Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed when the heart stops beating effectively, a condition known as cardiac arrest. This sudden medical event causes the immediate collapse of the circulatory system, preventing the delivery of oxygen to the body. Because cardiac arrest affects hundreds of thousands of people outside of a hospital setting each year, CPR is recognized as a foundational skill in emergency response. The immediate action of a bystander using CPR is the first and most direct intervention against this life-threatening condition.
Sustaining Brain and Organ Function
During cardiac arrest, the heart ceases its pumping action, instantly halting the circulation of oxygenated blood throughout the body. This lack of blood flow starves the body’s cells of oxygen, leading to cellular damage and eventual death. The brain is particularly sensitive to this deprivation, and its cells can begin to suffer irreversible injury in as little as four to five minutes without oxygen supply.
The purpose of CPR is to manually take over the function of the stopped heart and lungs, temporarily maintaining a minimal level of blood flow and oxygenation. Chest compressions, when performed correctly, physically squeeze the heart, forcing blood to move to the brain and other vital organs. In conventional CPR, rescue breaths supply oxygen to the lungs, which is then picked up by the limited circulating blood. This mechanical process does not restart the heart, but it buys time by delivering enough oxygenated blood to delay the progression of tissue death.
The Critical Importance of Immediate Action
The probability of survival decreases rapidly without intervention when cardiac arrest is caused by a shockable rhythm, such as ventricular fibrillation. For every minute that passes without CPR, the chance of survival can decline by an estimated 7% to 10%.
Delaying the start of CPR by even a few minutes severely impacts the patient’s prognosis. For example, a delay of four to five minutes in starting bystander CPR makes the patient approximately 27% less likely to survive to hospital discharge compared to receiving CPR within the first minute. After ten minutes without any form of intervention, the survival probability drops below 5%. When a bystander does start CPR, this mechanical support slows the rate of decline in survival to a more gradual 3% to 4% per minute until advanced care arrives.
Empowering the First Responder
Professional emergency services, such as paramedics and ambulances, cannot arrive instantly after a cardiac arrest is reported. The average time interval from a 9-1-1 call to the arrival of Emergency Medical Services (EMS) is often several minutes, sometimes averaging seven to eight minutes. This unavoidable gap is where the layperson bystander becomes the crucial link in the chain of survival. The bystander’s willingness to act immediately bridges the time between collapse and advanced medical care, keeping the patient alive.
This early intervention is impactful because bystander CPR can double or even triple the victim’s chance of survival from out-of-hospital cardiac arrest. Performing CPR also lessens the increase in patient mortality and the worsening of neurological outcomes typically resulting from longer ambulance response times. The skill is designed to be accessible, making widespread training a simple strategy for improving overall community survival rates from cardiac arrest.