Interactions between CPR and defibrillation waveforms: effect on resumption of a perfusing rhythm after defibrillation.

Background: Cardiopulmonary resuscitation (CPR) improves survival from cardiac arrest. The interactions between CPR and the new biphasic (BiP) defibrillation waveforms have not been defined. Our purpose was to compare the effect of CPR versus no CPR during BiP and damped sinusoidal (DS) shocks on the termination of ventricular fibrillation (VF) and the resumption of a perfusing rhythm. Methods: We studied 20 pigs; VF was induced electrically and allowed to persist for 6 min. During VF episodes each pig received (in random order): (a) 6 min of full CPR (continuous ventilation and closed chest mechanical compression (Thumper, Michigan Instruments)) followed by DS defibrillation at 100 J; (b) no CPR, DS defibrillation; (c) 6 min of full CPR and BiP defibrillation at 100 J; and (d) no CPR, BiP defibrillation. Results: BiP shocks with CPR terminated VF in 83% of attempts versus 45% without CPR (15/18 and 5/11 respectively, P<0.05). DS shocks with CPR were successful in terminating VF in 53% of attempts; DS shocks without CPR were successful in 44% (8/15 and 7/16, respectively, P=NS). No animal achieved a perfusing rhythm after shocks of either waveform if CPR did not precede the shocks during the 6-min VF period, whereas if CPR was administered during VF 46% (11/24) of the combined BiP/DS shocks restored a perfusing rhythm (P<0.01). Conclusion: In this experimental long duration VF model, CPR was essential for a perfusing rhythm after termination of VF by shocks with either waveform. CPR facilitated the termination of VF and resumption of a perfusing rhythm after biphasic waveform defibrillation but not after damped sinusoidal waveform defibrillation.