Automated external defibrillators (AEDs) are designed so that anyone can use them, even with zero medical training. The device talks you through every step with voice prompts, analyzes the heart rhythm on its own, and only allows a shock if one is needed. Your job is to turn it on, place the pads, and follow directions. Speed matters: survival chances drop by 10% for every minute defibrillation is delayed after cardiac arrest.
The Basic Steps, Start to Finish
If someone collapses and isn’t breathing or responding, call 911 first (or have someone else call), then grab the nearest AED. Here’s the sequence:
- Turn the AED on. Open the case and press the power button. The device will immediately begin giving you voice prompts.
- Expose the chest. Remove or cut away all clothing covering the person’s chest. Most AED kits include scissors for this. If the chest is wet, dry it thoroughly with a towel or clothing. If there’s thick chest hair preventing the pads from making contact, use the razor included in the kit to shave the pad areas.
- Attach the pads. Peel the backing off each pad and stick them to bare skin. One goes on the upper right side of the chest, below the collarbone. The other goes on the lower left side, a few inches below the armpit. Diagrams on the pads themselves show you exactly where.
- Plug in the connector. Some AEDs require you to plug the pad cable into the unit. Others come pre-connected. The voice prompts will tell you.
- Let the AED analyze. The device will read the heart’s rhythm. Make sure nobody is touching the person. Say “CLEAR!” loudly so bystanders step back.
- Deliver the shock if prompted. If the AED detects a rhythm that needs a shock, it will tell you to press the shock button. Confirm again that nobody is touching the person, say “CLEAR!” and press the button. If no shock is needed, the AED will tell you that too.
After a shock is delivered, immediately begin CPR (chest compressions and rescue breaths). Continue for two minutes, which is roughly five cycles of 30 compressions and 2 breaths. After two minutes, the AED will re-analyze and tell you whether another shock is needed. Keep repeating this cycle until emergency medical services arrive.
Why the Pads Must Make Good Contact
The pads need to stick firmly to dry, bare skin so the electrical current travels through the chest and across the heart. Anything that creates a gap, whether moisture, chest hair, or clothing, weakens the shock or prevents the AED from reading the rhythm accurately. That’s why AED kits typically include a small razor, scissors, gauze pads, and a towel or wipes. Take the few extra seconds to prep the chest properly.
Pad Placement for Children
For children under about 8 years old or weighing less than 55 pounds, use pediatric pads if the AED has them. These deliver a lower energy dose. If pediatric pads aren’t available, use the standard adult pads. On a small chest where the two pads might touch each other, place one pad in the center of the chest and the other on the back between the shoulder blades. The same front-and-back placement applies to infants.
Using an AED Near Water or Metal
Never use an AED on someone who is submerged in water. Electricity travels through water and can injure bystanders while reducing the shock’s effectiveness. Pull the person out of the water first and move them to a dry surface. Dry the entire chest area thoroughly, including the neck, ribs, and underarms, before attaching the pads.
Metal surfaces like bleachers or warehouse floors are safe to use an AED on, despite the common myth. Just make sure the pads don’t touch the metal directly and that the person’s bare skin isn’t in direct contact with the metal surface either. If needed, slide a dry towel or piece of clothing under them. As always, confirm nobody is touching the person before delivering the shock.
Medication Patches, Jewelry, and Pacemakers
If the person has a medication patch on their chest (commonly nitroglycerin patches), peel it off before placing the AED pads. Don’t touch the patch with your bare hands, as the medication can absorb through your skin. Use the gloves included in the AED kit. Wipe the area dry after removing the patch.
Metal jewelry like necklaces or body piercings doesn’t need to be removed. Just make sure the pads aren’t placed directly on top of any metal. If a necklace is in the way, push it to the side. As long as the pads have full contact with bare skin, the AED works correctly.
A pacemaker or other implanted device is not a reason to skip the AED. If you notice a hard lump under the skin on the upper chest (which is where pacemakers sit), try to place the pad at least an inch away from it. But never withhold defibrillation from someone in cardiac arrest, regardless of implants or pregnancy.
What the AED Does on Its Own
The part that intimidates most people, deciding whether to shock, is entirely handled by the machine. The AED analyzes the heart’s electrical activity and determines whether the rhythm is one that responds to defibrillation. If the heart is in a rhythm that a shock won’t help, the device simply won’t let you deliver one, even if you press the button. You cannot accidentally shock someone who doesn’t need it.
The voice prompts guide you through every decision point. Some newer models also give feedback on CPR quality, telling you to push harder or faster during chest compressions. The device is essentially a coach that happens to deliver electrical therapy.
What Happens After the Shock
A single shock doesn’t always restart normal heart rhythm on the first try. That’s why the protocol is to immediately resume CPR after each shock rather than stopping to check for a pulse. Two minutes of chest compressions helps circulate whatever oxygen is still in the blood, keeping the brain and organs alive while giving the heart another chance to recover.
After those two minutes, the AED will automatically re-analyze and prompt you for another shock if needed. This cycle of shock, CPR, re-analyze continues until paramedics take over or the person starts breathing and moving on their own. Staying calm and following the voice prompts is the most important thing you can do. The machine handles the complicated decisions. You provide the hands and the speed.