If the heart does not return to a regular rhythm within 5-7 minutes, this fibrillation could be fatal. To stop the fibrillation, an AED is used to administer an external electric shock through the chest wall to the heart with the use of conductive adhesive pads. Built-in computers analyze the patient's heart rhythm, and interpret the rhythms that require defibrillation shocks. Most AEDs require an operator to initiate the delivery of the shock in some way, such as pushing a button.
Public access refers to accessibility for trained users to use AEDs in public places.
Public access does not mean that any member of the public witnessing a sudden cardiac arrest should be able to use the device. AEDs are to be used only by individuals with the proper training and certification in accordance with state and local laws.