An AED is safe to use. Studies have shown the devices to be 90 percent sensitive (able 90 percent of the time to detect a rhythm that should be defibrillated) and 99 percent specific (able 99 percent of the time to recommend not shocking when defibrillation is not indicated).
Because of the wide variety of situations in which it will typically be used, the AED is designed with multiple safeguards and warnings before any energy is released. The AED is programmed to deliver a shock only when it has detected V-fib or V-tach. However, potential dangers are associated with AED use. That's why training — including safety and maintenance — is important.
The American Heart Assoication recommends that persons who live or work where an AED is available for use by lay rescuers participate in a Heartsaver AED Course. AEDs are so user-friendly that untrained rescuers can generally succeed in attaching the pads, pressing ANALYZE (if required), and delivering shocks. However, untrained rescuers may not know when to use an AED, and they may not use an AED safely, posing some danger of electric shock to themselves and others. Also, untrained rescuers probably would not know how to respond to the victim if the AED prompts "no shock indicated."
An operator needs only to follow the illustrations on the electrode pads and the control panel and listen and follow the voice prompts (for example, "Do not touch the patient."). An AED will deliver a shock only when a shock is advised and the operator pushes the SHOCK button. This prevents a shock from being delivered accidentally.