Cardiopulmonary Resuscitation (CPR) is an emergency procedure combining chest compressions with artificial ventilation to manually preserve brain function until spontaneous circulation and breathing are restored. While the traditional memory aid was A-B-C, modern resuscitation science prioritizes the C-A-B sequence—Compressions, Airway, Breathing—to ensure the most time-sensitive intervention begins immediately.
Initial Safety and Victim Assessment
The emergency response begins with a rapid assessment of the scene to ensure the safety of the rescuer and the victim. Check for immediate hazards like traffic or electrical wires before approaching. Once the scene is safe, determine if the person is unresponsive by gently tapping them and shouting, “Are you okay?”
If the person does not respond and is not breathing or is only gasping, activate the emergency response system immediately by calling the local emergency number. This action brings professional medical help and an Automated External Defibrillator (AED) to the location. If a bystander is present, instruct them to retrieve an AED, as early defibrillation is a major factor in survival.
Circulation Compressions
Modern CPR guidelines focus on circulation, making chest compressions the first step in the C-A-B sequence. This recognizes that in most adult cardiac arrests, residual oxygen in the blood can sustain the brain for a few minutes if the blood is circulated. Prioritizing compressions ensures oxygenated blood reaches the heart and brain without delay.
Effective compressions require the victim to be on their back on a firm surface. The rescuer must place the heel of one hand on the center of the chest, directly over the breastbone. The other hand is placed on top, with fingers interlaced. Push straight down hard and fast, using the weight of the upper body and keeping the elbows straight.
The chest must be compressed to a depth of at least two inches, but no more than 2.4 inches (5 to 6 centimeters) for an average adult. Compressions should be delivered at a rate of 100 to 120 times per minute. Allowing the chest to fully recoil after each compression is equally important, as this permits the heart to refill with blood before the next pump.
Airway Opening and Rescue Breathing
After 30 chest compressions, the next step addresses the Airway and Breathing components. A blocked airway in an unconscious person is usually caused by the tongue relaxing and obstructing the throat. Rescuers counter this using the head-tilt/chin-lift maneuver.
This technique involves placing one hand on the forehead and gently tilting the head backward, while placing the fingers of the other hand under the chin to lift it upward. This action creates a clear passage for air. The standard ratio for trained rescuers is 30 compressions followed by two rescue breaths. To deliver a breath, pinch the victim’s nose shut and create a complete seal over their mouth.
Each breath should be a smooth, steady blow lasting about one second, just enough to make the chest visibly rise. If the chest does not rise with the first breath, repeat the head-tilt/chin-lift maneuver before attempting the second breath. For bystanders unwilling or unable to perform mouth-to-mouth ventilation, hands-only CPR—continuous compressions without breaths—is a recommended alternative.
The Importance of Early Defibrillation
While chest compressions and rescue breaths are holding actions, the most effective treatment for many adult cardiac arrests is the delivery of an electrical shock via a defibrillator. The most common cause of sudden cardiac arrest is ventricular fibrillation (VF), an abnormal rhythm where chaotic electrical signals cause the heart muscle to merely quiver instead of pumping blood.
An Automated External Defibrillator (AED) is a portable device that automatically analyzes the heart’s electrical rhythm. If the AED detects a shockable rhythm, it advises or delivers an electrical shock. This controlled current momentarily stuns the heart, stopping chaotic activity to allow the heart’s natural pacemaker to re-establish a normal rhythm. Survival rates from ventricular fibrillation decrease by an estimated seven to ten percent for every minute that passes without defibrillation. Early access to an AED is therefore vital. CPR must continue until the AED is ready for use, the person shows signs of life, or emergency medical services personnel take over care.