Abstract 4036: Optimal Phase Relationship between Defibrillation and Mechanical Chest Compressions Improves Shock Success
Pauses in chest compression for defibrillation are detrimental to the success of resuscitation and may be eliminated with the use of mechanical chest compressors. However, the optimal phasic relationship between chest compression and defibrillation is still unknown. We therefore examined relationships between the phase of mechanical compression and the timing of defibrillation based on measurement of the 50% defibrillation threshold (DFT50). Ventricular fibrillation (VF) was electrically induced and untreated for 10 seconds in 12 domestic pigs weighing between 22–31 kg. Mechanical chest compression was performed by AutoPulse (ZOLL Medical Corporation, Chelmsford, MA) for 15 seconds. A biphasic electrical shock of variable energies ranging from 30~150J was delivered at 4 phases of the compression period as shown in Figure 1-A. A group in which defibrillation was attempted at a constant 2 seconds following discontinued of chest compression served as a control. There was no difference between the measured coronary perfusion pressures (CPP) prior to each of the shocks in the five groups. As shown in Figure 1-B, the calculated energy DFT50 was significantly lower when the shock was delivered during latter decompression as represented by group C. Defibrillation efficacy is maximal when an electrical shock is delivered during the latter phase of decompression.