When someone collapses in cardiac arrest, bystander action in the first few minutes is the single biggest factor in whether they survive. People who receive bystander CPR have a 28% greater chance of surviving compared to those who don’t, according to data from the National Institutes of Health. You don’t need medical training to make that difference. Here’s exactly what to do.
Recognize Cardiac Arrest Quickly
Cardiac arrest looks different from a heart attack, and confusing the two costs time. A heart attack causes chest pain, radiating discomfort in the jaw or arm, and lightheadedness, but the person is still conscious and breathing. Cardiac arrest is more dramatic and more dangerous: the person suddenly collapses, has no pulse, and stops breathing. They may gasp irregularly for a few seconds, but that’s not real breathing.
If someone drops and you can’t feel a pulse or see normal breathing, treat it as cardiac arrest. You have minutes, not hours. Every second without blood flow to the brain reduces the chance of survival.
Call 911 and Start Chest Compressions
Your first move is to call 911 or shout for someone nearby to call while you begin CPR. If you’re alone, put your phone on speaker. The 911 dispatcher can walk you through every step in real time, so even if you’ve never taken a CPR class, stay on the line and follow their instructions.
Here’s how to perform chest compressions on an adult:
- Position your hands. Place the heel of one hand in the center of the person’s chest, right between the nipples. Stack your other hand on top and interlace your fingers.
- Push hard and fast. Compress the chest at least 2 inches deep at a rate of 100 to 120 compressions per minute. That’s roughly the tempo of the song “Stayin’ Alive.”
- Let the chest fully recoil. After each compression, lift enough to let the chest spring all the way back before pushing again. Don’t lean on the chest between compressions.
- Minimize interruptions. Every pause in compressions means blood stops flowing to the brain. Keep gaps as short as possible.
If you’re trained and willing, give 2 breaths after every 30 compressions. Tilt the head back, lift the chin, seal your mouth over theirs, and blow until you see the chest rise. The 2025 American Heart Association guidelines recommend adding breaths when rescuers are able, noting that compressions with breaths produces better outcomes than compressions alone. But if you’re uncomfortable giving breaths or unsure how, hands-only CPR (continuous chest compressions without breaths) is far better than doing nothing.
Use an AED as Soon as One Is Available
Automated external defibrillators (AEDs) are designed for untrained bystanders. They’re found in airports, gyms, offices, schools, and many other public spaces, usually mounted on a wall in a bright case. Send someone to grab the nearest one while you continue compressions.
When the AED arrives:
- Turn it on. The device will start giving you spoken instructions the moment you open it or press the power button.
- Expose the chest. Remove or cut away clothing. If the chest is wet, wipe it dry quickly.
- Attach the pads. Place one pad on the upper right chest, below the collarbone. Place the second on the lower left side, a few inches below the armpit. Peel-and-stick diagrams on the pads show you exactly where.
- Let the AED analyze. The device will tell everyone to stand clear while it checks the heart rhythm. Don’t touch the person during this step.
- Deliver a shock if prompted. Press the flashing shock button only when the AED tells you to, and only after confirming nobody is touching the person. If no shock is advised, the AED will tell you to resume CPR immediately.
After a shock (or if no shock is needed), go right back to chest compressions. Continue cycling between CPR and AED analysis until paramedics take over or the person starts breathing and moving on their own.
CPR for Infants and Children
The approach changes with size. For children (roughly age 1 through puberty), push on the center of the chest with one or two hands to a depth of about 2 inches, 30 compressions followed by 2 breaths. For infants under 1 year old, use just two fingers pressed on the center of the chest, compressing about 1.5 inches deep. The ratio stays the same: 30 compressions, then 2 breaths.
Breaths matter more in children and infants than in adults. Cardiac arrest in kids is more often caused by breathing problems than by heart rhythm issues, so providing breaths alongside compressions significantly improves outcomes. Large observational studies consistently show that children who receive CPR with breaths fare better than those who receive compressions alone.
Standard AED pads work for children 8 and older or those weighing more than 55 pounds. Many AEDs include smaller pediatric pads. If pediatric pads aren’t available and the child is small enough that adult pads might touch or overlap, place one pad on the center of the chest and the other on the back between the shoulder blades.
When to Stop
Continue CPR until one of these things happens: emergency medical services arrive and take over, an AED is ready to analyze the rhythm (pause briefly, then resume), or the person starts breathing normally and you can feel a pulse. If someone regains consciousness, roll them gently onto their side and monitor them until paramedics arrive.
CPR is physically exhausting. If another bystander is available, switch off every two minutes to keep compressions strong and effective. The person who isn’t compressing can manage the AED, stay on the phone with 911, or prepare to swap back in.
There are situations where CPR should not be started: if there are obvious signs that death occurred well before you arrived (such as rigor mortis or skin discoloration from pooled blood), or if the person has a valid do-not-resuscitate order. In any ambiguous situation, start CPR. It’s always better to act.
You’re Legally Protected
Every U.S. state has some form of Good Samaritan law that shields bystanders who provide emergency care in good faith. These laws protect you from liability for ordinary negligence, meaning if you crack a rib during compressions (which happens frequently and is considered normal), you won’t face legal consequences. The protection applies as long as you’re acting voluntarily, not expecting payment, and not being recklessly harmful. Cracked ribs heal. A stopped heart without help does not.
Why Every Minute Counts
The American Heart Association describes survival from cardiac arrest as a chain with six links: recognizing the arrest and calling for help, starting CPR early, defibrillating as quickly as possible, advanced care from paramedics, hospital treatment after the arrest, and long-term recovery support. The first three links are entirely in the hands of bystanders. Paramedics typically take 7 to 10 minutes to arrive, and brain damage begins within 4 to 6 minutes without blood flow. Your compressions bridge that gap.
The survival statistics are uneven. NIH research found that white men who received bystander CPR had 41% greater odds of surviving, while Black women saw only a 5% increase. These disparities likely reflect differences in where cardiac arrests happen, how quickly bystanders intervene, and access to AEDs in different neighborhoods. Knowing CPR and being willing to act on anyone, anywhere, is part of closing that gap.