This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-075631, filed on Apr. 1, 2013; the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to an electrocardiograph, a method for measuring an electrocardiogram, and a computer program product.
Recently, awareness of health care has been increasing. In accordance with this, an electrocardiograph that allows electrocardiographic measurement in daily life has been proposed. This electrocardiograph typically performs electrocardiographic measurement by disposing electrodes with sandwiching a heart and measuring a bioelectric potential.
However, the conventional electrocardiograph requires, for example, expertise and guidance by a doctor and fastening the electrodes using, for example, a belt during installation. Accordingly, an examinee is difficult to perform electrocardiographic measurement in daily life without burden.
According to an embodiment, an electrocardiograph includes a first electrode pair, a second electrode pair, a first electric potential detector, a second electric potential detector, and an electrocardiogram detector. The first electrode pair includes a first measurement electrode and a first reference electrode. The first measurement electrode is apart from the first reference electrode with a first distance on a first line. The second electrode pair includes a second measurement electrode and a second reference electrode. The second measurement electrode is apart from the second reference electrode with a second distance on a second line. A difference between the first distance and the second distance is equal to or less than a first threshold. An angle formed by the first line related to the first electrode pair and the second line related to the second electrode pair is equal to or more than a second threshold. The first electric potential detector is configured to detect a first differential electric potential of the first electrode pair. The second electric potential detector is configured to detect a second differential electric potential of the second electrode pair. The electrocardiogram detector is configured to detect an electrocardiogram by performing a subtraction process on the first differential electric potential and the second differential electric potential.
The following describes embodiments of an electrocardiograph, a method for measuring electrocardiogram, and an electrocardiographic program in detail with reference to the accompanying drawings.
Electrocardiograph
The CPU 101 is an arithmetic device that controls the entire device and achieves equipped functions. The ROM 102 is a non-volatile semiconductor memory storing, for example, a program achieving functions and function setting data. The RAM 103 is a volatile semiconductor memory from which a program and data are read and where the program and data are temporarily held. The CPU 101, for example, reads the program and data from the ROM 102 on the RAM 103 and achieves a control of the entire device and the equipped functions by performing processes.
The external storage 104, for example, is a non-volatile memory such as a Hard Disk Drive (HDD) and a memory card. The external storage 104 includes a storage medium such as a flexible disk (FD), a Compact Disk (CD), and a Digital Versatile Disk (DVD). The input device 105 is a numeric keypad and a touchscreen, for example, and is used for input of each operation signal to the electrocardiograph 100. The display device 106 is a display, for example, and displays a result of a process by the electrocardiograph 100.
The electrocardiograph 100 of the embodiment includes at least four electrodes 108 (hereinafter referred to as “electrode group 108”) including a measurement electrode 1, a reference electrode 1, a measurement electrode 2, and a reference electrode 2; and a driving circuit 107. In the electrocardiograph 100 of the embodiment, the driving circuit 107 is coupled via the bus B.
The electrode group 108 detects a bioelectric potential by contacting the skin of the examinee. The driving circuit 107 drives each electrode. The driving circuit 107 outputs the detected bioelectric potential value obtained from the electrode group 108 to, for example, the CPU 101 via the bus B.
Here, appearances and installation examples of the electrocardiograph 100 of the embodiment and exemplary arrangements of the electrode group 108 will be described.
Appearance and Exemplary Arrangement 1
Thus, the examinee installs the electrocardiograph 100 as illustrated in
Exemplary Arrangements of Electrode Group 108
As illustrated in
Appearances and Exemplary Arrangements 2 and 3
The electrocardiograph 100 of the embodiment may be built into clothing W itself as illustrated in
Some conventional measuring instruments are installed to a chest for electrocardiographic measurement. However, this measuring instrument requires, for example, a belt to secure the electrodes for installation, complicated work for the examinee. Some of the conventional measuring instruments are installed to an arm for electrocardiographic measurement. However, this measuring instrument is displaced due to the body motion of the examinee and may fail the electrocardiographic measurement.
In contrast to this, the electrocardiograph 100 of the embodiment allows simple installation with the configuration, providing an electrocardiographic measurement environment available for daily use for the examinee.
Electrocardiographic Measurement Function
The electrocardiographic measurement function of the embodiment will be described. The electrocardiograph 100 of the embodiment includes at least two sets of electrode pairs, the measurement electrode 1 and the reference electrode 1; and the measurement electrode 2 and the reference electrode 2. Each electrode pair of the measurement electrode 1 and the reference electrode 1 and the measurement electrode 2 and the reference electrode 2 of the embodiment are arranged on the electrode-fitting surface considering the direction of the muscle fiber and the transmission direction of electrocardiogram at the installation position on the body member of the examinee (installation position of the electrocardiograph 100 during measurement). The electrocardiograph 100 of the embodiment detects differential electric potentials between electrodes of the measurement electrode 1 and the reference electrode 1 and between electrodes of the measurement electrode 2 and the reference electrode 2 as two sets of bioelectric potentials, respectively. The electrocardiograph 100 of the embodiment performs a subtraction process on the two sets of bioelectric potentials and detects an electrocardiogram. The electrocardiograph 100 of the embodiment features such electrocardiographic measurement function.
The conventional measuring instrument may cause reduction in measurement accuracy by generating noise of, for example, myoelectricity by motion of the muscle fiber at the installation position and due to smallness of detected bioelectric potentials (amplitude of electrocardiographic complex is small) compared with the electrocardiographic measurement sandwiching the heart with electrodes.
Therefore, the electrocardiograph of the embodiment detects each differential electric potential of the two sets of electrode pairs arranged on the electrode-fitting surface considering the direction of the muscle fiber and the transmission direction of electrocardiogram at the installation position as bioelectric potentials. The electrocardiograph of the embodiment performs a subtraction process on the detected two sets of bioelectric potentials and detects an electrocardiogram.
The following describes the configuration and the operation of the electrocardiographic measurement function of the embodiment.
The bioelectric potential detector 11 detects the two sets of differential electric potentials of each electrode pair 1 and 2 based on an electric potential measured at the electrode pair 1 of the measurement electrode 1 and the reference electrode 1 (first electrode pair) and the electrode pair 2 of the measurement electrode 2 and the reference electrode 2 (second electrode pair). Then, the bioelectric potential detector 11 obtains a difference between an electric potential measured at the measurement electrode 1 and an electric potential measured at the reference electrode 1 and detects a differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1 (first electric potential). The bioelectric potential detector 11 obtains a difference between an electric potential measured at the measurement electrode 2 and an electric potential measured at the reference electrode 2 and detects a differential electric potential between the electrodes of the measurement electrode 2 and the reference electrode 2 (second electric potential). Thus, the bioelectric potential detector 11 detects each detected differential electric potential as two sets of bioelectric potentials.
The baseline-wander eliminator 12, for example, eliminates extra high-frequency components from the waveform of the detected bioelectric potentials by a low-pass filter function at a cutoff frequency of 15 [Hz]. Then, the baseline-wander eliminator 12 eliminates baseline wander by performing a first derivation process on the waveforms after the high-frequency components are eliminated.
The electrocardiogram detector 13 performs a subtraction process on an output after baseline wander is eliminated (two sets of bioelectric potentials) and detects an electrocardiogram with myoelectricity eliminated.
The following describes a method for detecting an electrocardiogram of the embodiment.
Method for Detecting Electrocardiogram
Accordingly, the myoelectricity of rectus abdominis muscle transmits to the direction of the fiber of rectus abdominis muscle, that is, a linear direction connecting from the head to the leg of the living body (direction indicated by solid line arrows in the drawing). Therefore, in this embodiment, as illustrated in (b) of
As illustrated in (a) of
Thus, in the electrocardiograph 100 of the embodiment, the electrode pair 2 of the measurement electrode 2 and the reference electrode 2 is disposed parallel (horizontal direction) to the transmission direction of the electrocardiogram when appropriately installed. The electrode pair 1 of the measurement electrode 1 and the reference electrode 1 is disposed vertical (vertical direction) to the transmission direction of the electrocardiogram.
Accordingly, the electrocardiograph 100 of the embodiment includes the same level of myoelectricity (same electric potential) in the differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1 and the differential electric potential between the electrodes of the measurement electrode 2 and the reference electrode 2. In this embodiment, electrocardiogram is not included in the differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1 but included in the differential electric potential between the electrodes of the measurement electrode 2 and the reference electrode 2.
The electrocardiogram detector 13 of the embodiment focuses on a difference in property of the differential electric potentials. The electrocardiogram from which myoelectricity is eliminated is detected by subtracting the differential electric potential not including electrocardiogram from the differential electric potential including electrocardiogram.
Electrocardiographic Complex
Thus, after the removal process by the baseline-wander eliminator 12, the electrocardiographic measurement function of the embodiment outputs two sets of bioelectric potentials after baseline wander is eliminated, which are as illustrated in (a) and (b) of
Here, the arrangement of the electrode group 108 of the embodiment is additionally described.
However, as described in the method for detecting an electrocardiogram, regarding a distance between each electrode in the electrode group 108, to eliminate myoelectricity, between the electrodes of the measurement electrode 1 and the reference electrode 1, and between the electrodes of the measurement electrode 2 and the reference electrode 2, the distance where the same level of myoelectricity can be detected is required to be maintained. That is, each electrode is preferred to be disposed on the electrode-fitting surface to provide a distance contacting on the same rectus abdominis muscle in the case where the electrocardiograph 100 is appropriately installed. Therefore, the distance between each electrode in the electrode group 108 is preferred to be the same as or smaller than the length of the cross-sectional width of the rectus abdominis muscle. A distance between each electrode in the electrode group 108 is, for example, equal to or less than 50 [mm]. Thus, in the arrangement of the electrode group 108 of the embodiment, a first distance is kept between the electrodes of the measurement electrode 1 and the reference electrode 1, while a second distance is kept between the electrodes of the measurement electrode 2 and the reference electrode 2. The second distance is a distance where difference from the first distance is equal to or less than the threshold.
The electrocardiographic measurement function of the above-described embodiment can be achieved by executing an electrocardiograph program in the electrocardiograph 100, where the functional units each operate collaboratively.
The electrocardiographic program is provided by being preliminarily incorporated in the ROM 102 included in the electrocardiograph 100, which is execution environment. The electrocardiographic program has a module configuration including each of the functional units. The CPU 101 reads and executes the program from the ROM 102, thus generating each functional unit on the RAM 103. A method for providing the electrocardiographic program is not limited to this. The electrocardiographic program may be stored in a device coupled to, for example, the Internet, may be downloaded via network so as to be distributed, for example. An installable format or executable format file may be stored in a storage medium readable by the electrocardiograph 100 and may be provided as a computer program product.
The following describes a process during execution of the electrocardiographic program (collaborative operation by each functional unit) using a flowchart.
Process During Electrocardiographic Measurement
Next, the bioelectric potential detector 11 detects bioelectric potentials from two sets of the electrode pairs 1 and 2 of the electrode group 108 (Step S102). Then, the bioelectric potential detector 11 obtains a difference in the electric potential measured at measurement electrode 1 and the electric potential measured at the reference electrode 1 and detects a differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1. The bioelectric potential detector 11 obtains a difference in the electric potential measured at measurement electrode 2 and the electric potential measured at the reference electrode 2 and detects a differential electric potential between the electrodes of the measurement electrode 2 and the reference electrode 2. Accordingly, the bioelectric potential detector 11 detects each detected differential electric potential as two sets of bioelectric potentials.
Next, the baseline-wander eliminator 12 performs a baseline wander removal process on the two sets of detected bioelectric potentials (Step S103). Then, the baseline-wander eliminator 12 eliminates extra high-frequency components from waveforms of the detected bioelectric potentials and performs a first derivation process on the waveforms after the high-frequency component is eliminated. Accordingly, the baseline-wander eliminator 12 eliminates the high-frequency components and baseline wanders.
Next, the electrocardiogram detector 13 detects the electrocardiogram with myoelectricity eliminated based on the outputs after the baseline wanders are removed (two sets of bioelectric potentials) (Step S104). Then, the electrocardiogram detector 13 subtracts the bioelectric potential not including electrocardiogram from the bioelectric potential including electrocardiogram among two sets of the bioelectric potentials. Thus, the electrocardiogram detector 13 detects an electrocardiogram with myoelectricity eliminated.
Next, the electrocardiograph 100 of the embodiment determines whether the electrocardiographic measurement of the examinee is terminated or not (Step S105).
As a result, if the electrocardiographic measurement is determined as not being terminated (Step S105: NO), the electrocardiograph 100 of the embodiment returns to the process of Step S102 and continues the electrocardiographic measurement process.
On the other hand, in the electrocardiograph 100 of the embodiment, when the electrocardiographic measurement is determined as terminated (Step S105: YES), the display controller 14 displays the measurement result, for example, the detected electrocardiographic complex, on the display device 106 (Step S106).
As described above, with the electrocardiograph 100 of the embodiment, at least two sets of the electrode pairs 1 and 2 of: the measurement electrode 1 and the reference electrode 1; and the measurement electrode 2 and the reference electrode 2 are disposed on the electrode-fitting surface considering the direction of the muscle fiber and the transmission direction of electrocardiogram at the installation position on the body member of the examinee. In the electrocardiograph 100 of the embodiment, the bioelectric potential detector 11 detects each differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1 and between the electrodes of the measurement electrode 2 and the reference electrode 2 as two sets of bioelectric potentials. In the electrocardiograph 100 of the embodiment, the electrocardiogram detector 13 performs a subtraction process on the two sets of bioelectric potentials and detects an electrocardiogram.
Accordingly, the electrocardiograph 100 of the embodiment can prevent generation of myoelectricity by motion of the muscle fiber at the installation position and reduction in measurement accuracy due to smallness of detected bioelectric potentials compared with the electrocardiographic measurement sandwiching the heart with electrodes.
Thus, the electrocardiograph 100 according to the embodiment allows the examinee to perform electrocardiographic measurement in daily life without burden. The electrocardiograph 100 of the embodiment can improve measurement accuracy.
The above-described embodiment describes the configuration achieving the electrocardiographic measurement function by execution of the electrocardiographic program. However, this should not be construed in a limiting sense. The electrocardiographic measurement function may be achieved by various hardware, for example, functionality of the bioelectric potential detector 11 may be achieved with a differential amplifier circuit and functionality of the baseline-wander eliminator 12 may be achieved with a low-pass filter circuit.
The above-described embodiment describes an exemplary display method as a method for notifying the measurement result of electrocardiogram of the examinee. However, this should not be construed in a limiting sense. In the case where the electrocardiograph 100 of the embodiment includes a communication interface (IF: not illustrated), for example, the measurement result of the electrocardiogram may be transmitted to an external device via a network to notify the measurement result of the electrocardiogram. It should be understood that the “network” is irrespective of communications scheme, wired or wireless, etc. It is only necessary that an external terminal is a device with a communication function, such as a mobile phone or an information terminal.
The following describes a modification of the electrocardiograph 100 of the embodiment. Like reference numerals designate corresponding or identical elements throughout the following modification and the embodiment, and therefore such elements will not be further elaborated here.
Modification 1
The R wave detector 15 of Modification 1 detects an R wave from the electrocardiographic complex detected by the electrocardiogram detector 13. The R wave detector 15 detects the R wave by the following method. The R wave detector 15 sets, for example, 1.5 [sec] as detection time width and detects a local maximal value V of the electrocardiographic complex in the detection time. Then, the R wave detector 15 detects the R wave by the following Conditional expression.
V≧μ+α+σ
where V is a local maximal value of the electrocardiographic complex, μ is an average value of the local maximal value of the detected electrocardiographic complex, σ is a variance, α is a coefficient (for example, 0.8), and μ+α×σ represents a threshold.
Thus, the electrocardiographic measurement function of Modification 1 outputs the electrocardiographic complex detected by the electrocardiogram detector 13 from the electrocardiogram detector 13 to the R wave detector 15. The R wave detector 15 detects the local maximal value V equal to or more than the threshold as illustrated in
As described above, the electrocardiograph 100 of Modification 1 can notify not only the detection result of electrocardiogram but also the detection result of R wave of the examinee.
Modification 2
The bioelectric potential amplifier 16 of Modification 2 amplifies the bioelectric potential in accordance with the magnitude of amplitude of myoelectricity component included in the bioelectric potential after baseline wander is eliminated.
As described in the embodiment, the differential electric potential between the electrodes of the measurement electrode 1 and the reference electrode 1 and the differential electric potential between the electrodes of the measurement electrode 2 and the reference electrode 2 include the same level of myoelectricity. However, depending on installation state of the electrocardiograph 100, for example, the electrocardiograph 100 is installed at a position slightly shifted from the rectus abdominis muscle and the electrocardiograph 100 is inclinedly installed with respect to the vertical direction indicated with the mark M, amplitude of the myoelectricity included in each differential electric potential differs.
Therefore, in the electrocardiographic measurement function of Modification 2, the bioelectric potential amplifier 16 amplifies and corrects a bioelectric potential according to the magnitude of the amplitude of the myoelectricity component included in the bioelectric potential after baseline wander is eliminated.
The bioelectric potential amplifier 16 sets a period of 1.5 [sec] as detection time width for each two sets of output waveforms after baseline wander is eliminated, for example, and detects all the local maximal values and local minimal values of output waveforms detected in the detection time. The bioelectric potential amplifier 16 obtains an average value of differences between the adjacent local maximal values and local minimal values and sets the average value as a myoelectricity amplitude value. Accordingly, the bioelectric potential amplifier 16 obtains two sets of myoelectricity amplitude values corresponding to the output waveform measured from the electrode pair 1 of the measurement electrode 1 and the reference electrode 1 and the output waveform measured from the electrode pair 2 of the measurement electrode 2 and the reference electrode 2, respectively.
As a result, the bioelectric potential amplifier 16 amplifies the output waveform corresponding to the electrode pair 1 of the measurement electrode 1 and the reference electrode 1 according to Amplification factor 1 calculated by the following Equation (1).
Amplification factor 1=Myoelectricity amplitude value 2/(Myoelectricity amplitude value 1+Myoelectricity amplitude value 2) (1)
where Myoelectricity amplitude value 1 is a myoelectricity amplitude value corresponding to the electrode pair 1 of the measurement electrode 1 and the reference electrode 1, and Myoelectricity amplitude value 2 is a myoelectricity amplitude value corresponding to the electrode pair 2 of the measurement electrode 2 and the reference electrode 2.
The bioelectric potential amplifier 16 amplifies an output waveform corresponding to the electrode pair 2 of the measurement electrode 2 and the reference electrode 2 according to Amplification factor 2 calculated by the following Equation (2).
Amplification factor 2=Myoelectricity amplitude value 1/(Myoelectricity amplitude value 1+Myoelectricity amplitude value 2) (2)
The amplification factor should not be construed in a limiting sense. The amplification factor may be an amplification factor predetermined in accordance with the magnitude of myoelectricity amplitude, for example.
Thus, in the electrocardiographic measurement function of Modification 2, when the bioelectric potential amplifier 16 performs the amplifying process, two sets of bioelectric potentials after amplification is output from the bioelectric potential amplifier 16 to the electrocardiogram detector 13.
As described above, even if the amplitude of myoelectricity included in the two sets of differential electric potentials detected from each electrode pair 1 and 2 differs, the electrocardiograph 100 of Modification 2 prevents degrade of measurement accuracy by performing correction before electrocardiogram detection.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2013-075631 | Apr 2013 | JP | national |