Cardiopulmonary Resuscitation (CPR) is a life-saving procedure used when a person’s heart has stopped beating or they are no longer breathing. Its effectiveness relies on the immediate application of standardized actions. These guidelines evolve based on scientific research to maximize the chance of survival for victims of cardiac arrest. The current recommended sequence for basic life support is represented by a three-letter acronym that provides a simple framework for rescuers.
Defining the CAB Acronym
The modern sequence of CPR is represented by the acronym CAB: Compressions, Airway, and Breathing. This ordering was formally introduced by the American Heart Association (AHA) and has been the standard for most cardiac arrest scenarios since the 2010 Guidelines. This revised sequence directs the rescuer to focus on the most time-sensitive action, emphasizing that starting blood circulation is the first priority in an adult cardiac emergency.
Why CAB Replaced ABC
The CAB sequence marked a significant shift from the previous standard, which began with Airway and Breathing (ABC). Research demonstrated that prioritizing airway opening and rescue breaths often caused a delay in starting chest compressions. This delay was detrimental because immediate blood flow is the most important factor for improving outcomes in sudden cardiac arrest.
When an adult collapses suddenly, enough oxygen often remains in the blood and lungs for the first few minutes. The immediate need is to circulate that existing oxygenated blood to the brain and heart. Placing Compressions first allows rescuers to begin mechanically pumping the blood right away, minimizing the time vital organs are deprived of oxygen. The CAB method also simplifies the initial response for lay rescuers, encouraging quick action without the complexity of airway management.
Executing the CAB Sequence
The first step is Compressions, requiring the rescuer to push hard and fast on the center of the victim’s chest. For adults, compressions should be delivered at a rate of 100 to 120 beats per minute (approximately two per second). The correct depth is at least 2 inches (5 centimeters), but should not exceed 2.4 inches (6 centimeters). Allowing the chest to fully recoil after each compression permits the heart to refill with blood before the next pump.
After the initial cycle of compressions, the rescuer moves to Airway management. This involves using the head tilt-chin lift maneuver to move the tongue away from the back of the throat, which is the most common obstruction. The rescuer places one hand on the victim’s forehead and two fingers of the other hand under the chin to gently tilt the head back and lift the jaw.
The final step is Breathing, where the rescuer delivers two rescue breaths after every 30 compressions, establishing the 30:2 compression-to-ventilation ratio for single rescuers. Each breath should last about one second and be delivered with enough force to cause the victim’s chest to visibly rise. Interruptions to compressions for delivering these two breaths must be kept to less than ten seconds to maintain consistent blood circulation. The full CAB sequence is repeated continuously until emergency medical services arrive or the person shows signs of life.