Method for configuring parameters in disposable electrocardio-electrode-skin contact impedance test

Abstract

A parameter configuration method in a disposable electrocardio-electrode-skin contact impedance test comprises the following steps: (1) selecting a voltage source with an adjustable sine excitation amplitude, preparing a reference resistor R0 with an adjustable resistance value, preparing three disposable electrocardio-electrodes A, B and C, and equidistantly pasting the three disposable electrocardio-electrodes on the skin; (2) connecting the selected and prepared adjustable voltage source, a reference resistor R0 and an impedance between the two skin electrodes in series to form a test circuit; (3) repeatedly testing the alternating-current impedance spectrum of the to-be-tested electrode-skin contact impedance for multiple times by pairing one amplitude of sine excitation of each given voltage source with one resistance value of the reference resistor R0, and calculating a repeatability index; (4) changing pairs of sine excitation amplitudes of enough voltage sources and the resistance value of the reference resistor R0, repeatedly testing the alternating current impedance spectrum of the electrode-skin contact impedance for multiple times under each pair, and calculating a repeatability index value of the alternating current impedance spectrum; and (5) comparing the repeatability index values to obtain optimal parameter pairing.

Description

Technical Field

[0001] The present application relates to a method for parameter configuration in a disposable electrocardiogram electrode-skin contact impedance test.

[0002] ECG equipment, especially ECG monitoring equipment, uses a large number of disposable ECG electrodes, also called electrode patches. The most important performance of disposable ECG electrodes is reflected in the size of the contact impedance with the skin when testing the ECG. The smaller the contact impedance, the better. The industry standard YY / T0196-2005 currently stipulates that the AC impedance of the disposable ECG electrode gel-to-gel electrode pair should be tested to replace its contact impedance with the skin for evaluation. However, in the case of lax skin treatment, the AC impedance of the disposable ECG electrode gel-to-gel electrode pair is not highly correlated with the electrode-skin contact impedance. It would be more direct if the size of the disposable ECG electrode-skin contact impedance could be directly tested.

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

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

[0005] When testing the disposable ECG electrode-skin contact impedance in the above manner, the amplitude of the voltage source excitation sine wave and the series reference resistor R0 need to be configured. Background Art

[0006] The industry standard YY / T0196-2005 stipulates that when testing the AC impedance of disposable ECG electrodes connected to each other at 10Hz, the peak-to-peak value of the test current should not exceed 100μA. It is recommended that a sinusoidal signal voltage source and a 1MΩ or greater resistor (i.e. R0) be used 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, the peak-to-peak value of the test current is less than 2μA, much less than 100μA. One of the reasons why the industry standard recommends using a conservative and relatively large reference resistor is that the test current is too large and affects the charged state of the electrode pair, thereby affecting the stability of the electrode AC impedance.

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

[0009] There is no literature discussing the optimization of the voltage source sinusoidal excitation amplitude and reference resistor configuration when a sinusoidal voltage source is connected in series with a reference resistor R0 to test the gel electrode-skin contact impedance value. A good optimized configuration scheme should be one that has good repeatability in the measured electrode-skin contact impedance spectrum. Summary of the invention

[0010] Purpose of the Invention

[0011] A parameter configuration scheme for testing gel electrode-skin contact impedance by connecting a sinusoidal voltage source in series with a reference resistor R0 is proposed, including the optimal configuration scheme for the amplitude of the excitation sinusoidal wave and the size parameters of the reference resistor R0, aiming to ensure that the electrode-skin contact impedance spectrum measured under this parameter configuration has high repeatability.

[0012] Technical Solution

[0013] A method for parameter configuration in a disposable ECG electrode-skin contact impedance test, wherein three disposable ECG electrode sheets A, C and B are pasted on the body surface at equal intervals, and the impedance values ​​between the electrodes are tested respectively, namely, the impedance Z1 between the AC electrodes, the impedance Z2 between the CB electrodes and the impedance Z3 between the AB electrodes, and then the contact impedance Zx between the C electrode and the skin can be calculated as (Z1+Z2-Z3) / 2, such as Figure 1 As shown, it is characterized in that it includes the following steps: (1) selecting a voltage source with adjustable sinusoidal excitation amplitude, preparing a reference resistor R0 with adjustable resistance, preparing three disposable ECG electrodes A, C, and B, and sequentially placing the three electrodes on the skin at equal intervals; (2) 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 to form a test circuit, such as Figure 2As shown; (3) for each pairing of a given voltage source sinusoidal excitation amplitude and a reference resistor R0 resistance value, the electrode-skin contact impedance spectrum to be tested is repeatedly tested multiple times, and the repeatability index is calculated; (4) the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 resistance value is changed, and the electrode-skin contact impedance spectrum to be tested is repeatedly tested multiple times and the corresponding repeatability index is calculated, and this process is continued until a sufficient number of sinusoidal excitation amplitudes and reference resistor R0 pairs are changed, and the electrode-skin contact impedance spectrum is repeatedly tested multiple times under each pairing and its repeatability index value is calculated; (5) the repeatability index values ​​of the electrode-skin contact impedance spectra under all the calculated pairs are compared, and the pairing of the excitation voltage amplitude and the reference resistor R0 value corresponding to the best repeatability index value is determined as the optimal pairing.

[0014] According to the above method for parameter configuration in a disposable ECG electrode-skin contact impedance test, when changing the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 resistance value in step (4) to search for the optimal pairing, a simplified search strategy can be considered, which is characterized in that the R0 resistance value can be first determined as a value similar to the electrode-skin contact impedance based on the prior knowledge of the electrode-skin contact impedance size, such as setting it to 10kΩ, and then, only the voltage source sinusoidal excitation amplitude is changed to form pairs, and then the electrode-skin contact impedance spectrum is repeatedly tested for each pairing multiple times 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 changing the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 resistance value to search for the optimal pairing in step (4), a simplified search strategy can be considered, characterized in that: (a) the R0 resistance value can be first determined as a value similar to the electrode-skin contact impedance based on the prior knowledge of the electrode-skin contact impedance size, such as setting it to 10kΩ, and then, only the voltage source sinusoidal excitation amplitude is changed to form pairs, and then the electrode-skin contact impedance spectrum is repeatedly tested for each pairing multiple times and its repeatability index value is calculated; (b) the voltage source sinusoidal excitation amplitude with the best repeatability index in step (a) is determined, and then, only the reference resistor R0 size is changed to form pairs, and then the electrode-skin contact impedance spectrum is repeatedly tested for each pairing multiple times, and its corresponding repeatability index value is calculated, so that the reference resistor R0 is finally determined based on the best repeatability index value.

[0016] According to the above parameter configuration method in the disposable ECG electrode-skin contact impedance test, it is necessary to calculate the repeatability index, which is characterized in that the repeatability index adopts the average correlation coefficient and can be calculated as follows:

[0017] If m contact impedance spectra are monitored under a certain parameter configuration, each complex impedance spectrum records the complex impedance of n frequency points. Assuming that one of the complex impedance spectra is X and the average complex impedance spectrum of 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, is the mean value of the complex impedance spectrum X, is the mean of the average complex impedance spectrum Y; in this way, 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 , thus defining the repeatability index 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 disposable ECG electrode-skin contact impedance. 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 measured at different excitation voltages using a 10 kΩ reference resistor

[0024]

[0025] Table 2 Repeatability of electrode-skin contact impedance measured with 1280mV test voltage and different reference resistances

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 , the schematic diagram of the electrode-skin contact impedance measurement scheme

[0028] Figure 2 , measurement equivalent circuit diagram

[0029] Figure 3 , Schematic diagram of the instrument for testing the electrode-skin contact impedance spectrum in the experiment of this application scheme

[0030] Figure 4, when the reference resistance is 10kΩ, the electrode-skin contact impedance spectrum is measured 10 times under the excitation voltage of 80mV. The horizontal axes of the upper and lower figures are both frequency f, in Hz; the upper figure is the real resistance spectrum, and the vertical axis is resistance, in ohm; the lower figure is the imaginary reactance spectrum, and the vertical axis is reactance, in ohm.

[0031] Figure 5 , when the reference resistance is 10kΩ, the electrode-skin contact impedance spectrum is measured 10 times under the excitation voltage of 320mV. The horizontal axes of the upper and lower figures are both frequency f, in Hz; the upper figure is the real resistance spectrum, and the vertical axis is resistance, in ohm; the lower figure is the imaginary reactance spectrum, and the vertical axis is reactance, in ohm.

[0032] Figure 6 , when the reference resistance is 10kΩ, the electrode-skin contact impedance spectrum is measured 10 times under the excitation voltage of 1280mV. The horizontal axes of the upper and lower figures are both frequency f, in Hz; the upper figure is the real resistance spectrum, and the vertical axis is resistance, in ohm; the lower figure is the imaginary reactance spectrum, and the vertical axis is reactance, in ohm.

[0033] Figure 7 , 100Ω series resistance is selected to measure the electrode-skin contact impedance spectrum 10 times under 1280mV excitation voltage. The horizontal axes of the upper and lower figures are both frequency f, in Hz; the upper figure is the real resistance spectrum, the vertical axis is resistance, in ohm; the lower figure is the imaginary reactance spectrum, the vertical axis is reactance, in ohm.

[0034] Figure 8 , 1280mV excitation voltage, 1MΩ reference resistance is selected to measure the electrode-skin contact impedance spectrum 10 times. The horizontal axis of the upper and lower figures is the frequency f, in Hz; the upper figure is the real resistance spectrum, the vertical axis is the resistance, in ohm; the lower figure is the imaginary reactance spectrum, the vertical axis is the reactance, in ohm.

[0035] Fig. 9 , 100MΩ reference resistance is selected to measure the electrode-skin contact impedance spectrum 10 times under 1280mV excitation voltage. The horizontal axes of the upper and lower figures are both frequency f, in Hz; the upper figure is the real resistance spectrum, the vertical axis is resistance, in ohm; the lower figure is the imaginary reactance spectrum, the vertical axis is reactance, in ohm.

[0036] Fig.10 , schematic diagram of a certain brand of electrode sticker used in the embodiments. DETAILED DESCRIPTION

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

[0038] (1) Use Figure 2 The constant voltage low frequency impedance spectrum analyzer with the principle shown in the figure sets 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 to be measured and the skin can be expressed by the formula Z x =(Z1+Z2-Z3) / 2 calculation, the schematic diagram is as follows Figure 1 ;

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

[0041] (3) When the reference resistance is 10 kΩ, the contact impedance spectrum between the same electrode C and the skin is tested 10 times under the conditions of excitation sinusoidal voltage amplitudes of 80 mV, 320 mV, and 1280 mV, respectively. The interval between each test is 30 seconds. The average correlation coefficient of the 10 measurements under the same set of parameter configurations is calculated, as shown in Table 1. The 10 test conditions for each excitation voltage are plotted in the same figure, as shown in Table 1. Figure 4 --6. From Table 1 and Figure 4-6 See, in the case of measuring electrode-skin contact impedance, when the reference resistance is 10 kΩ, 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, respectively. The interval between each test is 30 seconds. The average correlation coefficient of the 10 measurements under the same set of parameter configuration is calculated, as shown in Table 2. The 10 test conditions for each reference resistance are plotted in the same figure, as shown in Table 2. Figure 6-9 As shown in Table 2 and Figure 6-9See, in the case of measuring electrode-skin contact impedance, the repeatability is highest when testing 10 times with a reference resistor of 10 kΩ.

Claims

1. A method for parameter configuration in a disposable ECG electrode-skin contact impedance test, wherein three disposable ECG electrode sheets A, C and B are pasted on the body surface at equal intervals, and the impedance values ​​between the electrodes are tested respectively, namely, the impedance Z1 between the AC electrodes, the impedance Z2 between the CB electrodes and the impedance Z3 between the AB electrodes, and then the contact impedance Zx between the C electrode and the skin can be calculated as (Z1+Z2-Z3) / 2, as shown in FIG1, characterized in that: The method comprises the following steps: (1) selecting a voltage source with an adjustable sinusoidal excitation amplitude, preparing a reference resistor R0 with an adjustable resistance value, preparing three disposable ECG electrodes A, C, and B, and sequentially placing the three electrodes at equal intervals on the skin; (2) using the selected and prepared adjustable voltage source, the reference resistor R0, and the impedance between the two electrodes on the skin to be tested to form a test circuit in series, as shown in FIG2 ; (3) for each pairing of a given voltage source sinusoidal excitation amplitude and a given reference resistor R0 resistance value, repeatedly testing the electrode to be tested-skin contact impedance spectrum for multiple times, and calculating the repeatability index; (4) changing the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 resistance value, and then repeatedly testing the electrode to be tested-skin contact impedance spectrum for multiple times and calculating the corresponding repeatability index, and continuing until enough sinusoidal excitation amplitudes and reference resistor R0 pairs are changed, and the electrode-skin contact impedance spectrum is repeatedly tested for multiple times under each pairing and its repeatability index value is calculated; (5) Compare the values ​​of the repeatability index of the electrode-skin contact impedance spectrum under all 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. According to the method for parameter configuration in a disposable ECG electrode-skin contact impedance test as described in claim 1, when changing the pairing of the voltage source sinusoidal excitation amplitude and the reference resistor R0 resistance value to search for the optimal pairing in step (4), a strategy of simplifying the search can be considered, wherein: Based on the prior knowledge of the electrode-skin contact impedance, the R0 resistance can be determined to be a similar value, such as 10kΩ. Then, only the sinusoidal excitation amplitude of the voltage source is changed to form pairs. The electrode-skin contact impedance spectrum is tested repeatedly for each pairing and its repeatability index value is calculated.

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

4. According to claim 1, the method for parameter configuration in a disposable ECG electrode-skin contact impedance test requires calculation of a repeatability index, which is characterized in that: The repeatability index uses the average correlation coefficient, which can be calculated as follows: If m contact impedance spectra are monitored under a certain parameter configuration, each complex impedance spectrum records the complex impedance of n frequency points. Assuming that one of the complex impedance spectra is X and the average complex impedance spectrum of 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: in, is the mean value of the complex impedance spectrum X, is the mean of the average complex impedance spectrum Y; in this way, 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 , thus defining the repeatability index as the average correlation coefficient

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