Automated external defibrillation versus manual defibrillation for prolonged ventricular fibrillation: lethal delays of chest compressions before and after countershocks.

STUDY OBJECTIVE: We sought to determine whether the delays in chest compressions and defibrillation associated with an automated external defibrillator would adversely affect outcome compared with manual defibrillation in a swine model of out-of-hospital prolonged ventricular fibrillation.

METHODS: After 8 minutes of untreated ventricular fibrillation, 16 swine (33+/-4 kg) were randomly assigned to automated external defibrillator defibrillation or manual defibrillation with the same biphasic truncated exponential waveform 150-J shock through the same type of pads. Defibrillation with the automated external defibrillator was performed as recommended by the manufacturer, and manual defibrillation was provided per American Heart Association Guidelines. The primary outcome measure was 24-hour survival with good neurologic outcome. Data are described as means+/-SD.

RESULTS: None of 8 animals in the automated external defibrillator group survived for 24 hours, whereas 5 of 8 animals in the manual defibrillation group survived 24 hours, all with good neurologic outcome (P=.027). The time interval from simulated defibrillator arrival to first compressions was 98+/-18 seconds in the automated external defibrillator group versus 68+/-15 seconds in the manual defibrillation group. In particular, the interval from first shock to first chest compressions was 46+/-18 seconds versus 22+/-16 seconds, respectively. The mean percentage of time that chest compressions were performed in the first minute after the first countershock was 15%+/-13% versus 40%+/-15%, respectively. As a result, return of spontaneous circulation within 5 minutes of simulated defibrillator arrival occurred in only 1 of 8 animals in the automated external defibrillator group versus 6 of 8 animals in the manual defibrillation group.

CONCLUSION: The longer delays in chest compressions with automated external defibrillator defibrillation versus manual defibrillation can worsen the outcome from prolonged ventricular fibrillation.