Application of the Geselowitz relationship to the murine conductance catheter

Conductance catheters are known to have a nonuniform spatial sensitivity due to the distribution of the electric field. The Geselowitz relation is applied to the murine conductance catheter using a finite element model to determine catheter's spatial sensitivity in uniform media. Further analysis of FEM numerical modeling results using the Geselowitz relation provides a true measure of parallel conductance in a simplified murine left ventricle for assessment of the admittance method and hypertonic saline techniques. The spatial sensitivity of blood conductance (G
_b
) is determined throughout the cardiac cycle. G
_b
is converted to volume using Wei's equation to determine if the presence of myocardium alters the nonlinear relationship through changes to the electric field shape. Results show that the admittance method correctly calculates G
_b
in comparison to the Geselowitz relation, and that the relationship between G
_b
and volume is accurately fit using Wei's equation.