Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed when a person’s heart stops beating, a condition known as cardiac arrest. This life-saving technique combines chest compressions and rescue breathing to manually maintain some blood flow and oxygenation. CPR’s true function is limited and specific; it does not completely restore a normal heartbeat and breathing. The technique’s primary role is to temporarily deliver a small amount of oxygen to the most vulnerable organ: the brain.
The Primary Goal of Cardiopulmonary Resuscitation
The objective of CPR is not to restart the heart, but rather to maintain minimal circulation until professional help arrives. When the heart stops, the circulatory system halts, and the remaining oxygen in the blood quickly becomes depleted. CPR acts as an artificial pump, moving partially oxygenated blood throughout the body to sustain basic cellular function.
High-quality chest compressions circulate this blood to the brain and the heart itself, preventing immediate, widespread death of cells. CPR buys time, extending the window for definitive medical interventions, like defibrillation, to be successful. The flow generated by CPR is only a small fraction of the body’s normal circulatory output, creating a sporadic, low-pressure pulse. This limited artificial circulation is sufficient to prevent the complete shutdown of vital systems.
Mechanics of Blood and Oxygen Movement
CPR achieves its effect through the physical action of chest compressions, performed at a rate of 100 to 120 times per minute. During a compression, the heart is squeezed between the sternum and the spine, forcing blood out into the major arteries. When the chest is allowed to fully recoil, the heart relaxes and refills with blood from the veins, preparing for the next compression.
This constant cycle mimics the heart’s natural pumping action, pushing blood toward the brain and the body’s core. The oxygen component of CPR is delivered through rescue breaths, given at a ratio of 30 compressions to every two breaths. These breaths help replenish the supply of oxygen available in the lungs and blood. While rescue breaths are part of the standard protocol, the compressions are the main driver of blood flow, which carries the oxygen. The movement of this partially oxygenated blood prevents the immediate, catastrophic consequences of total circulatory collapse.
The Neurological Damage Timeline
The immediate initiation of CPR is paramount because the brain has a limited tolerance for oxygen deprivation, known as cerebral hypoxia. The brain is a high-metabolism organ, consuming about 20% of the body’s total oxygen supply. Without a constant supply, its cells begin to suffer quickly.
Brain cells begin to lose efficiency within one minute of oxygen deprivation. Irreversible damage can begin in as little as four minutes without oxygen, and by six minutes, the risk of severe, long-term injury increases significantly. After ten minutes, the chances of a meaningful recovery are minimal, as widespread neuronal death becomes nearly inevitable.
The goal of CPR is to interrupt this rapid timeline of cellular death. By sustaining a minimal flow of oxygenated blood, CPR extends the window of viability for brain cells. The procedure slows the catastrophic cascade of events that leads to permanent neurological injury, preserving the possibility of survival.
Factors Determining CPR Effectiveness
The effectiveness of CPR in preserving brain function depends on several variables in the emergency setting. The quality of chest compressions is a primary factor. Compressions must be performed at the correct depth—at least 2 inches for adults—and at the correct rate to generate adequate blood flow.
The promptness of initiation is another major factor, as the chances of survival decrease by approximately 7 to 10 percent for every minute CPR is delayed. The underlying cause of the cardiac arrest also plays a role; a sudden heart rhythm problem often responds better to intervention than arrests resulting from trauma or prolonged illness. CPR is a temporary measure, acting as a bridge until definitive treatment can be administered. The most effective intervention is the rapid use of an Automated External Defibrillator (AED), which delivers an electrical shock to reset the heart’s rhythm.