Four time-critical decisions shape your first minute with an AED: confirming unresponsiveness and absent breathing, exposing the bare chest, placing pads exactly where the diagrams show, and keeping everyone clear during rhythm analysis and shock delivery. An automated external defibrillator (AED) is designed to analyze the heart rhythm and deliver a shock only when it detects ventricular fibrillation or pulseless ventricular tachycardia, the two rhythms that respond to defibrillation.
This checklist covers how to recognize sudden cardiac arrest, apply pads correctly on adults, children, and infants with or without an implanted device, handle water, metal, and medication patches, and pair every step with CPR for the best survival odds.
Recognizing Sudden Cardiac Arrest Before You Power On the AED
Sudden cardiac arrest collapses a person without warning and stops effective breathing within seconds, which is different from a heart attack where the person usually stays awake, talking, and in pain. AED safety precautions begin with that distinction, because the device is built only for the first scenario. The internal analyzer will not deliver a shock unless it detects a shockable rhythm, so the AED will not rescue someone who does not need it.
Confirm Unresponsiveness and No Normal Breathing
Tap the shoulders firmly and shout, then look for chest movement, listen near the mouth for breath sounds, and feel the carotid pulse in the neck for no more than ten seconds. No response, no normal breathing, and no definite pulse mean the brain is losing oxygen fast. That combination is the trigger to power on the AED and begin CPR within the first few minutes.
Let the Rhythm Analyzer Decide Whether to Shock
Modern AEDs from Philips HeartStart, ZOLL AED Plus, Cardiac Science Powerheart, and Defibtech Lifeline analyze the rhythm through the pads and only arm a shock when the reading is shockable. If the rhythm is asystole (a flat line) or a perfusing rhythm the person still has, the unit will refuse to fire and will prompt you to keep CPR going instead. That built-in safeguard removes the risk of a “mistake” shock.
Preparing the Patient, the Chest, and the Surrounding Scene
Pull or cut away clothing from the chest the moment unresponsiveness is confirmed, because pads cannot read a heartbeat through a shirt, bra, or jacket. Jewelry, chains, and metal accessories in the pad zone must come off as well, since they can arc, spark, or burn the skin during shock delivery. Wipe away sweat, blood, or water from the chest so the adhesive pads stick firmly and the rhythm signal stays clean.
Move the person to a dry, stable surface when possible. Concrete, dry pavement, wood flooring, or low-pile carpet all work; standing water, hot tubs, and rain-soaked grass do not. Once the scene is clear, kneel beside the patient, switch the AED on, and follow the voice prompts without rushing past them.
With the scene secured and the unit now speaking its prompts, the next decision is where the pads must land on the body.
Heads up: shave or clip excessive chest hair only in the spot where the pads will land. A razor lives in most AED kits for exactly this reason, and skipping the step often means pads lift mid-analysis and the device asks you to start over.
Placing Pads Correctly on Adults, Children, and Infants
Correct electrode pad placement is the difference between a clean current path through the heart and a shock that travels across the chest wall instead of through it. The two pads work as a matched pair, and the diagrams printed on each one are not suggestions.
| Patient Type | Recommended Pad Position | Key Adjustment |
|---|---|---|
| Adult, no implant | Upper right chest below the collarbone; lower left side under the armpit | Standard placement for Philips HeartStart, ZOLL, Powerheart, and Lifeline units |
| Adult with pacemaker or ICD | Same as standard, but offset 1 inch or more from the visible device bump | Do not place the pad directly over the implanted hardware |
| Child 1–8 years or under 55 lb | Use pediatric pads or pediatric setting; anterior-posterior (front and back) is acceptable | Switch the AED to pediatric mode or use the pediatric pad cartridge |
| Infant under 1 year | Anterior-posterior placement with pediatric pads if available; adult pads are acceptable when pediatric pads are not on hand | Use whatever pads are present rather than delay shock delivery |
| Wet or sweaty chest | Dry the chest first, then place pads in standard adult position | Moisture reduces adhesion and confuses rhythm analysis |
Mind the Pacemaker or ICD Bump
A visible square or round lump under the skin on the upper chest signals an implantable pacemaker or cardioverter-defibrillator. Place the pad at least one inch away from that bump so the current does not travel through the implant and damage it or reduce the energy reaching the heart. Pad placement that skips the implant still delivers a life-saving shock when the rhythm requires one.
Switch to Pediatric Mode for Younger Patients
Children under eight years old or under 55 pounds need pediatric pads or the pediatric energy setting on a dual-mode device. Adult pads deliver higher energy than a small heart should receive, and pediatric pads reduce that energy to a safer range. Many AEDs carry a child key, a pediatric cartridge, or a switch on the front that flips between adult and pediatric modes without changing the pads.
Avoiding Hazards That Turn a Rescue Into a Risk
An AED is built to survive field use, but a few environments will still cause problems and a small number of situations call for restraint. Treating these scenarios as hard rules keeps both you and the patient out of harm’s way.
Stay Clear of Standing Water and Flammable Atmospheres
Do not analyze or shock a patient who is lying in a puddle, submerged in a pool, or soaked by rain without first dragging them to a dry surface. Water conducts electricity, and a shock delivered while the patient is wet can travel up the rescuer’s arms. Likewise, move the patient away from gasoline spills, propane tanks, or oxygen-rich atmospheres before pushing the shock button, because the spark can ignite the fumes.
Skip Medication Patches and Metal Jewelry
Nitro patches, nicotine patches, hormone patches, and pain-relief patches can spark or burn the skin if a pad is laid on top of them. Peel the patch off, wipe the skin clean, and place the pad in the diagram position. Chains, necklaces, and metal piercings in the pad path should also be removed or shifted aside so the current does not arc against the metal.
Never Use an AED on a Responsive Patient
Refuse to attach pads to anyone who is awake, breathing normally, talking, or has a definite pulse, even if they feel faint or are clutching their chest. Those signs point to a different emergency, and a shock delivered to a beating heart can trigger a lethal arrhythmia instead of correcting one. Call emergency services, keep the person calm and seated, and wait for trained help.
That is exactly why no AED rescue should happen without chest compressions running in parallel.
Pairing AED Use With CPR for the Best Survival Odds
An AED and CPR are partners, not substitutes. The defibrillator stops a chaotic rhythm so the heart can restart in a coordinated way, and CPR keeps oxygenated blood flowing to the brain during the seconds it takes to attach pads, wait for analysis, and deliver a shock. Skipping compressions while you fiddle with the device cuts survival odds quickly.
Follow the Built-In Compression Cadence
Begin chest compressions at a depth of two inches and a rate of 100 to 120 per minute the moment unresponsiveness is confirmed. Continue compressions while a bystander powers on the AED, attaches the pads, and clears the patient. The device will prompt you to stop compressions for rhythm analysis and during shock delivery, then resume CPR immediately after the shock or after the “no shock advised” prompt.
Resume CPR Right After the Shock
Do not pause to check for a pulse after a shock. Begin compressions again at once, and continue for two minutes until the AED prompts the next analysis. Survival rates climb when compressions start within ten seconds of a shock and run with minimal interruption, which is why hands-only CPR is taught alongside AED use in every basic life support course.
Maintenance, Training, and Legal Confidence for Bystanders
An AED that has sat in a hallway for three years with dead batteries or dried-out pads is a paperweight, not a rescue tool. A few minutes of scheduled attention keeps the device ready and keeps your confidence high the moment a real arrest happens.
Run a Maintenance Check on a Set Schedule
Check the status indicator light weekly, confirm pads have not expired, and verify the battery has enough life left to deliver a shock.
- Pad replacement: swap pads every two to four years depending on the model.
- Battery replacement: follow the schedule printed on the unit, usually every two to five years.
- Backup kit: keep a sealed spare set of pads and a spare battery inside the case.
- Inspection log: record each check so the chain of custody stays clear for auditors or attorneys.
- Storage location: keep the AED in a visible, unlocked cabinet at room temperature, since cold cars and hot trunks shorten pad adhesive life and drain batteries.
Tip: store the AED in a visible, unlocked cabinet at room temperature. Cold cars in winter and hot car trunks in summer shorten pad adhesive life and drain batteries faster than the printed shelf life suggests.
Train Before the Crisis Arrives
Complete a certified CPR and AED course so your hands know the cadence of compressions and your eyes know the pad diagrams by heart. Practice on a manikin until you can place pads and deliver a simulated shock in under a minute, because adrenaline will not give you a second chance to read the manual during a real arrest. Refresher courses every two years keep the steps fresh, since skill fade is steep after the first six months.
Know That Good Samaritan Law Protects Bystanders
Every state has Good Samaritan legislation that shields bystanders who act in good faith during a medical emergency, including AED use. The laws cover off-duty medical professionals and lay rescuers alike, as long as you act within the scope of basic training and do not abandon the person once you start. Bystander AED use is treated as a public-health priority, which is why the legal framework is built to encourage action rather than punish honest mistakes.
Final Take
An AED saves lives only when bystanders act fast, place it right, and avoid the few hazards that turn a rescue into a risk. Confirm cardiac arrest, expose the chest, dry the skin, position the pads exactly as drawn, and keep clear while the device analyzes and shocks. Train ahead of time, check the unit on a schedule, and trust that the law is on the side of anyone willing to try.
FAQ
What should you be aware of when using an AED?
Confirm the person is unresponsive and not breathing normally before powering on the device, expose the bare chest, place pads exactly as the diagrams show, and keep everyone clear during rhythm analysis and shock delivery. Watch for water, metal jewelry, medication patches, and pacemaker bumps that change how the pads sit on the skin.
What should you not do when using an AED?
Never touch the patient during rhythm analysis or shock delivery, and never place pads over a pacemaker bump, medication patch, or metal jewelry. Avoid wet surfaces, flammable atmospheres, and using the device on a person who is responsive and breathing normally.
When should an AED not be used?
Skip AED use when the person is awake, breathing normally, or has a definite pulse, since those conditions rule out the rhythm an AED is designed to correct. Also avoid analyzing or shocking in standing water, rain without cover, or near flammable vapors.
What safety precautions are needed before applying AED pads?
Expose the bare chest, dry off sweat or water, shave excessive hair in the pad zone, and remove jewelry or medication patches where the pads will sit. Move the person to a dry, non-conductive surface and confirm the chest is clear before pressing the power button.
Can you use an AED on a person with a pacemaker?
Yes. Place the pad at least one inch away from the visible pacemaker or implantable defibrillator bump and continue with the standard adult position for the second pad. The shock is still appropriate and may save the person’s life.
Should an AED be used on someone lying in water or on a wet surface?
Move the patient to a dry area first. Water conducts current and can injure rescuers while reducing the energy that reaches the heart, so dry pavement, wood flooring, or any non-conductive surface is required before analysis or shock.
