Chest compressions are indicated whenever a person is unresponsive, not breathing normally, and has no detectable pulse. In adults, these three signs together signal cardiac arrest, and compressions should begin immediately. For infants and children, compressions are also indicated when the heart rate drops below 60 beats per minute with signs of poor blood flow, even before the heart stops completely.
Recognizing Cardiac Arrest in Adults
The core question is simple: Is this person unconscious, and are they breathing normally? If someone is unresponsive and either not breathing at all or only gasping, you should assume cardiac arrest is happening. The American Heart Association recommends that bystanders skip the pulse check entirely and start compressions based on unresponsiveness and abnormal breathing alone, because even trained healthcare professionals frequently make mistakes when checking for a pulse under pressure.
Healthcare providers who do check for a pulse should spend no more than 10 seconds feeling for it at the neck. If no definite pulse is felt within that window, compressions should start. Spending longer than 10 seconds delays treatment and worsens outcomes.
Why Agonal Breathing Counts as “Not Breathing”
One of the most common reasons bystanders hesitate is agonal breathing. This looks like slow, irregular gasps, sometimes described as snoring or labored breathing. It is not effective breathing. It does not deliver oxygen to the body. Agonal gasps are present in 40% to 60% of out-of-hospital cardiac arrests, and they frequently trick bystanders into thinking the person is still breathing on their own.
If someone is unconscious and gasping in this way, treat it the same as no breathing at all. Starting compressions on someone who turns out not to need them carries far less risk than withholding compressions from someone who does.
Different Rules for Infants and Children
Pediatric guidelines set a lower threshold for starting compressions. In infants and children, chest compressions are indicated when the heart rate falls below 60 beats per minute and the child shows signs of poor perfusion, things like pale or bluish skin, weak responsiveness, or poor muscle tone. You don’t need to wait for the heart to stop completely. A heart beating that slowly in a child often cannot maintain adequate blood flow, and compressions help bridge the gap before the situation worsens into full cardiac arrest.
The American Heart Association also specifically recommends full CPR with both compressions and rescue breaths for infants, children, drowning victims, drug overdose victims, and anyone who collapsed due to a breathing problem. These situations typically involve oxygen deprivation as the root cause, so breaths matter more than in a typical adult cardiac arrest.
When Bystanders Should Act
If you see a teenager or adult suddenly collapse, the steps are straightforward: call 911 and begin pushing hard and fast in the center of the chest. This is hands-only CPR, and it has been shown to be as effective as CPR with rescue breaths during the first several minutes of an adult cardiac arrest outside a hospital. You do not need formal training to do this. Pushing at a rate of about 100 to 120 pushes per minute (roughly the tempo of “Stayin’ Alive” by the Bee Gees) keeps blood circulating to the brain and heart until paramedics arrive.
If you’re unsure whether someone is in cardiac arrest, act anyway. The risk of doing compressions on someone who doesn’t need them is minimal compared to the risk of doing nothing for someone who does.
What Compressions Actually Do
When the heart stops pumping on its own, blood flow to the brain and heart muscle drops to zero within seconds. Chest compressions manually squeeze the heart between the breastbone and spine, generating enough pressure to push blood through the body. Animal and human studies show that compressions need to produce a certain level of blood pressure in the coronary arteries (the vessels feeding the heart itself) before the heart can potentially restart, either on its own or with a defibrillator shock.
For adults, compressions should reach a depth of at least 5 centimeters (about 2 inches) but no deeper than 6 centimeters. Research involving over 13,700 patients found the best survival rates with compression rates between 100 and 119 per minute. For infants, the target depth is roughly 4 centimeters (1.5 inches), and for children about 5 centimeters. Newborns require even less, around 3 centimeters for full-term babies and about 2.5 centimeters for premature infants.
When Compressions Are Not Indicated
There are situations where starting compressions is not appropriate. If a person shows obvious signs of irreversible death, such as rigor mortis (body stiffness from prolonged death) or visible decomposition, CPR will not help and should not be attempted. A valid do-not-resuscitate order also means compressions should be withheld, as the person has made a legal decision to decline resuscitation efforts.
Compressions are also not indicated when someone is unconscious but clearly breathing normally and has a pulse. Fainting, seizures, and deep sleep can all cause unresponsiveness without cardiac arrest. The key distinction is always whether normal breathing is present. If it is, place the person on their side in a recovery position and monitor them until help arrives.
Minimizing Pauses During Compressions
Once compressions have started, interruptions should be as brief as possible. Guidelines recommend that any pause for pulse checks or rhythm assessment last no longer than 10 seconds, and that at least 80% of total CPR time be spent actively compressing. Longer pauses allow the blood pressure built up by compressions to drop rapidly, forcing you to essentially start over in building circulation each time you stop. This is why the emphasis in modern CPR training has shifted heavily toward continuous, high-quality compressions with minimal breaks.