When giving compressions, the first aid responder should position themselves directly over the person’s chest, lock their arms straight, and push hard and fast to a depth of at least 2 inches (5 cm) at a rate of 100 to 120 compressions per minute. Getting the technique right matters enormously: the quality of your compressions is the single biggest factor in whether someone survives cardiac arrest outside a hospital.
Where to Place Your Hands
Place the heel of one hand in the center of the person’s chest, on the lower half of the breastbone. Put your other hand directly on top and interlace your fingers. That’s it. One of the most common mistakes untrained rescuers make is placing their hands too far to the left or too high on the chest. Research on hand placement found that when people were simply told to find “the center of the chest,” both trained and untrained rescuers landed close to the correct spot. So think center of the chest, not left side where you imagine the heart to be.
For children, use one or two hands in the same position depending on the child’s size. For infants under one year old, use just two fingers placed on the center of the chest.
Arm Position and Body Mechanics
Kneel beside the person so your shoulders are directly above your hands. Lock your elbows straight and keep your arms rigid. You should be compressing using your upper body weight, not your arm muscles. If you bend your elbows or lean back, you lose force and will tire out much faster.
Think of your body as a hinge at the hips. Each compression comes from rocking your weight forward and down through straight arms. This technique lets you maintain consistent depth without burning through your energy in the first minute.
How Deep and How Fast
For adults, push at least 2 inches (5 cm) deep but no more than 2.4 inches (6 cm). Studies have found improved survival to hospital discharge when compressions reached at least 5 cm compared to shallower efforts. Pushing too deep, beyond 6 cm, has been linked to reduced survival as well, so there is a real sweet spot.
Your rate should be 100 to 120 compressions per minute. A common way to keep this pace is to compress to the beat of “Stayin’ Alive” by the Bee Gees, which sits right at about 104 beats per minute. Faster is not better here. Going above 120 per minute tends to make compressions too shallow.
For children, compress to the same 2-inch depth. For infants, the target is about 1.5 inches (4 cm), roughly one-third the depth of the infant’s chest.
Let the Chest Come Back Up
Between each compression, let the chest fully rise back to its normal position before pushing down again. This is called complete chest recoil, and skipping it is one of the most common errors rescuers make, especially as they get tired. When you let the chest fully rebound, it creates a slight vacuum inside the chest cavity that draws blood back into the heart. That returning blood is what gets pumped out on the next compression. If you lean on the chest between pushes, you cut off that refill and each compression moves less blood.
Compressions and Rescue Breaths
The current standard ratio is 30 compressions followed by 2 rescue breaths, whether you’re alone or working with a second rescuer. After every 30 compressions, tilt the person’s head back, lift their chin, seal your mouth over theirs, and deliver two breaths, each lasting about one second. Then immediately resume compressions.
If you’re untrained in rescue breathing, uncomfortable with it, or don’t have a barrier device, hands-only CPR (continuous compressions with no breaths) is still effective for adults with cardiac arrest. For children and infants, however, rescue breaths make a meaningful difference. A systematic review of pediatric cardiac arrests found that one-month survival was 18% with traditional CPR compared to 12.3% with compressions alone, and neurological outcomes were also better with the addition of breaths. Children are more likely to arrest from breathing problems rather than heart rhythm issues, which is why ventilation matters more for them.
Managing Fatigue
Compression quality starts declining faster than you’d expect. Research shows that the depth and effectiveness of compressions begin to deteriorate after just 60 to 90 seconds, and most rescuers don’t realize it’s happening. You’ll feel like you’re still pushing hard, but the actual depth drops.
If a second rescuer is available, switch roles every 2 minutes, or sooner if you feel yourself getting tired. The switch should take no more than a few seconds. Minimizing any pause in compressions is critical because blood flow drops to nearly zero the moment you stop pushing, and it takes several compressions to build pressure back up. If you’re the only rescuer, pace yourself but don’t stop. Even declining compressions are better than none.
If You Feel a Crack
Hearing or feeling a rib crack during compressions is startling, but it is not a reason to stop or lighten up. Rib fractures occur in roughly 55% of people who receive CPR, based on a large meta-analysis covering more than 12,000 patients. Two-thirds of cardiac arrest patients who receive CPR sustain some form of compression-related injury. These injuries are treatable. Cardiac arrest without compressions is not. If you feel something give way, keep going at the same depth and rate.
When to Stop Compressions
Continue compressions until one of these things happens: the person starts breathing normally or clearly responds (moving, coughing, opening their eyes), emergency medical services arrive and take over, an AED becomes available and prompts you to stop for a shock, or you become physically unable to continue and no one else can step in.
If you’re using an AED, follow its voice prompts. It will tell you when to pause compressions for rhythm analysis and when to resume. Keep pauses as short as possible. Every second without compressions reduces the chance of survival.