TempoLife › Features › Defibrillators and cardiac arrest response › how-to-use-an-aed
Using a defibrillator, step by step
Open it, turn it on, bare the chest, follow the voice. What the machine decides for you, what it will never do, and the one instruction people get wrong — go straight back to compressions after the shock.
CPR in sixty seconds
- Unresponsive and not breathing normally? Gasping is not breathing. Treat it as a cardiac arrest.
- Call 112 (113 in Norway). Speaker on, phone on the floor. Stay on the line — the dispatcher will coach you.
- Push hard and fast in the centre of the chest: 5–6 cm in an adult, 100–120 per minute, letting the chest come all the way back up.
- Send somebody else for a defibrillator. Do not go yourself unless it is seconds away. Keep compressing.
- Turn the device on and do what it says. It decides whether to shock. After a shock, go straight back to compressions.
This is a reference written for bystanders, not a diagnosis, a training course or medical advice. It cannot tell you what is wrong with a particular person, and it does not replace the dispatcher on the other end of an emergency call — they can see what is near you and they will talk you through it. If you are worried about your own heart, or about a symptom, that is a conversation with a clinician rather than a page on a website.
It talks you through it, and that is the design
An automated external defibrillator is built to be used by a frightened stranger. Open the lid or press the green button and it starts speaking — in the local language, and usually with pictures on the pads themselves. From that point on the correct behaviour is to do exactly what the voice says and nothing else. There is no menu to understand, no dose to choose and no way to shock a heart that does not need it: the device analyses the rhythm itself and simply refuses to charge if a shock would not help.
The sequence
One person keeps compressing while a second person works the machine — the compressions only stop for the analysis and the shock. Turn it on. Bare the chest completely: cut or tear the clothing, take off a wet shirt, unhook a bra with an underwire and move it clear. Peel the pads and press them firmly onto dry skin exactly as the picture on each pad shows. Plug in the connector if it is not already attached. When it says "analysing", say "hands off" loudly and make sure nobody is touching the person. If it says shock, look along the body, shout "clear", press the flashing button, and go straight back to compressions.
Straight back to compressions is the part people miss
After a shock the heart is typically stunned rather than instantly beating, and the blood pressure has to be rebuilt by hand. Guidelines are blunt about it: resume chest compressions immediately, do not stop to look for a pulse, do not stop to see whether it worked. The machine will tell you to do this and then count down two minutes before it analyses again. Every second spent watching the patient after a shock is circulation the brain does not get.
What the device will and will not do
It will decide whether the rhythm is shockable, charge itself, refuse to deliver a shock into a beating heart, record the whole event for the hospital, and in most models coach your compression rate with a metronome. It will not manage the airway, it will not restart a heart that has been still for a long time, and it will not tell you to stop CPR. Leave the pads on and the unit switched on when the ambulance arrives — the crew will read the recording off it, and re-pading wastes their time.
Semi-automatic and fully automatic
Two kinds are in public use. A semi-automatic model charges and then waits for you to press a flashing shock button; a fully automatic model announces the shock and delivers it on its own after a countdown. Neither needs a decision from you beyond keeping everybody clear when told. If you find yourself waiting for a button that never lights, listen again — you are probably holding a fully automatic unit that is about to fire on its own.
| Step | You | The device |
|---|---|---|
| Open and switch on | Press the button or lift the lid | Starts spoken prompts |
| Expose the chest | Cut clothing, dry the skin, move metal jewellery aside | Waits |
| Attach pads | Press firmly, follow the picture on each pad | Detects contact quality |
| Analyse | Stop compressions, shout "hands off", touch nobody | Reads the rhythm, decides |
| Shock advised | Shout "clear", look along the body, press the button | Charges and delivers |
| Immediately after | Resume compressions at once — no pulse check | Counts down two minutes |
A pacer, and your coordinates
Two things a phone can genuinely do at the scene. The first paces your compressions at 110 a minute — the middle of the recommended band — and counts the two-minute marks at which a second rescuer should take over. The second reads your position out of the browser so you can say it aloud to the dispatcher, which is the fastest way to fix the hardest question in a rural emergency. Neither replaces the call.
Compression pacer
Pacer stopped
Target 100–120 per minute · 5–6 cm in an adult · swap rescuer every 2 minutes.
Read your position to the dispatcher
Say the street address if you have one. If you are on a trail, a lake, a forest road or a large site, decimal latitude and longitude are what the dispatcher wants — read the whole number including the decimals, slowly.
Sources: European Resuscitation Council Guidelines · Käypä hoito national guideline: Elvytys · checked 2026-09-08
Frequently asked questions
Can I hurt someone by using an AED wrongly?
The device will not shock a rhythm that does not need shocking, so the realistic risk is delay rather than harm. The one genuine hazard is touching the patient during analysis or discharge, which is why the machine tells everybody to stand clear.
Do I need training to use one?
No. Public-access defibrillators are designed for untrained bystanders and every step is spoken aloud. Training makes you faster and calmer, which is worth having, but a trained rescuer who is not there helps nobody.
Should I take the pads off when the ambulance arrives?
No. Leave the pads attached and the unit running. The crew will transfer the patient onto their own monitor and will want the event recording the device has been making.
What to do, right now
Is this a cardiac arrest?
Two checks decide it: not responding, and not breathing normally. The noisy gasping that fools nearly everyone, why a brief seizure at the start is a cardiac sign, and why a heart attack is a different emergency.
Hands-only CPR, in sixty seconds
Centre of the chest, 100 to 120 pushes a minute, 5 to 6 cm deep, let the chest come all the way back up, and do not stop. The rate, the depth, the fatigue problem, and a pacer that keeps you on the beat.
The emergency call, and the address problem
What the dispatcher asks, why the phone goes on speaker on the floor, how dispatcher-guided CPR works, and the single hardest question in a rural arrest: where exactly are you?
Where the pads go, and what gets in the way
Right collarbone and left ribs, or front and back. Chest hair, sweat, snow, a medicine patch, a pacemaker lump, an underwired bra, a tattoo: which of these actually matter and what to do about each.
"No shock advised" does not mean stop
The most misread sentence in public-access defibrillation. What the machine has actually detected, why roughly two thirds of arrests are not shockable, and why the pads stay on and the compressions continue.
Everything on this subject
Before the emergency, there is a long quiet stretch
Blood pressure, resting heart rate, movement and sleep are the part of this you can act on for years beforehand. TempoLife keeps them in one place, free to start.