ECG signal analysis device

Abstract

To provide an electrocardiographic signal analysis device capable of acquiring a good quality electrocardiographic signal with less noise by safely and accurately measuring an electrocardiographic signal of a subject in a daily environment of an office or the like, and also contributing to an accurate evaluation of a health state of the subject by analyzing the electrocardiographic signal with a plurality of methods.SOLUTION: A measurement part 1 includes: a pair of capacitance coupling type detection electrodes 6 and 6 for detecting heartbeats of a subject in a non-contact state to output them as a primary signal; a pair of active guard circuits 7 and 7 for reducing noise included in the primary signal to output a secondary signal; amplification means 8 for amplifying a potential difference of the secondary signal to output an electrocardiographic signal; and a feedback electrode 33 for eliminating the influence of an in-phase signal of the secondary signal. An analysis part 2 includes: linear analysis means 3 for linearly analyzing the electrocardiographic signal to calculate an autonomous nerve index; and nonlinear analysis means 4 for nonlinearly analyzing the electrocardiographic signal to calculate a Lyapunov index.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrocardiogram signal analyzer for measuring and analyzing the electrocardiogram signals of subjects such as office workers. The analysis results of the electrocardiogram signals obtained by this device can be used to evaluate the subject's health condition, fatigue level, stress level, external adaptability, etc. [Background technology]

[0002] In recent years, interest in preventive medicine to prevent illness has risen due to rising health consciousness, and the demand for systems that monitor mental and physical health on a daily basis is increasing. In addition to medical institutions, there is a demand for technology that can measure and analyze biometric information on a daily basis in various environments such as ordinary homes and offices. In office environments in particular, there is a growing need to measure and analyze the biometric information of employees while they are working to help them maintain their health and to detect stress levels early.

[0003] As an example of a prior art document related to the measurement and analysis of bioinformation, Patent Document 1 can be mentioned. Patent Document 1 discloses a sensor device that measures a subject's bioinformation and an evaluation device that evaluates the state of the subject's autonomic nerves based on the obtained bioinformation. The sensor device includes a heart rate sensor that acquires heart rate information as bioinformation, and the sensor is composed of, for example, a pair of detection electrodes that contact the surface of the subject's body. The evaluation device calculates RRI, which is the interval between R waves, from the obtained heart rate information, performs frequency analysis on the evenly spaced time series data of RRI using, for example, fast Fourier transform, calculates the ratio of the low frequency component LF to the high frequency component HF of the heart rate fluctuation, i.e., LF / HF, as an autonomic nerve index, and evaluates the state of the subject's autonomic nerves based on the index. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-30389 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 exemplifies a detection electrode that contacts the surface of the subject's body as a heart rate sensor. When worn for a long period of time, this type of electrode may not only cause skin rashes or metal allergies, but may also cause the subject to feel uncomfortable or restrained, and the resulting stress may affect the electrocardiogram signal. Therefore, although this type of electrode is suitable for situations such as medical checkups where electrocardiogram signals are measured temporarily, it is not suitable for measuring electrocardiogram signals on a daily basis, which is the main target of the present invention.

[0006] Furthermore, unlike hospitals where the environment for measuring ECG signals is well-established, various kinds of environmental noise exist in everyday environments. In particular, in office environments, where there are many computers and other electrical devices, there is a lot of hum noise originating from commercial power sources (50Hz or 60Hz). If large environmental noise is mixed into the ECG signal, the obtained ECG signal may become inappropriate, making subsequent analysis difficult, so it is essential to reduce the environmental noise.

[0007] Furthermore, the inventors discovered that if electrocardiogram signals could be analyzed by a method different from the conventional one to obtain analysis results different from known autonomic nerve indices such as LF / HF, it would be possible to more accurately evaluate the subject's health condition, fatigue level, stress, external adaptability, etc., and thus completed the present invention.

[0008] The object of the present invention is to provide an electrocardiogram signal analysis device that can safely and accurately measure a subject's electrocardiogram signal in an everyday environment such as an office, obtain a high-quality electrocardiogram signal with little noise, and analyze the electrocardiogram signal using multiple techniques, which can contribute to an accurate evaluation of the subject's health condition, etc. [Means for solving the problem]

[0009] The present invention is directed to an electrocardiogram signal analysis device comprising a measurement unit 1 that detects the heartbeat of a subject and outputs an electrocardiogram signal, and an analysis unit 2 that analyzes the electrocardiogram signal obtained from the measurement unit 1. The measurement unit 1 includes a pair of capacitively coupled detection electrodes 6·6 that detect the heartbeat of the subject in a non-contact manner and output it as a primary signal, a pair of active guard circuits 7·7 that reduce noise contained in the primary signal and output a secondary signal, an amplification means 8 that amplifies the potential difference of the secondary signal and outputs an electrocardiogram signal, and a feedback electrode 33 for removing the influence of an in-phase signal of the secondary signal. teeth The electrocardiogram signal is linearly analyzed to calculate an autonomic nerve index, and a nonlinear analysis means is nonlinearly analyzed to calculate a Lyapunov index. The linear analysis means 3 linearly analyzes the fluctuation of RRI, which is the interval between R waves of an electrocardiogram signal, and calculates the ratio of low frequency components (LF) to high frequency components (HF) of heart rate fluctuation as an autonomic nerve index. The nonlinear analysis means 4 defines the one-dimensional axis as the x1 axis, the two-dimensional axis as the x2 axis, the three-dimensional axis as the x3 axis, and the n-dimensional axis as the xn axis, and calculates a coordinate P derived from the time series data of RRI in a multidimensional space formed by the x1 axis to the xn axis. i (x1 i 、x2 i 、x3 i , xn i ) are plotted sequentially from P1, the RRI time series data is multi-dimensionalized to three or more dimensions to obtain an exponentially expanding attractor, and the time fluctuation of this exponentially expanding attractor is calculated up to infinity to quantify the chaotic nature of the trajectory and calculate the Lyapunov exponent. When the value on the RRI time series data at time t is R(t), the above coordinate P i Related to x1 i 、x2 i 、x3 i , xn i Each value of x1 i = R(i), x2 i = R(i+τ), x3 i =R(i+2τ), xni=R(i+(n-1)τ) (τ is a given time) It is characterized by the above.

[0010] The measurement unit 1 includes a high-pass filter 13 and a low-pass filter 14 that remove noise contained in the electrocardiogram signal amplified by the amplifier 8 .

[0011] The amplifying means 8 is composed of a first amplifier 11 which receives as input the secondary signals output from both active guard circuits 7·7, and a second amplifier 12 which further amplifies the signal amplified by the first amplifier 11, and a high-pass filter 13 and a low-pass filter 14 are disposed between the first amplifier 11 and the second amplifier 12.

[0014] The active guard circuit 7 includes a guard electrode 18 that pairs with the detection electrode 6, and the detection electrode 6 and the guard electrode 18 are joined via an insulating layer 23 and integrated into an electrode unit .

[0015] The entire electrode unit 28 including the detection electrode 6 and the guard electrode 18 is made of a flexible material. Effect of the Invention

[0016] In the electrocardiogram signal analyzer according to the present invention, the subject's heartbeat is detected in a non-contact state using the capacitively coupled detection electrodes 6. This allows the subject's heartbeat to be detected safely without causing skin rash or metal allergies, which are concerns when electrodes are directly attached to the body for a long period of time. In addition, the discomfort and sense of restraint felt by the subject due to the attachment of the electrodes is significantly reduced, suppressing the effect on the electrocardiogram signal associated with the stress, and allowing an accurate electrocardiogram signal to be obtained. In addition, the present invention provides an active guard circuit 7 that reduces noise contained in the primary signal output by the detection electrodes 6, so that a good quality electrocardiogram signal with less noise can be obtained even when there is a lot of noise such as hum noise around the subject. The measurement unit 1 of the present invention, which includes the above detection electrodes 6 and the active guard circuit 7, allows the electrocardiogram signal of the subject to be measured safely and accurately in an everyday environment such as an office, and allows a good quality electrocardiogram signal that can withstand subsequent analysis by the analysis unit 2 to be obtained.

[0017] Furthermore, in the present invention, the analysis unit 2 for analyzing the electrocardiogram signal includes a nonlinear analysis means 4 for nonlinearly analyzing the electrocardiogram signal in addition to the linear analysis means 3 for linearly analyzing the electrocardiogram signal as in the conventional method. The advantage of nonlinear analysis is that it can handle information that cannot be handled by linear analysis. The electrocardiogram signal contains nonlinear phenomena, such as "fluctuations" that were previously considered to be variations while the periodicity of the electrocardiogram signal is recognized, and are found to be nonlinear phenomena. According to the knowledge of the present inventor, the Lyapunov exponent is useful as an index of the subject's adaptability to external stimuli. The analysis unit 2 of the present invention, which performs nonlinear analysis in addition to linear analysis, can contribute to more accurate evaluation of the subject's health condition, fatigue level, stress, external adaptability, etc., compared to conventional evaluation methods that perform only linear analysis.

[0018] By providing a high-pass filter 13 and a low-pass filter 14 to remove noise contained in the electrocardiogram signal amplified by the amplifier means 8, a clear electrocardiogram signal can be obtained from which noise that interferes with analysis by the analysis unit 2 has been removed.

[0019] By disposing a high-pass filter 13 and a low-pass filter 14 between the first amplifier 11 and the second amplifier 12 that constitute the amplification means 8, noise can be removed by the filters 13 and 14 before it is further amplified by the second amplifier 12, thereby making the electrocardiogram signal clearer.

[0020] When the detection electrode 6 and the guard electrode 18 are joined via the insulating layer 23 and integrated into the electrode unit 28, it is easier to attach the electrode unit to the subject than when the two electrodes are separate.

[0021] If the entire electrode unit 28 including the detection electrode 6 and the guard electrode 18 is made of a flexible material, the adhesion of the electrode unit 28 to the subject can be improved, enabling stable measurement of electrocardiogram signals. [Brief description of the drawings]

[0022] [Figure 1]1 is a block diagram showing an overall configuration of an electrocardiogram signal analysis device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a measurement unit for measuring an electrocardiogram signal. [Diagram 3] 4 is a cross-sectional view of an electrode unit and a coaxial cable that constitute a measuring section. FIG. [Figure 4] 1A is an electrocardiogram output by the measurement unit of this embodiment, and FIG. 1B is an electrocardiogram when the active guard circuit is omitted. [Diagram 5] FIG. 1(a) is an external view of the attachment belt to which the electrode unit is attached, and FIG. 1(b) is an explanatory diagram of how to attach the attachment belt. [Figure 6] 1 is a diagram illustrating an example of a waveform of an electrocardiogram signal to be analyzed. [Figure 7] 1A and 1B are explanatory diagrams relating to linear analysis of electrocardiographic signals, in which (a) shows an example of equally spaced time series data of heartbeat intervals, and (b) shows an example of the power spectral density of low-frequency and high-frequency components of heartbeat fluctuations. [Figure 8] FIG. 1 is an explanatory diagram relating to nonlinear analysis of an electrocardiogram signal, illustrating a procedure for obtaining an attractor by making time series data of heartbeat intervals multidimensional. [Figure 9] A stress load experiment (task) was conducted on subjects, and the result is a scatter plot with the autonomic nervous index before and during the task on the horizontal axis and the Lyapunov exponent on the vertical axis. [Figure 10] This is a scatter plot with the autonomic nervous index before, during, and after the task on the horizontal axis and the Lyapunov exponent on the vertical axis. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] 1 to 10 show an embodiment of an electrocardiogram signal analysis device (hereinafter simply referred to as an analysis device) according to the present invention. As shown in Fig. 1, the analysis device comprises a measurement unit 1 that detects the heartbeat of a subject and outputs an electrocardiogram signal, and an analysis unit 2 that analyzes the electrocardiogram signal obtained from the measurement unit 1. The analysis unit 2 comprises linear analysis means 3 that linearly analyzes the electrocardiogram signal to calculate an autonomic nerve exponent, and nonlinear analysis means 4 that nonlinearly analyzes the electrocardiogram signal to calculate a Lyapunov exponent. Details of the analysis means 3 and 4 will be described later.

[0024] As shown in Fig. 2, the measurement unit 1 is composed of a pair of detection electrodes 6·6 that detect the subject's heartbeat and output it as a primary signal, a pair of active guard circuits 7·7 that reduce environmental noise contained in the primary signal and output a secondary signal, an amplifier 8 that amplifies the potential difference of the secondary signal and outputs an electrocardiogram signal, and an analog filter 9 that removes line noise and interference noise from the electrocardiogram signal. The amplifier 8 is composed of a first amplifier 11 that receives the output of both active guard circuits 7·7, i.e., the secondary signal, as input, and a second amplifier 12 that further amplifies the signal amplified by the first amplifier 11. The analog filter 9 is composed of a high-pass filter 13 and a low-pass filter 14 that are arranged in series between the amplifiers 11·12. Both amplifiers 11·12 are composed of operational amplifiers, with the first amplifier 11 having an amplification factor of 100 times and the second amplifier 12 having an amplification factor of 11 times. The electrocardiogram signal amplified 1100 times through the amplifiers 11·12 is converted into a digital signal by an analog-to-digital converter 15 and then sent to the analysis unit 2.

[0025] When the measurement unit 1 is used in an everyday environment such as an office, various environmental noises such as hum noise derived from commercial power sources are likely to be mixed into the primary signal output by the detection electrode 6. In order to reduce this environmental noise, an active guard circuit 7 is provided for each detection electrode 6. The active guard circuit 7 includes a guard electrode 18 that pairs with the detection electrode 6, a voltage follower 20 that uses an operational amplifier 19 with an amplification factor of 1, and a coaxial cable 21 that connects both electrodes 6 and 18 to the voltage follower 20.

[0026] As shown in FIG. 3, the guard electrode 18 is joined to the back surface of the detection electrode 6 (the surface opposite to the surface facing the subject) via an insulating layer 23, and is connected to the inverting input terminal (-) of the operational amplifier 19 via an outer conductor (shield) 24 of the coaxial cable 21. The detection electrode 6 is connected to the non-inverting input terminal (+) of the operational amplifier 19 via an inner conductor 25 of the coaxial cable 21. The end of the coaxial cable 21 on the side of the electrodes 6 and 18 may be connected to the edges of the electrodes 18 and 6 at the conductors 24 and 25 as shown in (a), or may be connected to the detection electrode 6 by penetrating the guard electrode 18 and the insulating layer 23 together with the insulating tube 26 that covers the inner conductor 25 as shown in (b). The output terminal of the operational amplifier 19 is connected to the input terminal of the first amplifier 11 (the inverting input terminal of the operational amplifier 19 of one active guard circuit 7, and the non-inverting input terminal of the operational amplifier 19 of the other active guard circuit 7) and is connected (feedback) to the inverting input terminal of the operational amplifier 19 via the outer conductor 24. That is, the output terminal and the inverting input terminal of the operational amplifier 19 are at the same potential. According to the above configuration, the output terminal of the operational amplifier 19 outputs a secondary signal in which environmental noise has been reduced from the primary signal input to the non-inverting input terminal.

[0027] Fig. 4(a) shows an electrocardiogram output by the measurement unit 1 of this embodiment equipped with the active guard circuit 7, and Fig. 4(b) shows, for comparison, an electrocardiogram without the active guard circuit 7. As is clear from a comparison of the two figures, the active guard 7 of this embodiment is extremely useful in reducing environmental noise.

[0028] The detection electrode 6 and the guard electrode 18 are joined via an insulating layer 23 to form an electrode unit 28. Each electrode unit 28 is attached near the heart of the subject, specifically, on the front surface of the front part of clothing (insulator) such as underwear worn by the subject on the upper body, with the detection electrode 6 facing the subject. Any attachment means may be used, but as shown in FIG. 5, for example, a belt 29 with two electrode units 28 attached side by side can be wrapped around the subject over the clothing. In this attached state, the clothing is interposed between the detection electrode 6 and the skin of the subject. In other words, each detection electrode 6 is arranged on the subject in a non-contact state to form a capacitively coupled electrode. A capacitively coupled electrode is one in which a capacitor is formed between an electrical signal source in the living body (heart) and a metal plate (detection electrode 6) outside the living body, and an electrical signal in the living body is derived from outside the living body in a non-contact manner.

[0029] In this embodiment, the detection electrode 6 and the guard electrode 18 are made of the same rectangular sheet-like conductive foam, and the insulating layer 23 is made of insulating urethane foam that is slightly larger than both the electrodes 6 and 18. By making the entire electrode unit 28 out of a material with excellent flexibility, the adhesion of the electrode unit 28 to the subject can be improved, and the electrocardiogram signal can be measured stably. Note that the material of the detection electrode 6 and the guard electrode 18 is not limited to conductive foam, and for example, both the electrodes 6 and 18 can be made of thin metal plates made of stainless steel.

[0030] As shown in Fig. 2, the first amplifier 11 includes an inverting output means 31 that inverts and outputs an in-phase signal of the secondary signal input from the active guard circuit 7. The inverting output means 31 is connected to one input terminal of a feedback amplifier 32, and the other input terminal of the feedback amplifier 32 is set to a reference potential. The output terminal of the feedback amplifier 32 is connected to a feedback electrode 33 provided on the seat of a chair on which the subject sits. In this embodiment, the feedback electrode 33 is made of conductive rubber. The effect of the in-phase signal of the secondary signal can be eliminated by the action of this feedback electrode 33 etc.

[0031] As described above, in the measurement unit 1 of the analysis device according to this embodiment, the subject's heartbeat is detected in a non-contact state using the capacitively coupled detection electrodes 6. This allows the subject's heartbeat to be detected safely without causing skin rash or metal allergies, which are concerns when electrodes are directly attached to the body for a long period of time. In addition, the discomfort and sense of restraint caused by the attachment of the electrodes to the subject is significantly reduced, suppressing the effect on the electrocardiogram signal associated with the stress, and allowing an accurate electrocardiogram signal to be obtained. In addition, in this embodiment, an active guard circuit 7 is provided that reduces noise contained in the primary signal output by the detection electrodes 6, so that a good quality electrocardiogram signal with less noise can be obtained even when there is a lot of noise such as hum noise around the subject. According to the measurement unit 1 of this embodiment, which is equipped with the above detection electrodes 6 and active guard circuit 7, the electrocardiogram signal of the subject can be safely and accurately measured in an everyday environment such as an office, and a good quality electrocardiogram signal that can withstand subsequent analysis by the analysis unit 2 can be obtained.

[0032] The analysis unit 2, which has obtained the electrocardiogram signal from the measurement unit 1, simultaneously calculates the autonomic nerve index and the Lyapunov index using the linear analysis means 3 and the nonlinear analysis means 4. First, the linear analysis means 3 calculates the RRI (heartbeat interval), which is the interval between R waves, from the electrocardiogram signal illustrated in FIG. 6, and linearly analyzes the fluctuation of the RRI. Specifically, the linear analysis means 3 performs frequency analysis using the fast Fourier transform on the equally-spaced time series data of the RRI (see FIG. 7(a)), obtains the power spectrum density (see FIG. 7(b)) of the low-frequency component LF (0.04-0.15 Hz) and the high-frequency component HF (0.15-0.4 Hz) of the heartbeat fluctuation, and calculates the ratio of the low-frequency component LF to the high-frequency component HF, i.e., LF / HF, as a stress index indicating the activity of the sympathetic nerves.

[0033] In low stress states where the parasympathetic nervous system is activated, both the HF and LF components appear, but in high stress states where the sympathetic nervous system is activated, the LF component appears but decreases. In other words, in low stress states, the HF component becomes relatively large, so the LF / HF value becomes small, and conversely, in high stress states, the LF component becomes large relative to the HF component, so the LF / HF value becomes large.

[0034] The nonlinear analysis means 4 nonlinearly analyzes the fluctuation of the RRI (heartbeat interval), specifically, performs chaos analysis to calculate the Lyapunov exponent. First, as shown in Fig. 8, the time series data of the RRI is multidimensional (six-dimensional in this embodiment, three-dimensional in Fig. 8 for simplification) to obtain an attractor. That is, if the coordinate P i (x i ,y i ,z i ) are plotted in order from P1. If the value of RRI is R(t), then x i = R(i), y i = R(i+τ), z i =R(i+2τ), and in this embodiment, τ=1 (second).

[0035] The Lyapunov exponent is a quantification of the chaotic nature of the trajectory in an attractor. The Lyapunov exponent can be calculated by calculating the time fluctuation of the exponentially expanding attractor up to infinity. If the Lyapunov exponent is positive, it can be said that the trajectory is chaotic, and the larger the value, the more complex the trajectory is and the more the fluctuation increases. According to the findings of the present inventor, the Lyapunov exponent is useful as an index of the subject's adaptability to external stimuli, and can be an index of the concentration level and stress state.

[0036] The advantage of nonlinear analysis such as chaos analysis is that it can handle information that cannot be handled by linear analysis. While the periodicity of the electrocardiogram signal is recognized, the "fluctuation" that was thought to be a variance is found to be a nonlinear phenomenon, and the electrocardiogram signal contains nonlinear phenomena. The analysis unit 2 of this embodiment, which performs nonlinear analysis in addition to linear analysis, can contribute to more accurate evaluation of the subject's health condition, fatigue level, stress, external adaptability, etc., compared to conventional evaluation methods that perform only linear analysis. As described above, the analysis device according to this embodiment can contribute to Goal 3 (Good Health and Well-Being) of the Sustainable Development Goals (SDGs) proposed by the United Nations.

[0037] Next, we will explain the stress loading experiment in which the subject was given stress and their electrocardiogram signals were measured and analyzed. Here, a stress loading task was performed on one female subject in her twenties, and the electrocardiogram signals were measured before and after the task, and the autonomic nerve index (LF / HF) and Lyapunov exponent were calculated. The task was performed for 200 seconds, and the measurement time before and after was 200 seconds. The stress loading task was the Stroop Color Word Test, which is known as a neuropsychological test for measuring the attention and interference inhibition functions of the frontal lobe.

[0038] Figure 9 is a scatter plot with LF / HF before and during the task on the horizontal axis and Lyapunov exponent on the vertical axis. This scatter plot shows that both LF / HF and Lyapunov exponent are larger during the task than before the task, and that there is a certain correlation between LF / HF and Lyapunov exponent (correlation coefficient before the task = 0.57, correlation coefficient during the task = 0.52). However, the proportionality coefficient of the linear approximation line is relatively large before the task and relatively small during the task (proportionality coefficient before the task = 3.17, proportionality coefficient during the task = 0.66). From the above results, it is considered that the Lyapunov exponent may reflect the small influence that the subject receives from the environment in its value more than LF / HF.

[0039] Figure 10 shows the scatter plot of Figure 9 with the post-task values ​​added. This scatter plot shows that the LF / HF value decreases relatively quickly after the task (returning to the value before the task), whereas the Lyapunov exponent value does not decrease easily (maintains the value during the task). For this reason, it is considered that the Lyapunov exponent is more suitable for evaluating stress over a relatively long period of time than the LF / HF. [Explanation of symbols]

[0040] 1. Measurement section 2 Analysis section 3 Linear analysis means 4. Nonlinear analysis methods 6 Detection electrode 7 Active Guard Circuit 8 Amplification means 11 First amplifier 12 Second Amplifier 13 High Pass Filter 14 Low-pass filter 18 Guard electrode 23 Insulating layer 28 Electrode Unit 33 Feedback electrode

Claims

1. An electrocardiogram signal analysis device comprising a measurement unit (1) that detects the heartbeat of a subject and outputs an electrocardiogram signal, and an analysis unit (2) that analyzes the electrocardiogram signal obtained from the measurement unit (1), The measurement unit (1) includes a pair of capacitively coupled detection electrodes (6, 6) that detect the heartbeat of the subject in a non-contact manner and output the detected heartbeat as a primary signal, a pair of active guard circuits (7, 7) that reduce noise contained in the primary signal and output a secondary signal, an amplifier (8) that amplifies the potential difference of the secondary signals and outputs an electrocardiogram signal, and a feedback electrode (33) that removes the influence of an in-phase signal of the secondary signal. The analysis unit (2) includes a linear analysis means (3) for linearly analyzing the electrocardiogram signal to calculate an autonomic nerve index, and a nonlinear analysis means (4) for nonlinearly analyzing the electrocardiogram signal to calculate a Lyapunov exponent, The linear analysis means (3) linearly analyzes the fluctuation of RRI, which is the interval between R waves of the electrocardiogram signal, and calculates the ratio of low frequency components (LF) to high frequency components (HF) of the heart rate fluctuation as an autonomic nerve index; The nonlinear analysis means (4) defines a one-dimensional axis as the x1 axis, a two-dimensional axis as the x2 axis, a three-dimensional axis as the x3 axis, and an n-dimensional axis as the xn axis, and plots coordinates P i (x1 i , x2 i , x3 i , ..., xn i ) derived from the time series data of the RRI in a multidimensional space formed by the x1 axis to the xn axis in sequence starting from P1, thereby multiplying the time series data of the RRI into three or more dimensions to obtain an exponentially expanding attractor, and then calculates the time fluctuation of the exponentially expanding attractor up to infinity, thereby quantifying the chaoticity of the trajectory and calculating the Lyapunov exponent; When the value of the time series data of RRI at time t is R(t), the values ​​of x1i, x2i, x3i, ..., xni relating to the coordinate Pi are x1i = R(i), x2i = R(i + τ), x3i = R(i + 2τ), xni = R(i + (n-1) τ) (τ is a predetermined time).

2. 2. The electrocardiogram signal analyzer according to claim 1, wherein the measuring unit (1) includes a high-pass filter (13) and a low-pass filter (14) for removing noise contained in the electrocardiogram signal amplified by the amplifier means (8).

3. the amplifying means (8) is composed of a first amplifier (11) which receives as input the secondary signals output from both the active guard circuits (7, 7) and a second amplifier (12) which further amplifies the signal amplified by the first amplifier (11); 3. The electrocardiogram signal analyzer according to claim 2, further comprising a high-pass filter (13) and a low-pass filter (14) disposed between the first amplifier (11) and the second amplifier (12).

4. The active guard circuit (7) includes a guard electrode (18) paired with the detection electrode (6), 4. The electrocardiogram signal analyzer according to claim 1, wherein the detection electrode (6) and the guard electrode (18) are joined via an insulating layer (23) and integrated as an electrode unit (28).

5. An electrocardiogram signal analysis device as described in claim 4, wherein the entire electrode unit (28) including the detection electrode (6) and the guard electrode (18) is made of a flexible material.

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