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.