Relationships between parameters describing low-frequency electrical admittance locus plot of human palmar skin

Using a two-frequency three-electrode method, unipolar electrical admittance was measured in the palmar skin of 48 normal healthy humans. Characteristics of and relationships between the phase angle pi alpha/2, the conductance extrapolated at zero frequency G(O) and ion relaxation time tau obtained from the Cole-Cole equation were examined in a low-frequency region (up to 354 Hz). At base-line resting values, the three admittance parameters were interrelated according to the regression model; log tau i = A + B alpha i + D log G(O)i + epsilon i with R2 > or = 0.7434 (p < or = 0.0001), where A, B and D determined from regression analysis showed inter- and intra-individual variation. Multi-factor analyses of variance showed that alpha was greater in women than men (0.8025 versus 0.7545, p < 0.0023), and log G(O) decreased significantly with age (covariate coefficient = -0.0058 log microS cm-2 per year, p < 0.04). For evoked responses, alpha showed a very small change (maximum < 5%), tau decreased while G(O) increased. With increasing frequency, conductance responses increased in absolute amplitudes but decreased in relative changes (amplitude change divided by static level). Statistical analyses from clinical experimental materials (total 130 subjects) showed that the capacitive behaviour of admittance (due to alpha) presented significant variation between controls and patient groups. This may shed new light on the nature of the skin electrical admittance/impedance.