CAB stands for Compressions, Airway, Breathing. It’s the recommended sequence for performing CPR, designed to help you remember the correct order of steps when someone’s heart has stopped. The American Heart Association adopted this sequence in 2010, replacing the older ABC (Airway, Breathing, Compressions) approach after evidence showed that starting with chest compressions saves more lives.
Why Compressions Come First
The switch from ABC to CAB was driven by one key insight: every second without chest compressions matters. When someone’s heart stops, blood flow to the brain and other organs drops to zero. Chest compressions manually pump blood through the body, and even brief pauses cause an almost immediate drop in the pressure needed to keep blood flowing to the heart itself. That pressure is difficult to rebuild once lost.
Under the old ABC method, rescuers spent valuable time tilting the head back, opening the airway, and delivering breaths before ever pushing on the chest. Studies using training manikins found that starting with compressions instead of ventilation led to faster first compressions, faster first breaths, and faster completion of the entire first CPR cycle. In other words, CAB doesn’t just get compressions started sooner; it gets everything started sooner. The American Heart Association now calls immediate initiation of chest compressions “one of the most impactful interventions for survival from cardiac arrest.”
C: Chest Compressions
Compressions are the most critical step in CPR. For adults, you push hard and fast on the center of the chest at a rate of 100 to 120 compressions per minute, which is roughly the tempo of the song “Stayin’ Alive.” Each compression should be at least 2 inches (5 cm) deep. Let the chest fully recoil between each push so the heart can refill with blood.
For infants under one year old, the technique changes significantly. You use the tips of two fingers on the breastbone rather than your full hand. The target depth is about 1.5 inches (4 cm). If you can’t reach that depth with two fingers, switch to the heel of one hand. For children between ages one and puberty, use one or two hands depending on the child’s size, compressing at least one-third the depth of the chest.
Minimizing interruptions is essential. Guidelines recommend that compressions should account for at least 60% of total resuscitation time, a metric called the chest compression fraction. Every time you stop pushing, blood flow drops and you lose the perfusion pressure you’ve built up.
A: Open the Airway
Once compressions are underway, the next step is opening the person’s airway so air can reach the lungs. The standard technique is the head-tilt, chin-lift: place one hand on the forehead and gently tilt the head back while lifting the chin with your other hand’s fingertips. This moves the tongue away from the back of the throat, which is the most common airway obstruction in an unconscious person.
If you suspect a neck or spinal injury (from a fall, car accident, or similar trauma), the head-tilt method can worsen the damage. In that case, a jaw-thrust maneuver is preferred: you push the lower jaw forward without moving the neck. This technique produces the least movement in the upper spine. If the jaw thrust doesn’t open the airway enough, you may need to carefully tilt the head back anyway, because getting oxygen into the lungs ultimately takes priority.
For infants, keep the head in a neutral position rather than tilting it far back. Overtilting can actually collapse an infant’s airway. Lift the chin gently and avoid pressing on the soft tissue under the chin.
B: Rescue Breathing
After opening the airway, you deliver rescue breaths. The standard ratio for adults is 30 compressions followed by 2 breaths, then repeat. Each breath should be about one second long and deliver enough air to make the chest visibly rise. If the chest doesn’t rise, reposition the head and try again.
For newborns, the ratio shifts to 3 compressions for every 1 breath, reflecting that cardiac arrest in newborns is almost always caused by breathing problems rather than heart problems. Getting air into tiny lungs is proportionally more important in this age group.
Before giving breaths, check for breathing for no more than 10 seconds. If the person is gasping or not breathing at all, that’s your cue to begin CPR.
When You Can Skip the A and B
If you haven’t been trained in CPR or you’re uncomfortable giving mouth-to-mouth, hands-only CPR (compressions without rescue breaths) is still effective for adults who collapse suddenly. The blood already contains enough oxygen to sustain vital organs for several minutes if you keep it circulating with compressions. The American Heart Association explicitly supports a compression-only approach for untrained or unwilling bystanders.
This doesn’t apply to all situations. Drowning victims, children, and infants are more likely to need rescue breaths because their cardiac arrest typically stems from a breathing problem. In these cases, the full CAB sequence with breaths is more appropriate if you’re able to provide it.
When to Stop CPR
Once you start the CAB sequence, keep going until one of a few things happens: the person starts breathing or moving on their own, emergency medical services arrive and take over, you become physically too exhausted to continue, or an automated external defibrillator (AED) becomes available and prompts you to stop for analysis. If someone with equal or greater training arrives, you can transfer care to them.
There are situations where CPR should not be started at all. If the person has obvious signs of death (such as rigor mortis), or if attempting CPR would put you in serious danger, resuscitation isn’t appropriate. A valid do-not-resuscitate order also means CPR should not be initiated.