The electrical impedance of the human thorax as a guide in evaluation of intrathoracic fluid volume.

The modelling of the human thorax and the impedance characteristics of the thorax are presented. A two-dimensional model of the thorax was constructed by using more than four hundred reference points. The input impedance was calculated by solving the Helmholtz equation for zero charge density and low frequencies. Variation in the impedance corresponds to the fluid in the lung and the degree of inflation, which is related to a given degree of pulmonary oedema.