The half-cycle sinusoid as an alternative defibrillating waveform in low-energy applications

Abstract

The standard Lown-type capacitor discharge waveform was compared with a single half-cycle 60-Hz sinusoid for effectiveness of defibrillation. Both shock types were used in attempts to defibrillate a series of dogs over a range of intensities from that below the minimum required for defibrillation to values well above those which consistently were successful. An on-line computer was used to monitor energy, peak current, and peak voltage of each shock. The results were plotted as percent success vs each parameter and comparisons were made at the 80% level. The half-cycle sinusoid required 18% more energy but 20% less peak current and 15% less peak voltage for 80% probability of success at these intensity levels. These results indicate that the half-cycle 60-Hz sinusoid is a reasonable alternative as a defibrillating waveform for low-energy applications (open chest surgery, some pediatric cases, and small animal applications) where its advantages of waveform unaffected by load impedance, and simplicity of circuit, may be realized.