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Skin-electrode impedance was measured for four different types of conventional electrocardiographic electrodes applied under different conditions. All types of contacts were frequency dependent; a decrease in impedance was found with increasing frequency. Occasionally, impedance values at a frequency range of 6 to 100 cycles per second were in the tens of thousands of ohms with all electrode types. Tracings obtained under working conditions were evaluated to determine the influence of skin-electrode impedance on the recorded data. Single channel electrocardiographs accurately recorded cardiac potentials; however, simultaneously recorded multiple channel data had considerable distortion in half of the subjects. Frank vectorcardiograms demonstrated significant amplitude loss in half of the patients, with the most prominent distortion occurring in the T wave as compared to QRS. The inclusion of a buffer amplifier between the skin-electrode contacts and the resistor network produced distortionfree tracings. The inclusion of such devices is suggested to obviate any potential error produced by the highest skin-electrode impedance contact values obtained under working conditions.
Spach et al. (Sat,) studied this question.