Biological signal measurement device

Abstract

To provide a biological signal measurement device capable of selecting a set of electrodes suitable for electrocardiographic measurement from a plurality of sets of electrodes.SOLUTION: A biological signal measurement device comprises: a belt-like fixing member to be wound around a person to be measured; a plurality of sets of electrodes arranged on the fixing member; a selection unit that on the basis of a feature quantity based on the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction when an electric potential of a base line of electrocardiogram waveforms of the person to be measured acquired by plurality of sets of electrodes is used as a reference, selects a set of measurement electrodes to be used for acquiring the electrocardiogram waveforms; and a detection unit that uses the selected set of the measurement electrodes to detect a feature of the electrocardiogram waveforms.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a biosignal measuring device. [Background technology]

[0002] Wearable biosignal measuring devices that are worn continuously for a long period of time and monitor electrocardiogram waveforms are known. For example, there are various products ranging from medical devices such as 24-hour Holter electrocardiogram monitors to consumer devices such as smart watches. For example, Patent Document 1 describes an electrocardiogram measuring device that places multiple electrodes in contact with the upper arm, focuses on the amplitude of the R wave of the acquired electrocardiogram waveform, selects a set of electrodes that maximizes the amplitude, and uses the selected set to measure the electrocardiogram waveform. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5428889 Summary of the Invention [Problem to be solved by the invention]

[0004] Even if a pair of electrodes that maximizes the amplitude of the R wave in the electrocardiogram waveform is selected, the selected pair of electrodes may not measure the waveform information used for electrocardiogram analysis. For example, atrial fibrillation is detected when the P wave disappears and cannot be confirmed, or when the R wave period is not constant, but there is a risk that the P wave is not measured in the signal acquired by the pair of electrodes that maximizes the signal amplitude. Therefore, there is a risk that the selected pair of electrodes will not perform electrocardiogram analysis correctly.

[0005] One aspect of the disclosed technique has an object to provide a biosignal measuring device capable of selecting a set of electrodes suitable for electrocardiogram measurement from among a plurality of sets of electrodes. [Means for solving the problem]

[0006] One aspect of the disclosed technology is exemplified by the following biosignal measuring device: This biosignal measuring device includes a band-shaped fixing member wrapped around a subject, a plurality of sets of electrodes arranged on the fixing member, a selection unit that selects a set of measurement electrodes to be used for acquiring an electrocardiogram waveform from the plurality of sets of electrodes based on a feature based on an absolute value of a maximum amplitude in a positive direction and an absolute value of a maximum amplitude in a negative direction when a potential of a baseline of an electrocardiogram waveform of the subject acquired by each of the plurality of sets of electrodes is taken as a reference, and a detection unit that detects a feature of the electrocardiogram waveform using the selected set of measurement electrodes.

[0007] According to the present biosignal measuring device, a set of measurement electrodes is selected based on the feature amount. By providing such a feature, the present biosignal measuring device can select a set of electrodes suitable for detecting a feature of an electrocardiogram waveform from among a plurality of sets of electrodes. The feature detected by the detection unit may be, for example, an RRI, which is an interval between peaks of R waves in the electrocardiogram waveform, or the presence or absence of a P wave. The feature amount may be a value obtained by dividing the greater of the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform by the smaller of the absolute values. The feature amount may be a difference between the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform when the electrocardiogram waveform is adjusted so that the difference between the maximum amplitude and the minimum amplitude of each waveform included in the electrocardiogram waveform is constant, or a difference between a first absolute value of the maximum amplitude in the positive direction and a second absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform. and at least one of a second absolute value of the maximum amplitude at the measurement point and a second absolute value of the maximum amplitude at the measurement point. Furthermore, the selection section may select, as the measurement electrode pair, a pair of electrodes having a larger feature amount than other pairs of electrodes.

[0008] The present biosignal measuring device may further include the following features. The selection unit selects the pair of measurement electrodes at a predetermined interval, and further includes a control unit that stops the supply of power to the electrodes other than the pair of measurement electrodes when the same pair of electrodes is selected as the pair of measurement electrodes consecutively. According to the present biosignal measuring device, the supply of power to the electrodes other than the pair of measurement electrodes is stopped, so that the power consumption of the biosignal measuring device can be reduced. Furthermore, when the same pair of electrodes is selected as the pair of measurement electrodes consecutively, there is a high probability that the same pair of electrodes will be selected as the pair of measurement electrodes consecutively. Therefore, it is considered that the impact on the measurement accuracy of electrocardiogram measurement is low even if the supply of power to the electrodes other than the pair of measurement electrodes is stopped.

[0009] The present biosignal measuring device may further include the following feature: The selection unit receives a designation of the number of pairs of the measurement electrodes to be selected, and selects the same number of pairs of the measurement electrodes as the received number. With a biosignal measuring device having such a feature, the number of pairs of the measurement electrodes can be flexibly changed according to the needs of the subject.

[0010] The biosignal measuring device may further include the following feature: the detection unit detects atrial fibrillation based on the detected feature. With a biosignal measuring device having such a feature, atrial fibrillation can be detected using the set of measurement electrodes selected by the selection unit. Effect of the Invention

[0011] According to the disclosed technique, a set of electrodes suitable for electrocardiogram measurement can be selected from a plurality of sets of electrodes. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing an electrocardiograph according to an embodiment worn on the upper arm. [Diagram 2] FIG. 2 is a plan view of the electrocardiograph according to the embodiment. [Diagram 3] FIG. 3 is a perspective view of the electrocardiograph according to the embodiment. [Figure 4]FIG. 4 is a block diagram showing an example of a functional configuration of the control main body. [Diagram 5] FIG. 5 is a diagram illustrating an example of an electrocardiogram waveform acquired by the acquisition unit. [Figure 6] FIG. 6 is a diagram illustrating an example of a processing flow of a selection process of an electrode pair by an electrode selection unit in the embodiment. [Figure 7] FIG. 7 is a block diagram showing an example of a functional configuration of a control main body according to the first modified example. [Figure 8] FIG. 8 is a diagram showing an example of a processing flow of a selection process of an electrode pair by the electrode selection unit in the first modified example. [Figure 9] FIG. 9 is a block diagram showing an example of a functional configuration of a control main body according to the second modified example. [Figure 10] FIG. 10 is a diagram showing an example of an operation mode designation screen that the mode control unit outputs to the output unit in the second modified example. [Figure 11] FIG. 11 is a diagram showing a first example of a processing flow of a selection process of an electrode pair by the electrode selection unit in the second modified example. [Figure 12] FIG. 12 is a diagram illustrating the correspondence between the cycle executed every 10 minutes and the time. [Figure 13] FIG. 13 is a diagram showing a second example of the processing flow of the selection process of an electrode pair by the electrode selection unit in the second modified example. [Figure 14] FIG. 14 is a diagram showing an example of a process flow of electrocardiogram measurement when a power saving operation is started in the second modified example. [Figure 15] FIG. 15 is a diagram illustrating an example of switching the power saving operation on and off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] <Application Examples> An application example of the present invention will be described. An electrocardiograph 1 according to this application example is a wearable electrocardiograph that is fixed by wrapping a band 10 around a measurement site of a subject as shown in Fig. 1. A plurality of electrodes 11 and a control body 12 are fixed to the band 10. Examples of measurement sites to which the band 10 is attached include the upper limbs (upper arms, forearms, wrists, hands, fingers), lower limbs (thighs, lower legs, ankles, feet, fingers), head, neck, chest, abdomen, earlobes, etc., and are appropriately selected depending on the measurement algorithm, etc.

[0014] An electrocardiogram signal used to detect the characteristics of an electrocardiogram waveform is acquired, for example, using two electrodes 11 (one electrode pair). Three or more electrodes 11 are arranged side by side on the band 10, and a pair of electrodes 11 to be used for electrocardiogram measurement is selected by a pair selection unit 242 (see FIG. 4).

[0015] In the selection of pairs of electrodes 11 by the pair selection unit 242, for example, potential differences are obtained for all pairs of electrodes 11 selected from the plurality of electrodes 11, and are acquired as electrocardiogram signals. The pair selection unit 242 calculates feature amounts based on the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction when the potential of the baseline in the electrocardiogram waveform indicating the time series change of the electrocardiogram signal is used as a reference, and selects pairs of electrodes 11 to be used for detecting features of the electrocardiogram waveform based on the calculated feature amounts. Hereinafter, in this specification, detecting features of the electrocardiogram waveform is also referred to as electrocardiogram measurement. According to this application example, by using the feature amounts, a pair of electrodes suitable for detecting features of the electrocardiogram waveform can be selected from a plurality of pairs of electrodes.

[0016] <Embodiment> Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a diagram showing an electrocardiograph 1 according to an embodiment worn on the upper arm. Fig. 2 is a plan view of the electrocardiograph 1 according to an embodiment. Fig. 3 is a perspective view of the electrocardiograph 1 according to an embodiment. Note that the electrocardiograph 1 is not limited to a device that performs only electrocardiographic measurement, and may be a biosignal measuring device that measures biosignals other than electrocardiogram signals, such as blood pressure and blood oxygen concentration.

[0017] The electrocardiograph 1 of this embodiment is an upper arm electrocardiogram device that is worn on the user's upper arm (preferably the left upper arm close to the heart) and is used to measure an electrocardiogram signal as a biosignal.

[0018] The electrocardiograph 1 mainly comprises a band 10, a plurality of electrodes 11 fixed to the band 10, and a control unit 12 fixed to the band 10.

[0019] The band 10 is a member (fixing member) for fixing the electrodes 11 in a state where they are pressed against the living body. In this embodiment, a strip-shaped band 10 made of a flexible and malleable material (e.g., chemical fiber, silicone, leather, etc.) is used. A fixing mechanism 13 is provided at the longitudinal end of the band 10. As shown in Figs. 1 and 3, the band 10 is made into a loop and fastened with the fixing mechanism 13, so that the electrocardiograph 1 can be worn on the upper arm. The fixing mechanism 13 may be any type of fastener, hook, connector, button, magnet, etc.

[0020] A number of electrodes 11 (also called an electrode array) are embedded and fixed in the band 10 such that the surface that comes into contact with the living body is exposed on the inside (living body side) of the band 10. The multiple electrodes 11 are arranged in a row at equal intervals in the longitudinal direction of the band 10. In this way, when the band 10 is wrapped around the arm, the electrodes 11 come into contact with different positions around the arm. The number of electrodes 11 can be designed as desired. For the purpose of measuring an electrocardiogram signal, at least two electrodes 11 (one electrode pair) are sufficient, and three or more electrodes 11 should be provided to increase the reliability and robustness of the measurement. In this embodiment, a configuration in which six electrodes 11 are provided is adopted.

[0021] The electrodes 11 are dry metal electrodes. Wet electrodes (gel electrodes, etc.) have problems such as the possibility of causing skin rashes and itching when worn for a long time, and low durability and ease of maintenance, whereas the dry electrodes 11 do not have such problems. The electrocardiograph 1 of this embodiment is intended to be worn for a long time and to monitor electrocardiogram signals for 24 hours, so that the dry electrodes 11 are preferable.

[0022] The control body 12 is a processing unit that controls the electrocardiograph 1 and performs signal processing. The control body 12 has a structure in which a processor, a memory, a battery, and other circuits are mounted inside a case made of, for example, resin or metal. The control body 12 may be provided with a physical switch and a display. Although not shown, the control body 12 and the multiple electrodes 11 are connected via signal lines.

[0023] (Control unit) 4 is a block diagram showing an example of the functional configuration of the control body 12. The control body 12 includes an acquisition unit 22, an electrode selection unit 24, a storage unit 25, an output unit 26, and a detection unit 27. For example, a processor is disposed in the control body 12, and the processor executes a program stored in the storage unit 25 to realize each processing unit such as the acquisition unit 22, the electrode selection unit 24, the output unit 26, and the detection unit 27. In other words, the control body 12 can be regarded as a computer. Note that each processing unit such as the acquisition unit 22, the electrode selection unit 24, the output unit 26, and the detection unit 27 may be realized by a dedicated hardware circuit.

[0024] The acquisition unit 22 is a circuit that amplifies the potential difference between an electrode pair selected from the multiple electrodes 11 included in the electrocardiograph 1 by using a differential amplifier and outputs it as an electrocardiogram signal. For example, when the electrode selection unit 24 selects a pair of electrodes 11, the acquisition unit 22 acquires the potential difference for all pairs of electrodes 11 selected from the multiple electrodes 11 and outputs it as an electrocardiogram signal. The electrocardiogram signal is a signal that indicates the electrical activity of the heart. In this embodiment, electrode pairs are selected from the six electrodes 11 included in the electrocardiograph 1, so that the total number of electrode pairs is 15 pairs. In addition, after the electrode selection unit 24 selects a pair of electrodes 11 to be used for electrocardiogram measurement, the acquisition unit 22 acquires the potential difference of the selected pair of electrodes 11 and outputs it as an electrocardiogram signal.

[0025] The electrode selection unit 24 selects a pair of electrodes 11 to be used for electrocardiogram measurement. The electrode selection unit 24 selects, for example, a pair of electrodes 11 from which an electrocardiogram signal suitable for detecting atrial fibrillation can be acquired. Atrial fibrillation is detected, for example, when an RR Interval (RRI), which is an interval between peaks of R waves, is irregular and a P wave does not exist in the electrocardiogram waveform. The electrode selection unit 24 has a calculation unit 241 and a pair selection unit 242. The calculation unit 241 calculates a feature amount related to the position of a baseline in the electrocardiogram waveform that shows a time-series change in the input electrocardiogram signal. The baseline is a straight line that connects the start point of a P wave and the start point of the next P wave in the electrocardiogram waveform. The position of the baseline in the electrocardiogram waveform is, for example, a straight line that shows a state in which no part of the heart is excited in the electrocardiogram waveform. The position of the baseline may be, for example, a straight line connecting the start point of a P wave and the start point of the next P wave when the electrocardiogram waveform is adjusted so that the difference between the maximum amplitude and the minimum amplitude of each waveform included in the electrocardiogram waveform is constant. The feature amount related to the position of the baseline may be, for example, the position of a straight line showing a state in which no part of the heart is excited in the electrocardiogram waveform. Also, the feature amount related to the position of the baseline may be the ratio of maximum amplitudes (baseline division ratio). The baseline division ratio is calculated, for example, by "(absolute value of the positive maximum amplitude) / (absolute value of the negative maximum amplitude)". Also, the baseline division ratio may be calculated by "(the greater value of the absolute value of the positive maximum amplitude and the absolute value of the negative maximum amplitude) / (the smaller value of the absolute value of the positive maximum amplitude and the absolute value of the negative maximum amplitude)". The calculation unit 241 calculates the baseline division ratio for all pairs of the electrodes 11. In the following description, the feature amount related to the position of the baseline may be the baseline division ratio. The case where a proportional ratio is adopted will be described as an example.

[0026] 5A and 5B are diagrams illustrating electrocardiogram waveforms acquired by the acquisition unit 22. The vertical axis of FIG. 5A and FIG. 5B illustrates potential difference (mV), and the horizontal axis illustrates time (seconds). The electrocardiogram waveform acquired by the acquisition unit 22 has a different waveform depending on the electrode pair used for measurement. FIG. 5A and FIG. 5B are electrocardiogram waveforms measured by the acquisition unit 22 using different electrode pairs. The amplitude of the R wave, which indicates the maximum amplitude of the electrocardiogram waveform, is larger in FIG. 5A than in FIG. 5B, while the amplitude of the P wave, which is used for detecting atrial fibrillation, is larger in FIG. 5B than in FIG. 5A. That is, in consideration of the detection of atrial fibrillation, the waveform in FIG. 5B is more preferable than the waveform in FIG. 5A. In addition, the baseline division ratio is larger in the waveform in FIG. 5B than in the waveform in FIG. 5A. As a result of observing the electrocardiogram waveforms of many subjects in subject experiments, the inventors have found that the lower the baseline of an electrocardiogram waveform is, the larger the amplitude of the P wave tends to be. The baseline division ratio is an index that increases as the baseline is lower than the QRS wave.

[0027] The pair selection unit 242 selects a pair of electrodes 11 to be used for electrocardiogram measurement based on the baseline division ratio calculated by the calculation unit 241. For example, the pair selection unit 242 selects a pair of electrodes 11 having the largest calculated baseline division ratio as a pair of electrodes 11 to be used for electrocardiogram measurement. The pair selection unit 242 stores information indicating the selected pair of electrodes 11 in the storage unit 25. The pair selection unit 242 also stores an electrocardiogram signal acquired by the selected pair of electrodes 11 in the storage unit 25. The storage unit 25 is a non-volatile memory.

[0028] The output unit 26 is, for example, a Liquid Crystal Display (LCD), a Plasma Display Panel (PDP), an inorganic electroluminescence (EL) panel, or an organic EL panel. The output unit 26 displays, for example, information indicating the pair of electrodes 11 selected by the pair selection unit 242 and an electrocardiogram waveform indicating a time-series change in the electrocardiogram signal acquired by the acquisition unit 22. For example, a touch panel that detects a touch operation by a user's finger or the like may be provided superimposed on the output unit 26. By providing a touch panel superimposed on the output unit 26, the electrocardiograph 1 can provide the user with an intuitive operating environment.

[0029] The detection unit 27 detects features of the electrocardiogram signal from the electrocardiogram signal stored in the storage unit 25, and detects atrial fibrillation based on the detected features. The detection unit 27 causes the output unit 26 to output the detection result of atrial fibrillation.

[0030] (Selection of electrode pair 11) Fig. 6 is a diagram showing an example of a processing flow of a selection process of a pair of electrodes 11 by the electrode selection unit 24 in the embodiment. In the example illustrated in Fig. 6, the electrode selection unit 24 selects one pair of electrodes 11. Hereinafter, an example of a processing flow of a selection process of a pair of electrodes 11 by the electrode selection unit 24 in the embodiment will be described with reference to Fig. 6.

[0031] In step S1, the electrode selection unit 24 acquires the electrocardiogram signal acquired by the acquisition unit 22. In step S2, the calculation unit 241 calculates a baseline division ratio. In step S3, the pair selection unit 242 selects a pair of electrodes 11 to be used for electrocardiogram measurement based on the baseline division ratio calculated in step S2. The pair selection unit 242 stores information indicating the selected pair of electrodes 11 in the storage unit 25. Thereafter, the electrocardiogram signal acquired by the selected electrodes 11 is stored in the storage unit 25, and the detection unit 27 detects atrial fibrillation using the electrocardiogram signal stored in the storage unit 25.

[0032] When a pair of electrodes 11 is selected based on the maximum amplitude of the waveform of the electrocardiogram signal, an electrode that acquires an electrocardiogram signal with a large maximum amplitude (amplitude of the R wave) but a small amplitude of the P wave, as shown in the waveform of FIG. 5A, is selected. According to the present embodiment, by using the baseline division ratio, a pair of electrodes 11 capable of acquiring an electrocardiogram signal in which P waves appear more clearly can be selected as a pair of electrodes 11 to be used for electrocardiogram measurement.

[0033] <First Modification> In the process by the control body 12 described in the embodiment, the process of removing noise components from the electrocardiogram signal acquired by the acquisition unit 22 is not performed. Therefore, when the subject wearing the electrocardiograph 1 is not stationary but moving, the electrocardiogram signal acquired by the acquisition unit 22 contains noise, so that it may be difficult to calculate the baseline division ratio with high accuracy. In the first modified example, a modified example in which a process of removing noise from the electrocardiogram signal acquired by the acquisition unit 22 is further performed will be described. The same components as those in the embodiment will be assigned the same reference numerals, and the description thereof will be omitted. Hereinafter, the first modified example will be described with reference to the drawings.

[0034] 7 is a block diagram showing an example of a functional configuration of a control body 12A according to Modification 1. The control body 12A differs from the control body 12 according to the embodiment in that it further includes a signal processing unit .

[0035] The signal processing unit 23 performs AD conversion and filtering of the electrocardiogram signal acquired by the acquisition unit 22. The signal processing unit 23 outputs the electrocardiogram signal after AD conversion and filtering to the electrode selection unit 24. The signal processing unit 23 has an extraction unit 231 and a filter unit 232. The extraction unit 231 extracts a normally acquired electrocardiogram signal from the electrocardiogram signal output by the acquisition unit 22. Examples of normally acquired electrocardiogram signals include signals that are not saturated and signals that do not have consecutive "0". The length of the electrocardiogram signal to be extracted is, for example, 10 seconds.

[0036] The filter unit 232 removes high-frequency noise and low-frequency noise from the electrocardiogram signal cut out by the cut-out unit 231 to increase the signal-to-noise ratio. High-frequency noise can be generated, for example, by myoelectricity or power supply noise present around the subject. Low-frequency noise can be generated, for example, by the position of the electrodes 11 being shifted due to the subject's movement or the like. The filter unit 232 is, for example, a band-pass filter. The signal processing unit 23 outputs the electrocardiogram signal processed by the cut-out unit 231 and the filter unit 232 to the electrode selection unit 24.

[0037] Fig. 8 is a diagram showing an example of a processing flow of the selection process of a pair of electrodes 11 by the electrode selector 24 in the first modified example. Hereinafter, an example of the processing flow of the selection process of a pair of electrodes 11 by the electrode selector 24 in the first modified example will be described with reference to Fig. 8.

[0038] In step S21, the extraction unit 231 extracts a normal signal from the electrocardiogram signal read in step S1. In step S22, the filter unit 232 removes high-frequency noise and low-frequency noise from the signal extracted in step S21 to increase the S / N ratio.

[0039] In the process illustrated in FIG. 8, noise is removed by the processing of the signal processing unit 23 in step S22, so that even if the subject wearing the electrocardiograph 1 is moving freely, the baseline division ratio can be calculated with high accuracy, and thus the pair selection of the electrodes 11 can be performed with high accuracy.

[0040] <Second Modification> In the embodiment and the first modified example described above, the designation of the operation mode, such as the number of pairs of electrodes 11 used for electrocardiogram measurement or the frequency of selection of pairs of electrodes 11, was not accepted. In the second modified example, a modified example in which the designation of these operation modes is accepted will be described. The same components as those in the embodiment and the first modified example are given the same reference numerals, and the description thereof will be omitted. The second modified example will be described below with reference to the drawings.

[0041] 9 is a block diagram showing an example of a functional configuration of a control main unit 12B according to the second modified example. The control main unit 12B differs from the control main unit 12A according to the first modified example in that it further includes a mode control unit 21.

[0042] The mode control unit 21 receives a designation of an operation mode related to electrocardiogram measurement from a user. The operation mode includes, for example, designation of whether or not to select a pair of electrodes 11 to be used for electrocardiogram measurement, the frequency of selecting a pair of electrodes 11, whether or not to save power, the number of pairs of electrodes 11 to be selected, and a criterion for selecting a pair of electrodes 11.

[0043] The mode control unit 21 may, for example, output an operation mode designation screen to the output unit 26 and accept the designation of the operation mode from the user. Fig. 10 is a diagram showing an example of the operation mode designation screen that the mode control unit 21 outputs to the output unit 26 in the second modified example. The operation mode designation screen illustrated in Fig. 10 displays the items "electrode selection", "selection frequency", "power saving", "number of selected pairs", and "selection criteria". In the operation mode designation screen illustrated in Fig. 10, for example, the selected parameter is indicated by coloring the background of the selected value.

[0044] In the "electrode selection" item, whether or not to select electrodes 11 is specified. When "Yes" is specified in the "electrode selection" item, a pair of electrodes 11 to be used for electrocardiogram measurement is selected by processing exemplified in FIG. 11 described later. When "No" is specified in the "electrode selection" item, for example, a default pair of electrodes 11 is used for electrocardiogram measurement. Information indicating the default pair of electrodes 11 is stored in the memory unit 25, for example, when the electrocardiograph 1 is manufactured.

[0045] The "selection frequency" item specifies how often the selection of a pair of electrodes 11 is performed. When "10 min" is specified in the "selection frequency" item, the selection of a pair of electrodes 11 is performed once every 10 minutes. When "30 min" is specified in the "selection frequency" item, the selection of a pair of electrodes 11 is performed once every 30 minutes. The period from one selection of an electrode 11 to the next is also referred to as "one cycle."

[0046] In the "power saving" item, the presence or absence of a power saving mode is specified. When "Yes" is specified in the "power saving" item, the power saving mode is executed. In the power saving mode, for example, when the same pair of electrodes 11 is selected for two consecutive cycles, a power saving operation is started in which the supply of power to electrodes other than the pair of electrodes 11 is turned off for four cycles. When the four cycles have ended since the start of the power saving operation, the supply of power to all electrodes 11 is resumed, and a new pair of electrodes 11 to be used for electrocardiogram measurement is selected by the pair selection unit 242. When "No" is specified in the "power saving" item, the power saving mode is not executed.

[0047] The "number of selected pairs" field specifies the number of pairs of electrodes 11 to be used for electrocardiogram measurement. When "1" is specified in the "number of selected pairs" field, the pair selection unit 242 selects one pair of electrodes 11 to be used for electrocardiogram measurement. When "3" is specified in the "number of selected pairs" field, the pair selection unit 242 selects three pairs of electrodes 11 to be used for electrocardiogram measurement.

[0048] In the "Selection Criteria" item, the criteria for selecting a pair of electrodes 11 are specified. When "Low Baseline" is selected in the "Selection Criteria" item, a pair of electrodes 11 with a low baseline (large baseline division ratio) in the waveform of the electrocardiogram signal is preferentially selected as a pair of electrodes 11 to be used for electrocardiogram measurement. When "High-Low Baseline" is selected in the "Selection Criteria" item, a pair of electrodes 11 with a low baseline (large baseline division ratio) and a pair of electrodes 11 with a high baseline (small baseline division ratio) in the waveform of the electrocardiogram signal are selected as a pair of electrodes 11 to be used for electrocardiogram measurement. For example, When the "number of selected pairs" is "1" and the "selection criterion" is "high and low baseline", the pair selection unit 242 may select two pairs of electrodes 11 in total: one pair of electrodes 11 with the largest baseline division ratio and one pair of electrodes 11 with the smallest baseline division ratio.

[0049] Fig. 11 is a diagram showing a first example of a processing flow of a selection process of a pair of electrodes 11 by the electrode selector 24 in the second modified example. In the processing flow illustrated in Fig. 11, for example, it is assumed that the operation mode illustrated in Fig. 10 is specified. That is, it is assumed that "Yes" is specified for "electrode selection", "10 min" is specified for "selection frequency", "No" is specified for "power saving", "3" is specified for "number of selected pairs", and "low baseline" is specified for "selection criterion" as the operation mode.

[0050] In step S3A, the pair selection unit 242 selects pairs of the electrodes 11 to be used for electrocardiogram measurement, the number of pairs being the "number of selected pairs" accepted by the mode control unit 21. Here, the three pairs of the electrodes 11 to be used for electrocardiogram measurement are selected in ascending order of the baseline position, i.e., in ascending order of the baseline division ratio.

[0051] Since "10 min" is specified as the "selection frequency", the processes of steps S1, S21, S22, S2 and S3A are repeatedly executed every 10 minutes.

[0052] FIG. 12 is a diagram illustrating the correspondence between a cycle executed every 10 minutes and time. In FIG. 12, the items of "time" and "cycle" are illustrated. In FIG. 12, for example, it is assumed that measurement by the control body 12 is started at 11:38:40. In this case, the control body 12 waits without starting measurement until 11:39:59. Then, at 11:40:00, the process of steps S1, S21, S22, S2, and S3 is executed to select a pair of electrodes 11 to be used for electrocardiogram measurement, and electrocardiogram measurement is performed using the selected pair of electrodes 11. Then, at 11:50:00, the process of steps S1, S21, S22, S2, and S3 is executed to reselect a pair of electrodes 11 to be used for electrocardiogram measurement, and electrocardiogram measurement is performed using the reselected pair of electrodes 11. The same applies after 11:50.

[0053] Next, a process when "Yes" is selected for "power saving" as the operation mode will be described. Fig. 13 is a diagram showing a second example of the process flow of the selection process of a pair of electrodes 11 by the electrode selection unit 24 in the second modified example. In the second example, it is assumed that "Yes" is specified for "electrode selection", "10 min" for "selection frequency", "Yes" for "power saving", "1" for "number of selected pairs", and "low baseline" for "selection criterion" as the operation mode.

[0054] In step S31, the mode control unit 21 determines whether or not the same pair of electrodes 11 has been selected in consecutive cycles by the pair selection unit 242. If the same pair of electrodes 11 has been selected in consecutive cycles (YES in step S31), the process proceeds to step S32. If the same pair of electrodes 11 has not been selected in consecutive cycles (NO in step S32), the process ends.

[0055] In step S32, the mode control unit 21 starts a power saving operation. When the power saving operation starts, the supply of power to the electrodes 11 other than the pair of electrodes 11 selected in step S31 is stopped.

[0056] FIG. 14 is a diagram showing an example of a process flow of electrocardiogram measurement when the power saving operation is started in the second modified example. Hereinafter, with reference to FIG. 14, the power saving operation in the second modified example will be described. An example of a process flow for electrocardiogram measurement once it has been started will be described.

[0057] In step S41, the acquisition unit 22 acquires an electrocardiogram signal using the pair of electrodes 11 stored in the storage unit 25. In step S42, the electrocardiogram signal filtered by the filter unit 232 in step S22 is stored in the storage unit 25. The detection unit 27 detects, for example, the presence or absence of atrial fibrillation using the electrocardiogram signal stored in the storage unit 25. When the processing from step S41 to step S42 is repeated a predetermined number of cycles (for example, four cycles), the processing proceeds to step S43. In step S43, power supply to all of the electrodes 11 is resumed.

[0058] FIG. 15 is a diagram illustrating switching of the power saving operation on and off. In FIG. 15, it is assumed that electrocardiogram measurement is started at 11:38:40, similarly to FIG. 12. In FIG. 15, the items of "time", "cycle", "selected pair" and "power saving" are illustrated. "Time" and "cycle" are the same as in FIG. 12, and therefore their explanation is omitted. "Selected pair" illustrates information indicating the pair of electrodes 11 selected by the pair selection unit 242. In the example of FIG. 15, a unique ID is assigned to each pair of electrodes 11, and "selected pair" illustrates an ID indicating the pair of electrodes 11. "Power saving" illustrates whether or not the power saving operation is being performed. In "power saving", "ON" illustrates that the power saving operation is being performed, and "OFF" illustrates that the power saving operation is not being performed.

[0059] 15, the same pair of electrodes 11 is selected consecutively from the second cycle to the third cycle. Therefore, power saving operation is performed for four cycles from the fourth cycle to the seventh cycle, and power supply is stopped to the electrodes 11 other than the pair of electrodes 11 indicated by ID "7". In the eighth cycle, power supply to all the electrodes 11 is resumed, and the pair selection unit 242 selects a pair of electrodes 11.

[0060] According to the second modification, since the mode control unit 21 accepts the designation of the operation mode, it is possible to perform electrocardiogram measurement in an operation mode according to the subject's preference. Furthermore, in the second modification, when the power saving mode is turned on, the power supply to the electrodes 11 other than the pair of electrodes 11 selected in successive cycles is stopped, so that the power consumption of the electrocardiograph 1 can be reduced.

[0061] In the power saving mode, when the same pair of electrodes 11 is selected for two consecutive cycles, a power saving operation is initiated, and power supply to the electrodes 11 other than the selected pair of electrodes 11 is stopped. When the same pair of electrodes 11 is selected for two consecutive cycles, there is a high probability that the same pair of electrodes 11 will continue to be selected due to reasons such as the posture of the subject being stable. Therefore, even if the power saving operation is initiated when the same pair of electrodes 11 is selected for two consecutive cycles, it is considered that the impact on the measurement accuracy of the electrocardiogram measurement by the electrocardiograph 1 is small.

[0062] <Other variations> In the above-described embodiment and modified example, the baseline division ratio is used as the feature quantity related to the position of the baseline, but other values ​​can be used as the feature quantity related to the position of the baseline. The feature quantity related to the position of the baseline may be, for example, a value obtained by dividing the larger of the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction by the smaller value when the potential of the baseline of the electrocardiogram waveform is used as a reference. In addition, the feature quantity related to the position of the baseline may be, for example, a difference between the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform when the difference between the maximum amplitude and the minimum amplitude of each waveform included in the electrocardiogram waveform is adjusted to be constant. In addition, the feature quantity related to the position of the baseline may be, for example, the average amplitude of the P wave, R wave, S wave, and Q wave in the electrocardiogram waveform.

[0063] The embodiments and modifications disclosed above can be combined with each other.

[0064] <Appendix 1> a belt-shaped fixing member (10) that is wrapped around a subject; A plurality of sets of electrodes (11) disposed on the fixing member; a selection unit (242) that selects a set of measurement electrodes to be used for acquiring the electrocardiogram waveform from among the plurality of sets of electrodes, based on a feature based on an absolute value of a maximum amplitude in a positive direction and an absolute value of a maximum amplitude in a negative direction with respect to a baseline potential of the electrocardiogram waveform of the subject acquired by each of the plurality of sets of electrodes; a detection unit (27) that detects a feature of the electrocardiogram waveform using the selected set of measurement electrodes. Biosignal measuring device (1). <Appendix 2> the feature amount includes a value obtained by dividing a larger value of an absolute value of the maximum amplitude in the positive direction and an absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform by a smaller value of the absolute value of the maximum amplitude in the positive direction and an absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform. A biosignal measuring device (1) as described in Appendix 1. <Appendix 3> the electrocardiogram waveform is adjusted so that a difference between a maximum amplitude and a minimum amplitude of each waveform included in the electrocardiogram waveform is constant; the feature amount includes a difference between the absolute value of the maximum amplitude in the positive direction in the electrocardiogram waveform and the absolute value of the maximum amplitude in the negative direction; A biosignal measuring device (1) according to appendix 1 or 2. <Appendix 4> the electrocardiogram waveform is adjusted so that a difference between a maximum amplitude and a minimum amplitude of each waveform included in the electrocardiogram waveform is constant; the feature amount includes at least one of a first absolute value of the maximum amplitude in the positive direction in the electrocardiogram waveform and a second absolute value of the maximum amplitude in the negative direction; A biosignal measuring device (1) according to any one of appendices 1 to 3. <Appendix 5> The selection unit (242) selects a pair of electrodes having a larger feature amount than other pairs of electrodes as the pair of measurement electrodes. A biosignal measuring device (1) according to any one of claims 1 to 4. <Appendix 6> The features include at least one of an RRI, which is an interval between peaks of an R wave in the electrocardiogram waveform, and the presence or absence of a P wave in the electrocardiogram waveform. A biosignal measuring device (1) according to any one of appendices 1 to 5. <Appendix 7> The selection unit (242) selects the set of measurement electrodes at predetermined intervals, and a control unit (21) that stops the supply of power to the electrodes (11) other than the pair of measurement electrodes when the same pair of electrodes (11) is consecutively selected as the pair of measurement electrodes. A biosignal measuring device (1) according to any one of appendices 1 to 6. <Appendix 8> The selection unit (242) Accepting a designation of the number of sets of measurement electrodes to be selected; selecting the set of measurement electrodes as many as the number of sets received; A biosignal measuring device (1) according to any one of appendices 1 to 7. <Appendix 9> The detection unit detects atrial fibrillation based on the detected features. A biosignal measuring device (1) according to any one of appendices 1 to 8. [Explanation of symbols]

[0065] 1. Electrocardiograph 10. Band 11...electrode 12. Control unit 12A··Control unit 12B Control unit 13...Fixing mechanism 21 Mode control section 22··Acquisition part 23 Signal Processing Unit 24 Electrode selection unit 25...Storage section 26 Output section 27 Detection section 231·cutting part 232 Filter section 241 Calculation section 242 Pair selection section

Claims

1. A belt-shaped fixing member that is wrapped around the subject; A plurality of sets of electrodes disposed on the fixing member; a selection unit that selects a set of measurement electrodes to be used for acquiring the electrocardiogram waveform from the plurality of sets of electrodes based on a feature based on an absolute value of a maximum amplitude in a positive direction and an absolute value of a maximum amplitude in a negative direction with respect to a baseline potential of the electrocardiogram waveform of the subject acquired by each of the plurality of sets of electrodes; A detection unit that detects a feature of the electrocardiogram waveform using the selected set of measurement electrodes. Biosignal measuring device.

2. the feature amount includes a value obtained by dividing a larger value of the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform by a smaller value of the absolute value of the maximum amplitude in the positive direction and the absolute value of the maximum amplitude in the negative direction in the electrocardiogram waveform. The biosignal measuring device according to claim 1 .

3. the electrocardiogram waveform is adjusted so that a difference between a maximum amplitude and a minimum amplitude of each waveform included in the electrocardiogram waveform is constant; the feature amount includes a difference between the absolute value of the maximum amplitude in the positive direction in the electrocardiogram waveform and the absolute value of the maximum amplitude in the negative direction; The biosignal measuring device according to claim 1 .

4. the electrocardiogram waveform is adjusted so that a difference between a maximum amplitude and a minimum amplitude of each waveform included in the electrocardiogram waveform is constant; the feature amount includes at least one of a first absolute value of the maximum amplitude in the positive direction in the electrocardiogram waveform and a second absolute value of the maximum amplitude in the negative direction; The biosignal measuring device according to claim 1 .

5. The selection unit selects a pair of electrodes having a larger feature amount than other pairs of electrodes as the pair of measurement electrodes. The biosignal measuring device according to claim 1 .

6. The characteristic includes at least one of an RRI, which is an interval between peaks of an R wave in the electrocardiogram waveform, and the presence or absence of a P wave in the electrocardiogram waveform. The biosignal measuring device according to claim 1 .

7. The selection unit selects the set of measurement electrodes at predetermined intervals, and a control unit that stops supplying power to the electrodes other than the set of measurement electrodes when the same set of electrodes is consecutively selected as the set of measurement electrodes. The biosignal measuring device according to claim 1 .

8. The selection unit is Accepting a designation of the number of sets of measurement electrodes to be selected; selecting the set of measurement electrodes as many as the number of sets received; The biosignal measuring device according to claim 1 .

9. The detection unit detects atrial fibrillation based on the detected features. The biosignal measuring device according to claim 1 .

Images