An AED is a portable device that analyzes heart rhythm and delivers a shock if needed to restore normal rhythm during sudden cardiac arrest.
For the full breakdown, see our best Automated External Defibrillator guide.
An automated external defibrillator (AED) is a life-saving medical tool designed for use by bystanders during sudden cardiac arrest. It automatically detects shockable rhythms like ventricular fibrillation and guides the rescuer through voice prompts, making it accessible even without formal medical training. The FDA classifies AEDs as critical emergency devices, and they are a standard fixture in public places like airports, gyms, and offices across the U.S.
How an AED Works
Inside the device, a microprocessor analyzes the patient’s heart rhythm through adhesive electrode pads placed on the bare chest. If a shockable rhythm is detected, the AED charges its capacitor and either automatically delivers the shock (fully automatic models) or prompts the user to press a button. After the shock, the AED will prompt the rescuer to begin CPR immediately.
Using an AED: Step-by-Step
Following these steps increases survival odds:
- Call 911 and have someone retrieve the nearest AED.
- Turn on the AED and follow its voice prompts.
- Expose the chest — remove clothing and wipe dry if the chest is wet or has heavy hair.
- Place the pads as shown: one on the upper right chest, the other on the lower left side below the armpit. If pads risk touching (small child or thin chest), use the front‑back placement (center of chest and between shoulder blades).
- Plug in the cable if the pads aren’t pre‑connected.
- Stand clear — the AED will analyze. Say “CLEAR!” and ensure no one touches the patient.
- Deliver the shock if advised (on semi‑automatic models press the button; fully automatic models shock on their own).
- Start CPR immediately after the shock or if “no shock advised.” Continue until emergency services arrive or the patient shows signs of life.
Types of AEDs
The FDA separates AEDs into two main categories: public access and professional use. Public access models are designed to be used by untrained bystanders; they typically feature clear voice prompts and require a button press to deliver the shock. Professional use units may offer advanced monitoring, manual override, and more rugged construction for paramedics or first responders. Both types rely on disposable electrode pads and a battery that must be maintained according to the manufacturer’s schedule.
A key safety point from the FDA’s overview of AEDs: the device should never be used on a person who is conscious and breathing normally. It is specifically intended for sudden cardiac arrest, not a heart attack. Cpr certification and familiarity with your local AED’s prompts can make all the difference when seconds count.
FAQs
Can an AED be used on a child?
Yes, but always use pediatric‑sized pads or a pediatric mode if available. If not, standard adult pads can be used by placing one pad in the center of the chest and the other on the back between the shoulder blades. Never let adult pads touch each other on a small child.
Is it safe to use an AED on a wet person?
Yes, but you must dry the chest thoroughly before applying pads. Water can conduct electricity and reduce the shock’s effectiveness. Wipe the chest with a towel, remove the person from standing water, and proceed normally.
Do AED pads expire?
Yes. Most electrode pads have a printed expiration date, usually two to five years from manufacture. Using expired pads can result in poor adhesion or incorrect rhythm analysis. Check the pads regularly and replace them before they expire.
References & Sources
- U.S. FDA. “Automated External Defibrillators (AEDs)” Official FDA overview covering regulation, types, and use guidance.
- Mayo Clinic. “Automated external defibrillators: Do you need one?” Detailed explanation of AED function and safety precautions.
- OSHA. “Automated External Defibrillators (AEDs)” Workplace safety guidelines on AED placement and use.