Automated external defibrillators: everywhere?

Out of hospital cardiac arrest (OHCA) is a common cause of death. 30 000 people sustain cardiac arrest outside hospital and are treated by emergency medical services (EMS) each year (Nolan et al, 2010). Electrical defibrillation is well established as the only effective therapy for cardiac arrest caused by ventricular fibrillation (VF) or pulseless ventricular tachycardia (VT). Death ensues in the untreated within minutes due to cerebral hypoxia. This provides a very narrow window in which definitive treatment can given by defibrillation, though this window can be prolonged with effective cardiopulmonary resuscitation (CPR) (Wik et al, 2003).

The scientific evidence to support early defibrillation is definitive. The delay from collapse to delivery of the first shock is the single most important determinant of survival. If defibrillation is delivered promptly, survival rates as high as 75% have been reported (Handley et al, 2005). However, the presence of an automated external defibrillator (AED) alone does not increase survival. Box 1 identifies three interventions that, if immediately available, can increase survival.