• Marc D Berg, Lani L Clark, Terence D Valenzuela, Karl B Kern, and Robert A Berg.
• Department of Pediatrics, Steele Memorial Children's Research Center, Sarver Heart Center, University of Arizona College of Medicine, P.O. Box 245073, 1501 N Campbell Avenue, Tucson, AZ 85724, USA. marcb@peds.arizona.edu
• Resuscitation. 2005 Mar 1;64(3):287-91.

Primary ObjectiveIn a swine model of out-of-hospital ventricular fibrillation (VF) cardiac arrest, we established that automated external defibrillator (AED) defibrillation could worsen outcome from prolonged VF compared with manual defibrillation. Worse outcomes were due to substantial interruptions and delays in chest compressions for AED rhythm analyses and shock advice. In particular, the mean interval from first AED shock to first post-shock compressions was 46+/-6s. We hypothesized that the delay from shock to provision of chest compressions is similar in the out-of-hospital setting.Materials And MethodsWe conducted a retrospective observational review of AED-treated adult VF cardiac arrest victims over a 26-month period to determine the interval from the first AED defibrillation attempt to the initial provision of post-shock chest compressions for out-of-hospital VF cardiac arrests. A two-tiered, single emergency medical service (EMS) system with AED-equipped first responders serves our area of 400 km2 with a population of 487,000 people. The defibrillators record a detailed sequence of events during the resuscitation effort that includes the electrocardiogram with real clock times and a recording of surrounding audible actions.ResultsA median of 38 s (IQR 15, 61 s) elapsed between the first shock and the initiation of chest compressions. Approximately half of the delay was due to mechanical/electronic factors and the remainder due to human factors. Of 64 adults in VF, 45 (70%) died before hospital admission, 19 (30%) survived to admission and 10 (16%) survived to hospital discharge.ConclusionSubstantial delays in the provision of post-shock chest compressions are typical in this EMS system with AED-equipped first responders.

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