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"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.
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.
What the machine just told you
A defibrillator does one job: it looks for a chaotic electrical rhythm that a shock can reset. Ventricular fibrillation and pulseless ventricular tachycardia are those rhythms. Asystole — a flat, silent heart — and pulseless electrical activity, where the electrics run but the muscle does not pump, are not. A shock into either does no good and can do harm, so the device declines. "No shock advised" is a statement about the rhythm at this instant, not a verdict on the patient and never an instruction to stop.
Most arrests are not shockable, and that is not new
When someone collapses in front of you the rhythm is often shockable at first; by the time an unwitnessed arrest is found, the heart has usually deteriorated to asystole. Across European registry data the majority of out-of-hospital arrests are found in a non-shockable rhythm, and the proportion rises with every minute of delay. So an early "no shock advised" often means you arrived late, not that the machine has malfunctioned. It is also exactly the situation in which good compressions have the most to add.
Compressions can make a rhythm shockable again
Fine ventricular fibrillation degenerates into asystole when the heart muscle runs out of oxygen, and good chest compressions can push it back the other way. This is the practical reason the guidelines insist on immediate, uninterrupted compressions after a no-shock decision: you are perfusing the myocardium so that the next analysis, two minutes later, has something to work with. A device that says no shock at the first analysis and shock at the third is doing its job and so are you.
Leave everything attached
Do not take the pads off, do not switch the unit off, and do not move the patient because "it did not work". The device will re-analyse on its own roughly every two minutes and will announce a shock the moment one is warranted. Between analyses it wants continuous compressions, and many units will nag you about the rate. If a second rescuer is available, use the two-minute analysis prompt as your changeover cue.
When it is reasonable to stop
That is not a bystander decision. Continue until the ambulance crew takes over, until the person shows definite signs of life — moving, opening their eyes, breathing normally — or until you are physically unable to continue. A defibrillator never tells you to stop CPR, and neither will a dispatcher who is still on the line.
Sources: European Resuscitation Council Guidelines · International Liaison Committee on Resuscitation (ILCOR) · checked 2026-09-08
Frequently asked questions
The AED said no shock advised. Is the person dead?
It means the current rhythm cannot be corrected by a shock, which is a statement about the electrical pattern and not a pronouncement. Keep doing compressions — the machine will re-check within about two minutes.
Should I take the pads off if it will not shock?
No. Leave the pads attached and the unit switched on so it can keep re-analysing, and so the ambulance crew can read the recorded event data.
Why did it shock the first time and not the second?
Because the rhythm changed, which is what a successful shock does. Continue compressions; the device is monitoring and will shock again if fibrillation returns.
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?
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.
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.
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.