Machine and operator performance analysis of automated external defibrillator utilization.

BACKGROUND AND PURPOSE: The availability of an automated external defibrillator (AED) can improve the outcome of patients with out-of-hospital cardiac arrest (OHCA). On June 1, 2000, Taipei City became the first city in Taiwan to equip emergency medical services personnel with AEDs. This study was conducted to assess the performance of the AED machine in detecting ventricular fibrillation (VF) and ventricular tachycardia (VT) in the population, and to assess operator performance in its use.

METHODS: AED use in OHCA patients was assessed over a 1-year period. Electrocardiography and voice records retrieved from AED data cards were analyzed. A shockable rhythm was defined as either VF or VT. AED machine performance was assessed based on the correct identification of these rhythms. Operator performance was evaluated according to American Heart Association guidelines.

RESULTS: A total of 978 AED rhythm analyses were obtained for 653 OHCA patients. The sensitivity and specificity for detecting shockable rhythms by the AED machine were 90.0% (95% confidence interval [CI], 85.3% to 93.3%) and 100% (95% CI, 99.5% to 100%), respectively. Sensitivity for coarse VF, fine VF, rapid VT, and slow VT was 97.5%, 74.2%, 63.6% and 60.0%, respectively. An AED was deployed in 18 non-OHCA patients and in 119 patients after they had been moved into the ambulance. Non-compliance with standard procedures occurred during AED use in 162 patients, including interference of movement by cardiopulmonary resuscitation (CPR) in progress in 69, untimely machine turn-off in 49, leads fell off or disconnected in 33, failure of shock delivery after charge in 28, and interference of movement other than CPR in 22.

CONCLUSIONS: This study found that the AED machine has high specificity and high sensitivity in detecting VF and VT, especially coarse VF. Efforts are needed to improve the timing of AED deployment and emergency medical technician compliance with standard procedures.