CPR is needed whenever someone collapses and is not breathing normally or not breathing at all. The three key signs: the person is unresponsive, has no normal breathing, and shows no signs of movement or circulation. Every minute without CPR reduces the chance of survival, so recognizing these signs quickly matters more than getting a perfect diagnosis of what went wrong.
The Three Signs That Call for CPR
Cardiac arrest looks dramatic but is surprisingly simple to identify. The person suddenly collapses, does not respond when you shout at them or tap them firmly, and is either not breathing or breathing in a way that clearly isn’t normal. You don’t need to figure out why they collapsed. You need to confirm those three things: unresponsive, no normal breathing, no signs of life.
For adults, speak loudly and ask if they’re okay. If there’s no response, check the wrist briefly for a pulse. If you can’t find one within a few seconds, or you’re unsure, start chest compressions. Research shows that at least 35% of untrained rescuers are wrong about whether a victim has a pulse, which is why current guidelines no longer recommend that the general public rely on a pulse check at all. Instead, look for normal breathing, movement, or any response to stimulation. If none of those are present, begin CPR.
For infants and children, the approach differs slightly. Tap on their heel or chest to see if they respond. If they don’t respond and aren’t breathing (or are only gasping), check for a pulse. No pulse means start compressions.
Gasping Is Not Breathing
This is the single most important thing bystanders get wrong. In about 40% of out-of-hospital cardiac arrest cases, bystanders tell 911 dispatchers that the person is “breathing” when what they’re actually seeing is agonal breathing, a reflexive gasping that looks like slow, labored, noisy gulps of air. It can sound like gurgling or snoring. It is not real breathing. It means the heart has stopped and the brain is running out of oxygen.
People with agonal breathing actually have a higher chance of surviving if CPR is started immediately. In one study, patients identified with agonal breaths had significantly higher rates of survival to hospital admission compared to cardiac arrest patients without them. The gasping is, paradoxically, a hopeful sign, but only if someone recognizes it for what it is and starts compressions. If a person is unresponsive and their breathing looks slow, irregular, or sounds wet and strained, treat it as cardiac arrest.
Why Minutes Matter
When the heart stops pumping, the brain loses its oxygen supply within about 20 seconds, which is why the person loses consciousness almost immediately. By five minutes, brain cells begin to break down as they run out of glucose and oxygen. The longer the brain goes without circulation, the more severe and permanent the damage becomes.
CPR bridges that gap. It doesn’t restart the heart, but it pushes enough oxygenated blood to the brain and vital organs to buy time until a defibrillator or paramedics arrive. On average, people who receive bystander CPR have a 28% greater chance of surviving compared to those who don’t, according to a 2024 analysis from the National Institutes of Health.
Cardiac Arrest vs. Other Emergencies
Not every collapse is cardiac arrest. People faint, have seizures, or lose consciousness from low blood sugar or dehydration. The difference is straightforward: someone who faints will typically start breathing normally again within seconds and may respond to stimulation. A person having a seizure may appear unresponsive during the episode, but they are breathing (even if it’s noisy) and will usually regain some awareness afterward.
Cardiac arrest is different because it doesn’t resolve on its own. The person stays down, stays unresponsive, and either stops breathing entirely or displays that abnormal gasping pattern. If you’re standing over someone who collapsed and 10 to 15 seconds have passed with no signs of recovery, no normal breathing, no response to your voice or touch, act as though it’s cardiac arrest.
Adults vs. Children: Different Causes, Same Urgency
In adults, cardiac arrest is usually caused by a heart problem, most often an electrical malfunction triggered by a heart attack or an underlying rhythm disorder. The heart suddenly stops beating effectively, and circulation ceases.
In children, the chain of events typically runs in the opposite direction. A breathing emergency, like choking, drowning, or a severe asthma attack, cuts off oxygen first, and the heart stops as a consequence. This is why rescue breaths are especially important for children and infants, while adult CPR guidelines emphasize that hands-only compressions (pushing hard and fast on the center of the chest without mouth-to-mouth) are effective for bystanders who aren’t trained in full CPR.
What Effective CPR Looks Like
For adults, push hard 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 deep. For infants and children, the target depth is about one-third the thickness of the chest. Let the chest fully rise between compressions. These details matter because shallow or slow compressions don’t generate enough blood flow to protect the brain.
If an automated external defibrillator (AED) is available, use it as soon as possible. The device analyzes the heart’s rhythm and delivers a shock only if one is needed, so you can’t accidentally shock someone who doesn’t require it. The goal is to deliver that shock within three to five minutes of collapse. Keep doing compressions while someone retrieves the AED, and follow the voice prompts once it’s attached.
Common Fears That Delay Action
Many bystanders hesitate because they’re afraid of doing CPR wrong or causing injury. Rib fractures occur in over 70% of CPR cases, with an average of about seven to eight broken ribs per person. That sounds alarming, but broken ribs heal. An oxygen-starved brain does not. The person is already in the worst medical emergency of their life, and imperfect CPR is vastly better than no CPR.
Others worry about legal consequences. All 50 U.S. states have some form of Good Samaritan law that protects people who provide emergency care in good faith. You are not expected to perform like a paramedic. You are expected to try.
If you’re uncertain whether someone is in cardiac arrest or just unconscious, starting compressions on someone who doesn’t need them is far less dangerous than withholding them from someone who does. The risk of doing nothing is death. The risk of acting is a sore chest.