Cardiopulmonary resuscitation, known as CPR, keeps blood carrying oxygen moving to the brain and heart when someone’s own heart has stopped pumping effectively. Starting CPR quickly and doing it well can double or triple a person’s chance of surviving cardiac arrest, which is why the technique is worth understanding properly rather than half remembering from a class taken years ago.
When to Start CPR
Begin CPR on an adult who is unresponsive and not breathing normally. Occasional gasping breaths, known as agonal breathing, are not normal breathing and should not delay you starting compressions. Send someone to call emergency services and bring an automated external defibrillator, known as an AED, if one is available, while you begin compressions yourself.
Current Compression to Breath Ratio
Current resuscitation guidelines, most recently reaffirmed by the American Heart Association, use a ratio of 30 compressions to 2 breaths for adult CPR, whether there is one rescuer or two. This replaced older ratios taught in earlier decades, so if your training is more than a few years old it is worth checking you are using 30:2 rather than an outdated ratio.
If you are an untrained bystander, hands only CPR, meaning continuous chest compressions with no rescue breaths, is now widely recommended and considered easier to perform correctly under stress while still being highly effective for adult cardiac arrest.
Compression Technique
Kneel beside the patient and place the heel of one hand in the centre of their chest, on the lower half of the breastbone. Place your other hand on top and interlock your fingers, keeping them off the ribs. Position your shoulders directly above your hands and keep your arms straight.
- Depth: push down at least 5 centimetres, or about 2 inches, for an average adult, while avoiding excessive depth beyond 6 centimetres.
- Rate: 100 to 120 compressions per minute. A steady rhythm around this speed matches the tempo of many familiar songs, which some rescuers find helps them keep pace.
- Recoil: allow the chest to fully rise back up between compressions rather than leaning on it, since incomplete recoil reduces blood flow back into the heart.
- Minimise pauses: keep interruptions to compressions as short as possible, pausing only for breaths, rhythm checks or a shock from an AED.
Giving Rescue Breaths
If you are trained and willing to give breaths, tilt the head back, lift the chin, pinch the nose closed, seal your mouth over theirs and give a breath lasting about one second, watching for the chest to rise. Give two breaths after every 30 compressions. Avoid breathing too hard or too fast, since this can push air into the stomach instead of the lungs.
Using an AED
Turn the AED on as soon as it arrives and follow its spoken instructions. Attach the pads to the bare chest as shown in the diagrams on the pads themselves. Make sure nobody is touching the patient while the device analyses the heart rhythm, and again while it delivers a shock if one is advised. Resume compressions immediately after a shock rather than pausing to check for a pulse.
How Long to Continue
Continue CPR until the person shows signs of life such as normal breathing or movement, a trained responder or ambulance crew arrives and takes over, an AED advises no further shocks are needed and the person recovers, or you are physically unable to continue. Do not stop to reassess every few compressions, since this wastes valuable time and interrupts blood flow.
Frequently Asked Questions
What is the current CPR ratio for adults?
30 compressions to 2 breaths, for both single rescuer and two rescuer adult CPR.
How deep should adult chest compressions be?
At least 5 centimetres, or about 2 inches, without exceeding around 6 centimetres.
Is hands only CPR effective without rescue breaths?
Yes, for an untrained bystander responding to adult cardiac arrest, continuous chest compressions alone are considered effective and easier to sustain than stopping for breaths.
References and Last Reviewed
- American Heart Association, Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
- International Liaison Committee on Resuscitation (ILCOR), Consensus on Science and Treatment Recommendations
Jurisdiction: General first aid guidance, based on current American Heart Association and ILCOR recommendations. Some regional councils may phrase guidance slightly differently, so follow your local training provider’s current course where it differs.
Last technically reviewed: September 2026
Reviewed by: EHS Guidelines Editorial Team
This article is educational and does not replace accredited CPR training or professional medical care. In a real emergency, call your local emergency number immediately.
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