Study objective: To assess the feasibility of consistent acquisition of precise and clinically important time intervals in a city police department defibrillation study.
Design: On a daily basis, clocks at 911 dispatch were synchronized with those at ambulance dispatch, and all clocks on all defibrillators were synchronized to this time. Times were obtained from recordings at dispatch centers and from defibrillator memory modules.
Setting: City with a population of 70,745 and an area of 30 square miles.
Participants: All patients in ventricular fibrillation (VF) treated by police officers using semiautomated defibrillators.
Interventions: On receipt of a call at 911 dispatch, the nearest squad car was dispatched. If police arrived before the ambulance and a cardiac arrest was confirmed, the closest squad car with a defibrillator was dispatched. Police delivered up to three shocks before ambulance arrival.
Results: Of 44 patients in VF, 14 were initially treated by police. Seven of 14 regained a spontaneous circulation with police shocks and seven required additional advanced life support care for restoration of pulses. Ten of the 14 were discharged home. The 911 call-to-shock time interval was 4.9 +/- 1.3 minutes for the seven who regained a spontaneous circulation with police shocks and 6.1 +/- 0.7 minutes for the seven without restoration of pulses by police (P = .035, one-sided, two-sample t-test).
Conclusion: Acquisition of precise times for determination of time intervals is feasible with a concerted effort to synchronize all clocks from which times are derived. Even small differences in call-to-shock time intervals appear to be critical determinants of restoration of a spontaneous circulation.