Skin resistance during square-wave electrical pulses of 1 to 10 mA

Several problems concerning an electrical model equivalent to the skin are discussed. The two components of pure resistance, derivable from the model, were tested with square-wave electrical pulses of 1 to 10 mA. The larger resistance component, shown to be localised in the stratum corneum, varied markedly with the current intensity, the intensity of a previous pulse and the interval between the pulses. This component decreased with time and the decrease was dependent on the amount of electrical change transferred through the skin. When constant-voltage pulses were used, the decrease could be equated to a process that reinforces itself. The smaller resistance component showed only relatively small variations with the different stimulus properties previously mentioned. It was concluded that the current intensity of transcutaneous electrical stimulation can only be controlled satisfactorily when current-regulated stimuli are used.