The ABC mnemonic is a foundational tool in emergency patient assessment and first aid, providing a structured sequence to address immediate threats to life. This method prioritizes the bodily functions that lead most rapidly to death if compromised. The ABC protocol serves as a memory aid for rescuers, ensuring a systematic approach to evaluating and treating an unconscious or unresponsive person. It establishes a necessary order of intervention, as the success of each step depends on the completion of the one before it.
A is for Airway
The first step in any emergency assessment is to ensure the patient has an open airway, as obstruction quickly leads to oxygen deprivation. The most common obstruction in an unconscious person is the tongue, which relaxes and falls back to block the pharynx. Foreign objects, blood, or vomit also pose a threat to a clear passage for air.
Rescuers use specific maneuvers to open the airway. The head-tilt/chin-lift technique is the standard approach for patients without a suspected spinal injury, involving gently tilting the head backward and lifting the chin. If a head, neck, or spinal injury is possible, the jaw thrust maneuver is used instead to avoid excessive cervical spine movement. This technique involves lifting the jaw forward and upward, which opens the airway while maintaining the head in a neutral position.
B is for Breathing
Once the airway is clear, the rescuer must assess the adequacy of the patient’s breathing to ensure oxygen is reaching the lungs. Assessment uses the Look, Listen, Feel technique, which should be performed quickly, taking no more than ten seconds.
The rescuer looks for the rise and fall of the chest, indicating air movement. They listen for the sound of air passing in and out, noting abnormal sounds like gasping or wheezing. The rescuer feels for the flow of expired air against their cheek or hand. If breathing is absent or inadequate, immediate interventions like rescue breaths or ventilation support are required.
C is for Circulation
Circulation focuses on ensuring that oxygenated blood is distributed throughout the body, particularly to the brain and vital organs. In a general first aid assessment, the rescuer must check for the presence of a pulse, which indicates the heart is generating a pump action.
The assessment also includes rapidly checking for and controlling severe external hemorrhage, or profuse bleeding. This can lead to a rapid and life-threatening drop in blood volume. The goal of assessing circulation is to identify and manage any issue that prevents the effective transport of oxygen and nutrients via the bloodstream.
Understanding the Shift to CAB
While ABC remains the standard for general trauma and respiratory emergencies, the sequence for adult Cardiopulmonary Resuscitation (CPR) has shifted to CAB (Circulation, Airway, Breathing) for most sudden cardiac arrests. This change, adopted by organizations like the American Heart Association (AHA) in 2010, emphasizes the immediate importance of chest compressions.
Research showed that in sudden cardiac arrest, the patient’s blood contains enough residual oxygen to sustain the brain for a few minutes. Prioritizing compressions minimizes the time delay and ensures blood flow is initiated sooner, capitalizing on existing oxygen reserves. The CAB approach is simpler for lay rescuers, reducing hesitation associated with performing rescue breaths. This has led to an increased rate of bystander intervention and improved survival rates in certain scenarios.
The CAB change is specific to cardiac arrest and does not replace the traditional ABC for non-cardiac emergencies, such as drowning or respiratory failure, where lack of oxygen is the primary cause.