Defibrillation impedance: including an inductive element

A new equivalent circuit model is proposed to quantify the defibrillation impedance for short pulses. Six male guinea pigs (850-1050g) were used. A defibrillator delivered square voltage pulses (200V). Three electrode placements were tested randomly: Normal, abdominal, and subcutaneous. The equivalent circuit model was determined according to the best fitting curves of current waveforms in the first 3ms. An inductor was included in the model to account for the rising current waveforms. The inductors were 213 ± 57, 40 ± 10 and 236 ± 39 for the normal, subcutaneous and abdominal placements, respectively. The skin to the electrodes appears to be the major source of the inductance; the heart and lungs do not make substantial contributions. The mechanism of the inductance could be electroporation of the stratum corneum and cell membranes. The inductive model better predicts defibrillation impedance for short waveforms.