Linearity of transthoracic conductance with respect to electrode force and area during high-voltage defibrillation shocks.

Canine transthoracic conductance (GT) was measured during high-voltage defibrillation shocks to test the hypothesis that (GT) is a linear function of electrode force (F) and electrode area (A). Symmetric protocols were used to compensate for changes in (GT) with respect to shock number (n). Stainless steel electrodes were employed with a force-control system for precise selection and control of both F and A at each shock. For a constant A = 60 cm2, GT was linear (r = 0.996, 0.995, 0.971, 0.992, 0.995) over five dogs for 30 N < or = F < or = 70 N. For a constant F = 50 N, GT was linear (r = 0.992, 0.998, 0.994, 0.992) over four dogs for 20 cm2 < or = A < or = 60 cm2, and in one dog (r = 0.996) for 40 cm2 < or = A < or = 90 cm2. The quantitative relationship demonstrated for GT and F and A can be used in the design of experiments and interpretation of results used for validation of numerical defibrillation models.