What is an AED?

An Automated External Defibrillator (AED) is a small, lightweight, portable device used to assess a person’s heart rhythm. If necessary, it administers an electric shock to restore a normal rhythm in victims of sudden cardiac arrest. AEDs are programmed to recognize different heart rhythms and to make the shock/no shock decision so that users don’t have to. They were designed so that lifesaving defibrillation could be performed as quickly as possible.

How does an AED work?

A microprocessor inside the defibrillator analyzes the victim’s heart rhythm through adhesive electrodes (some AED models require the person to press an ANALYZE button). The computer then advises the operator (voice and/or visual prompts) whether a shock is needed. When the operator responds to the prompt to give a shock, an electric current is delivered through the victim’s chest wall through adhesive electrode pads. When a person suffers a sudden cardiac arrest, the chance of survival decreases by 7 percent to 10 percent for each minute that passes without defibrillation.

Who can use an AED?

Most AEDs are designed to be used by people without medical backgrounds, such as police, firefighters, flight attendants, security guards, and lay rescuers. AEDs are most effective when standards are in place for appropriate training, equipment maintenance and ongoing quality-of-care monitoring. 

Will an AED always resuscitate someone in cardiac arrest?

No. The AED treats only a heart in ventricular fibrillation, an irregular heart rhythm. In cardiac arrest without ventricular fibrillation, the heart does not respond to electric currents, but needs medications. The victim also needs breathing support. AEDs are less successful when the victim has been in cardiac arrest for more than a few minutes, especially if no CPR was provided.

Do AEDs replace the use of CPR?

No. When a person experiences cardiac arrest, CPR will help keep oxygen flowing to the brain, but the electric shock of an AED vastly improves the chances of restarting the heart. AEDs can be used as part of cardiopulmonary resuscitation. CPR is still needed, starting with determining whether a person is unconscious, without breath or pulse. 

Remember:  call 911, administer CPR, use an AED!  The 911 operator will assist you with CPR and use of an AED if necessary.

Visit our website at or call us at 1-800-441-8378 with your questions about which AED is right for your needs.