Electrical impedance in the lower limbs of patients with Duchenne muscular dystrophy: a preliminary study

Electrical impedances were measured, at a range of frequencies from 2 to 200 kHz, in the lower limbs of nine patients with Duchenne muscular dystrophy and 12 normal subjects. The specific admittance was calculated from the impedance, based on the assumption that the shape of the part of the limb measured is a truncated cone. Curve-fitting to the admittance locus on the complex plane gave the intracellular and extracellular resistances and the membrane capacitance. The intracellular resistance was higher and the membrane capacitance was lower in the patients than in the normal subjects. The membrane capacitance in the normal subjects increased with age. In the patients, the membrane capacitance decreased, and the intracellular resistance increased with the stage of disability, which was assessed by a physician. These experimental results agree well with the theoretical explanation, which uses simplified spherical models to represent living tissue.