Performance and error analysis of automated external defibrillator use in the out-of-hospital setting

Study objective: We determined whether automated external defibrillators (A EDs) can meet the American Heart Association performance criteria to detect and shock unstable cardiac rhythms (ventricular fibrillation [VF], ventric ular tachycardia [VT]) in the setting of an out-of-hospital cardiac arrest. Methods: AED performance was reviewed for cardiac arrests occurring between January 1, 1995, and December 31, 1997. After every cardiac arrest, data r egarding each rhythm analyzed and subsequent response (shock or no shock) w ere downloaded from the AED memory module. The study paramedic and study ph ysician independently reviewed each case and interpreted cardiac rhythms fr om downloaded AED data. The emergency medical services medical director res olved all discrepancies in a blinded manner. All cases of out-of-hospital c ardiac arrest in which an AED was turned on and a rhythm analyzed were incl uded. The primary objective was the correct identification and defibrillati on of VF or VT. Sensitivity, specificity, and predictive values with 95% co nfidence intervals (CIs) were calculated. Sources of error in AED rhythm ma nagement are also described. Results: A total of 3,448 AED rhythms were available for interpretation. Se nsitivity and specificity for appropriate AED management of a shockable (VF or VT) rhythm were 81.0% (95% CI 77.9% to 83.8%) and 99.9% (95% CI 99.7% t o 100%), respectively. Positive and negative predictive values were 99.6% ( 95% Ci 98.7% to 99.9%) and 95.5% (95% CI 94.7% to 96.2%), respectively. The re were 132 errors associated with AED management. Two errors resulted in d elivery of an inappropriate shock. In the remaining 130 errors, a shockable rhythm was not shocked. Fifty-five (42.3%) errors were AED dependent, 70 ( 53.9%) were operator dependent, and 5 (3.9%) were unclassified. Conclusion: The AED had high specificity and moderately high sensitivity in detecting and shocking unstable cardiac rhythms in the out-of-hospital set ting. Few cardiac rhythms were mismanaged by the AED. Elimination of operat or-dependent errors could increase AED sensitivity.