title: Fully discharging phases. A new approach to biphasic waveforms for external defibrillation.
abstract: BACKGROUND
  Phase-2 voltage and maximum pulse width are dependent on phase-1 pulse characteristics in a single-capacitor biphasic waveform. The use of 2 separate output capacitors avoids these limitations and may allow waveforms with lower defibrillation thresholds. A previous report also suggested that the optimal tilt may be >70%. This study was designed to determine an optimal biphasic waveform by use of a combination of 2 separate and fully (95% tilt) discharging capacitors.
  
  
  RESULTS
  We performed 2 external defibrillation studies in a pig ventricular fibrillation model. In group 1, 9 waveforms from a combination of 3 phase-1 capacitor values (30, 60, and 120 microF) and 3 phase-2 capacitor values (0=monophasic, 1/3, and 1.0 times the phase-1 capacitor) were tested. Biphasic waveforms with phase-2 capacitors of 1/3 times that of phase 1 provided the highest defibrillation efficacy (stored energy and voltage) compared with corresponding monophasic and biphasic waveforms with the same capacitors in both phases except for waveforms with a 30-microF phase-1 capacitor. In group 2, 10 biphasic waveforms from a combination of 2 phase-1 capacitor values (30 and 60 microF) and 5 phase-2 capacitor values (10, 20, 30, 40, and 50 microF) were tested. In this range, phase-2 capacitor size was more critical for the 30-microF phase-1 than for the 60-microF phase-1 capacitor. The optimal combinations of fully discharging capacitors for defibrillation were 60/20 and 60/30 microF. Conclusions-Phase-2 capacitor size plays an important role in reducing defibrillation energy in biphasic waveforms when 2 separate and fully discharging capacitors are used.
authors.affiliation: Department of Cardiology, Cleveland Clinic Foundation, Cleveland, Ohio, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanouchi
authors.forename: J E
authors.initials: JE
authors.lastname: Brewer
authors.forename: K F
authors.initials: KF
authors.lastname: Olson
authors.forename: K A
authors.initials: KA
authors.lastname: Mowrey
authors.forename: T N
authors.initials: TN
authors.lastname: Mazgalev
authors.forename: B L
authors.initials: BL
authors.lastname: Wilkoff
authors.forename: P J
authors.initials: PJ
authors.lastname: Tchou
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D013552:Swine; D014693:Ventricular Fibrillation / Q000628:therapy*