CROSS REFERENCE TO RELATED APPLICATION

This Application is a 371 of PCT/JP2018/034221 filed on Sep. 14, 2018 which, in turn, claimed the priority of Japanese Patent Application No. 2017-177818 filed on Sep. 15, 2017, both applications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electrocardiogram waveform measurement system and an electrocardiogram waveform measurement method. Particularly, the present invention relates to an electrocardiogram waveform measurement system or the like that measures an electrocardiogram waveform using multiple fabric electrodes fixed to a shirt.

BACKGROUND ART

In order to obtain effective and highly reliable information using a wearable sensor for supporting a medical diagnosis or health care, an electrocardiogram measurement is employed as an essential method. A commercially available method for measuring a photoelectric pulse wave on a subject's wrist provides only insufficient precision. Accordingly, other measurement methods have been proposed as prospective methods, examples of which include a measurement method employing disposable electrodes and a measurement method employing shirt-type electrocardiogram electrodes. In Patent document 1, a measurement method is described in which a shirt is provided with multiple electrodes, with one or two configured as different electrodes and the remaining electrodes configured as an indifferent electrodes (positive reference potential electrodes), so as to detect a biological signal.

CITATION LIST

Patent Literature[Patent Document 1]

International Publication WO 2015/115441 pamphlet

SUMMARY OF INVENTION

Technical Problem

However, in a case of measuring the RRI using disposable electrodes according to conventional techniques, in some cases, such an arrangement has a problem of the occurrence of redness or inflammation of the skin, or a problem of the occurrence of adhesive paste marks.

Furthermore, it is known that even in such a case in which measurement is performed using a shirt provided with such multiple electrodes, such an arrangement has a problem in that the optimum electrode layout changes depending on individual difference such as the physique of the wearer. With shirt-type electrodes, the shirt size and electrode positions are configured to be fixed. Accordingly, with measurements using such shirt-type electrodes, individual differences are likely to have a large effect. This leads to a large problem in that, in about 10% of subjects, such an arrangement provides an electrocardiogram with a very small amplitude, or such an arrangement provides an inverted characteristic wave.

The sole countermeasure for solving such a problem is to provide a shirt with many electrode members at many positions as in the background art described in Patent document 1. However, in a case of generating a multi-channel electrocardiogram, this leads to a problem of complicated wiring. In a case of providing wireless multiplexing transmission thereof, such an arrangement requires large electric power. Such an arrangement cannot be provided from the viewpoint of wearable size and wearable weight.

Furthermore, conventionally, a specialist supports the measurement. Accordingly, the measurement is performed assuming that all the electrodes arranged at predetermined portions of a shirt are able to detect biological signals as in the background art described in Patent document 1. However, such electrodes provided to a shirt or the like have the potential to cause a problem in that a correct biological signal cannot be detected due to the occurrence of a gap between it and the living subject. Also, due to individual differences, such a correct biological signal cannot necessarily be detected using such an electrode fixed to the shirt. If there will be an increased need in the future for electrocardiogram measurement without involving a specialist so as to provide improved health care, or for a wearable device used for health promotion, and for prevention and early detection of diseases, it is difficult to realize the assumption that the biological signals can be measured via all the multiple electrodes of a shirt-type wearable device. This leads to difficulty in measuring the biological signals using such electrodes.

Accordingly, it is a purpose of the present invention to propose an electrocardiogram waveform measurement system or the like configured to be suitable for measuring an electrocardiogram waveform with high precision using multiple electrodes provided to an article of clothing.

Solution of Problem

A first aspect of the present invention relates to an electrocardiogram waveform measurement system configured to measure an electrocardiogram waveform using multiple electrodes fixed to an article of clothing. The electrocardiogram waveform measurement system comprises: an electrocardiogram waveform generating unit configured to generate an electrocardiogram waveform using measurement values acquired by the electrodes for each of multiple channels with a combination of a part of the multiple electrodes as a channel; an R wave processing unit configured to measure an R wave in the electrocardiogram waveform for each channel; a degree-of-concentration calculation unit configured to calculate a degree of data concentration in a dynamic range of the electrocardiogram waveform for each channel; and a channel selecting unit configured to select a combination of the electrodes to be used to measure the electrocardiogram waveform using the number of times the R wave has been measured by the R wave processing unit and the degree of data concentration calculated by the degree-of-concentration calculation unit.

A second aspect of the present invention relates to the electrocardiogram waveform measurement system according to the first aspect. The electrodes are each configured as a fabric electrode. The electrocardiogram waveform measurement system comprises: a saturation processing unit configured to detect a portion that deviates from the dynamic range; and an amplitude detection unit configured to detect an amplitude of the electrocardiogram waveform. The electrocardiogram waveform generating unit generates an electrocardiogram waveform for each of the combinations using the measurement values acquired in a predetermined period of time by the fabric electrodes. The channel selecting unit selects, from the multiple channels, a channel at which the number of times the R wave has been detected is within a predetermined range, which is detected by the R wave processing unit, with higher priority than a channel at which the number of times the R wave has been detected deviates from a predetermined range. The channel selecting unit selects, from the multiple channels, a channel that exhibits a higher degree of data concentration, which is calculated by the degree-of-concentration calculation unit, with higher priority than a channel that exhibits a lower degree of data concentration. The channel selecting unit selects, from the multiple channels, a channel that does not deviate from a dynamic range, which is detected by the saturation processing unit, with higher priority than a channel that deviates from the dynamic range. The channel selecting unit selects, from the multiple channels, a channel that provides an electrocardiogram waveform having a larger amplitude, which is detected by the amplitude detection unit, with higher priority than a channel that provides an electrocardiogram waveform having a smaller amplitude.

A third aspect of the present invention relates to an electrocardiogram waveform measurement method for measuring an electrocardiogram waveform using multiple electrodes fixed to an article of clothing. The electrocardiogram waveform measurement method comprises: electrocardiogram waveform measuring in which, with a combination of a part of the multiple electrodes as a channel, an electrocardiogram waveform is generated using measurement values acquired by the electrodes for each of multiple channels; R wave processing in which an R wave in the electrocardiogram waveform is measured for each channel; degree-of-concentration calculation in which a degree of data concentration is calculated for each channel in a dynamic range of the electrocardiogram waveform; and channel selecting in which a combination of the electrodes to be used to measure the electrocardiogram waveform is selected using the number of times the R wave has been measured in the R wave processing and the degree of data concentration calculated in the degree-of-concentration calculation.

Advantageous Effects of Invention

The present inventors have found that continuous measurement and analysis of variation of the R wave interval (R-R interval), which is a characteristic wave of an electrocardiogram, allows prediction of epileptic seizures or drowsy driving, screening for sleep apnea syndrome, and early diagnosis of dementia with Lewy bodies, to be supported based on irregularity in the autonomic nervous system. The shirt-type electrode is applied as a wearable health care device, which allows the user to use it in daily life without specialized knowledge. The present invention proposes a combination of the findings of the present inventors and a shirt-type electrode. With such an arrangement, each channel, which is a combination of multiple fabric electrodes, is evaluated in a two-dimensional manner using the time axis and other axes that differ from the time axis, i.e., at least the number of R wave detections and the degree of R wave concentration in the dynamic range. The electrocardiogram waveform is measured using the channel selected based on the evaluation result, thereby allowing the electrocardiogram waveform to be detected with improved detection precision using the multiple electrodes.

For example, in a case in which the electrocardiogram waveforms are detected at multiple channels, there is a large difference between them in the detection precision in the electrocardiogram waveform detection due to the disposition of the heart or the like. With each aspect of the present invention, such an arrangement ensures that, when a given fabric electrode is not in contact with a living subject, such a channel is not selected. Furthermore, when the electrocardiogram waveforms are detected at multiple channels, such an arrangement selects the optimum-layout channel determined depending on individual differences or the like, thereby providing improved detection precision. In actuality, as described later, even in a case of measuring a subject for which it has not been possible to measure the R-R interval at all due to lead setting failure in measuring the electrocardiogram using the shirt-type electrode, such an application according to the present invention provides measurement with extremely high precision. Furthermore, with the second aspect of the present invention, the electrocardiogram waveform is measured giving consideration to the saturation processing and the amplitude, thereby providing the electrocardiogram waveform measurement with improved precision.

Here, channel selecting processing is performed before the electrocardiogram waveform measurement, for example. Also, this arrangement may support electrocardiogram waveform measurement with channel selecting during sleep. For example, the channel may be re-selected when the electrocardiogram waveform measurement accuracy becomes poor due to a change in the subject's orientation when the subject turns over in bed or the like. Also, the channel selection may be periodically performed. A program developed as an example of the present invention is implemented on a compact-size, low-power microcontroller. Accordingly, such a signal processing system can be provided on a compact-size circuit substrate having a size of 3 cm×7 cm, which may be suitably applied to a wearable device.

