Thorax resistivity in children and adults.

Abstract

Measurements of thorax resistivity were made in children and adults. Alternating currents of 300 cycles/sec and 2 ma were passed through the subject from the shoulders and neck to the legs. Equipotential lines were determined around the chest as well as cross-sectional areas. From the potential difference between isopotential lines, their average separation, and cross-sectional areas, it was possible to calculate mean torso resistivity. A linear and significant relationship was found between cross-sectional area and mean thorax resistivity. Significant differences were found between the mean torso resistivities of adults and children. Intraindividual variations in torso resistivities were also noted. These data suggest that if the human torso is considered as a homogeneous conductor, individual torso resistivity must be taken into consideration in the Gabor-Nelson equation for calculation of the dipole moment of the heart. However, the presence of intra-individual variations in torso resistivity may invalidate calculations of the heart dipole moment by single integration of body surface potential.