How to Use an AED: Complete Guide
Every minute without defibrillation during cardiac arrest drops survival chances by 10%. By the time paramedics arrive—average response time 8-12 minutes—the person's odds have plummeted near zero. Automated external defibrillators sitting in gyms, schools, and office buildings exist to close that gap. They can restart a heart in under two minutes.
Most people walk past these devices daily without understanding they're designed for anyone to operate. The machine talks you through every step, analyzes the heart rhythm automatically, and won't let you make dangerous mistakes. Your job is to turn it on and follow directions.
Quick Reference - 5 Steps
- Turn it on - Open case or press power, listen to voice prompts
- Expose and dry the chest - Remove clothing, wipe off water/sweat
- Attach pads - Follow diagram, press firmly for contact
- Stand clear - Don't touch while device analyzes rhythm or when its shocking
- Shock if advised - Press button when told, immediately resume CPR
What It Does and Why
When someone's heart stops during cardiac arrest, it doesn't always flatline like in movies. Often the heart quivers chaotically—ventricular fibrillation—pumping no blood despite electrical activity. CPR keeps blood moving manually, but it can't fix the rhythm. An AED delivers an electrical shock that resets the heart, giving it a chance to resume normal beating.
The device analyzes the heart's electrical pattern through pads stuck to the chest. If it detects a dangerous rhythm that responds to shocking, it charges and tells you to press the button. If the rhythm won't respond to electricity, it says "no shock advised" and tells you to continue CPR.
You can't shock someone who doesn't need it. The machine won't charge unless it detects a shockable rhythm. That safety feature is what makes these devices suitable for anyone—the machine makes the medical decision, you just operate it.
When Someone Needs It
Use it for sudden cardiac arrest: person collapses, unresponsive, not breathing normally. Don't waste time checking pulse or trying to diagnose what happened. If they're unconscious and not breathing, start CPR while someone gets the device.
Cardiac arrest looks different than most people expect. Not always dramatic chest-clutching followed by collapse. Sometimes the person just drops. Sometimes they gasp irregularly, which looks like breathing but isn't adequate. If a person is clearly unconscious, and you're unsure whether they're breathing normally, they're not. Start CPR and get the device.
When NOT to Use It
Don't use it on someone who's conscious or breathing adequately. If they're talking, moving, or taking regular breaths—even if they're having chest pain—they don't need defibrillation yet. Call 911 for them, keep them calm, but save the device for actual cardiac arrest.
Don't use it in standing water or while either you or the person is in a puddle. Pull them a few feet to dry ground first. Light rain isn't a problem once pads are attached.
Operating the Device
Power It On
Find the device in its clearly marked cabinet. Grab it, run to the person, open the case. Many models power on automatically when you lift the lid. Others have a green button. Press it. The device starts talking: "Stay calm. Follow the voice prompts."
That voice is your instructor. Everything you need to know, it will tell you. Listen and follow directions exactly.
Get the Chest Ready
Remove all clothing from the chest. Shirts, bras, everything comes off so the pads can stick directly to skin. Speed matters more than modesty. If the person has excessive chest hair where the pads will go, most kits include a razor. Quick shave just where pads attach.
Wet chest? Dry it fast with a towel, shirt, anything available. Water conducts electricity and can cause burns or reduce shock effectiveness.
Check for medication patches—small adhesive squares, often beige or white. Nitroglycerin, nicotine, or pain medication patches can burn or interfere. Peel them off and wipe the area clean.
Stick the Pads On
Open the pad package. You'll see two adhesive pads with wires, each showing a diagram of where it goes. One pad goes on the upper right chest below the collarbone. The other goes on the lower left side below the armpit along the ribs.
Peel the backing and stick them firmly. Press down the edges to ensure complete contact. Air bubbles or lifted edges prevent accurate analysis. If the person has an implanted pacemaker or defibrillator—you'll feel a hard lump under the skin, usually upper left chest—place pads at least an inch away from it if possible. If you can't avoid it perfectly, stick them anyway. Don't delay for ideal placement.
Analysis Time
Once pads are attached, it says: "Analyzing rhythm. Do not touch the patient." Everyone steps back. No hands on the person, not leaning on them, not resting a hand on their shoulder. You're not even allowed to be doing CPR during analysis.
Make it obvious by saying aloud to everyone in the area: "Everyone clear! Nobody touch!" Do a visual check. Analysis takes 5-10 seconds. Any movement or contact creates interference.
The Shock
If a shock is needed, the device says "Shock advised" and begins charging automatically. You'll hear a rising tone as it charges—about 5 seconds. It then says "Push the flashing button now."
Before pressing that button, do one more visual sweep and say out loud: "I'm clear, you're clear, everyone's clear!" Look at hands. Nobody touching the person or the surface they're on. Once you've confirmed everyone is clear, press the button firmly.
The person's muscles will contract. Their chest may lift slightly or arms might jerk. That's normal.
Back to CPR
As soon as the shock delivers, go straight back to CPR. Don't check for pulse, don't see if they're breathing, don't wait for signs of life. Start compressions: 30 compressions, 2 breaths, repeat. The device will tell you when to stop—after 2 minutes—for the next analysis.
If "no shock advised," start or continue CPR immediately. That means the heart rhythm can't be fixed by shocking right now. CPR maintains blood flow until the rhythm changes or paramedics arrive with medications.
Keep this cycle going: 2 minutes of CPR, pause for analysis, shock if advised, immediately resume CPR. The device stays on and keeps monitoring. Leave it attached and powered on until professional help takes over.
Common Concerns
What If I Make a Mistake?
The device prevents harmful mistakes. It won't charge unless it detects a shockable rhythm. You can't accidentally shock someone who doesn't need it. The worst error is hesitation—not using it when needed.
Pad placement doesn't have to be perfect. Within a couple inches of ideal is fine. Speed matters more than perfection.
Legal Protection
Good Samaritan laws in all 50 states protect people who use AEDs in emergencies. You can't be sued for trying to help someone in cardiac arrest, even if something goes wrong or they don't survive. These laws were specifically written to encourage bystander intervention.
Cardiac arrest is fatal without intervention. Using the device gives the person a chance they otherwise wouldn't have.
Pediatric Use
Children over 8 or over 55 pounds: Use adult pads and regular settings.
Children 1-8 or under 55 pounds: Use pediatric pads or pediatric setting if available. Pediatric pads deliver a lower energy shock appropriate for small bodies. If pediatric pads aren't available, adult pads still work—don't delay for ideal equipment.
Infants under 1: Check the device labeling for infant approval. If labeled for infants, use infant pads or pediatric setting. If not, CPR alone is your best option until paramedics arrive.
Training Makes the Difference
Anyone can grab one and follow the voice prompts. That's the point—bystander access saves lives. But training eliminates hesitation. CPR and AED certification courses walk you through hands-on practice with training devices, so when a real emergency happens, your hands know what to do without your brain having to remember instructions.
Courses teach you when to use it versus when someone needs CPR alone. How to coordinate with other bystanders—one person doing CPR while another sets up the device. How to handle wet environments, medication patches, implanted devices, pediatric cases. How to troubleshoot when pads won't stick or the device gives unexpected prompts.
Studies show trained rescuers deliver the first shock 60-90 seconds faster than untrained bystanders using the same device. That minute matters. Survival rates double when defibrillation happens within the first 3-5 minutes of collapse.
Working Together with CPR
Defibrillation and CPR aren't competing techniques—they're partners. CPR maintains minimal blood flow manually. The shock attempts to fix the underlying rhythm problem. You need both for maximum survival chances.
One person starts CPR immediately, another retrieves the device. As soon as it arrives, attach pads and follow prompts, but don't stop compressions until it says to clear for analysis. After shock delivery, immediately resume CPR. Continue this pattern until professional help arrives. If both people are trained, they can switch places whenever the person performing CPR is tired. This is great because it prevents fatigue and improves the victim’s chances of survival.
Early CPR plus early defibrillation produces survival rates 3-4 times higher than either intervention alone.
⚠️ Important
Reading this article doesn't replace hands-on training. While AEDs are designed for untrained users, proper certification teaches you to respond confidently under pressure and handle complications that aren't immediately obvious from device prompts. If you might encounter a cardiac emergency at work or home, take a certification course that includes practice with the device.
Frequently Asked Questions
Can anyone use an AED?
Answer: Yes, AEDs are designed for anyone to use. The device gives clear voice instructions and won't let you shock someone who doesn't need it. Every second counts during cardiac arrest, and bystanders using AEDs save lives regularly. Good Samaritan laws in all 50 states protect people who use AEDs in emergencies. The device analyzes the heart rhythm and only allows a shock if dangerous patterns are detected. You cannot hurt someone with an AED—the worst outcome is not using it when it's needed.
What if the AED says "no shock advised"?
Answer: Start CPR immediately and keep going. "No shock advised" means the heart rhythm cannot be fixed by shocking right now. CPR is still critical to maintain minimal blood flow to the brain and heart until paramedics arrive with medications. The device will continue monitoring and will tell you to stop CPR every 2 minutes to reanalyze. If the rhythm changes to one that can be shocked, you'll be told. Continue CPR cycles of 30 compressions and 2 breaths until help arrives or the person recovers.
Can I use an AED if the person has a pacemaker?
Answer: Yes, use it. You'll feel or see a hard lump under the skin where the implanted device sits. Place the pads at least one inch away from the lump if possible, but if you can't avoid it perfectly, attach the pads anyway. The external shock is much stronger than what implanted devices deliver and takes priority during cardiac arrest. Don't delay using the AED simply because you’re trying to achieve perfect pad placement around implanted devices.
What if the person is lying in water?
Answer: Move them to a dry surface if you can do so quickly—pull them a few feet onto dry ground or floor. If the chest is wet, dry it with a towel, shirt, or any cloth before attaching pads. Water conducts electricity and can cause burns or reduce shock effectiveness. Don't use the device while standing in a puddle. Light rain or dampness isn't dangerous once the chest is dried and pads are attached—the concern is pools of water creating electrical pathways away from the heart.
Do I need CPR training to use an AED?
Answer: No, but training dramatically improves your confidence and effectiveness. AEDs are designed for untrained bystanders and will guide you through the process. However, CPR certification teaches you when to use an AED, how to coordinate with other rescuers, and how to maintain compression quality while setting up the device. Studies show trained rescuers use AEDs 60-90 seconds faster than untrained bystanders. Most cardiac arrests require both CPR and defibrillation for best survival chances.
When It Counts
Cardiac arrest kills fast. Effective response requires three things: immediate CPR, early defibrillation, and advanced care from paramedics. You control two of those three. The person's survival depends largely on what bystanders do in the first 4-6 minutes.
Hesitation is the enemy. Not using the device because you're afraid of making a mistake means the person dies of cardiac arrest instead of getting a fighting chance. Every study on bystander AED use shows the same result: people who get shocked by untrained bystanders survive more often than people who wait for paramedics.
If you work in a building with one, know where it is. If you exercise at a gym, note its location. Getting trained to use CPR and AEDs takes a few hours and gives you the confidence to act when it matters. Contact Eastern CPR at (347) 961-1341 for certification courses that include hands-on practice.
