Cardiopulmonary Resuscitation (CPR) is an emergency procedure performed when someone’s breathing or heartbeat has stopped. While often depicted in media as a way to “restart” a heart, CPR does not directly achieve this. Instead, it serves a different, yet equally important, function in emergencies such as sudden cardiac arrest. This article clarifies the actual purpose of CPR and explains what truly restarts a heart.
The Purpose of CPR
CPR manually circulates blood and oxygen throughout the body when the heart is no longer pumping effectively. This emergency technique involves chest compressions, often combined with rescue breaths, to maintain vital blood flow. The chest compressions physically squeeze the heart between the breastbone and spine, forcing blood to circulate to the brain and other organs. This manual circulation helps prevent damage, particularly to the brain, which can occur within minutes without oxygen.
CPR acts as a temporary measure, buying crucial time until advanced medical help arrives or a defibrillator can be used. For adults, guidelines recommend chest compressions at a rate of 100 to 120 per minute, with a depth of at least 2 inches (5 cm) but no more than 2.4 inches (6 cm).
How a Heart is Restarted
A heart in sudden cardiac arrest, especially when caused by an electrical problem, is restarted through defibrillation. This process involves delivering a controlled electrical shock to the heart using a device called a defibrillator. The electrical shock aims to momentarily stop the chaotic electrical activity, such as ventricular fibrillation or pulseless ventricular tachycardia, allowing the heart’s natural electrical system to reset and resume a normal, organized rhythm. Automated External Defibrillators (AEDs) are portable versions of these devices designed for public use, providing voice prompts to guide rescuers through the process of applying pads and delivering a shock if the device detects a shockable rhythm. It is important to note that defibrillation is only effective for specific types of electrical chaos in the heart; it will not work if there is no electrical activity, a condition known as asystole, or in cases of pulseless electrical activity.
The Critical Role of CPR
Even though CPR does not directly restart the heart, its immediate application significantly increases the likelihood of successful defibrillation and overall survival. High-quality CPR maintains a partial flow of oxygenated blood to the heart muscle and brain, which keeps these organs viable. This sustained blood flow prevents the heart’s electrical activity from deteriorating into a non-shockable rhythm, thereby preserving the opportunity for a defibrillator to be effective. Continuous, effective chest compressions minimize interruptions to blood flow, providing essential support until an AED can be deployed or emergency medical services take over. Therefore, CPR and defibrillation are complementary, with CPR creating the conditions necessary for defibrillation to succeed.
Factors Influencing Outcomes
Several factors influence the success rate of resuscitation efforts following sudden cardiac arrest. Prompt initiation of CPR by bystanders is a primary determinant, as early compressions maintain blood flow to the brain and heart. The quality of CPR, including adequate compression depth and rate with minimal interruptions, also plays a significant role in improving outcomes. Rapid access to and use of an Automated External Defibrillator (AED) can dramatically increase survival chances, particularly for shockable rhythms, with survival rates decreasing by 7% to 10% for every minute without defibrillation. Additionally, the timely arrival of emergency medical services and the underlying cause of the cardiac arrest contribute to the overall prognosis.