Biosignal measurement device

Abstract

Provided is a biosignal measurement device that makes it possible to achieve low power consumption while achieving highly accurate electrocardiographic measurement. A biosignal measurement device according to the present invention comprises: a plurality of electrodes; a measurement unit that includes a detection circuit which uses the plurality of electrodes to detect a potential difference and that uses the detection circuit to measure an electrocardiographic signal of a measurement subject; a battery that supplies power to the detection circuit; and a selection unit that selects a measurement electrode which is used to measure the electrocardiographic signal of the measurement subject from the plurality of electrodes on the basis of the electrocardiographic signal of the measurement subject measured using at least some electrodes of the plurality of electrodes and the detection circuit. The measurement unit uses the detection circuit and the measurement electrode to measure the electrocardiographic signal.

Description

Biosignal measurement device

[0001] The present invention relates to a biological signal measuring device.

[0002] Wearable electrocardiographs are known that are worn continuously on the body for an extended period of time to monitor electrocardiogram signals. Various products exist, ranging from medical devices such as 24-hour Holter electrocardiographs to consumer devices such as smart watches. For example, Patent Literature 1 proposes a Holter electrocardiograph that determines the number of channels for recording electrocardiograms based on impedance.

[0003] Patent No. 6778043

[0004] In electrocardiographs with multiple electrodes, power consumption is reduced by attaching only some of the electrodes and enabling only the detection circuits corresponding to the attached electrodes. However, in the case of electrocardiographs that can be attached by the user, such as upper arm electrocardiographs, the attached electrodes are not necessarily positioned in an optimal position for electrocardiographic measurement. Therefore, if the electrodes other than the attached electrodes are not attached, there is a risk of interference with electrocardiographic measurement.

[0005] One aspect of the disclosed technology aims to provide a biological signal measuring device that can achieve high-precision electrocardiogram measurement while consuming low power.

[0006] One aspect of the disclosed technology is exemplified by the following biosignal measuring device. The biosignal measuring device includes a measurement unit that includes multiple electrodes and a detection circuit that detects a potential difference using the multiple electrodes and measures an electrocardiogram signal of a subject using the detection circuit, a battery that supplies power to the detection circuit, and a selection unit that selects measurement electrodes to be used for measuring the electrocardiogram signal of the subject from the multiple electrodes based on the electrocardiogram signal of the subject measured using at least some of the multiple electrodes and the detection circuit. The measurement unit measures the electrocardiogram signal using the detection circuit and the measurement electrodes.

[0007] In the biosignal measuring device, the measurement electrodes are selected based on the electrocardiogram signal of the subject measured using at least some of the electrodes. Therefore, the biosignal measuring device can select measurement electrodes and detection circuits suitable for electrocardiogram measurement. Furthermore, because the electrocardiogram signal is measured using the selected measurement electrodes, the power consumption of the detection circuit is reduced compared to when the electrocardiogram signal is measured using all of the electrodes. Consequently, the biosignal measuring device can achieve high-precision electrocardiogram measurement while also achieving low power consumption.

[0008] The biosignal measuring device may have the following features. When an abnormality is detected in the electrocardiogram signal measured using at least some of the electrodes, the selector increases the number of electrodes selected as the measurement electrodes. When an abnormality is detected in the electrocardiogram signal, it is preferable to analyze the electrocardiogram signal in detail. With a biosignal measuring device having these features, when an abnormality is detected in the electrocardiogram signal, more electrodes can be used to measure the electrocardiogram signal by the measurement unit, thereby obtaining an electrocardiogram signal as detailed as possible. Here, examples of an abnormality in the electrocardiogram signal include an R-R interval (RRI) deviation in the time-series change of the electrocardiogram signal being equal to or greater than a first threshold, a P wave not being detected in the electrocardiogram signal, and a noise level included in the electrocardiogram signal being equal to or greater than a second threshold. Note that the selector may select all of the plurality of electrodes as the measurement electrodes when an abnormality is detected in the electrocardiogram signal acquired using at least some of the electrodes.

[0009] The biosignal measuring device may have the following feature: the selector performs measurement of the electrocardiogram signal using all of the plurality of electrodes at predetermined intervals, and determines which of the plurality of electrodes to use as the measurement electrode based on the electrocardiogram signal measured using all of the plurality of electrodes. A biosignal measuring device having such a feature can compare the electrocardiogram signals measured using all of the plurality of electrodes and select the electrode that is more suitable for acquiring the electrocardiogram signal as the measurement electrode.

[0010] The biosignal measuring device may have the following feature: it may further include a band-shaped fixing member that is wrapped around the subject, and the plurality of electrodes are arranged on the fixing member. A biosignal measuring device having such a feature makes it easy to attach the biosignal measuring device to the subject.

[0011] According to the disclosed technology, it is possible to realize highly accurate electrocardiogram measurement while realizing low power consumption.

[0012] FIG. 1 is a diagram illustrating an electrocardiograph according to an embodiment worn on the upper arm. FIG. 2 is a plan view of the electrocardiograph according to an embodiment. FIG. 3 is a perspective view of the electrocardiograph according to an embodiment. FIG. 4 is a diagram schematically illustrating connections between electrodes, detection circuits, and a battery of the electrocardiograph according to an embodiment. FIG. 5 is a block diagram illustrating an example of the functional configuration of a control main body. FIGS. 6A to 6D are diagrams schematically illustrating selection of a power-receiving circuit by a selector. FIG. 7 is a diagram illustrating an example of a processing flow of the control main body according to an embodiment. FIG. 8 is a first diagram illustrating variations in connection between electrodes and detection circuits in a first modified example. FIG. 9 is a second diagram illustrating variations in connection between electrodes and detection circuits in the first modified example. FIG. 10 is a third diagram illustrating variations in connection between electrodes and detection circuits in the first modified example. FIG. 11 is a diagram schematically illustrating selection of electrodes used to acquire electrocardiogram signals in a second modified example.

[0013] <Application Example> An application example of the present invention will be described. An electrocardiograph 1 according to this application example is a wearable electrocardiograph that is secured 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 unit 12 are secured to the band 10 (see FIG. 2). The control unit 12 includes a detection circuit 14 (see FIG. 4) that detects a potential difference using the plurality of electrodes 11, and a measurement unit 22 (see FIG. 5) that measures an electrocardiogram signal of the subject using the detection circuit 14. 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 the measurement site is selected appropriately depending on the measurement algorithm, etc.

[0014] An electrocardiogram signal used for electrocardiogram measurement is acquired using, for example, two electrodes 11 (one electrode pair). The electrocardiogram signal is, for example, a signal indicating the electrical activity of the heart. In the electrocardiograph 1, a selector 21 (see FIG. 5 ) selects measurement electrodes from the multiple electrodes 11 to be used for measuring the electrocardiogram signal based on an electrocardiogram signal acquired from at least some of the multiple electrodes 11. With this electrocardiograph 1, the measurement electrodes are selected based on an electrocardiogram signal measured using the detection circuit 14 and at least some of the electrodes 11, thereby allowing for the selection of measurement electrodes suitable for electrocardiogram measurement. Furthermore, with this electrocardiograph 1, the number of electrodes 11 used as measurement electrodes can be reduced, thereby reducing the power consumption of the detection circuit 14 and ultimately achieving low power consumption for the electrocardiograph 1.

[0015] <Embodiments> Hereinafter, embodiments 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 measurements, and may also be a biosignal measuring device that measures biosignals other than electrocardiogram signals, such as blood pressure and blood oxygen concentration.

[0016] 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 electrocardiogram signals as biosignals.

[0017] 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 .

[0018] 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 pliable 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 Figures 1 and 3, the electrocardiograph 1 can be worn on the upper arm by looping the band 10 and fastening it with the fixing mechanism 13. The fixing mechanism 13 may be any type of fastener, such as a hook and loop fastener, a hook, a connector, a button, or a magnet.

[0019] Multiple electrodes 11 (also called an electrode array) are embedded and fixed in the band 10 with the surface that comes into contact with the living body exposed on the inside (living body side) of the band 10. The multiple electrodes 11 are arranged in a row at equal intervals along the longitudinal direction of the band 10. This ensures that the electrodes 11 come into contact with different positions around the arm when the band 10 is wrapped around the arm. The number of electrodes 11 can be designed as desired. For the purpose of measuring electrocardiogram signals, at least two electrodes 11 (one electrode pair) are sufficient, but three or more electrodes 11 may be provided to improve the reliability and robustness of the measurement. In this embodiment, a configuration with six electrodes 11 is adopted.

[0020] The electrodes 11 are dry metal electrodes. Wet electrodes (gel electrodes, etc.) have problems such as the possibility of causing skin rash or itchiness when worn for a long period of 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 period of time and to monitor electrocardiogram signals for 24 hours, so dry electrodes 11 are preferred.

[0021] The control main unit 12 is a processing unit that controls and processes signals of the electrocardiograph 1. The control main unit 12 has a structure in which a processor, memory, battery 121, and other circuits are mounted inside a case made of, for example, resin or metal. The control main unit 12 may also be provided with a physical switch and a display.

[0022] Fig. 4 is a diagram schematically illustrating connections between the electrodes 11, the detection circuit 14, and the battery 121 of the electrocardiograph 1 according to the embodiment. In Fig. 4, the electrodes 11 connected to the detection circuit 14 are also illustrated by dotted lines. The six electrodes 11 are distinguished from one another by being referred to as electrodes 111, 112, 113, 114, 115, and 116. Of the six electrodes 11, electrode 116 is a GND electrode whose potential is fixed to ground.

[0023] The control unit 12 has five detection circuits 14. When distinguishing between the five detection circuits 14, they are also referred to as detection circuits 141, 142, 143, 144, and 145. The detection circuits 14 are circuits that receive power from the battery 121 and are used to detect potential differences using the connected electrodes 11. The detection circuits 14 include, for example, a differential amplifier. The detection circuit 141 is connected to the electrodes 111 and 116 and detects the potential difference between the electrodes 111 and 116. The detection circuit 142 is connected to the electrodes 112 and 116 and detects the potential difference between the electrodes 112 and 116. The detection circuit 143 is connected to the electrodes 113 and 116 and detects the potential difference between the electrodes 113 and 116. The detection circuit 144 is connected to the electrodes 114 and 116 and detects the potential difference between the electrodes 114 and 116. The detection circuit 145 is connected to the electrode 115 and the electrode 116 and detects the potential difference between the electrode 115 and the electrode 116. The battery 121 may be a primary battery or a secondary battery.

[0024] (Control Main Unit) Fig. 5 is a block diagram showing an example of the functional configuration of the control main unit 12. The control main unit 12 includes a selection unit 21, a measurement unit 22, a calculation unit 23, a storage unit 24, and an output unit 25. In the control main unit 12, each processing unit such as the selection unit 21, the measurement unit 22, the calculation unit 23, and the output unit 25 is realized by a processor executing a program stored in the storage unit 24. In other words, the control main unit 12 can be considered a computer. Note that each processing unit such as the selection unit 21, the measurement unit 22, the calculation unit 23, and the output unit 25 may be realized by a dedicated hardware circuit.

[0025] The selector 21 selects a power-receiving circuit from the detection circuit 14 that receives power from the battery 121 based on the electrocardiogram signal acquired by at least some of the detection circuits 14. The selector 21 selects a power-receiving circuit from the detection circuit 14 based on, for example, the presence or absence of a cardiac disease event detected based on the electrocardiogram signal, the magnitude of noise contained in the electrocardiogram signal, the amount of electrocardiogram signal acquired, the heart rate, the R-R interval (RRI), etc. Because different pairs of electrodes 11 are connected to the detection circuits 141, 142, 143, 144, and 145, it can also be said that the selector 21 selects the measurement electrodes to be used to measure the electrocardiogram signal.

[0026] 6A to 6D are diagrams schematically illustrating the selection of a power-receiving circuit by the selection unit 21. In Figures 6A to 6D, a unique number from "1" to "6" is assigned to each of the six electrodes 11, and the period during which power is supplied from the battery 121 to the detection circuit 14 corresponding to each electrode 11 is colored. The electrode 11 numbered "1" corresponds to electrode 111, the electrode 11 numbered "2" corresponds to electrode 112, the electrode 11 numbered "3" corresponds to electrode 113, the electrode 11 numbered "4" corresponds to electrode 114, the electrode 11 numbered "5" corresponds to electrode 115, and the electrode 11 numbered "6" corresponds to electrode 116.

[0027] In FIG. 6A , power is always supplied to the detection circuits 141 to which electrodes 11 labeled "1" and "6" are connected. That is, in FIG. 6A , electrodes 11 labeled "1" and "6" are always selected as measurement electrodes. In FIG. 6A , it is assumed that at time T11, a symptom of a cardiac disease such as atrial fibrillation is detected based on electrocardiogram signals acquired by the measurement unit 22 using electrodes 11 labeled "1" and "6" and the detection circuits 141 to which these electrodes 11 are connected. Here, an example of a symptom of a cardiac disease such as atrial fibrillation is when the deviation in RRI between electrocardiogram waveforms exceeds a predetermined threshold. In this case, at time T11, the selection unit 21 starts supplying power to the detection circuits 142, 143, 144, and 145 to which electrodes 11 labeled "2," "3," "4," and "5" are connected. That is, the selection unit 21 causes the measurement unit 22 to start acquiring electrocardiogram signals using all of the electrodes 11 and detection circuits 141, 142, 143, 144, and 145 included in the electrocardiograph 1. At this stage, all of the electrodes "1," "2," "3," "4," "5," and "6" are selected as measurement electrodes. Then, when symptoms of cardiac disease are no longer detected at time T12, the selection unit 21 stops supplying power to the detection circuits 142, 143, 144, and 145 to which the electrodes 11 "2," "3," "4," and "5" are connected, and continues supplying power to the detection circuit 141 to which the electrodes 11 "1" and "6" are connected. At this stage, the electrodes 11 "1" and "6" are selected as measurement electrodes. That is, in the example of FIG. 6A , the detection of cardiac disease is triggered to start acquiring electrocardiogram signals using all of the electrodes 11 and detection circuits 14 as power-receiving circuits, thereby achieving acquisition of as many electrocardiogram signals as possible while symptoms of cardiac disease are being detected.

[0028] In FIG. 6B , power is always supplied to the detection circuits 141 to which electrodes 11 labeled "1" and "6" are connected. That is, in FIG. 6B , electrodes 11 labeled "1" and "6" are always selected as measurement electrodes. In FIG. 6B , it is assumed that, at time T21, noise contained in the electrocardiogram signals acquired by the measurement unit 22 using electrodes 11 labeled "1" and "6" and the detection circuits 141 to which these electrodes 11 are connected exceeds a threshold. In this case, at time T21, the selection unit 21 starts supplying power to the detection circuits 142, 143, 144, and 145 to which electrodes 11 labeled "2," "3," "4," and "5" are connected. That is, the selection unit 21 causes the measurement unit 22 to start acquiring electrocardiogram signals using all of the electrodes 11 and detection circuits 141, 142, 143, 144, and 145 included in the electrocardiograph 1. At this stage, all of electrodes 11 labeled "1," "2," "3," "4," "5," and "6" have been selected as measurement electrodes. Then, when the noise contained in the electrocardiogram signal becomes less than the threshold value at time T22, the selector 21 stops the supply of power to the detection circuits 142, 143, 144, and 145 to which the electrodes 11 "2," "3," "4," and "5" are connected, and causes the measurement unit 22 to continue acquiring electrocardiogram signals using the electrodes 11 "1" and "6" and the detection circuit 141 to which these electrodes 11 are connected. At this stage, the electrodes 11 "1" and "6" have been selected as the measurement electrodes. That is, in the example of FIG. 6B , while the noise contained in the electrocardiogram signal is equal to or greater than the threshold value, electrocardiogram signals are acquired using all the electrodes 11 and the detection circuits 14, so that the electrocardiogram signal can be acquired from the electrode 11 with the least noise among the six electrodes 11.

[0029] Referring to FIG. 6C , an example will be described in which power is supplied to all detection circuits 14 connected to electrodes 11 for a predetermined period, and the electrodes 11 to be used are selected in a predetermined cycle (10 minutes in the example of FIG. 6C ) based on the RRI of the electrocardiogram signal acquired during the predetermined period. When the electrocardiograph 1 is started (0 m00 s), power is supplied to all detection circuits 14 for a predetermined period (e.g., 30 seconds). The selector 21 selects the detection circuits 14 to which power is to be supplied from the start of the electrocardiograph 1 until 10 m00 s, based on the RRI of the electrocardiogram signal acquired during the 30 seconds. In the example of FIG. 6C , the detection circuit 141 to which electrodes 11 "1" and "6" are connected is selected. At this stage, electrodes 11 "1" and "6" are selected as measurement electrodes. After 10 m00 s have elapsed since the start of the electrocardiograph 1, the selector 21 supplies power to all detection circuits 14 for a predetermined period, and selects the electrodes 11 to which power is to be supplied for up to 20 m00 s. In the example of Fig. 6C, it is assumed that the detection circuit 143 connected to the electrodes 11 "3" and "6" is selected. At this stage, the electrodes 11 "3" and "6" are selected as measurement electrodes.

[0030] Next, when 20 msec has elapsed since the electrocardiograph 1 was started, the selector 21 supplies power to all detection circuits 14 for a predetermined time and selects a detection circuit 14 to which power is to be supplied for up to 30 msec. In the example of FIG. 6C , the selector 21 determines to stop the power supply to all detection circuits 14 based on electrocardiogram signals acquired between 30 msec and the predetermined time. Examples of when the selector 21 determines to stop the power supply to all detection circuits 14 include when electrocardiogram signals for a predetermined number of heartbeats (e.g., 30 beats) have been acquired, when electrocardiogram signals for a predetermined time period (e.g., 30 seconds) have been acquired, and when it is determined that there is no cardiac abnormality based on the electrocardiogram signals. Examples of when it is determined that there is no cardiac abnormality include when the RRI is constant. In this way, the selector 21 may repeatedly perform a process of supplying power to all detection circuits 14 and selecting a detection circuit 14 to use based on the acquired electrocardiogram signals in a predetermined cycle.

[0031] 6D , an example will be described in which power is supplied to all detection circuits 14 for a predetermined period, and based on the RRI of the electrocardiogram signal acquired during the predetermined period, it is determined whether or not to continue supplying power to only the detection circuits 14 corresponding to some of the electrodes 11. When the electrocardiograph 1 is started up, the selector 21 starts supplying power to the detection circuits 141 to which some of the electrodes 11 (electrodes 11 "1" and "6" in FIG. 6D ) are connected. At this stage, electrodes 11 "1" and "6" are selected as measurement electrodes. After 10 msec has elapsed since the electrocardiograph 1 was started up, the selector 21 supplies power to all detection circuits 14 for a predetermined period, and then determines whether or not to continue supplying power to only the detection circuits 141 to which electrodes 11 "1" and "6" are connected. In this determination, for example, if the RRI of the electrocardiogram signal is regular, it may be determined that power will continue to be supplied to only the detection circuits 141. Furthermore, in this determination, for example, if the RRI of the electrocardiogram signal is irregular, it may be determined to supply power to more detection circuits 14 (e.g., all detection circuits 14). An example of an irregular RRI is when the deviation of the RRIs between multiple waveforms in an electrocardiogram waveform showing the time-series changes of an acquired electrocardiogram signal is equal to or greater than a predetermined threshold. In the example of FIG. 6D , 10 msec after activation of the electrocardiograph 1, power is supplied to all detection circuits 14 for a predetermined period of time, and the selector 21 determines to continue power supply to only the detection circuit 141. At this stage, electrodes 11 labeled "1" and "6" are selected as measurement electrodes. In the example of FIG. 6D , power is supplied to all detection circuits 14 for a predetermined period of time, and the selector 21 determines to continue power supply to all detection circuits 14. At this stage, electrodes 11 labeled "1," "2," "3," "4," "5," and "6" are all selected as measurement electrodes.

[0032] Returning to Fig. 5, the measurement unit 22 performs electrocardiogram measurement using the detection circuit 14 selected by the selection unit 21. The measurement unit 22 is, for example, a circuit that acquires from the detection circuit 14 a potential difference between an electrode pair connected to the detection circuit 14 selected by the selection unit 21 and outputs the potential difference as an electrocardiogram signal. The calculation unit 23 calculates measurement results such as the heart rate and the presence or absence of atrial fibrillation using the electrocardiogram signal. The calculation unit 23 stores the calculated measurement results in the storage unit 24. The storage unit 24 is, for example, a non-volatile storage unit.

[0033] The output unit 25 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 25 displays, for example, information indicating the electrodes 11 selected by the selection unit 21 and time-series changes in the electrocardiogram signal (electrocardiogram waveform) acquired by the measurement unit 22. For example, a touch panel that detects touch operations by the user's finger or the like may be superimposed on the output unit 25. By superimposing a touch panel on the output unit 25, the electrocardiograph 1 can provide the user with an intuitive operating environment.

[0034] <Processing Flow> Fig. 7 is a diagram showing an example of a processing flow of the control main body 12 according to the embodiment. Hereinafter, an example of a processing flow of the control main body 12 according to the embodiment will be described with reference to Fig. 7 .

[0035] In step S1, the selection unit 21 selects a power-receiving circuit to which power from the battery 121 is to be supplied from the detection circuit 14 included in the electrocardiograph 1. The selection of the power-receiving circuit is as described with reference to, for example, Figures 6A to 6D. Note that when the processing of step S1 is executed upon startup of the electrocardiograph 1, the selection unit 21 may accept designation of an electrode 11 by the user, and may select the detection circuit 14 corresponding to the designated electrode 11 as the power-receiving circuit.

[0036] In step S2, the measurement unit 22 acquires an electrocardiogram signal using the detection circuit 14 selected in step S1 and the electrodes 11 connected to the detection circuit 14. In step S3, the calculation unit 23 calculates heartbeat information based on the electrocardiogram signal acquired in step S3. Examples of the heartbeat information include the heart rate and RRI.

[0037] In step S4, the selection unit 21 determines whether the heart rate information calculated in step S3 satisfies a change condition for changing the detection circuit 14 to be supplied with power. Examples of the change condition include when a symptom of a heart disease such as atrial fibrillation is detected, when noise contained in the electrocardiogram signal acquired by the measurement unit 22 exceeds a threshold, when it is determined that there is no abnormality in the heart based on the electrocardiogram signal, and when the RRI of the electrocardiogram signal is irregular. If the change condition is satisfied (YES in step S4), the process proceeds to step S1. If the change condition is not satisfied (NO in step S4), the process proceeds to step S5.

[0038] In step S5, it is determined whether or not the measurement has ended. Examples of whether or not the measurement has ended include when a predetermined measurement time has elapsed or when an instruction to end the measurement has been received from the user. If the measurement has ended (YES in step S5), the process ends. If the measurement has not ended (NO in step S5), the process proceeds to step S2.

[0039] <Effects of the Embodiment> When a large number of electrodes 11 and detection circuits 14 connected to each of the electrodes 11 are arranged on the band 10 and power is supplied from the battery 121 to all of the detection circuits 14, the power consumption of the electrocardiograph 1 increases, which may shorten the time that electrocardiographic measurement can be continued by the electrocardiograph 1. On the other hand, when electrocardiographic measurement is performed using a minimum number of electrodes 11 (e.g., two electrodes 11) arranged on the band 10 and the detection circuits 14 connected to the electrodes 11, the power consumption of the electrocardiograph 1 can be reduced, but the question arises as to whether the two arranged electrodes 11 are in a suitable position for electrocardiographic measurement. In this embodiment, by arranging a large number (six) of electrodes 11 on the band 10, it is expected that any one of the electrodes 11 will be located in a suitable position for electrocardiographic measurement. Furthermore, in this embodiment, power is not constantly supplied from the battery 121 to all of the detection circuits 14, but power is supplied from the battery 121 to the detection circuit 14 selected by the selector 21. Therefore, according to this embodiment, the power consumption of the electrocardiograph 1 can be reduced, and the measurement time for electrocardiogram measurement by the electrocardiograph 1 can be extended as long as possible.

[0040] In this embodiment, when the noise contained in the electrocardiogram signal acquired by some of the electrodes 11 reaches or exceeds a predetermined noise threshold, acquisition of the electrocardiogram signal by all of the electrodes 11 arranged on the band 10 is started. Among the electrodes 11 other than some of the electrodes 11, there may be electrodes 11 that can acquire electrocardiogram signals with less noise. Therefore, according to this embodiment, electrocardiogram measurement can be continued even if the electrocardiogram signal acquired by any of the electrodes 11 contains noise.

[0041] In this embodiment, when the deviation in RRI is equal to or greater than a threshold, acquisition of electrocardiogram signals is started by all of the electrodes 11 and detection circuit 14 arranged on the band 10. When the deviation in RRI is equal to or greater than a threshold, the occurrence of a cardiac disease such as atrial fibrillation is suspected. In this embodiment, when cardiac disease is suspected, acquisition of electrocardiogram signals by all of the electrodes 11 and detection circuit 14 is started, allowing for more detailed electrocardiogram measurement.

[0042] In this embodiment, power is supplied to all detection circuits 14 for a predetermined period, and the detection circuit 14 to which power is supplied from the battery 121 is selected based on the RRI of the electrocardiogram signal acquired during the predetermined period. Therefore, according to this embodiment, the electrocardiogram signals acquired from all of the multiple electrodes 11 and detection circuits 14 are compared, and power can be supplied from the battery 121 to the detection circuit 14 that is more suitable for acquiring the electrocardiogram signal.

[0043] Furthermore, in this embodiment, since the electrodes 11 are arranged on the band 10, it is easy to wear the electrocardiograph 1 so that the electrodes 11 come into contact with the living body of the subject.

[0044] <First Modification> In the embodiment described above, detection circuits 141, 142, 143, 144, and 145 are provided to connect pairs of electrode 116, the potential of which is fixed to ground, and other electrodes 11. However, the connection between electrodes 11 and detection circuits 14 is not limited to this configuration. In the first modification, variations in the connection between electrodes 11 and detection circuits 14 will be described.

[0045] 8 to 10 are diagrams illustrating variations in the connection between the electrodes 11 and the detection circuit 14 in the first modified example. In FIG. 8 , electrodes 111, 112, 113, 114, and 115 are connected to the switch 15. The output of the switch is connected to the detection circuit 241. Furthermore, the electrode 116, whose potential is fixed to ground, is connected to the detection circuit 241. The switch 15 selects the electrode 11 to be connected to the detection circuit 241 from among the electrodes 111, 112, 113, 114, and 115, and switches to the selected electrode 11. The switch 15 is switched by, for example, the selector 21. The configuration illustrated in FIG. 8 also allows switching of the electrodes 11 used to acquire electrocardiogram signals. Furthermore, power consumption of the detection circuit 241 can be reduced by using a selected portion of the electrodes 11 rather than using all of the electrodes 11.

[0046] In FIG. 9 , two switches, switches 151 and 152, are provided to switch the electrodes 11. Electrodes 111, 112, and 113 are connected to switch 151. Electrodes 114, 115, and 116 are connected to switch 152. The outputs of switches 151 and 152 are input to detection circuit 141. Switch 151 selects the electrode 11 to be connected to detection circuit 141 from among electrodes 111, 112, and 113. Switch 152 selects the electrode 11 to be connected to detection circuit 141 from among electrodes 114, 115, and 116. Switches 151 and 152 are switched by, for example, selector 21. Note that in the configuration of FIG. 9 , the potential of electrode 116 is not fixed to ground. The configuration illustrated in FIG. 9 also allows switching of the electrodes 11 used to acquire electrocardiogram signals. Furthermore, the power consumption of the detection circuit 341 can be reduced by using a selected portion of the electrodes 11 rather than by using all of the electrodes 11 .

[0047] In FIG. 10 , detection circuits 441, 442, and 443 to which a set of electrodes 11 are connected are provided. Electrodes 111 and 112 are connected to detection circuit 441. Electrodes 113 and 114 are connected to detection circuit 442. Electrodes 115 and 116 are connected to detection circuit 443. The selector 21 selects, for example, one of the detection circuits 441, 442, and 443 as the detection circuit to which power is supplied from battery 121. Note that in the configuration of FIG. 10 , the potential of electrode 116 is not fixed to ground. The configuration illustrated in FIG. 10 also allows switching of the electrodes 11 used to acquire electrocardiogram signals. Furthermore, the configuration illustrated in FIG. 10 , which uses only some of the detection circuits to measure electrocardiogram signals, can reduce power consumption of the electrocardiograph 1 compared to a configuration in which all of the detection circuits 441, 442, and 443 are used to measure electrocardiogram signals.

[0048] In the embodiment described above, electrocardiogram signals are acquired using a selected portion of the electrodes 11, and the number of electrodes 11 used to acquire electrocardiogram signals is increased when symptoms of cardiac disease are detected, when noise increases, etc. In the second modification, a configuration will be described in which the pair of electrodes 11 used to acquire electrocardiogram signals is switched within a sampling period.

[0049] Fig. 11 is a diagram schematically illustrating the selection of electrodes 11 used to acquire electrocardiogram signals in the second modified example. In Fig. 11, as in Fig. 6, the electrode 11 numbered "1" corresponds to electrode 111, the electrode 11 numbered "2" corresponds to electrode 112, the electrode 11 numbered "3" corresponds to electrode 113, the electrode 11 numbered "4" corresponds to electrode 114, the electrode 11 numbered "5" corresponds to electrode 115, and the electrode 11 numbered "6" corresponds to electrode 116. In the example of Fig. 11, the electrode 116 numbered "6" is a GND electrode whose potential is fixed to ground.

[0050] The selector 21 switches the electrode 11 to be combined with the electrode 116 whose potential is set to ground within a sampling period. The switching of the electrodes 11 may be achieved, for example, by connecting the electrodes 111, 112, 113, 114, and 115 to the switch 15, as described with reference to FIG. 8 , and by having the selector 21 select which of the electrodes 111, 112, 113, 114, and 115 to connect to the detection circuit 241. FIG. 11 illustrates an example in which the electrodes 111, 112, 113, 114, and 115 are connected to the detection circuit 241 in this order within a sampling period. In FIG. 11 , the sampling period is illustrated by, for example, T1 and T2. According to the second modification, electrocardiogram signals are acquired using some of the electrodes 11 within a sampling period, thereby reducing the power consumption of the electrocardiograph 1.

[0051] <Other Modifications> In the embodiment described above, when the deviation in RRI is equal to or greater than a threshold, acquisition of electrocardiogram signals by all of the electrodes 11 arranged on the band 10 is started. However, other events may be used as triggers to start acquisition of electrocardiogram signals by all of the electrodes 11. For example, when a P wave is not detected in electrocardiogram signals acquired by some of the electrodes 11, the selector 21 may start acquisition of electrocardiogram signals by all of the electrodes 11.

[0052] In the embodiment described above, when the deviation in RRI is equal to or greater than the threshold value, acquisition of electrocardiogram signals is started by all of the electrodes 11 and detection circuits 14 arranged on the band 10, but the electrocardiograph 1 is not limited to this configuration. For example, when the deviation in RRI is equal to or greater than the threshold value, the electrocardiograph 1 may acquire electrocardiogram signals using more detection circuits 14 than the already selected detection circuits 14.

[0053] The embodiments and modifications disclosed above can be combined with each other.

[0054] <Supplementary Note 1> A biosignal measuring device (1) comprising: a plurality of electrodes (11); a measurement unit (22) including a detection circuit (14) that detects a potential difference using the plurality of electrodes (11) and that measures an electrocardiogram signal of a subject using the detection circuit (14); a battery (121) that supplies power to the detection circuit (14); and a selection unit (21) that selects measurement electrodes (11) from the plurality of electrodes (11) to be used for measuring the electrocardiogram signal of the subject, based on the electrocardiogram signal of the subject measured using at least some of the electrodes (11) and the detection circuit (14), wherein the measurement unit (22) measures the electrocardiogram signal using the detection circuit and the measurement electrodes. <Supplementary Note 2> The biosignal measuring device according to Supplementary Note 1, wherein the selection unit (21) increases the number of the electrodes (11) selected as the measurement electrodes when an abnormality is detected in the electrocardiogram signal measured using at least some of the electrodes (11). <Supplementary Note 3> The biological signal measuring device (1) according to Supplementary Note 1, wherein the selector (21) selects all of the plurality of electrodes (11) as the measurement electrodes (11) when an abnormality is detected in the electrocardiogram signal measured using at least some of the electrodes (11). <Supplementary Note 4> The biological signal measuring device (1) according to Supplementary Note 2 or 3, wherein the abnormality in the electrocardiogram signal includes a case where an R-R interval (RRI) deviation in a time-series change in the electrocardiogram signal is equal to or greater than a first threshold. <Supplementary Note 5> The biological signal measuring device (1) according to any one of Supplements 2 to 4, wherein the abnormality in the electrocardiogram signal includes a case where a P wave is not detected in the electrocardiogram signal. <Supplementary Note 6> The biological signal measuring device (1) according to any one of Supplements 2 to 5, wherein the abnormality in the electrocardiogram signal includes a case where a magnitude of noise included in the electrocardiogram signal is equal to or greater than a second threshold. <Supplementary Note 7> The biological signal measuring device (1) according to any one of Supplementary Notes 1 to 6, wherein the selection unit (21) executes measurement of the electrocardiogram signal using all of the plurality of electrodes (11) at predetermined intervals, and determines which of the plurality of electrodes (11) should be used as the measurement electrode (11) based on the electrocardiogram signal measured using all of the plurality of electrodes (11).<Supplementary Note 8> The biosignal measuring device (1) according to any one of Supplementary Notes 1 to 7, further comprising a belt-shaped fixing member that is wrapped around the subject, and the plurality of electrodes are arranged on the fixing member.

[0055] DESCRIPTION OF SYMBOLS 1. Electrocardiograph 10. Band 11. Electrode 12. Control unit 13. Fixing mechanism 14. Detection circuit 15. Switch 21. Selection unit 22. Measurement unit 23. Calculation unit 24. Storage unit 25. Output unit 111. Electrode 112. Electrode 113. Electrode 114. Electrode 115. Electrode 116. Electrode 141. Detection circuit 142. Detection circuit 143. Detection circuit 144. Detection circuit 145. Detection circuit 151. Switch 152. Switch 121. Battery 241. Detection circuit 341. Detection circuit 441. Detection circuit 442. Detection circuit 443. Detection circuit

Claims

1. A biosignal measuring device comprising: a plurality of electrodes; a measurement unit including a detection circuit that detects a potential difference using the plurality of electrodes and measures an electrocardiogram signal of a subject using the detection circuit; a battery that supplies power to the detection circuit; and a selection unit that selects measurement electrodes to be used for measuring the electrocardiogram signal of the subject from the plurality of electrodes based on the electrocardiogram signal of the subject measured using at least some of the plurality of electrodes and the detection circuit, wherein the measurement unit measures the electrocardiogram signal using the detection circuit and the measurement electrodes.

2. The biosignal measuring device of claim 1, wherein the selection unit increases the number of electrodes selected as the measurement electrodes when an abnormality is detected in the electrocardiogram signal measured using at least some of the electrodes.

3. The biosignal measuring device of claim 1, wherein the selection unit selects all of the plurality of electrodes as the measurement electrodes when an abnormality is detected in the electrocardiogram signal measured using at least some of the electrodes.

4. The biosignal measuring device of claim 2, wherein the abnormality in the electrocardiogram signal includes a case where an R-R Interval (RRI) deviation in the time series change in the electrocardiogram signal is equal to or greater than a first threshold value.

5. The biosignal measuring device according to claim 2, wherein the abnormality in the electrocardiogram signal includes a case where a P wave is not detected in the electrocardiogram signal.

6. The biosignal measuring device according to claim 2, wherein the abnormality in the electrocardiogram signal includes a case where the magnitude of noise contained in the electrocardiogram signal is equal to or greater than a second threshold value.

7. The biosignal measuring device of claim 1, wherein the selection unit executes measurement of the electrocardiogram signal using all of the plurality of electrodes at predetermined intervals, and determines which of the plurality of electrodes to use as the measurement electrode based on the electrocardiogram signal measured using all of the plurality of electrodes.

8. A biosignal measuring device as described in any one of claims 1 to 7, further comprising a band-shaped fixing member that is wrapped around the subject, and the multiple electrodes are arranged on the fixing member.

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