing the signal shown in FIG. The period in which it was determined that atrial fibrillation has developed by electrocardiogram analysis using a Holter electrocardiograph is also illustrated. In the figure, the portion indicated by the bold line is the period in which it is determined that atrial fibrillation has developed according to this embodiment, and the hatched portion is determined to have atrial fibrillation developed by electrocardiogram analysis using a Holter electrocardiograph Period. In the present embodiment, it is determined that atrial fibrillation has occurred with respect to the period in which it is determined by the Holter electrocardiograph that atrial fibrillation has occurred. In the present embodiment, some noise is detected as atrial fibrillation. For example, when it is determined that atrial fibrillation is shorter than a predetermined threshold, the determination result is rejected (that is, If it is continuously determined that atrial fibrillation is longer than the threshold, a determination result indicating atrial fibrillation may be employed).

  As described above, in the pulse wave measuring device 1 according to the embodiment of the present invention, the influence of body motion noise is reduced by measuring the average pulse wave RR interval instead of the pulse wave RR interval for each beat, and the atrium. Fibrosis can be determined.

<Modification>
As mentioned above, although embodiment of this invention was described, this invention can be implemented in various aspects as follows.
[Modification 1]
In the embodiment described above, the detection waveform signal L is a signal indicating a result of detecting a pulse wave in the pulse wave detection unit 20, but may be a waveform signal obtained as a result of detecting an electrocardiogram. That is, any waveform signal that can acquire a parameter corresponding to the RR interval may be used.

[Modification 2]
In the above-described embodiment, the noise reduction unit 111 is provided as a functional configuration of the atrial fibrillation determination device 100. However, the noise reduction unit 111 is not necessarily provided. In this case, the RR interval calculation unit 112 may acquire the detection waveform signal L for performing frequency analysis from the detection waveform signal storage area 121.

[Modification 3]
In the above-described embodiment, the atrial fibrillation determination device 100 is realized in the pulse wave measurement device 1, but may be realized in an information processing device such as a personal computer. In this case, the information processing apparatus may acquire the detection waveform signal L measured in advance from the external device and store it in the detection waveform signal storage area 121. Then, the information processing apparatus may analyze the detected waveform signal L by atrial fibrillation determination processing to determine the presence or absence of atrial fibrillation.

[Modification 4]
In the above-described embodiment, the apparatus main body 10 and the pulse wave detection unit 20 are connected by wire with the cable 30, but may be connected wirelessly. In this case, the apparatus main body 10 and the pulse wave detection unit 20 wirelessly communicate various signals such as a control signal necessary for controlling the pulse wave detection unit 20 and a detection waveform signal L generated in the pulse wave detection unit 20. You can communicate with each other. Moreover, what is necessary is just to make it have the structure of the battery etc. which can supply electric power in each of the apparatus main body 10 and the pulse wave detection part 20. FIG.

[Modification 5]
In the embodiment described above, the determination result of atrial fibrillation is displayed on the display unit 15 and notified to the user, but may be notified by sound, vibration, or the like. For example, when notifying the user with sound, a sound control unit for controlling the sound emission content of the speaker may be provided based on information from the speaker and the determination unit 114. When notifying the user by vibration, a vibration control unit that controls the vibration content of the vibration actuator based on the information from the vibration actuator and the determination unit 114 may be provided. Thus, the display control unit 115 and the display unit 15 in the embodiment can also be conceptualized as a notification unit that notifies the user according to the determination result of atrial fibrillation.

[Modification 6]
Various parameters described in the embodiment, for example, threshold for cluster separation (± 30%), a predetermined range with respect to the average barycentric coordinate (variation coefficient 10.0 or more and power 0.5 or more), data of moving average processing The score (20 points) and the frame period (120 seconds) are examples, and the values of these parameters are not limited thereto. Further, the clustering algorithm is not limited to the k-means method. The data group may be separated into two clusters by an algorithm other than the k-means method. Moreover, the specific determination method of the presence or absence of atrial fibrillation is not limited to what was demonstrated in FIG. For example, the presence or absence of atrial fibrillation may be determined by a method other than that described in FIG. 11, such as comparing at least one of power and a coefficient of variation with a threshold value.

[Modification 7]
The control program in the above-described embodiment is provided in a state stored in a computer-readable recording medium such as a magnetic recording medium (magnetic tape, magnetic disk, etc.), an optical recording medium (optical disk, etc.), a magneto-optical recording medium, or a semiconductor memory. Can do. Moreover, the pulse wave measuring apparatus 1 may download each program via a network.

DESCRIPTION OF SYMBOLS 1 ... Pulse wave measuring device, 10 ... Apparatus main body, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... Operation part, 15 ... Display part, 16 ... Oscillation circuit, 17 ... Time-counting circuit, 18 ... A / D conversion Circuit: 19 ... Amplifier circuit, 20 ... Pulse wave detector, 30 ... Cable, 40 ... Fixed band, 50 ... Wristband, 100 ... Atrial fibrillation determination device, 111 ... Noise reduction unit, 112 ... RR interval calculation unit, 113 DESCRIPTION OF SYMBOLS ... Power calculation part, 114 ... Determination part, 115 ... Display control part, 121 ... Detection waveform signal storage area, 122 ... RR waveform signal storage area, 123 ... Power waveform signal storage area, 1000 ... Hand

Claims (11)

An acquisition unit for acquiring a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave;
An RR interval calculation unit that calculates a parameter corresponding to the average RR interval of each frame based on the spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal;
A power calculation unit that calculates power in a predetermined frequency band in the RR waveform signal indicating the time change of the average RR interval calculated by the RR interval calculation unit;
An atrial fibrillation determination apparatus comprising: a determination unit that determines whether or not the power satisfies a specific condition and outputs information on the presence or absence of atrial fibrillation according to a determination result. A variation coefficient calculation unit that calculates a variation coefficient of the average RR interval in the RR waveform signal;
The said determination part determines whether the set of the said power and the said variation coefficient satisfy | fills the said specific conditions, and outputs the information regarding the presence or absence of atrial fibrillation according to the determination result. Atrial fibrillation determination device. The determination unit divides a plurality of sets of the power and the variation coefficient obtained in a plurality of frames into a first cluster having a relatively high power and a high variation coefficient and a second cluster having a low power and a low variation coefficient,
The presence or absence of atrial fibrillation is determined based on the positional relationship between the first centroid of the first cluster and the second centroid of the second cluster in a coefficient of variation-power space. Atrial fibrillation determination device. When the first center of gravity and the second center of gravity are separated by a predetermined first threshold or more, the determination unit determines that the first cluster is in a state in which atrial fibrillation has occurred. The atrial fibrillation determination device according to claim 3. In a case where the first centroid and the second centroid are not separated from each other by the first threshold value, an average centroid between the first centroid and the second centroid is a power having a predetermined second threshold value or more. When the coefficient of variation is equal to or greater than a third threshold, the determination unit determines that the first cluster and the second cluster are in a state in which atrial fibrillation has developed. 4. The atrial fibrillation determination device according to 4. In a case where the first centroid and the second centroid are not separated from each other by the first threshold value, an average centroid between the first centroid and the second centroid is a power having a predetermined second threshold value or more. And determining that the first cluster and the second cluster are in a state in which atrial fibrillation has not occurred when at least one of the coefficient of variation equal to or greater than the third threshold value is not included. The atrial fibrillation determination apparatus according to claim 5. The atrial fibrillation determination device according to any one of claims 1 to 6, wherein the lowest frequency of the frequency band is equal to or greater than the reciprocal of the time of the frame. A detection unit for detecting the electrocardiogram or the pulse wave of the person to be detected;
A notification unit for notifying a user based on the information output by the determination unit;
The atrial fibrillation determination apparatus according to any one of claims 1 to 7, wherein the acquisition unit acquires a detection waveform signal obtained according to the detected result. 9. The atrial cell according to claim 8, wherein the acquisition unit includes a noise reduction unit that performs a filtering process to reduce a body movement noise component on the detected waveform signal and outputs the detected waveform signal as the detected waveform signal. Motion determination device. Obtaining a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave;
Calculating a parameter corresponding to the average RR interval of each frame based on the spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal;
Calculating power of a predetermined frequency band in an RR waveform signal indicating a time change of the calculated average RR interval;
Determining whether the power satisfies a specific condition;
Outputting information on the presence or absence of atrial fibrillation according to the determination result. On the computer,
Obtaining a detection waveform signal indicating a detection result of an electrocardiogram or a pulse wave;
Calculating a parameter corresponding to the average RR interval of each frame based on the spectrum of each frame obtained by frequency analysis of the acquired detection waveform signal;
Calculating power of a predetermined frequency band in an RR waveform signal indicating a time change of the calculated average RR interval;
Determining whether the power satisfies a specific condition;
And a step of outputting information on the presence or absence of atrial fibrillation according to the determination result.

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