title: Comparison of six clinically used external defibrillators in swine.
abstract: BACKGROUND
  External defibrillation has long been practiced with two types of monophasic waveforms, and now four biphasic waveforms are also widely available. Although waveforms and clinical dosing protocols differ among defibrillators, no studies have adequately compared performance of the monophasic or the biphasic waveforms. This is the first study to compare defibrillation efficacy among biphasic external defibrillators, and does so as part of a study comparing all commonly available waveforms using their respective manufacturer-provided and clinically used doses.
  
  
  RESULTS
  Efficacy of six waveforms was tested in 852 short-duration ventricular fibrillation episodes in 14 swine. Protocol 1: 200-J monophasic damped sine (MDS) and monophasic truncated exponential (MTE) shocks were compared to 150-J biphasic shocks in six swine at the low-impedance of these animals. Protocol 2: Four commercially available biphasic defibrillators were compared using their respective manufacturer-recommended dose protocols in eight swine at low and simulated high-impedance. At low-impedance, all biphasic shocks achieved near-perfect success, while efficacy was significantly lower for MDS (67%) and MTE (30%) shocks. In protocol 2, first-shock success rates of the four biphasic defibrillators were uniformly high (97, 100, 100, and 94%) for low-impedance shocks, and decreased for high-impedance shocks (62, 92, 82, and 64%). There were statistically significant differences in efficacy among devices.
  
  
  CONCLUSIONS
  Commonly used MDS and MTE waveforms provide markedly dissimilar efficacies. Despite impedance-compensation schemes in biphasic defibrillators, impedance has an impact on their efficacy. At high-impedance, modest efficacy differences exist among clinically available biphasic defibrillators, reflecting differences in both waveforms and manufacturer-provided doses.
authors.affiliation: Medtronic Physio-Control Corporation, 11811 Willows Road NE, 98073-9706, Redmond, WA, USA. rob.walker@medtronic.com
authors.forename: Robert G
authors.initials: RG
authors.lastname: Walker
authors.forename: Sharon B
authors.initials: SB
authors.lastname: Melnick
authors.forename: Fred W
authors.initials: FW
authors.lastname: Chapman
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Walcott
authors.forename: Paul W
authors.initials: PW
authors.lastname: Schmitt
authors.forename: Raymond E
authors.initials: RE
authors.lastname: Ideker
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004554:Electric Countershock / Q000295:instrumentation* / Q000379:methods; D017097:Electric Impedance; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D008297:Male; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013552:Swine; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000628:therapy*