四肢單極誘導に及ぼす皮膚電極間impedanceの影響に就いて

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Since Wilson et al described a method of obtaining unipolar limb leads, this procedure has been widely utilized in clinical use. But the effect of skin-electrode impedance on the unipolar leads is not sufficiently investigated. For this reason, the subject shall be discussed here.In 180 cases unipolar limb leads were taken by two methods ; A method, in which the electrodes for exploring were separated from the electrodes for central terminal, and B, in which the each electrode for exploring as connected to the corresponding arms for central terminal. The amplitude in the B method was smaller than that in the A as illustrated in Fig. 2. From the calculation by using the function shown in Fig. 4,the deflection in the B method with 5,000 ohms resistors of a central terminal should be smaller than in the A method, and should be influenced by the areas of electrodes. See the Fig. 5. Moreover the B method should tend to distort the lower frequency elements of the curve, this was proved in experiments. These phenomena would be explained that the skin-electrode impedance and the internal tissue impedance were in the comparable order with the 5,000 ohms resistance of a central terminal. When the larger resistors of a central terminal were arranged, the potential of the B method enlarged as illustrated in Fig. 6. This finding was also ascertained by calculation in another material, as shown in Fig. 7. Consequently the potential in the B method with 50,000 ohms or more resistors resembled closely the potential in the A method, as supported by theoretical and experimental grounds.In the augmented limb leads, a variable resistor was arranged in parallel with the grid leak resistor. The greater the arranged resistor, the larger the deflection obtained by both calculation and photography. Thus the augmented unipolar limb lead must be considered as a variation of the B method. See the Fig. 9.In augmented unipolar limb lead by Goldberger, the electrocardiograms of aVR, aVL, and aVF should be recorded separately one by one, but not simultaneously. This procedure is very troublesome. Adopting six equal resistors r between each limb electrode by twos, as illustrated in Fig. 10,the augmented unipolar limb leads would be recorded simultaneously with three push-pull amplifiers. On this method, named aV' method by us, the voltage wou ldbe calculated by the function (IX). In Fig. 12,the amplitude of aV' lead corresponding to the change in resistance r would be calculated, applying the function mentioned above. The maximum amplitude was obtained, when the resistor of 200,000 ohms or 500,000 ohms was employed. Such an amplitude was approximated to that in the aV, and larger than that in the A method. This phenomenon was confirmed in the experiments, too. In thirty two cases, the proportion of the amplitude of aV'R to that of aVR was like that shown in Fig. 14. The former was smaller than the latter. The more the greatness of skin-electrode impedance r_a increased, the smaller became the gains of aV' lead. And when the employed resistor r was small, this phenomenon was more remarkable as shown in Fig. 15. If the resistor r ranging from 200,000 ohms to 500,000 ohms is employed, the aV' lead would be satisfactorily useful in practice.
社団法人日本循環器学会の論文
1955-11-20

四肢單極誘導に及ぼす皮膚電極間impedanceの影響に就いて

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