Compression-only CPR, also called hands-only CPR, is a simplified form of cardiopulmonary resuscitation that uses only chest compressions, with no mouth-to-mouth breathing. The American Heart Association recommends it for untrained bystanders and for anyone who witnesses an adult suddenly collapse and become unresponsive. You push hard and fast on the center of the chest at a rate of 100 to 120 compressions per minute until emergency medical services arrive.
Why It Works Without Rescue Breaths
When someone’s heart suddenly stops, their blood still contains several minutes’ worth of oxygen. Chest compressions act as a manual pump, forcing that oxygenated blood out of the heart and toward the brain and other vital organs. Each time you release the chest, a slight vacuum inside the rib cage draws blood back into the heart, reloading it for the next compression. This cycle keeps a minimal but critical flow of oxygen-rich blood moving through the body.
Over time, that residual oxygen does get used up. Animal studies show that the small amount of air moved by chest compressions alone (roughly 100 milliliters per push) isn’t enough to meaningfully ventilate the lungs after about 10 minutes. But for the most common scenario, an adult who collapses from a cardiac event, the oxygen already in the bloodstream buys enough time for paramedics to arrive and take over with advanced equipment. The first few minutes are when circulation matters most; adequate breathing support becomes more important in a later phase.
How It Compares to Traditional CPR
For adults who collapse from a cardiac cause, compression-only CPR performs as well as, or better than, traditional CPR with rescue breaths when performed by bystanders. A meta-analysis pooling data from multiple studies found that 11.5% of patients who received compression-only bystander CPR survived to hospital discharge, compared with 9.4% of those who received standard CPR with breaths. That translates to roughly a 24% relative improvement in survival.
The likely reason isn’t that rescue breaths are harmful. It’s that pausing compressions to deliver breaths interrupts blood flow at exactly the moment it matters most. Untrained rescuers tend to take too long positioning themselves, forming a seal, and blowing air, and each pause lets blood pressure in the brain drop. Continuous compressions avoid those interruptions entirely.
More Bystanders Actually Step In
One of the biggest barriers to bystander CPR has always been the mouth-to-mouth component. Surveys consistently show that people are far more willing to help when rescue breaths aren’t required. In one Canadian study, 61.5% of respondents said they would perform compression-only CPR on any victim, but only 39.7% were willing to do traditional CPR. The gap widened further when the victim was a stranger or appeared unkempt: nearly 48% would do compressions alone, versus under 29% for mouth-to-mouth.
This matters enormously. The single biggest predictor of surviving an out-of-hospital cardiac arrest is whether someone starts CPR before the ambulance arrives. A technique that doubles the number of people willing to act saves more lives at a population level, even if it delivers slightly less oxygen per cycle than the full protocol.
The Right Technique
Place the heel of one hand on the center of the person’s chest, between the nipples. Stack your other hand on top and interlock your fingers. Keep your arms straight, position your shoulders directly above your hands, and use your body weight to compress the chest. Current AHA guidelines call for a depth of at least 5 centimeters (about 2 inches) but no more than 6 centimeters. Studies of over 13,700 patients found that compressions in the range of 100 to 119 per minute were associated with the best survival rates.
Letting the chest fully rise back to its resting position between compressions is just as important as pushing down. Complete recoil creates negative pressure inside the chest cavity, which pulls venous blood back into the heart. If you lean on the chest between pushes, you reduce that refill effect and deliver less blood with each subsequent compression. Think of it as a two-part motion: push hard, then completely release.
To keep the right pace without a metronome, the AHA suggests compressing to the beat of a song in the 100 to 120 beats-per-minute range. The organization maintains curated playlists of popular songs at that tempo. “Stayin’ Alive” by the Bee Gees is the most commonly cited example, but dozens of well-known songs fall in that range.
When Rescue Breaths Still Matter
Compression-only CPR is designed for adults whose heart stops due to a cardiac event. In certain situations, the problem starts with breathing rather than the heart, and the blood’s oxygen supply is already depleted by the time the heart stops. Rescue breaths become important in these cases.
Drowning is the clearest example. Because the person has been deprived of air, cerebral hypoxia is the primary threat. Guidelines for drowning victims recommend starting with five rescue breaths before beginning chest compressions, reversing the usual priority. Drug overdoses involving opioids, choking events, and prolonged collapses where the person may have been down for many minutes before being found also fall into this category. In all of these, the blood has little usable oxygen left, so compressions alone move oxygen-poor blood.
Children and Infants
Pediatric cardiac arrests are more often caused by breathing problems than by heart rhythm issues, which makes rescue breaths more valuable. Large observational studies show the best outcomes for children when bystanders provide both compressions and breaths. The AHA and American Academy of Pediatrics encourage lay rescuers to add breaths for infants and children if they are able and willing. That said, compression-only CPR is still far better than doing nothing. If you’re unwilling or unable to give breaths to a child, continuous compressions remain the right choice.
Broken Ribs and Legal Protection
Rib fractures are common during CPR, especially in older adults. Effective compressions require real force, and cracking a rib is considered a normal, expected side effect of pushing hard enough to circulate blood. It is not a sign you did something wrong.
Every U.S. state has some form of Good Samaritan law that protects bystanders who provide emergency care in good faith. These laws don’t prevent someone from filing a lawsuit, but they give you a strong legal defense. A broken rib sustained during CPR is specifically the type of outcome these laws are designed to cover. The legal system treats it as an ordinary consequence of a reasonable attempt to save a life.
Putting It All Together
If you see an adult collapse and become unresponsive, call 911 (or ask someone nearby to call), then immediately begin pushing hard and fast on the center of their chest. Don’t stop to check for a pulse, don’t worry about mouth-to-mouth, and don’t be afraid of pushing too hard. Aim for at least 2 inches of depth, a rate near 110 compressions per minute, and full chest recoil between each push. Keep going until paramedics take over or the person starts moving.