The heart stops; the brain holds on for a few minutes. Every minute without chest compressions takes away about ten percent of the chances. It's the most worthwhile skill a human being can learn.
ACT
1. Check in ten seconds. Shake their shoulders, speak loudly. No answer? Tilt the head back, lift the chin, and watch the chest for ten seconds.
The trap that kills: gasping. In the first minutes of an arrest, many people make noisy, irregular, jerky breaths — it looks like they're breathing. It isn't breathing, it's a sign of cardiac arrest. Someone asleep breathes calmly and regularly; this is different.
Unconscious, and not breathing or not breathing normally: it's an arrest. Don't look for a pulse; even professionals get it wrong.
2. Have someone call for help and fetch a defibrillator. Point at someone and give them a precise order. If you're alone, call on speakerphone and start.
3. Push on the chest, and don't stop.
- Heel of your hand in the center of the chest, the other hand on top, fingers interlaced.
- Arms straight, shoulders directly above: you push with the weight of your upper body, not with your arms.
- Five to six centimeters (2 to 2.4 inches) deep in an adult. That's much harder than people think.
- A hundred to a hundred and twenty times a minute.
- Let the chest come all the way back up between compressions, without lifting your hands. The heart has to refill. It's the most common mistake, and it cancels half of the benefit.
4. Give rescue breaths only if you know how. Thirty compressions, two breaths of one second each, head tilted back, nose pinched. If you don't know how, if you hesitate, if you can't bring yourself to do it: keep compressing without interruption. Compressions alone are far better than compressions chopped up by failed breaths.
5. The defibrillator, as soon as it arrives. Switch it on and do what it says. It talks, it's designed for someone who has never seen one, and it will never shock a heart that's beating. You can't get it wrong. Pads on bare, dry skin, one below the right collarbone, the other below the left armpit. During the analysis, nobody touches the person. After the shock, start compressions again immediately.
6. Swap every two minutes. The quality of compressions drops after two minutes, long before you feel tired. The swap takes less than five seconds.
7. You stop when emergency services take over, when the person breathes normally, or when you're physically unable to go on. Not before.
ADAPT
It's a child or a baby. The arrest is almost always caused by a lack of oxygen, not by the heart. Start with five rescue breaths, then compressions. Depth: a third of the chest's thickness. A child: the heel of one hand. A baby: two fingers, or both thumbs with your hands wrapped around the chest. Same rate. A defibrillator can be used too, with pediatric pads if there are any, otherwise adult pads placed front and back.
It's a drowning. Same logic: five breaths first, because the cause is asphyxia. See Drowning.
It's an electric shock. Cut the power before touching them, no exceptions. Then the normal protocol.
It's deep hypothermia. Keep going, and don't conclude too quickly. A very cold body can look dead and come back. The mountain rescuers' phrase is literal: nobody is dead until they're warm and dead. See Hypothermia.
You're alone, with no help you can reach. Keep compressing anyway. Without a defibrillator or backup, the chances are small, but they aren't zero — some rhythms restart. Keep going as long as you can.
The person comes back. Put them on their side, cover them, and watch their breathing continuously. An arrest can happen again in the minutes that follow. See Unconscious person.
You're afraid of breaking ribs. You probably will, especially with an older person. That isn't a complication, it's a sign you're pushing hard enough. Ribs heal; a brain doesn't.
UNDERSTAND
Why minutes matter so much
The brain stores neither oxygen nor sugar. Once circulation stops, its reserves last a few seconds; damage starts at around four to five minutes and quickly becomes irreversible.
National registries all give the same order of magnitude: every minute lost costs about ten percent of the chances of survival. With no bystander doing compressions, survival is a few percent. With immediate compressions and a defibrillator within a few minutes, it goes above forty percent in the best conditions.
So what makes the difference isn't medicine: it's what the person who happens to be there does.
What chest compressions do
They don't restart the heart. They replace the pump: they keep a weak but sufficient circulation going, enough to keep the brain and the heart viable until an electric shock can restore a rhythm.
Hence the importance of letting the chest come fully back up: as it rises, the heart refills. Compressions that stay pressed down pump nothing.
What the defibrillator does
Most arrests start with fibrillation: the heart muscle contracts chaotically and pumps nothing out. The shock doesn't restart the heart; it stops it completely for an instant, so that the normal rhythm can take over again.
Over time, fibrillation degrades into a flat line that no shock can correct. Compressions slow that degradation: that's why you keep compressing even while you wait for the device.
The only real mistake
Doing nothing, for fear of doing it wrong. Imperfect compressions are infinitely better than none, and a person in cardiac arrest can't be made worse. See Examining a casualty for the general assessment and Décider sous stress for what freezes people at the moment they need to act.