Abstract 2082: Less Time without Chest Compressions, but More Inappropriate Shocks when Defibrillators are used in Manual Mode
Background: Prolonged pre-shock pauses in chest compressions have been shown to reduce chance of return of spontaneous circulation. Semi-automatic defibrillation requires time without chest compressions during ECG analysis and charging. We hypothesized that when trained rescuers use defibrillators in manual mode these pauses are shorter, but at the expense of increased number in inappropriate shocks defined as shocks on a nonVF/nonVT rhythm when compared to semi-automatic mode use
Methods: From a prospective study of quality of CPR during out-of- and in-hospital cardiac arrest, all shocks were identified and peri-shock pauses in chest compressions (pre-shock pause (T1), pause between shocks (T2), and pause from last shock to resumed CPR (T3)) were recorded. Peri-shock pauses during manual and semi-automatic use of defibrillators were compared with Mann-Whitney U-tests and proportions of inappropriate shocks were compared with Chi-squares test.
Results: 637 manual and 403 semi-automatic shocks were studied. Number of shocks per episode and proportions of shocks given as 1st, 2nd, or 3rd in a stack were similar between the two groups. All peri-shock pauses (s) were shorter for manual use; median (25, 75 percentiles); T1 16 (11, 21) vs. 22 (18, 29); T2 13 (9, 20) vs. 23 (22, 26); T3 9 (5, 17) vs. 22 (15, 32), all P<0.001. Additionally, 167 (26%) of manual shocks were inappropriate compared with 22 (6%) of semi-automatic shocks; odds ratio (OR) 6.1 (95% CI; 4 –10), P<0.001. Of the 189 inappropriate shocks, 149 (79%) were delivered on an organized rhythm. Pauses for inappropriate and appropriate shocks were similar. For semi-automatic shocks the proportion of inappropriate shocks were similar for shocks given as 1st, 2nd, or 3rd in a stack (P=0.7), but for manual shocks the proportion was higher for 2nd and 3rd shocks (P=0.002). The proportion of inappropriate shocks in manual mode was higher for resident physicians in-hospital than for paramedics out-of-hospital; 81/230 vs. 86/407, OR 2.0 (95% CI; 1.4 –2.9), P<0.001.
Conclusion: Manual use of defibrillators resulted in less time without chest compressions, but a higher frequency of inappropriate shocks may outweigh the benefits. Higher formal level of education did not prevent inappropriate shocks.