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

Canine transthoracic conductance (G _T) was measured during high-voltage defibrillation shocks to test the hypothesis that (G _T) is a linear function of electrode force (F) and electrode area (A). Symmetric protocols were used to compensate for changes in (G _T) 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 cm ², G _T was linear (r=0.996, 0.995, 0.971, 0.992, 0.995) over five dogs for 30 N≤F≤70 N. For a constant F=50 N, G _T was linear (r=0.992, 0.998, 0.994, 0.992) over four dogs for 20 cm ²≤A≤60 cm ², and in one dog (r=0.996) for 40 cm ²≤A≤90 cm ². The quantitative relationship demonstrated for G _T and F and A can be used in the design of experiments and interpretation of results used for validation of numerical defibrillation models.