JP6535575B2 - Physiological index detection device, physiological index detection method, physiological index detection processing program - Google Patents

Description

  Embodiments of the present invention relate to a physiological index detection device, a physiological index detection method, and a physiological index detection processing program.

  A biological signal acquired using a wearable device such as a Holter electrocardiograph may be mixed with various noises due to body movement or static electricity. For this reason, it is necessary to perform feature amount extraction and analysis of a biological signal on the assumption that noise is mixed.

FIG. 4 is a diagram showing an example of an electrocardiogram.
In the case of a biological signal of a circulatory system such as an electrocardiogram, a signal synchronized with the contraction of the ventricle is periodically observed. In the case of electrocardiogram, a QRS group (which may be hereinafter referred to as an R wave for convenience) shown in FIG. 4A corresponds to the signal. As shown in FIG. 4 (b) and FIG. 4 (c), with regard to the electrocardiogram, RRI (RR Interval (e.g. http://hclab.sakura.ne.jp/stress_novice_hartrate.) Which is the interval between adjacent R waves. Since the heart rate is determined by the reciprocal of html), it is important to detect R-waves for purposes other than medical treatment.

FIG. 5 is a view showing an example of a pulse wave.
In addition, as shown in FIG. 5, as for the pulse wave which is a biological signal of the circulatory system as in the case of the electrocardiogram, PPI which is the interval between adjacent P waves (because the pulse rate is determined from the reciprocal of PP Interval (for example, See JP 2009-82292 A)) and P wave detection is also important for purposes other than medical treatment.

Nakai et.al, Noise Tolerant QRS Detection using Template Matching with Short-Term Autocorrelation, IEEE EMBC 2014, pp. 34-37, 2014.

  As a simple method of detecting a physiological index such as R wave (electrocardiogram) or P wave (pulse wave), a method using a threshold can be considered. However, since the size of the biological signal measured by the wearable device varies depending on the device configuration, the user, and the environment, depending on the setting of the threshold, there is a risk of causing missed detection, excessive detection, or false detection of a target physiological index.

  FIG. 6 is a diagram showing an example in which excess detection, detection failure, and false detection occur in the electrocardiogram. In FIG. 3, A indicates a threshold value, W1 indicates a portion of overdetection, W2 indicates a portion of detection failure, and W3 indicates a portion of false detection.

As another method, a method using autocorrelation of a biological signal can be considered.
However, if the template window and the width of the search window based on the template window are set so as to include all P waves to T waves that are signals related to expansion and contraction of the heart, noise caused by noise etc. There is a possibility that the correlation coefficient is low and the target physiological index can not be detected.

  On the other hand, if the width of each window described above is set to the same level as the QRS complex (electrocardiogram) or P wave (pulse wave), a case in which a similar biosignal such as myoelectric potential is erroneously detected as a target physiological index Can occur.

  An object of the present invention is to provide a physiological index detection device, a physiological index detection method, and a physiological index detection processing program that can accurately detect a physiological index without using a fixed threshold.

In order to achieve the above object, an aspect of a physiological index detection apparatus according to an embodiment of the present invention calculates a waveform of a template in the biological signal based on known characteristics of a physiological index to be detected from the biological signal. First calculating means, a value indicating the degree of similarity between the waveform of the biological signal within a plurality of predetermined periods and the waveform of the template calculated, and the magnitude of the biological signal within the plurality of predetermined periods Second calculating means for calculating first and second statistical values indicating variation in height , and the physiology to be detected when the value indicating the calculated height of the similarity exceeds a predetermined value detecting means for detecting the candidates of the index from the biological signal at said plurality of predetermined periods, the first statistics of the candidate detected by the detecting means, one or more of n past biological signal And a value obtained by multiplying the average value of the first statistical value calculated above for the physiological index contained therein by a factor larger than 0 and smaller than 1 and included in the n-1 past biological signals The second statistical value calculated for the physiological index and the detected candidate is one or more arbitrary positive values with respect to the second statistical value calculated for the physiological index included in the n past biological signals when the real condition is satisfied with that magnification it is less than a value obtained by multiplying the, to provide a device and a determining means for determining a candidate the detected as physiological index to be the detection target.

An aspect of a physiological index detection method according to an embodiment of the present invention is a method applied to a physiological index detection device, and a template in the biological signal based on a known feature of the physiological index to be detected from the biological signal. A first calculation step of calculating a waveform of the value, a value indicating the degree of similarity between the waveform of the biological signal within a plurality of predetermined periods and the waveform of the template calculated, and the plurality of predetermined periods within the predetermined period A second calculation step of calculating first and second statistical values indicating variations in magnitude of the biological signal, and the value indicating the calculated height of the similarity exceeds a predetermined value ; a detection step of detecting a candidate of physiological indices to be detected from the biological signal at said plurality of predetermined periods, the first statistic of the detected candidate, one or more of the n A value obtained by multiplying the average value of the first statistical value calculated as described above for the physiological index included in the last biological signal by a factor larger than 0 and less than 1; The second statistical value calculated for the physiological index included in the signal and the detected candidate is one or more with respect to the second statistical value calculated for the physiological index included in the n past biological signals when any positive real numbers satisfying the possible magnification is less than a value obtained by multiplying a, to provide a method and a determining step of determining a candidate the detected as physiological index to be the detection target.

  According to the present invention, it is possible to accurately detect a physiological index without using a fixed threshold.

The figure which shows the structural example of the physiological index detection system in embodiment of this invention. The flowchart which shows an example of the processing operation of the physiological index detection system in the embodiment of the present invention. The figure for demonstrating evaluation of the feature-value of R wave candidate by the physiological index detection system in embodiment of this invention. The figure which shows an example of an electrocardiogram. The figure which shows an example of a pulse wave. The figure which shows an example which causes excess detection, a detection omission, and a misdetection in an electrocardiogram.

Hereinafter, an embodiment according to the present invention will be described.
In the present invention, “a biological signal in which a similar waveform repeatedly appears” like an electrocardiogram is an object of measurement. The range which the value of the feature value obtained from the biosignal having the feature can take is roughly known medically and physiologically.

  Further, in the present invention, in addition to the waveform shape of the biological signal captured by autocorrelation, the magnitude of the waveform is included in the evaluation target. For candidate data detected based on the autocorrelation value, evaluating the upper and lower limits of the waveform size of the candidate data makes it possible to set the search window width to the same degree as the physiological index, which is similar Reduce false detection of shape.

FIG. 1 is a diagram showing a configuration example of a physiological index detection system according to an embodiment of the present invention.
The physiological index detection system includes a physiological index detection device 20 and a biological signal measurement device 30. The physiological index detecting device 20 includes a data receiving unit 10, a template calculating unit 11, a feature amount calculating unit 12, a physiological index detecting unit 13, a physiological index for evaluation recording unit 14, and a biological signal analysis processing unit 15.

  The data receiving unit 10 receives the biological signal detected by the biological signal measuring device 30. The biological signal received by the data reception unit 10 may be subjected to preprocessing such as filtering.

  The template calculation unit 11 calculates a waveform serving as a template based on known characteristics of the physiological index to be detected. The template is used to calculate the correlation coefficient (hereinafter also referred to as a correlation value), which is one of the feature amounts in the biological signal, in the feature amount calculation unit 12.

  The feature amount calculation unit 12 calculates a feature amount of the biological signal based on the waveform of the template calculated by the template calculation unit 11 and the input data of the biological signal, and sends it to the physiological index detection unit 13.

The physiological index detection unit 13 detects a physiological index based on the information of the feature amount received from the feature amount calculation unit 12.
The evaluation physiological index recording unit 14 is a storage device such as a non-volatile memory, for example, and holds the physiological index detected by the physiological index detection unit 13 for a certain period. The physiological index thus held is used as past correct data for detection by the physiological index detection unit 13 after the next time.
The biological signal analysis processing unit 15 performs predetermined analysis processing on the physiological index detected by the physiological index detection unit 13 and displays the analysis result on a display device (not shown).

Hereinafter, an example in which the present invention is applied to R wave detection of an electrocardiogram will be described.
<Characteristics of electrocardiogram>
The maximum duration of the QRS complex in healthy subjects is less than or equal to 0.10 [sec]. In the non-patent document 1 described above, the heart rate of a healthy person is 40 to 240 [bpm] (ie, the QRS group is measured once in 0.25 to 1.5 [sec]).
If the QRS complex can not be observed for 3.0 [sec] in the electrocardiogram, it is considered as a sinus arrest (see: http://nurse-senka.jp/contents/press/215681/).

  The heart rate of an athlete or the like who has a so-called "sports heart" is considered normal even if it is lower than 40 bpm. Since the Guinness record of Lowest-heart-rate is 27 [bpm], it is considered that the QRS group is measured in the electrocardiogram at least once every 2.3 [sec].

For the above-mentioned Lowest-heart-rate, for example,
http://www.guinnessworldrecords.com/world-records/lowest-heart-rate
Disclosed in

  Electrocardiogram is a biological signal in which similar waveforms repeatedly appear. Under ideal conditions in which noise does not enter, it is considered that the shape of the waveform observed in the QRS group and the magnitude of the potential take close values.

  FIG. 2 is a flowchart showing an example of the processing operation of the physiological index detection system according to the embodiment of the present invention. The present invention can be used in combination with other noise removal / reduction techniques such as filtering.

  First, the template calculation unit 11 of the physiological index detection device 20 calculates a R-wave template waveform to be used in the subsequent processing based on the known characteristics of the R-wave to be detected (S1). In this embodiment, 0.10 [sec] which is the above-mentioned maximum duration of the QRS group in a healthy person is set as the width of the template waveform in the electrocardiogram and the width of a plurality of search windows in the electrocardiogram. In addition, as long as it is possible to extract the section corresponding to the R wave, the method of calculating the template does not matter in this embodiment.

Next, the feature amount calculation unit 12 calculates the following two types of feature amounts for each waveform in the above-mentioned plurality of search windows after the template waveform in the electrocardiogram (S2). First, the feature quantity calculation unit 12 calculates (a) the correlation value between the electrocardiogram in each search window and the template waveform as the first feature quantity.
Specifically, the feature quantity calculation unit 12 calculates, for each of the search windows in the electrocardiogram, a correlation value between the biological signal included in the search window and the template waveform. Note that another feature value other than the above correlation value may be used as the first feature value, as long as it can represent the similarity of the waveform shape with the template waveform.

  Further, the feature quantity calculation unit 12 calculates the variance value and the standard deviation of a predetermined R-wave feature quantity calculation period for each of the electrocardiograms in each of the search windows described above. These variances and standard deviations are statistics indicating variations in magnitude of cardiac potential within each search window.

Specifically, in order to obtain the amount of steep potential change observed in the R wave, the feature amount calculation unit 12 sets the R wave feature amount calculation period to the above-mentioned maximum duration of 0.10 [R wave]. sec] or less. Note that other statistical values may be used as long as they can represent the above-mentioned variation in the magnitude of the cardiac potential.

Next, the physiological index detection unit 13 selects R wave candidates from the electrocardiograms in each search window based on the correlation value that is the first feature amount. The physiological index detection unit 13 manages the R wave candidate information by storing the information in the internal memory.
In addition, since it is conceivable that there is no R wave in the target search range, the physiological index detection unit 13 uses a search counter that manages the current search point.

  The R wave search period may be 1.5 [sec] or more which corresponds to the minimum heart rate of a healthy subject. Also, based on the judgment criteria for sinus arrest, if the R wave search period (= 3.0 [sec]), even in the case of an electrocardiogram of the above-mentioned sports heart such as athletes, at least one R wave within the search range. It is thought that the biological signal corresponding to can be observed. For this reason, in the present embodiment, the above-mentioned R wave search period (= 3.0 [sec]) is set as the maximum search range based on the determination criterion of the sinus stop.

The physiological index detection unit 13 performs the following processing a and processing b.
(Process a)
The physiological index detection unit 13 resets the value of the search counter and the R-wave candidate (S3), and if the value of the search counter does not exceed the predetermined threshold of the search period (NO in S4), the correlation coefficient of the search target Is selected (S5).

If the correlation value which is the first feature value calculated by the feature value calculation unit 12 exceeds the predetermined correlation coefficient threshold value and the maximum value so far (YES in S6), the physiological index detection unit 13 detects an electrocardiogram The waveform of the point corresponding to the said correlation value in is considered as an R wave candidate (S7). Here, the correlation coefficient is a value indicating the degree of correlation with the template. When the correlation coefficient is used, the range is −1 to 1, so that the range of the correlation coefficient is “0 <correlation coefficient ≦ 1”.
The physiological index detection unit 13 resets the search counter each time an R wave candidate is newly found (S8). After this reset, the process returns to S4.

(Process b)
On the other hand, if the correlation value, which is the first feature value calculated by the feature value calculation unit 12, is the maximum value at that time, or less than the correlation coefficient threshold (NO in S6), the physiological index detection unit 13 , And increment the value of the search counter (S9). After this increment, the process returns to S4.

  In addition, when the value of the search counter started from the discovery time of a certain R wave candidate exceeds the predetermined minimum R wave interval period (YES in S4), the physiological index detection unit 13 detects a point corresponding to the above correlation value in the electrocardiogram. Let R be a candidate R wave within the minimum R wave interval period. In the case of electrocardiogram, the physiological index detection unit 13 sets the minimum R-wave interval period to 0.25 [sec] based on the maximum heart rate (= 240 [bpm]) of a healthy subject, thereby achieving more than the relevant period. Since a similar waveform with a short duration can be avoided as an R wave candidate, overdetection of a candidate for a physiological index can be prevented.

  In addition, when the search counter exceeds the minimum R wave interval period = 0.25 [sec], and there is an R wave candidate detected in this minimum R wave interval period (YES in S10), the physiological index detection unit 13 The evaluation of the variance and the standard deviation, which are the second feature values of this R-wave candidate, is performed.

  Specifically, when the dispersion value average is represented by μ and the standard deviation is represented by σ, the physiological index detection unit 13 detects the past n pieces of R waves that are correct data in the past recorded in the physiological index storage unit 14 for evaluation. With respect to the dispersion value average value and the standard deviation, it is evaluated whether the dispersion value and the standard deviation, which are the above-mentioned second feature values of the R wave candidate, satisfy the following conditions (S11).

  The first condition is that the dispersion value of the R wave candidate to be evaluated is k times or more the average μ of the dispersion value of the past n R waves, which is the past correct data recorded in the evaluation physiological index recording unit 14 It is a certain thing. k is any real number such that 0 <k <1. The reason why k is determined is that if the R wave candidate is a waveform near the R wave, it is assumed that the dispersion of this candidate is equivalent to the dispersion near the R wave observed in the past.

  Under this condition, false detection of noise such as myoelectric potential or impulsive noise can be reduced while having high similarity to the R wave but small potential, so that excessive detection of a physiological index can be prevented.

FIG. 3 is a diagram for explaining the evaluation of the feature amount of the R wave candidate by the physiological index detection system according to the embodiment of the present invention. The second condition is the past n-1 R waves (corresponding to R _{2 to} R ₅ shown in FIG. 3) corresponding to the past correct data recorded in the evaluation physiological index recording unit 14 and the R to be evaluated. The standard deviation σ _candidate of the wave candidate and (total n data) is the standard of the past n R waves (corresponding to R _{1 to} R ₅ shown in FIG. 3) recorded in the evaluation physiological index recording unit 14 That is not more than l times the deviation σ _n . l is any positive real number greater than or equal to one.

  Under this condition, false detection of noise such as impulsive noise, which has high correlation with the R wave but the potential is too large, can be reduced, so excessive detection of the physiological index can be prevented.

  When the R wave candidate to be evaluated satisfies both the first and second conditions (YES in S11), the physiological index detecting unit 13 recognizes the R wave candidate as the correct R wave (S12), and the physiology for evaluation The oldest R-wave data recorded in the index recording unit 14 is updated with the recognized R-wave data (S13). After that, if there is subsequent data of the data identified as the R wave among the data of the electrocardiogram in each search window (YES in S14), the process returns to S3, and a new R wave candidate is searched for this data.

  When there is an R-wave candidate whose search counter value exceeds the minimum R-wave interval period (= 0.25 [sec]) and the first and second conditions described in S11 are not satisfied (NO in S11) The physiological index detection unit 13 discards the R wave candidate without recognizing it as an R wave. In this case, the process returns to S3, and new R-wave candidates are searched for the discarded R-wave candidate subsequent data among the electrocardiogram data in each search window.

  As described above, the physiological index detection system according to the present invention performs setting of a search range and selection of candidate data based on a known index of a physiological index to be processed, data in which only the waveform shape is similar. False positives can be reduced.

  In the case of R wave detection in the electrocardiogram, by setting the search range as a discrimination criterion of sinus arrest, for example, 3.0 [sec], it is possible to detect the R wave of the user having a sports heart. Also, in order to select candidate data, by setting the heart rate interval when the heart rate is the maximum heart rate to, for example, 0.25 [sec], R wave detection is enabled when the user's exercise intensity is high .

  In addition, in the case of targeting pulse waves, the maximum pulse rate (in one theory, “220-age” is referred to. Reference: “Omron pulsimeter HR-500U”, http://www.healthcare.omron.co. Similar effects can be obtained by using jp / sp / hr 500 u / s /) and the criteria for sinus arrest.

  Furthermore, by evaluating the selected candidate data from the two viewpoints of the waveform shape of the biological signal and the size of the waveform linked to the physiological index of interest, false detection of data having potential characteristics different from the physiological index is performed. It can be reduced.

  The present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  In addition, the method described in each embodiment is, for example, a magnetic disk (a floppy (registered trademark) disk, a hard disk, etc.), an optical disk (CD-ROM, etc.) as a program (software means) that can be executed by a computer. It can be stored in a recording medium such as a DVD, an MO, etc., a semiconductor memory (ROM, RAM, flash memory, etc.), and can be distributed via transmission via a communication medium. The program stored on the medium side includes a setting program for configuring the software means (not only the execution program but also the table and data structure) to be executed by the computer in the computer. A computer that implements the present apparatus reads a program recorded in a recording medium, and sometimes constructs a software means by a setting program, and executes the above-mentioned processing by controlling the operation by this software means. Incidentally, the recording medium referred to in the present specification is not limited to the distribution medium, but includes a storage medium such as a magnetic disk or a semiconductor memory provided in an apparatus connected inside a computer or via a network.

  10: data reception unit, 11: template calculation unit, 12: feature amount calculation unit, 13: physiological index detection unit, 14: physiological index recording unit for evaluation, 15: biological signal analysis processing unit, 20: physiological index detection device, 30 ... biomedical signal measurement device.

Claims (5)

First calculating means for calculating a waveform of a template in the biological signal based on known characteristics of a physiological index to be detected from the biological signal;
The indicating the variation in the size of the biological signal in similarity value indicating the height, and said plurality of predetermined periods of the waveform of the template waveform with the calculation of the biosignal in a plurality of predetermined periods 1 And second calculating means for calculating a second statistical value,
When the value indicating the similarity of the height the calculated exceeds a predetermined value, a detection means for detecting a candidate of physiological index to be the detection target from the biological signal at said plurality of predetermined periods,
The first statistical value of the candidate detected by the detection means is larger than 0 with respect to the average value of the first statistical values calculated for physiological indices included in one or more n past biological signals The second statistical value calculated for the value obtained by multiplying by a factor smaller than 1 and the physiological index included in the n-1 past biological signals and the detected candidate is the n past The above-mentioned candidate detected when satisfying the condition that the second statistical value calculated for the physiological index included in the biological signal is equal to or less than a value obtained by multiplying the magnification of any positive real number by one or more A determination unit that determines as the physiological index to be detected .
A physiological index detection device equipped with The physiological index detection device according to claim 1, wherein the first statistical value is a variance value, and the second statistical value is a standard deviation. A method applied to a physiological index detection device, comprising:
A first calculation step of calculating a waveform of a template in the biological signal based on known characteristics of a physiological index to be detected from the biological signal;
The indicating the variation in the size of the biological signal in similarity value indicating the height, and said plurality of predetermined periods of the waveform of the template waveform with the calculation of the biosignal in a plurality of predetermined periods 1 And a second calculating step of calculating a second statistical value;
When the value indicating the similarity of the height the calculated exceeds a predetermined value, a detection step of detecting a candidate of physiological index to be the detection target from the biological signal at said plurality of predetermined periods,
The first statistical value of the detected candidate is larger than 0 and smaller than 1 with respect to the average value of the first statistical value calculated for physiological indices included in one or more n past biological signals The second statistical value calculated for the value multiplied by the magnification, the physiological index included in the n-1 past biological signals, and the detected candidate is the n past biological signals. when satisfying the thing for the calculated second statistic is less than the value obtained by multiplying one or more arbitrary positive real number magnification for physiological index contained in said detecting candidates the detected A decision step to decide as a target physiological index ;
And a physiological index detection method. The physiological index detection method according to claim 3, wherein the first statistical value is a variance value, and the second statistical value is a standard deviation. A physiological index detection processing program for causing a computer to function as the first calculation unit, the second calculation unit, the detection unit, and the determination unit of the physiological index detection device according to claim 1 or 2 .