title: Waveform analysis of biphasic external defibrillators.
abstract: OBJECTIVE
  All internal defibrillators and some external defibrillators use biphasic waveforms. The study analysed the discharged waveform pulses of two manual and two semi-automated biphasic external defibrillators.
  
  
  RESULTS
  The defibrillators were discharged into resistive loads of 25, 50 and 100 Omega simulating the patient's transthoracic impedance. The tested biphasic defibrillators differed in initial current as well as initial voltage, varying from 10.9 to 73.3 A and from 482.8 to 2140.0 V, respectively. The energies of the manual defibrillators set at 100, 150 and 200 J deviated by up to +19.1 or -28.9% from the selected energy. Impedance-normalised delivered energy varied from 1.0 to 12.5 J/Omega. Delivered energy, shock duration and charge flow were examined with respect to the total pulse, its splitting into positive and negative phases and their impedance dependence. For three defibrillators pulse duration increased with the resistive load, whereas one defibrillator always required 9.9 ms. All tested defibrillators showed a higher charge flow in the positive phase. Defibrillator capacitance varied between approximately 200 and 100 mu F and internal resistance varied from 2.0 to 7.6 Omega. Defibrillator waveform tilt ranged from -13.1 to 61.4%.
  
  
  CONCLUSIONS
  The tested defibrillators showed remarkable differences in their waveform design and their varying dependence on transthoracic impedance.
authors.affiliation: Department of Anaesthesiology and Critical Care, University of Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria.
authors.forename: U
authors.initials: U
authors.lastname: Achleitner
authors.forename: K
authors.initials: K
authors.lastname: Rheinberger
authors.forename: B
authors.initials: B
authors.lastname: Furtner
authors.forename: A
authors.initials: A
authors.lastname: Amann
authors.forename: M
authors.initials: M
authors.lastname: Baubin
mesh_terms: D002138:Calibration / Q000592:standards; D004554:Electric Countershock / Q000295:instrumentation* / Q000592:standards*; D017097:Electric Impedance; D004632:Emergency Medical Services / Q000592:standards; D004869:Equipment Safety / Q000592:standards; D005069:Evaluation Studies as Topic; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans