What Is an Automated External Defibrillator? | SCA Lifesaver

An automated external defibrillator (AED) is a compact, battery-powered device that restarts a heart in sudden cardiac arrest. Alongside early CPR, AEDs form a vital link in the chain of survival. When someone collapses from sudden cardiac arrest, the AED reads the heart’s electrical activity through adhesive pad electrodes on the bare chest. If it detects a shockable rhythm (typically ventricular fibrillation, where the heart quivers without pumping), it delivers a controlled electric current to stop the chaos and let the natural pacemaker resume normal rhythm. The FDA’s official classification groups AEDs into public-access models for untrained bystanders and professional-use devices for trained responders.

What Does an AED Do?

Sudden cardiac arrest kills more than 350,000 people annually in the US; every minute without defibrillation lowers survival odds by roughly ten percent. The AED recognizes ventricular fibrillation or pulseless ventricular tachycardia and delivers a precisely timed shock that reboots the heart’s electrical system. Not every arrest is shockable: when the AED advises “no shock indicated,” the rescuer performs uninterrupted high-quality chest compressions until emergency medical services arrive. The device reanalyzes every two minutes.

Public Access vs. Professional-Use AEDs

Public-access AEDs are built for nonprofessionals — they use clear voice prompts and automate rhythm analysis, so they sit in bright cabinets at airports, schools, gyms, and offices. Professional-use devices for paramedics, EMTs, and hospital staff offer manual override and detailed cardiac data. For a home, workplace, or community space, our roundup of the best automated external defibrillators compares leading public-access models by features, ease of use, and cost.

How to Use an AED in an Emergency

First, call 911 and send someone to retrieve the nearest AED while you begin chest compressions. When the AED arrives, place it beside the victim’s head opposite the rescuer performing CPR, turn it on, and follow voice prompts. Expose the chest completely — it must be bare, dry, and free of clothing, jewelry, or patches. Shave excessive chest hair if needed and wipe away moisture. Apply pads as shown: one on the upper right chest below the collarbone, the other on the lower left side roughly 7 cm below the armpit. Press firmly. Ensure no one touches the victim. If analysis is manual, press the analyze button (most public-access models analyze automatically). If advised, press the shock button and confirm everyone is clear. Immediately resume CPR for two minutes, then let the AED reanalyze. Do not check for a pulse between shocks. Common mistakes include stopping compressions too long, applying pads to clothed or wet skin, and touching the patient during analysis. For children under 8 years or 55 pounds, use pediatric pads or child mode; otherwise, place one pad on the center of the chest and the other on the center of the back. The AED alternates shock analysis with two-minute CPR cycles until emergency medical services arrive.

FAQs

Can anyone use an AED without training?

Yes — public-access AEDs are designed for untrained bystanders. The device gives clear voice instructions for each step, from exposing the chest to delivering a shock. No medical knowledge is needed, and automated analysis ensures a shock is only delivered when a shockable rhythm is detected.

Can an AED shock someone who doesn’t need it?

No. The AED analyzes heart rhythm before any shock; if it does not detect ventricular fibrillation or pulseless ventricular tachycardia, it will not allow a shock. The system cannot be manually overridden.

Do AED pads expire?

Yes. Electrode pads have a manufacturer-specified expiration date on the sealed foil package. Expired pads may dry out and lose conductivity, preventing effective defibrillation. Check dates during routine inspections and replace per manufacturer schedule (typically every 2–5 years).