Method for parameter configuration in disposable ecg electrode-skin contact impedance test

Abstract

A method for parameter configuration in disposable ECG electrode-skin contact impedance test, the steps are: (1) selecting a voltage source with adjustable sinusoidal excitation amplitude, preparing a reference resistor R0 with adjustable resistance value, and preparing three disposable ECG electrodes A, B and C which are equidistantly attached to the skin; (2) forming a test circuit by connecting the selected and prepared adjustable voltage source, reference resistor R0 and the impedance between the two skin electrodes in series; (3) for each pair of a given voltage source sinusoidal excitation amplitude and a reference resistor R0 resistance value, repeating the test of the alternating current impedance spectrum of the electrode-skin contact impedance multiple times, and calculating the repeatability index; (4) changing the pairs of voltage source sinusoidal excitation amplitude and reference resistor R0 resistance value enough times, repeating the test of the alternating current impedance spectrum of the electrode-skin contact impedance multiple times under each pair, and calculating the repeatability index value; (5) comparing the repeatability index values to obtain the optimal parameter pair.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for configuring parameters in a disposable ECG electrode-skin contact impedance test.

[0002] ECG devices, especially ECG monitoring devices, use a large number of disposable ECG electrodes, also known as electrode patches. The most important performance of a disposable ECG electrode is reflected in the size of the contact impedance with the skin when testing an electrocardiogram. The smaller the contact impedance, the better. The industry standard YY / T0196-2005 currently stipulates that the AC impedance of a disposable ECG electrode gel-to-gel electrode pair is tested to replace the contact impedance with the skin for evaluation. However, under the condition that the skin is not strictly treated, the correlation between the AC impedance of the disposable ECG electrode gel-to-gel electrode pair and the electrode-skin contact impedance is not high. If the size of the contact impedance between the disposable ECG electrode and the skin can be directly tested, it will be more direct.

[0003] The principle of testing the contact impedance between the disposable ECG electrode and the skin is shown in Figure 1 Three disposable ECG electrode patches A, C and B are pasted at equal intervals on the body surface, and the impedance values between each pair of electrodes are tested, as shown in Figure 1 The impedance Z1 between the AC two electrodes, the impedance Z2 between the CB two electrodes, and the impedance Z3 between the AB two electrodes are tested, and then the contact impedance Z x between the C electrode and the skin is calculated as (Z1+Z2-Z3) / 2.

[0004] The impedance value between two electrodes can be tested by connecting a sinusoidal voltage source in series with a reference resistance R0 and the impedance between the two electrodes to be tested on the skin, as shown in Figure 2 The principle is: the sinusoidal voltage and between the external terminals of R0 and the two electrodes on the skin are recorded synchronously, and then the complex impedance including the real part resistance and the imaginary part reactance can be calculated.

[0005] When testing the contact impedance between the disposable ECG electrode and the skin by the above method, the amplitude of the sinusoidal wave excited by the voltage source and the size of the reference resistance R0 in series need to be configured. BACKGROUND

[0006] The industry standard YY / T0196-2005 stipulates that when testing the AC impedance of a disposable ECG electrode gel-to-gel connection at 10Hz, the peak-to-peak value of the test current should not exceed 100μA, and it is recommended to use a sinusoidal signal voltage source and a 1MΩ or larger resistance (i.e. R0) in series with the electrode pair to be tested.

[0007] In fact, if the peak-to-peak value of the sinusoidal voltage applied by the voltage source is 2V, and the series reference resistor R0 is 1MΩ or larger, then the peak-to-peak value of the test current is less than 2μA, far less than 100μA. One reason why industry standards recommend using a conservatively large reference resistor is to prevent the test current from being too large and affecting the charging state of the electrode pair, thereby affecting the stability of the electrode AC impedance.

[0008] However, under normal circumstances, the AC impedance between the two electrodes on the skin at frequencies above 10Hz is not large, generally around 100kΩ. An excessively large reference resistor R0 will cause the voltage drop across the electrode pair to be too small, increasing the quantization error during analog-to-digital conversion in the detection circuit, thus affecting the estimation accuracy of the AC impedance to be measured.

[0009] No literature has been found discussing the optimization of the sinusoidal excitation amplitude of the voltage source and the resistance value of the reference resistor when testing the gel electrode-skin contact impedance using a sinusoidal voltage source connected in series with a reference resistor R0. A good optimized configuration should result in a measurement of the electrode-skin contact impedance spectrum with good repeatability. Summary of the Invention

[0010] Purpose of the invention

[0011] A parameter configuration scheme is proposed for testing the contact impedance of a gel electrode with skin by connecting a sinusoidal voltage source in series with a reference resistor R0. The optimal configuration scheme includes the amplitude of the excitation sine wave and the size of the reference resistor R0. The aim is to obtain a high repeatability of the electrode-skin contact impedance spectrum under this parameter configuration.

[0012] Technical solution

[0013] A method for configuring parameters in a disposable ECG electrode-skin contact impedance test involves attaching three disposable ECG electrode pads A, C, and B at equal intervals to the body surface. The impedance values ​​between each pair of electrodes are measured, specifically the impedance Z1 between electrodes A and C, the impedance Z2 between electrodes C and C, and the impedance Z3 between electrodes A and B. The contact impedance Zx between electrode C and the skin can then be calculated as Zx = (Z1 + Z2 - Z3) / 2. Figure 1 As shown, the feature is that it includes the following steps: (1) Selecting a voltage source with adjustable sinusoidal excitation amplitude, preparing a reference resistor R0 with adjustable resistance, and preparing three disposable ECG electrodes A, C, and B, and attaching the three electrodes to the skin at equal intervals; (2) Forming a test circuit by connecting the selected and prepared adjustable voltage source, the reference resistor R0, and the impedance between the two electrodes on the skin to be tested in series, such as... Figure 2As shown; (3) For each given voltage source sinusoidal excitation amplitude and reference resistor R0 value pairing, repeat the test of the electrode-skin contact impedance spectrum multiple times and calculate the repeatability index; (4) Change the pairing of voltage source sinusoidal excitation amplitude and reference resistor R0 value, and repeat the test of the electrode-skin contact impedance spectrum multiple times and calculate the corresponding repeatability index, continue until enough sinusoidal excitation amplitude and reference resistor R0 pairings are changed, repeat the test of the electrode-skin contact impedance spectrum multiple times under each pairing and calculate its repeatability index value; (5) Compare the magnitude of the repeatability index value of the electrode-skin contact impedance spectrum under all the calculated pairings, and determine the pairing of excitation voltage amplitude and reference resistor R0 value corresponding to the best repeatability index value as the optimal pairing.

[0014] According to the above method for parameter configuration in a disposable ECG electrode-skin contact impedance test, when the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 is changed in step (4) to search for the optimal pairing, a simplified search strategy can be considered. The feature is that the R0 resistance value can be determined to be a value that is close to the electrode-skin contact impedance based on the prior knowledge of the electrode-skin contact impedance, such as setting it to 10kΩ. Then, only the voltage source sinusoidal excitation amplitude is changed to form a pairing. Then, the electrode-skin contact impedance spectrum is tested multiple times for each pairing and its repeatability index value is calculated.

[0015] According to the above method for parameter configuration in a disposable ECG electrode-skin contact impedance test, when searching for the optimal pair by changing the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 in step (4), a simplified search strategy can be considered. The feature is that (a) the R0 resistance value can be determined to be a value close to that based on the prior knowledge of the electrode-skin contact impedance, such as setting it to 10kΩ. Then, only the voltage source sinusoidal excitation amplitude is changed to form pairs. The electrode-skin contact impedance spectrum is tested multiple times for each pair and its repeatability index value is calculated. (b) The voltage source sinusoidal excitation amplitude with the best repeatability index in step (a) is determined. Then, only the reference resistor R0 is changed to form pairs. The electrode-skin contact impedance spectrum is tested multiple times for each pair and its corresponding repeatability index value is calculated. Thus, the reference resistor R0 is finally determined based on the best repeatability index value.

[0016] Based on the parameter configuration method described above for a disposable ECG electrode-skin contact impedance test, it is necessary to calculate the repeatability index. The repeatability index uses the average correlation coefficient and can be calculated as follows:

[0017] If m contact impedance spectra are monitored under a certain parameter configuration, and each complex impedance spectrum records the complex impedance at n frequency points, assuming one of the complex impedance spectra is X, and the average complex impedance spectrum of the m complex impedance spectra is Y, then X and Y are both complex vectors containing n elements, and the Pearson correlation coefficient between them is defined as follows.

[0018]

[0019] in, It is the mean value of the complex impedance spectrum X. This is the mean of the average complex impedance spectrum Y; thus, the Pearson correlation coefficients r1, r2, ..., r between the monitored m complex impedance spectra and the average complex impedance spectrum Y can be calculated. m Therefore, the repeatability index is defined as the average correlation coefficient r:

[0020]

[0021] Beneficial effects

[0022] The optimal parameter configuration scheme obtained according to this scheme has the highest repeatability when measuring the impedance of disposable ECG electrodes to skin. As can be seen from Tables 1 and 2, when the excitation voltage amplitude is 1280mV and the reference resistance R0 is 10kΩ, the average correlation coefficient of 10 tests can reach 0.9980, which is significantly better than other parameter combinations.

[0023] Table 1. Repeatability of Electrode-Skin Contact Impedance Measurements at Different Excitation Voltages Using a 10kΩ Reference Resistor

[0024]

[0025] Table 2. Repeatability of Electrode-Skin Contact Impedance Measurements Using a 1280mV Test Voltage and Different Reference Resistances

[0026] Attached Figure Description

[0027] Figure 1 This solution measures the electrode-skin contact impedance.

[0028] Figure 2 Measurement equivalent circuit diagram

[0029] Figure 3 A schematic diagram of the instrument used to test the electrode-skin contact impedance spectrum in the experiment of this application.

[0030] Figure 4The diagram shows the results of 10 tests of electrode-skin contact impedance spectrum under an excitation voltage of 80mV, with a 10kΩ reference resistor. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0031] Figure 5 The diagram shows the electrode-skin contact impedance spectrum measured 10 times under an excitation voltage of 320mV with a 10kΩ reference resistor. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0032] Figure 6 The diagram shows the electrode-skin contact impedance spectrum measured 10 times under an excitation voltage of 1280mV with a 10kΩ reference resistor. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0033] Figure 7 The diagram shows the electrode-skin contact impedance spectrum measured 10 times under an excitation voltage of 1280mV, using a 100Ω series resistor. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0034] Figure 8 The diagram shows the electrode-skin contact impedance spectrum measured 10 times under an excitation voltage of 1280mV, using a 1MΩ reference resistor. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0035] Figure 9 The diagram shows the electrode-skin contact impedance spectrum measured 10 times under an excitation voltage of 1280mV and a reference resistor of 100MΩ. The horizontal axis of both graphs represents frequency f in Hz; the upper graph shows the real part resistance spectrum with resistance in ohms on the vertical axis; the lower graph shows the imaginary part reactance spectrum with reactance in ohms on the vertical axis.

[0036] Figure 10 A schematic diagram of an electrode patch of a certain brand used in the embodiment. Detailed Implementation

[0037] Example 1. Prepare three electrodes of a certain brand, such as Schindler.Figure 10 As shown; prepare a qualified low-frequency impedance spectroscopy analyzer, such as Figure 3 As shown, it includes a voltage source with adjustable sinusoidal excitation amplitude and an adjustable reference resistor. Electrode-skin contact impedance spectroscopy data were measured in the range of 0.1Hz-100Hz. The specific implementation steps are as follows:

[0038] (1) Use as follows Figure 2 The constant voltage type low frequency impedance spectroscopy analyzer based on the principle shown is configured with reference electrodes A and B and the electrode to be tested C on the skin.

[0039] (2) Measure the AC impedance Z1 between AC, the AC impedance Z2 between BC, and the AC impedance Z3 between AB respectively. Then, the contact impedance Zx between the electrode C and the skin can be obtained from the formula Z. x =Calculated as (Z1+Z2-Z3) / 2, schematic diagram as follows Figure 1 ;

[0040] (2) Each time the impedance spectrum is measured, 20 frequency points are selected in the 0.1Hz-100Hz band: 0.10Hz, 0.14Hz, 0.21Hz, 0.30Hz, 0.43Hz, 0.61Hz, 0.89Hz, 1.27Hz, 1.83Hz, 2.64Hz, 3.80Hz, 5.45Hz, 7.85Hz, 11.29Hz, 16.24Hz, 23.36Hz, 33.60Hz, 48.33Hz, 69.52Hz, and 100.00Hz, and their complex impedances are recorded.

[0041] (3) When the reference resistance is 10kΩ, the contact impedance spectrum between the same electrode C and the skin is tested 10 times under the excitation sinusoidal voltage amplitudes of 80mV, 320mV, and 1280mV, with a 30-second interval between each test. The average correlation coefficient of the 10 measurements under the same set of parameters is calculated, as shown in Table 1. The 10 tests for each excitation voltage are plotted on the same graph, as shown in Table 1. Figure 4 --6. From Table 1 and Figures 4-6 See, when measuring electrode-skin contact impedance, with a reference resistance of 10kΩ, the larger the amplitude of the sinusoidal excitation voltage, the closer the average correlation coefficient of 10 measurements is to 1, and the higher the repeatability of the measurement.

[0042] (4) When the excitation voltage amplitude is 1280mV, the contact impedance spectrum between the same electrode C and the skin is tested 10 times under the conditions of reference resistance of 100Ω, 10kΩ, 1MΩ, and 100MΩ, with a 30-second interval between each test. The average correlation coefficient of the 10 measurements under the same set of parameters is calculated, as shown in Table 2. The 10 test results for each reference resistance are plotted on the same graph, as shown in Table 2. Figures 6-9 As shown in Table 2. Figures 6-9As you can see, when measuring electrode-skin contact resistance, the repeatability is highest when testing 10 times using a 10kΩ reference resistor.

Claims

1. A method for parameter configuration in a disposable ECG electrode-skin contact impedance test, comprising attaching three disposable ECG electrode pads A, C, and B at equal intervals to the body surface, measuring the impedance values ​​between each pair of electrodes, i.e., the impedance Z1 between electrodes A and C, the impedance Z2 between electrodes C and C, and the impedance Z3 between electrodes A and B, and then calculating the contact impedance Zx between electrode C and skin as Zx = (Z1 + Z2 - Z3) / 2, characterized in that... The steps include: (1) Select a voltage source with adjustable sinusoidal excitation amplitude, prepare a reference resistor R0 with adjustable resistance value, prepare three disposable ECG electrodes A, C, and B, and attach the three electrodes to the skin at equal intervals; (2) Use the selected and prepared adjustable voltage source, reference resistor R0 and the impedance between the two electrodes on the skin to be tested to form a test circuit. (3) For each given voltage source sinusoidal excitation amplitude and reference resistor R0, repeat the test of the electrode-skin contact impedance spectrum multiple times and calculate the repeatability index; (4) Change the pairing of voltage source sinusoidal excitation amplitude and reference resistor R0, and repeat the test of the electrode-skin contact impedance spectrum multiple times and calculate the corresponding repeatability index. Continue until enough sinusoidal excitation amplitudes and reference resistor R0 are changed, and repeat the test of the electrode-skin contact impedance spectrum multiple times under each pairing and calculate its repeatability index value. (5) Compare the repeatability index values ​​of the electrode-skin contact impedance spectrum under all the calculated pairs, and determine the pairing of the excitation voltage amplitude and the reference resistance R0 value corresponding to the best repeatability index value as the optimal pairing.

2. The method for parameter configuration in a disposable ECG electrode-skin contact impedance test according to claim 1, wherein in step (4), when changing the pairing of the sinusoidal excitation amplitude of the voltage source and the resistance value of the reference resistor R0 to search for the optimal pairing, is characterized in that, Based on prior knowledge of the magnitude of electrode-skin contact impedance, the resistance value of R0 is first determined to be 10kΩ. Then, only the amplitude of the sinusoidal excitation of the voltage source is changed to form pairs. The electrode-skin contact impedance spectrum is then tested multiple times for each pair and its repeatability index value is calculated.

3. The method for parameter configuration in a disposable ECG electrode-skin contact impedance test according to claim 1, wherein in step (4), when changing the pairing of the sinusoidal excitation amplitude of the voltage source and the resistance value of the reference resistor R0 to search for the optimal pairing, is characterized in that, (a) Based on prior knowledge of the magnitude of the electrode-skin contact impedance, the resistance value of R0 is first determined to be 10kΩ. Then, only the amplitude of the sinusoidal excitation of the voltage source is changed to form pairs. The electrode-skin contact impedance spectrum of each pair is tested repeatedly and its repeatability index value is calculated. (b) Determine the voltage source sinusoidal excitation amplitude with the best repeatability index in step (a), then change the value of the reference resistor R0 to form pairs, and then repeat the electrode-skin contact impedance spectrum test multiple times for each pair and calculate its corresponding repeatability index value, so as to finally determine the reference resistor R0 based on the best repeatability index value.

4. The method for parameter configuration in a disposable ECG electrode-skin contact impedance test according to claim 1 requires calculation of repeatability index, characterized in that... The repeatability index uses the average correlation coefficient, calculated as follows: If m contact impedance spectra are monitored under a certain parameter configuration, and each complex impedance spectrum records the complex impedance at n frequency points, assuming one of the complex impedance spectra is X, and the average complex impedance spectrum of the m complex impedance spectra is Y, then X and Y are both complex vectors containing n elements. The Pearson correlation coefficient between them is defined as follows: in, It is the mean value of the complex impedance spectrum X. This is the mean of the average complex impedance spectrum Y; thus, the Pearson correlation coefficients r1, r2, ..., r between the monitored m complex impedance spectra and the average complex impedance spectrum Y can be calculated. m Therefore, the repeatability index is defined as the average correlation coefficient.

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