Ventricular Fibrillation Threshold vs Alternating Current Shock Duration.

Abstract

International basic safety limits for utility-frequency electrical currents have long been set by the International Electrotechnical Commission 60479-1 standard. These were inspired by a linear-section plot proposed by Biegelmeier in 1980 with current given as a function of the shock duration. This famous plot has contributed to safe electrical circuit design internationally and has properly earned significant amount of respect over its 35 years of life. However, some possible areas for improvement have been suggested. We searched for all animal studies of ventricular fibrillation threshold versus duration that used a forelimb to hindlimb connection that had at least 3 durations tested. We found 6 such studies and they were then used to calculate a new C3 curve after normalizing the data. A rational function model fit the animal data with r2 = .96. Such a correlation calculation tends to underweight the smaller values, so we also correlated the log threshold values and this had a correlation of r2=.94. Existing ventricular fibrillation threshold current versus duration data can be fitted with a simple rational function. This can provide a useful update to IEC 60479-1.