The ABCs represent the universally recognized mnemonic for assessing and managing life-threatening medical emergencies. This systematic approach provides a rapid, standardized framework for rescuers to prioritize immediate, life-sustaining actions. By focusing on these three core areas, the rescuer can quickly stabilize a person until professional medical help arrives.
The Foundation: Defining Airway, Breathing, and Circulation
The original framework establishes a hierarchy of needs, starting with the passage for air. Airway, represented by the “A,” refers to ensuring there is a clear, unobstructed path for air to move into the lungs. If the airway is blocked, no amount of effort to move air will be successful.
The next step, “B” for Breathing, involves the movement of air into and out of the lungs to oxygenate the blood. Even with an open airway, a person must be actively breathing for oxygen exchange to occur.
Finally, “C” stands for Circulation, which is the heart’s function of pumping oxygenated blood throughout the body. The blood carries oxygen from the lungs to the brain and other vital organs. If circulation fails, the body’s tissues quickly become starved of oxygen, leading to irreversible damage within minutes.
Practical Application: The Sequence and Context of Use
While the mnemonic is universally known as A-B-C, the practical application for lay rescuers responding to sudden cardiac arrest has undergone a significant change. In 2010, major resuscitation guidelines shifted the sequence to C-A-B, prioritizing chest compressions first. This change was based on evidence showing that in an adult who suddenly collapses, there is usually enough residual oxygen in the bloodstream for a few minutes. Starting with compressions, or “C,” immediately circulates that existing oxygenated blood to the brain and heart, which is the most time-sensitive intervention.
Any delay caused by checking the airway or delivering breaths was found to decrease the chance of survival. Therefore, the modern approach for an unresponsive, non-breathing adult is to call emergency services, initiate chest compressions, and then address the airway and breathing.
The traditional A-B-C sequence is still relevant for initial assessment in other medical emergencies, such as trauma or respiratory-based arrests like drowning or pediatric cases. In these situations, the underlying cause is often a lack of oxygen first, making the airway and breathing the immediate priorities.
Essential Techniques for Managing A, B, and C
Managing Airway (A)
The immediate physical action taken to manage the “A” (Airway) in a patient without suspected neck or spinal injury is the head-tilt/chin-lift maneuver. This technique involves placing one hand on the forehead and the fingers of the other hand under the bony part of the chin, then gently tilting the head back while lifting the chin. This action repositions the tongue, which is the most common cause of airway obstruction in an unconscious person. If a spinal injury is suspected, a jaw-thrust maneuver is used instead to open the airway without moving the neck.
Managing Breathing (B)
Managing “B” (Breathing) involves delivering rescue breaths, often in a 30:2 cycle with compressions for trained rescuers. The rescuer pinches the nose shut and seals their mouth over the person’s mouth, delivering a slow breath over approximately one second. The goal is to make the chest visibly rise, confirming that the air has entered the lungs.
Managing Circulation (C)
The core technique for “C” (Circulation) involves high-quality chest compressions. The rescuer places the heel of one hand in the center of the person’s chest, with the other hand on top, and pushes straight down. Compressions must be delivered at a rate of 100 to 120 beats per minute, which is roughly the tempo of the song “Stayin’ Alive.” For an adult, the compression depth should be at least two inches, but no more than 2.4 inches, allowing the chest to fully recoil after each compression to ensure adequate blood flow.