Recognise cardiac arrest, start hands-only CPR within seconds, use an AED if available, and know the variations for children and infants — every minute without CPR reduces survival by 10%.
Every minute that passes after cardiac arrest without CPR reduces the chance of survival by approximately 7–10%. Without CPR, brain death begins within 4–6 minutes. With immediate bystander CPR, survival rates can double or triple compared to waiting for emergency services. Cardiac arrest causes approximately 350,000 out-of-hospital deaths in the United States annually — and the fundamental skill that changes that outcome is one most adults can learn in under an hour.
This guide covers everything you need to recognise cardiac arrest, start CPR immediately, use an automated external defibrillator (AED), and adapt your technique for children and infants.
Cardiac arrest occurs when the heart stops pumping blood effectively — usually due to a sudden abnormal heart rhythm (typically ventricular fibrillation). It is different from a heart attack, though a heart attack can cause a cardiac arrest.
| Heart Attack | Cardiac Arrest |
|---|---|
| Blocked blood supply to heart muscle | Heart stops pumping effectively |
| Person is conscious and may be speaking | Person is unresponsive and not breathing normally |
| Chest pain, shortness of breath, sweating | Sudden collapse, unresponsiveness |
| Call emergency services; keep person calm and still | Call emergency services; begin CPR immediately |
A heart attack can progress to cardiac arrest. A cardiac arrest requires immediate CPR.
Act if you see someone who:
⚠️ Agonal breathing — occasional gasping or snoring-type breaths — often occurs in the first few minutes after cardiac arrest. This is not normal breathing. If the person is unresponsive and you observe agonal gasping, start CPR.
Survival from cardiac arrest depends on a chain of actions. Each link matters:
You can perform steps 1–4 as a bystander. Your actions in the first few minutes determine whether the later steps are even possible.
For an adult who suddenly collapses, hands-only CPR (chest compressions without rescue breaths) is as effective as CPR with breaths during the first few minutes, and it is what the American Heart Association now recommends for untrained bystanders.
Ensure the area is safe for both you and the victim before approaching.
Tap the person firmly on the shoulders and shout "Are you alright?" or "Can you hear me?"
If no response, shout for help immediately. Dial emergency services (999 UK / 911 US / 112 EU). If others are present, point to a specific person: "You — call 999 now."
Look for chest rise for no more than 10 seconds. If the person is not breathing or only gasping, begin compressions.
Push hard and push fast. This is the most common failure mode in bystander CPR — compressions that are too shallow do not circulate blood adequately.
If you are trained in CPR with rescue breaths, use a 30:2 ratio:
If the first breath does not cause chest rise, recheck the head tilt/chin lift before attempting the second breath — do not delay compressions to reposition repeatedly.
An AED (Automated External Defibrillator) delivers an electric shock to reset an abnormal heart rhythm. They are found in airports, shopping centres, sports facilities, and increasingly in public buildings.
⚠️ AEDs are designed to be used by untrained bystanders. They will talk you through every step. Turn it on and follow the voice prompts.
AED on hairy chest: If adhesion is poor, a razor (often included with the AED) may be needed. If not available, press the pads firmly and proceed.
AED near a pacemaker: Avoid placing a pad directly over a visible pacemaker lump under the skin — position it at least 8 cm away.
Wet patient: Quickly dry the chest before applying pads.
Use one or two hands rather than two — smaller children need less force:
⚠️ Compression depth matters just as much in children as in adults. Compressions that are too shallow do not circulate blood effectively. Do not hesitate to push firmly enough to achieve one-third chest depth.
Infant technique is different:
Continue CPR until:
Starting CPR and then stopping because you are unsure is far better than never starting at all.
| Element | Adult | Child (1–8) | Infant (<1 yr) |
|---|---|---|---|
| Compression site | Centre of chest | Lower sternum | Centre chest, below nipple line |
| Hand position | Two hands | One or two hands | Two fingers |
| Compression depth | 5–6 cm | ~5 cm (1/3 chest) | ~4 cm (1/3 chest) |
| Rate | 100–120/min | 100–120/min | 100–120/min |
| Hands-only CPR | Yes (untrained) | Yes (untrained) | No (breaths needed) |
| Breaths:compressions | 2:30 | 2:30 | 2:30 |
| AED | Yes | Paediatric preferred | Paediatric preferred |
This guide provides general CPR information based on current resuscitation guidelines. It does not replace hands-on certified CPR training. Take an accredited CPR course from a recognised organisation such as the Red Cross, American Heart Association, or St John Ambulance. Guidelines are updated periodically — confirm you are using the most current recommendations.
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