CPR Steps
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Direct answer
Adult basic life support follows the C-A-B sequence: check responsiveness and breathing, activate the emergency response and send for an AED, then begin chest compressions at 100–120 per minute, 5–6 cm deep in the centre of the chest, with 30 compressions to 2 breaths. Attach and use the AED as soon as it arrives, resuming compressions immediately after each shock, and continue until the victim responds, trained help takes over or you are exhausted. High-quality compressions — rate, depth, full recoil, minimal interruption — are the heart of survival.
What you must remember
- Adult sequence: shake and shout, look for normal breathing for no more than 10 seconds, call for the ambulance and AED, check the carotid pulse (also under 10 seconds, by trained rescuers) and start compressions if absent.
- Compression technique: heel of one hand on the lower half of the sternum, second hand on top, arms straight, shoulders over hands, push hard and fast with full recoil between compressions.
- Ventilations: 2 breaths of about 1 second each after every 30 compressions, just enough to make the chest rise; switch rescuers every 2 minutes or five cycles to avoid fatigue.
- Defibrillation: apply the AED as soon as it arrives, follow the prompts, ensure nobody touches the patient during analysis or shock, and resume CPR immediately after the shock for 2 minutes.
- Child (1 year to puberty): compress about one-third of chest depth (roughly 5 cm) at the same rate, 30:2 alone but 15:2 with two trained rescuers; infant: two-thumb encircling technique, about 4 cm.
- Paediatric arrests are often respiratory, so five rescue breaths open the sequence in children; choking adults receive abdominal thrusts, infants back blows and chest thrusts.
- Place a breathing, unresponsive victim in the recovery position, keep monitoring, and note the times of collapse and defibrillation in hospital.
Common confusion
The order — compressions before airway and breathing (C-A-B, adopted worldwide in 2010) — still catches students who learned the older A-B-C. Pulse checks must not exceed 10 seconds. The adult and paediatric ratios are swapped (30:2 versus two-rescuer 15:2), and defibrillable rhythms are confused: ventricular fibrillation and pulseless ventricular tachycardia are shocked; asystole and pulseless electrical activity are not. Finally, compression-only CPR is the answer only for untrained lay rescuers — trained nurses give breaths.
Exam-focused takeaway
Numbers carry the marks: rate 100–120, depth 5–6 cm in adults, ratio 30:2 (15:2 two-rescuer paediatric), checks under 10 seconds, rescuer switch every 2 minutes. Sequence questions ask the first action on finding an unresponsive person — confirm unresponsiveness and call for help — and scenario stems test the AED moment (clear, shock, resume compressions) and the post-shock action (immediate compressions, not reanalysis).
Frequently asked questions
What is the correct compression rate and depth for adults?
100–120 compressions per minute, 5–6 cm deep on the lower half of the sternum, allowing full recoil between compressions.
What ratio of compressions to breaths is used?
30:2 for adults and single-rescuer children; two trained rescuers use 15:2 for children and infants.
When should the AED be used?
As soon as it arrives — apply pads, follow prompts, deliver a shock if advised and immediately resume compressions for 2 minutes before reanalysis.
How long may a pulse or breathing check take?
No more than 10 seconds; if there is no pulse or no normal breathing, start compressions immediately.
How does paediatric CPR differ?
Children are compressed about 5 cm or one-third of chest depth at the same rate, infants with the two-thumb encircling technique about 4 cm, with five initial rescue breaths and 15:2 for two rescuers.