High-Quality CPR (Adult, Child, Infant)
High-quality chest compressions are the single most important intervention in cardiac arrest. Blood does not move to the brain and heart unless the compressions are fast enough, deep enough, allow full recoil, and are barely interrupted. The BLS exam expects you to know the exact numbers for adults, children, and infants and to defend why each number matters.
Rate, depth, and recoil
Compress the adult chest at a rate of 100 to 120 compressions per minute. Push at least 2 inches (5 cm) deep but no more than 2.4 inches (6 cm) — too shallow does not generate perfusion, too deep injures the chest. For a child, compress at least one-third the depth of the chest, about 2 inches (5 cm); for an infant, at least one-third the depth of the chest, about 1.5 inches (4 cm). After every compression, allow complete chest recoil — let the chest return fully to its resting position without leaning on it, because incomplete recoil raises intrathoracic pressure and reduces the blood that refills the heart between compressions.
Minimize interruptions and hand placement
Every pause in compressions drops coronary perfusion pressure almost immediately, so keep interruptions short and aim for a chest compression fraction (the share of arrest time spent compressing) of at least 60%. For adults, place the heel of the hand on the lower half of the sternum. For children, use one or two hands on the lower sternum; two hands gave greater depth in children aged 1 to 8. For infants, the 2025 Guidelines recommend the two thumb–encircling hands technique or the one-hand technique — and the heel of one hand if you cannot encircle the chest. Two-finger compressions were eliminated because they fail to reach proper depth.
Compression-to-ventilation ratios
A single rescuer uses a 30:2 ratio (30 compressions to 2 breaths) for adults, children and infants. When two rescuers care for a child or infant, use 15:2 so breaths come more often, because pediatric arrest is usually respiratory in origin. Once an advanced airway is placed, compressions continue without pauses: adults receive about 10 ventilations per minute and infants and children 20 to 30 per minute. Rotate the compressor about every 2 minutes at the rhythm check, because compression depth begins to fall after 90 to 120 seconds.
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