30 compressions, 2 breaths, 100 to 120 compressions a minute, at least a third of the chest deep. Those are the numbers. The rest of this page is what they mean in practice.
The numbers
- Rate — 100 to 120 compressions per minute, every age, every size of person
- Ratio — 30 compressions to 2 breaths
- Depth, adult — about one third of the chest, which works out at more than 5 cm
- Depth, child — about 5 cm
- Depth, infant — about 4 cm
One third of chest depth is the actual rule. The centimetre figures follow from it, which is why they differ by age while the rate does not.
Why 100 to 120, and not faster
Faster is not better. Above about 120 the chest does not have time to come back up between compressions, the heart does not refill, and you end up pushing on an empty pump. Below 100 there is not enough flow to keep the brain supplied.
Most people under pressure drift fast. If you are counting out loud and it feels slightly slower than panic, you are probably about right.
Let the chest come all the way back up
Full recoil between compressions is as important as the depth of the compression itself, and it is the thing people lose first when they tire — leaning on the chest between pushes. Equal time down and up, rhythmic, no rocking, no thumps or quick jabs.
Where your hands go
Heel of one hand on the lower half of the breastbone, in the centre of the chest, other hand on top. Do not compress below the end of the breastbone. For an infant, a lay rescuer uses two fingers.
The person needs to be on their back on a firm surface. Compressions on a soft mattress mostly compress the mattress.
Keep the interruptions short
Every pause drops the pressure you have built up, and it takes several compressions to get it back. Pause only for breaths, for the AED to analyse, and to swap rescuers.
Swap about every two minutes if there is someone to swap with. Quality falls off well before you feel tired, and most people overestimate how long they can maintain effective compressions. Make the handover quick.
If you will not do breaths
Do compressions. Compression-only CPR is far better than standing back, and for an untrained bystander it is the right call. Rescue breaths are for those who are trained and willing — and for a child, an infant, a drowning or a collapse caused by breathing problems, they matter more, because the cause is usually a lack of oxygen rather than a heart rhythm problem.
What this looks like in the assessment
If you are about to sit HLTAID009 or HLTAID011, the practical requires at least two minutes of uninterrupted single-rescuer CPR — five cycles of compressions and ventilations — on an adult manikin on the floor, and the same on an infant manikin on a firm surface, plus following an AED’s prompts to deliver a shock.
Five cycles in two minutes is the rate requirement expressed a different way. Kneeling on the floor for that long is part of it, so wear clothing you can move in.
This is a summary of what is taught in class, not a substitute for training. Skills like this are assessed practically for a reason — reading about them is not the same as having done them. In a real emergency, call 000.
Learn it properly
CPR is practised on manikins in HLTAID009 CPR and HLTAID011 first aid including CPR. CPR currency runs one year — if yours is due, see the CPR refresher course page. Best First Aid Training runs both at Parramatta, Penrith, Blacktown and Liverpool.
Sources: Australian and New Zealand Committee on Resuscitation, ANZCOR guidelines on chest compressions and basic life support; training.gov.au, HLTAID009 assessment requirements.
