How we restart a heart

It's a scene replayed in countless movies: someone collapses, and a hero starts rhythmic chest compressions and rescue breaths. Many assume CPR revives the heart, but its true purpose is much more grimly practical: to buy time. When someone's heart stops, their brain isn't receiving oxygen. Without CPR, permanent brain damage can begin in as little as four minutes, with the risk of irreversible injury increasing significantly after ten minutes. The compressions literally squeeze the heart, pushing residual blood to the brain and other vital organs, while rescue breaths attempt to oxygenate that blood.

The mechanism behind CPR is a brutal, mechanical stand-in for a functioning circulatory system. The chest compressions manually create an artificial blood flow, maintaining a trickle of oxygenated blood to the brain and heart muscle itself. This isn't enough to restart the heart, but it's just enough to keep those critical cells from dying, preserving them until professional medical help, like a defibrillator, can arrive. The chest compressions are intentionally aggressive, often resulting in broken ribs or a fractured sternum.

Rescue breaths, the other component, deliver oxygen into the lungs to be picked up by that forced blood flow. While less emphasized in some modern CPR guidelines (due to the critical importance of continuous compressions), they provide additional oxygen, though continuous chest compressions are often sufficient in the first few minutes of an adult's cardiac arrest because the blood still contains a reserve of oxygen. The combination creates a makeshift, temporary life-support system.

So, why do we do it? Because even a small chance of life is worth the physical trauma. CPR doesn't guarantee survival – far from it. Survival rates vary widely but are often low outside of hospitals. However, for those who do survive, the early application of effective CPR is the single most critical factor. It determines whether they wake up, and whether they wake up with their cognitive functions intact. It's a violent dance with death to snatch away precious minutes of brain life.