Waveforms of external defibrillators: analysis and energy contribution.
OBJECTIVE
Defibrillation is the most important therapy for terminating ventricular fibrillation in cardiac arrest patients. In addition to performing defibrillation at the earliest possible time, appropriate pulse energy and optimal waveform seem to be crucial for success. Emergency medical service personnel use different defibrillators and rely on their similarity of energy content. This study examined the true pulse energy content and waveform of 17 commonly used defibrillators.


RESULTS
Defibrillation energies were selected to be 30, 200 or 360 J and defibrillators were discharged into test resistors, simulating transthoracic impedances of 25, 50 or 100 Ohms. Pulse energy deviated by up to +23% or -29% from the selected energy. Pulse energy within the initial 8 ms ranged from 90 to 30% of total pulse energy. Fourteen defibrillators utilising damped sinusoidal waveforms produced a monophasic pulse when discharged into resistances of 50 Ohms and 100 Ohms.


CONCLUSIONS
Defibrillators used at the same energy settings do not necessarily produce the same defibrillation pulse energy. All but one defibrillator actually use monophasic waveforms, leaving the potential advantage of biphasic waveforms unused. Energy accuracy of defibrillators needs to be improved, and biphasic waveforms should be used more.
Achleitner
U
U
Department of Anaesthesia and Intensive Care Medicine, Leopold-Franzens University of Innsbruck, Institute for Emergency Medicine, Austria.
Amann
A
A
Stoffaneller
M
M
Baubin
M
M
D002138:Calibration; D004554:Electric Countershock / Q000295:instrumentation*; D004632:Emergency Medical Services / Q000379:methods; D004867:Equipment Design; D004869:Equipment Safety; D005069:Evaluation Studies as Topic; D006323:Heart Arrest / Q000628:therapy; D006801:Humans; D012680:Sensitivity and Specificity