An automated external defibrillator (AED) (
) designed for use by a rescuer with minimal or no training during a medical emergency is provided. The AED implements a user interface program (
) which guides the rescuer through operation of the AED and application of CPR and defibrillation therapy to a patient by displaying a series of visual instructions on a graphic display (
) or other visual output device, and by providing additional aural instructions via a speaker (
) or other aural output device. The rescuer merely needs to press a start button (
) to initiate operation of the AED and begin CPR and defibrillation instruction.