Pauses in chest compression and inappropriate shocks: A comparison of manual and semi-automatic defibrillation attempts

Background: Semi-automatic defibrillation requires pauses in chest compressions during ECG analysis and charging, and prolonged pre-shock compression pauses that pauses are shorter for manual defibrillation by trained rescuers, but with an increased number of inappropriate shocks given for a non-VF/VT rhythm. Methods: From a prospective study of CPR quality during in- and out-of-hospital cardiac arrest, the duration of pre-shock, inter-shock, and post-shock pauses were compared with Mann-Whitney U-test during manual and AED mode with the same defibrillator, and proportions of inappropriate shocks were compared with Chi-squared tests. Results: A 635 manual and 530 semi-automatic shocks were studied. Number of shocks per episode was similar for the two groups. All pauses measured seconds (s) were shorter for manual use (P< 0.0001); median (25, 75 percentiles); 15 (11, 21) versus 22 (18, 28) pre-shock, 13 (9, 20) versus 23 (22, 26) inter-shock, and 9 (6, 18) versus 20 (11, 31) post-shock, but 163 (26%) manual shocks were inappropriate compared with 30 (6%) AED shocks, odds ratio (OR) 5.7 (95% Cl; 3.8-8.7). A 150 (78%) of the inappropriate shocks were delivered for organised rhythms. The proportion of inappropriate manual shocks was higher for resident physicians in-hospital than paramedics out-of-hospital; 77/228 (34%) versus 86/407 (21%), OR 1.9 (1.3-2.7). Conclusion: Manual defibrillation resulted in shorter pauses in chest compressions, but a higher frequency of inappropriate shocks. A higher formal level of education did not prevent inappropriate shocks.