Optimal Parameters of Electrical Impulses for Defibrillation by Condenser Discharges

Abstract

The defibrillation threshold for various wave forms of condenser discharge, using capacitors from 4 to 200 µF, has been measured. Condenser discharge alone was used, or condenser discharge 0.25 henry (20 ohms) with an iron core series inductance, or condenser discharge, 0.29 henry (27 ohms) inductance, but without the iron core. Statistical analysis of the results showed that the last of these three circuits gave the lowest threshold voltage values. Optimal parameters of inductance-altered discharges are obtained with values of 24, 32, and 50 µF. Detailed analysis of the separate physical parameters of the discharge show that optimal pulse duration is 8.5 to 16.6 msec. Further increase of duration does not decrease the voltage or current for threshold shocks, but merely increases the energy delivered. Pulse duration appears to be one of the more important parameters for successful defibrillation, and for this reason, a series inductance is also important.

Twenty years of prehospital coronary care.

“…33 The waveform of 12 ms duration delivered by this machine had been found by Peleska to be optimal for defibrillation of laboratory animals. 34 A signpost to possible further miniaturisation was the observation by the Belfast workers that a stored energy of only 200 J is sufficient to defibrillate the hearts of 95% of patients. 35 The efficacy of low energy levels was confirmed by others.3637 Repeated shocks of 400 J stored energy cause myocardial damage in animals.38 Shocks of this magnitude, which are usually not necessary clinically, may cause functional disturbance in man.…”

Incidence of Arrhythmias in the Dog Following Transthoracic Ventricular Defibrillation with Unidirectional Rectangular Stimuli

“…In later papers he extended this study to include discharges in which an inductor was inserted in series with the capacitor (2,3). In all of these studies, the strength of the shock was adjustable, but the waveform could be changed in only a rather limited and restricted fashion.…”

The Strength‐Duration Relationship of Monophasic Waveforms with Varying Capacitance Sizes in External Defibrillation

“…Defibrillation threshold (DFT) for external shocks depends upon the shape of the defibrillation waveforms 1–6 as well as electrode pad size, 7,8 shock polarity, 9 and the sequence of shock pulse 10 . Since defibrillation waveforms are determined by the waveform time constant, 11 capacitance size and interelectrode resistance may play an important role in the determination of defibrillation efficacy 12 . The use of smaller capacitance sizes, 50–100 μF, has been advocated to improve defibrillation efficacy 12 …”

“…Since defibrillation waveforms are determined by the waveform time constant, 11 capacitance size and interelectrode resistance may play an important role in the determination of defibrillation efficacy 12 . The use of smaller capacitance sizes, 50–100 μF, has been advocated to improve defibrillation efficacy 12 …”