Electrocardiographic measurement device and electrocardiographic measurement method

Abstract

This electrocardiographic measurement device comprises: an electrode group including a plurality of electrodes which come into contact with the skin of a subject to be measured; a high-pass filter group including a plurality of high-pass filters to which potential signals output from the electrodes included in the electrode group are respectively input; a multiplexer to which processed signals output from the high-pass filters included in the high-pass filter group are input, and which selects and outputs the processed signals output from any pair of the high-pass filters included in the high-pass filter group; an amplifier which differentially amplifies the processed signals output from the multiplexer; an A / D converter which performs analog-to-digital conversion on the amplified signals output from the amplifier; and a storage unit which stores, in a time series manner, the converted signals output from the A / D converter.

Description

Electrocardiogram measuring device and electrocardiogram measuring method

[0001] The present invention relates to an electrocardiogram measuring device and an electrocardiogram measuring method.

[0002] 2. Description of the Related Art Up until now, upper arm electrocardiographs have been proposed that are worn on the upper arm of a subject to measure electrocardiographic waveforms (see, for example, Patent Documents 1 and 2).

[0003] With this type of upper arm electrocardiograph, the signal obtained through the electrodes in contact with the skin of the upper arm is only a few tenths weaker than when measuring electrocardiogram waveforms using lead I, making it difficult to observe unless the signal is amplified by nearly 60 dB.

[0004] In addition, such upper arm electrocardiographs generally use reusable stainless steel electrodes to monitor electrocardiogram waveforms over long periods of time. Stainless steel electrodes have a large and highly variable resting electrode potential, which must be removed to achieve high amplification of the signal acquired through the electrodes. Furthermore, because stainless steel electrodes are not adhesive, contact conditions change with body movement, resulting in noise.

[0005] Furthermore, since the locations at which characteristics of an electrocardiogram waveform appear vary depending on the subject, measurements must be taken at multiple locations to obtain an electrocardiogram waveform.

[0006] Furthermore, since the device is to be worn for a long period of time, it is required to be lightweight, small, and easy to wear, thereby reducing the discomfort of wearing it.

[0007] JP 2011-147582 A JP 2011-147583 A

[0008] The upper arm electrocardiographs described in Patent Documents 1 and 2 are designed to be used at a level where the influence of the electrode resting potential can be ignored, and in reality, the presence of the electrode resting potential causes the signal to saturate when highly amplified, making measurement impossible. Furthermore, if the contact of the reference electrode becomes unstable, noise may occur in all electrode signals. Furthermore, the upper arm electrocardiograph described in Patent Document 2 is provided with a circuit including an instrumentation amplifier, an LPF, and an A / D converter for each electrode, which increases the circuit size and power consumption.

[0009] The present invention aims to provide an electrocardiogram measuring device that can sufficiently amplify electrocardiogram signals, reduce power consumption, and be miniaturized, even when using materials such as stainless steel, where the magnitude and variation of the electrode resting potential cannot be ignored.

[0010] In order to solve the above problems, the present invention provides an electrocardiogram measuring device comprising: an electrode group including a plurality of electrodes that contact the skin of a person to be measured; a high-pass filter group including a plurality of high-pass filters to which potential signals output from the electrodes included in the electrode group are respectively input; a multiplexer that receives processed signals output from the high-pass filters included in the high-pass filter group and selects and outputs the processed signals output from a set of any two of the high-pass filters included in the high-pass filter group; an amplifier that differentially amplifies the processed signals output from the multiplexer; an AD converter that performs analog-to-digital conversion of the amplified signals output from the amplifier; and a memory unit that stores the converted signals output from the AD converter in chronological order.

[0011] This allows potential signals output from the electrodes included in the electrode group to be input to a high-pass filter, thereby removing electrode rest potential components, enabling sufficient amplification in the downstream amplifier. Furthermore, the multiplexer selects processed signals output from any two high-pass filter pairs included in the high-pass filter group, making it possible to measure electrocardiogram waveforms from electrode pairs that are less affected by body movement. Furthermore, the multiplexer selects processed signals output from any two high-pass filter pairs included in the high-pass filter group, making it possible to measure electrocardiogram waveforms from a larger number of electrode pairs with a smaller number of electrodes. Furthermore, the multiplexer selects and outputs processed signals output from any two high-pass filter pairs included in the high-pass filter group, thereby requiring only one downstream circuit system from the differential amplifier, thereby enabling the electrocardiogram measurement device to be more compact.

[0012] In the present invention, the multiplexer may be configured to switch the processed signal from any one of the high-pass filter groups in a time-division manner and output the processed signal to the amplifier.

[0013] According to this, the processed signals from any pair of high-pass filters included in the group of high-pass filters are switched in a time-division manner and output from the multiplexer, so that for all pairs of any two electrodes included in the group of electrodes, electrocardiographic waveforms based on the potential signals output from those pairs of electrodes can be obtained. As a result, electrocardiographic waveforms that satisfy appropriate conditions can be used from among the electrocardiographic waveforms obtained from the group of electrodes including multiple electrodes.

[0014] Furthermore, in the present invention, a signal extraction unit may be provided that extracts the converted signals stored in the storage unit in time series for each group.

[0015] According to this, the signal extraction unit obtains information on the time change of the converted signal obtained from a specific set of electrodes included in the electrode group.

[0016] In the present invention, the plurality of electrodes included in the electrode group may be made of stainless steel.

[0017] In this way, even if the electrodes included in the electrode group are made of stainless steel, which has a large and variable resting electrode potential component, the potential signals output from the electrodes are input to the high-pass filter, which removes the resting electrode potential component, allowing for sufficient amplification in the downstream amplifier.Furthermore, the electrodes can be used repeatedly for a long period of time.

[0018] In the present invention, the electrode group may be arranged on the upper arm of the person being measured.

[0019] The present invention also provides an electrocardiogram measurement method for measuring the electrocardiogram waveform of a subject, comprising the steps of: acquiring a potential signal from each electrode of an electrode group including a plurality of electrodes in contact with the skin of the subject; outputting a processed signal obtained by removing a resting electrode potential component from the potential signal; switching between pairs of any two of the electrodes included in the electrode group in a time-division manner to output the processed signal based on the potential signal acquired from the pair; differentially amplifying the processed signals of the pairs output by switching in a time-division manner to output amplified signals; outputting converted signals obtained by analog-to-digital conversion of the amplified signals; storing the converted signals in chronological order; and extracting the converted signals stored in chronological order for each pair in chronological order.

[0020] This removes the electrode rest potential component from the potential signal output from the electrodes included in the electrode group, enabling sufficient amplification in a downstream amplifier. Furthermore, because the processed signals based on potential signals acquired from a pair of any two electrodes included in the electrode group can be switched between pairs in a time-division manner, it becomes possible to measure electrocardiographic waveforms from a pair of electrodes that is less affected by body movement. Furthermore, because the processed signals based on potential signals acquired from a pair of any two electrodes included in the electrode group can be switched between pairs in a time-division manner, it becomes possible to measure electrocardiographic waveforms from a larger number of electrode pairs with a smaller number of electrodes. Furthermore, because the processed signals based on potential signals acquired from a pair of any two electrodes included in the electrode group are differentially amplified by switching between pairs in a time-division manner, only one system of circuitry is required from the differential amplifier onward, thereby enabling the device to be more compact.

[0021] According to the present invention, it is possible to provide an electrocardiogram measuring device that can sufficiently amplify electrocardiogram signals, reduce power consumption, and be miniaturized, even when materials such as stainless steel are used, in which the magnitude and variation of the electrode resting potential cannot be ignored.

[0022] FIG. 1 is a perspective view of the appearance of an electrocardiograph according to an embodiment. FIG. 2 is a block diagram showing the hardware configuration of the electrocardiograph according to an embodiment. FIG. 3 is a flowchart illustrating the processing procedure of an electrocardiographic measurement method in the electrocardiograph according to an embodiment. FIG. 4 is a schematic diagram showing sampling in the electrocardiograph according to an embodiment. FIG. 5 is a schematic diagram showing details of one sampling in the electrocardiograph according to an embodiment. FIG. 6 is a schematic diagram showing the structure of data stored in the electrocardiograph according to an embodiment.

[0023] An example of an embodiment of the present invention will be described below. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this example are not intended to limit the scope of the present invention to those only.

[0024] The electrocardiograph 10 is worn around the outer circumference of the subject's upper arm and measures electrocardiographic waveforms. The electrocardiograph 10 may also have a function of detecting biological signals other than electrocardiographic waveforms. The electrocardiograph 10 corresponds to the electrocardiographic measuring device of the present invention.

[0025] 1 is a perspective view showing the appearance of an electrocardiograph 10. The electrocardiograph 10 mainly includes a band 11 and a main body 12 provided on the band 11. The band 11 is fixed to the main body 12.

[0026] The main body 12 has a frame 121, an operation unit 123 provided on the frame 121, a display unit 124 (see FIG. 2 ) provided on the frame 121, a pair of support units 121a and 121b provided on the frame 121, a first electrode 21 provided on the support unit 121a, and a second electrode 22 provided on the support unit 121b. The operation unit 123 has operation buttons for inputting instructions such as turning the power of the main body 12 on / off, starting measurement, and stopping measurement. The display unit 124 is composed of a liquid crystal display or the like that displays various information such as electrocardiogram waveforms.

[0027] When the electrocardiograph 10 is attached to the user's upper arm, the support parts 121a and 121b are on the living body side (back side) of the frame 121, the operation part 123 is in a position where it can be operated with the user's fingers, etc., and the display part 124 is in a position where it can be seen by the user, i.e., on the side opposite the living body (front side). The support parts 121a and 121b are members formed in a generally wedge shape from a flexible material that can be elastically deformed.

[0028] A first electrode 21 is fixed to the support portion 121a. A second electrode 22 is fixed to the other support portion 121b. The first electrode 21 and the second electrode 22 are used as sensors or transducers that detect electric potential. The first electrode 21 and the second electrode 22 are formed into plate shapes, for example, from stainless steel plates, and are spaced apart from each other.

[0029] The band 11 includes a first band portion 111 and a second band portion 112. The first band portion 111 and the second band portion 112 are strip-shaped and extend longitudinally. Two electrodes, a third electrode 23 and a fourth electrode 24, are fixed to the first band portion 111. Two electrodes, a fifth electrode 25 and a sixth electrode 26, are fixed to the second band portion 64. The third electrode 23, the fourth electrode 24, the fifth electrode 25, and the sixth electrode 26 are formed into a plate-like shape using stainless steel plates. Here, an example is described in which six electrodes, the first electrode 21 to the sixth electrode 26, are arranged along the extension direction of the band 11. However, the number of electrodes and the arrangement of the electrodes are not limited to this, and electrodes may be arranged in a direction perpendicular to the extension direction of the band 11, i.e., offset along the longitudinal direction of the arm when worn.

[0030] The main body 12 is fixed to a desired position on the user's upper arm, for example, using the band 11. The lengths of the first band portion 111 and the second band portion 112 of the band 11 may be constant regardless of the intended user, or may be varied depending on the intended user. For example, a lineup of bands 11 with lengths intended for adults, children, men, women, etc. may be available.

[0031] The first band portion 111 has one end 111a, the other end 111b, and an elastic portion 111c. A hook-and-loop fastener is formed on the other end 111b side, and the length of the first band portion 111 can be adjusted by adjusting the position of a folded portion 111d that passes through a ring member 114b (described later) and folds back, and then connecting the hook-and-loop fasteners together.

[0032] The second band portion 112 has a strip-shaped band main body 113 and a ring-shaped ring member 114 provided at a position that will become the band end along the longitudinal direction of the second band portion 112. The band main body 113 has one end 113a, the other end 113b, and a folded-back portion 113c. The one end 113a and the other end 113b of the band main body 113 are continuous. The one end 113a of the band main body 113 is supported by the main body portion 12.

[0033] Fig. 2 is a diagram showing the hardware configuration of the electrocardiograph 10. Fig. 3 is a flowchart showing the processing steps of an electrocardiographic measurement method (method for measuring an electrocardiographic waveform) using the electrocardiograph 10. The electrocardiograph 10 mainly includes an electrode group 20, an electrode resting potential removal unit 30 including a high-pass filter group 320, a switching unit 40, an amplification and conversion unit 50, a control unit 60, a storage device 70, an operation unit 123, and a display unit 124.

[0034] The electrode group 20 includes a first electrode 21, a second electrode 22, a third electrode 23, a fourth electrode 24, a fifth electrode 25, and a sixth electrode 26. The first electrode 21 to the sixth electrode 26 included in the electrode group 20 contact the skin of the user's upper arm when the electrocardiograph 10 is worn. Potential signals S11 to S16 generated at the contact sites are acquired. As shown in FIG. 3 , it is determined whether or not sampling timing has arrived (step St101). When the sampling timing arrives, the potential signals S11 to S16 generated at the contact sites by the first electrode 21 to the sixth electrode 26 are acquired. The potential signals S11 to S16 are input via buffers 311 to 316 to a high-pass filter group 320 consisting of high-pass filters 321 to 326. That is, the potential signal S11 acquired by the first electrode 21 is input to the buffer 311, and the signal S21 output from the buffer 311 is input to the high-pass filter 221. The potential signal S12 acquired by the second electrode 22 is input to a buffer 312, and the signal S22 output from the buffer 312 is input to a high-pass filter 322. Similarly, the potential signal S16 acquired by the sixth electrode 26 is input to a buffer 316. The buffers 311 to 316 are circuits that adjust the impedance between the first electrode 21 to the sixth electrode 26 and the high-pass filters 321 to 326, respectively. The high-pass filters 321 to 326 are circuits that attenuate signals below a predetermined frequency, and by passing the signals through the high-pass filters 321 to 326, the electrode resting potential components included in the potential signals from the first electrode 21 to the sixth electrode 26 are removed. The high-pass filters 321 to 326 remove the electrode resting potential components due to the first to sixth electrodes 21 to 26 from the signals S21 to S26 input from the buffers 311 to 316, and output processed signals S31 to S36 to the multiplexer 41 (step St103). In this way, by removing the electrode resting potential components included in the potential signals from the first to sixth electrodes 21 to 26 using the high-pass filters 321 to 326, clipping in the amplification at the subsequent stage can be avoided, and the electrocardiographic signals obtained from the first to sixth electrodes 21 to 26 can be sufficiently amplified.Furthermore, with this configuration, stainless steel, which has a large electrode resting potential and a large variation in it, can be used as the electrode material, so that an electrocardiograph 10 that can be used repeatedly for a long period of time can be provided.

[0035] Based on a control signal from the control unit 60, the multiplexer 41 switches between sets of two processed signals from the six processed signals S31 to S36 input from the high-pass filters 321 to 326 in a time-division manner, according to a method described below, and outputs the signals to the instrumentation amplifier 42 (step St104). In this way, the multiplexer 41 switches between sets of two processed signals from the processed signals S31 to S36 in a time-division manner and outputs the signals to the instrumentation amplifier 42. This makes it possible to acquire electrocardiographic waveforms that satisfy appropriate conditions, such as electrode sets that are less affected by body movement. Furthermore, this configuration makes it possible to acquire electrocardiographic waveforms from a larger number of electrode sets using a smaller number of electrodes.

[0036] The instrumentation amplifier 42 is an operational amplifier for differential amplification having a high input impedance. The instrumentation amplifier 42 is a circuit that amplifies the difference between the two processed signals S41 and S42 input from the multiplexer 41 with a constant gain. Here, the instrumentation amplifier 42, or the instrumentation amplifier 42 and the amplifier circuit 51, correspond to the amplifier of the present invention.

[0037] The signal S50 output from the instrumentation amplifier 42 is input to the amplifier circuit 51 and amplified to a level at which the required resolution can be obtained. The amplified signal S60 output from the amplifier circuit 51 is input to the AD converter 52 (step St105).

[0038] The AD converter 52 is a circuit that converts the analog signal amplified by the amplifier circuit 51 into a digital signal. The converted signal S70, which is a digital signal output from the AD converter 52, is input to the control unit 60 (step St106). In this way, the multiplexer 41 switches between two sets of processed signals from the processed signals S31 to S36 in a time-division manner and outputs them to the instrumentation amplifier 42, the amplifier circuit 51, and the AD converter 52. This means that only one system of circuits downstream from the instrumentation amplifier 42 is required. This reduces electrode consumption, makes it possible to miniaturize the electrocardiograph 10, and reduces discomfort when wearing the device.

[0039] The control unit 60 is a microcomputer equipped with a CPU 61, a ROM (Read Only Memory) 62, and a RAM (Random Access Memory) 63. The electrocardiogram measurement method described herein is performed by executing a program stored in the ROM. The converted signal S70 input from the AD converter 52 is stored in the RAM 62 by the CPU 61 of the control unit 60, and then undergoes predetermined processing before being stored in the storage device 70, which is composed of a non-volatile memory (steps St107 and St108).

[0040] Next, details of the electrocardiogram measurement method according to this embodiment will be described. FIG. 4 is a graph illustrating the sampling timing of an electrocardiogram waveform, with the horizontal axis representing time [ms] and the vertical axis representing voltage [mV]. In reality, the first electrode 21 to the sixth electrode 26 constituting the electrode group 20 are in contact with different parts of the user's upper arm, and therefore do not measure a single electrocardiogram waveform. However, a single electrocardiogram waveform is shown here as a schematic diagram to explain the sampling timing. For example, the electrocardiogram waveform is sampled every 8 ms. The vertical dashed lines in FIG. 4 indicate the sampling timing every 8 ms.

[0041] 5 shows an enlarged view of the switching method of the multiplexer 41 in one sampling cycle indicated by the dotted circle in FIG. 4. The multiplexer 41 switches between pairs of two signals to be output to the instrumentation amplifier 42 from the processed signals S31 to S36 input from the six high-pass filters 321 to 326 in a time-division manner. There are 15 possible pairs of signals created from the six processed signals S31 to S36, and these 15 types of signal pairs are input to the instrumentation amplifier 42 as processed signals S41 and S42, which are pairs of signals that are sequentially switched in a time-division manner. As shown in FIG. 5, in one sampling cycle, the signal pairs output from the multiplexer 41 are switched in succession from pair 1 to pair 2 to pair 3, up to pair 15, in μs units.

[0042] In this way, each pair of processed signals is input in time series to the instrumentation amplifier 42 and the amplifier circuit 51, and is AD converted in the AD converter 52. The AD-converted converted signal S70 is stored in time series in the RAM 63 of the control unit 60 (step St107). The upper diagram of FIG. 6 schematically shows the configuration of the data stored in the RAM 63. In this way, data of each processed signal pair is stored in the RAM 63 in order from pair 1 to pair 15, and further, data of each processed signal sampled at the next timing is similarly stored in order from pair 1 to pair 15. Here, the RAM 63 corresponds to the storage unit of the present invention.

[0043] As described above, the data stored in the RAM 63 of the control unit 60 is sorted by pair by the control unit 60, and as shown in the lower part of Fig. 6, only the data of pair 1 is extracted and stored in the storage device 70. Similarly, for each of the signal pairs of pair 2, pair 3, and pair 15, only the data of each pair is extracted and stored in the storage device 70 (step St108). Here, the control unit 60 corresponds to the signal extraction unit of the present invention.

[0044] That is, the pairs of processed signals S41 and S42 output from the multiplexer 41 are switched in a time-division manner, and at a given time, only one signal pair is subject to subsequent processing, but by switching the multiplexer 41, all signal pairs are sequentially subject to subsequent processing. Then, in the control unit 60, the data of each signal pair is stored in RAM 63 as data arranged in chronological order. By sorting the data in which different signal pairs are arranged in chronological order as described above and extracting the signals of each pair, each signal pair, i.e., the electrocardiographic waveform of any two electrode pairs of the first electrode 21 to the sixth electrode 26 included in the electrode group 20, is measured.

[0045] 10 electrocardiograph 20 electrode group 21 to 26 electrodes 41 multiplexer 42 instrumentation amplifier 51 amplifier circuit 52 AD converter 63 RAM 320 high-pass filter group 321 to 326 high-pass filters

Claims

1. An electrocardiogram measuring device comprising: an electrode group including a plurality of electrodes that contact the skin of a person being measured; a high-pass filter group including a plurality of high-pass filters to which potential signals output from the electrodes included in the electrode group are respectively input; a multiplexer that receives processed signals output from the high-pass filters included in the high-pass filter group and selects and outputs the processed signals output from a set of any two of the high-pass filters included in the high-pass filter group; an amplifier that differentially amplifies the processed signals output from the multiplexer; an AD converter that performs analog-to-digital conversion of the amplified signals output from the amplifier; and a memory unit that stores the converted signals output from the AD converter in chronological order.

2. The electrocardiogram measuring device according to claim 1, wherein the multiplexer switches the processed signal from any one of the groups included in the group of high-pass filters in a time-division manner and outputs the processed signal to the amplifier.

3. The electrocardiogram measuring device according to claim 2, further comprising a signal extracting section for extracting the converted signals stored in the memory section in time series for each group.

4. The electrocardiogram measuring device according to claim 1, wherein the plurality of electrodes included in the electrode group are made of stainless steel.

5. An electrocardiogram measuring device according to any one of claims 1 to 4, characterized in that the electrode group is placed on the upper arm of the person being measured.

6. An electrocardiogram measurement method for measuring the electrocardiogram waveform of a subject, comprising: a step of acquiring a potential signal from each electrode of an electrode group including a plurality of electrodes in contact with the skin of the subject; a step of outputting a processed signal by removing an electrode resting potential component from the potential signal; a step of switching between pairs of any two of the electrodes included in the electrode group in a time-division manner and outputting the processed signal based on the potential signal acquired from the pair; a step of differentially amplifying the processed signals of the pair output by switching in a time-division manner and outputting an amplified signal; a step of outputting a converted signal by analog-to-digital converting the amplified signal; a step of storing the converted signals in chronological order; and a step of extracting the converted signals stored in chronological order for each pair in chronological order.

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