Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed during cardiac arrest, when a person’s heart stops beating. The common perception that CPR alone can “restart” the heart is inaccurate. CPR is a manual support system, not an electrical correction device. Its function is to temporarily sustain life by maintaining a minimal flow of oxygenated blood to the body’s most sensitive organs until definitive medical intervention can take place.
What CPR Actually Does
When cardiac arrest occurs, the heart ceases effective pumping, immediately stopping blood circulation. Without intervention, the lack of oxygen-rich blood causes brain damage within minutes. CPR combats this rapid deterioration by manually substituting for the heart’s pumping function. Chest compressions, performed hard and fast at a rate of 100 to 120 times per minute, create artificial circulation.
This mechanical pressure temporarily generates blood flow to the vital organs. The primary goal is to perfuse the brain and the heart muscle, delaying cellular death and keeping tissues viable. Rescue breaths, often combined with compressions, help maintain the oxygen content in the circulating blood. The procedure essentially buys time, extending the window of opportunity for a successful recovery once advanced care arrives.
Continuous, high-quality chest compressions are the most important part of this emergency support. CPR does not correct the underlying electrical or structural problem that caused the heart to stop. Instead, it keeps the heart and brain supplied with oxygen until the necessary treatment to fix the malfunction can be applied. The success of CPR is measured by its ability to preserve the person’s condition for the next stage of treatment.
The Electrical Component: When Defibrillation is Needed
Cardiac arrest is distinct from a heart attack; arrest is an electrical problem, while a heart attack is typically a circulation problem caused by a blocked artery. Sudden cardiac arrest often results from an electrical malfunction where the heart’s natural pacemaker becomes chaotic. This chaotic rhythm, known as ventricular fibrillation (VFib), causes the heart muscle to quiver uselessly instead of contracting in a coordinated pump.
Because the heart’s electrical activity is disorganized, CPR’s mechanical pumping is insufficient to restore a normal heartbeat. To correct this electrical chaos, an electrical shock must be delivered to the heart, a procedure called defibrillation. The shock from an Automated External Defibrillator (AED) momentarily stops all electrical activity. This sudden stop allows the heart’s natural pacemaker to potentially reset into a normal, perfusing rhythm.
An AED is the device that can “restart” the heart in cases of VFib, making it the definitive treatment for many cardiac arrests. The electrical shock is effective only for certain shockable rhythms, such as ventricular fibrillation or pulseless ventricular tachycardia. For non-shockable rhythms, like asystole (a flatline), defibrillation is ineffective; CPR must continue while medical professionals address other potential causes.
Realistic Expectations and Survival Outcomes
While CPR and defibrillation are powerful interventions, survival after an out-of-hospital cardiac arrest (OHCA) is often sobering. Overall survival rates to hospital discharge for OHCA patients are low, hovering around 10% in many communities. The chances of survival are influenced by the swiftness of action, often summarized by the “Chain of Survival” concept.
Every minute without CPR and defibrillation decreases the chance of survival by approximately 10%. Immediate bystander CPR can double or triple a victim’s chance of survival by bridging the time gap until emergency services arrive. When an AED is applied rapidly, particularly within the first few minutes, survival rates for shockable rhythms can increase significantly, sometimes reaching 40% or higher in targeted public access programs.
Survival is not the only measure of success; the neurological outcome, meaning survival without severe brain damage, is also a factor. Approximately 8.2% of discharged OHCA patients achieve a positive neurological outcome. These statistics emphasize that CPR is not a guaranteed fix but rather a time-sensitive, life-preserving action that is most effective when paired with rapid defibrillation.