Certain skills are considered essential to the provision of first aid, particularly the ABC of first aid, which focus on critical life saving intervention, must be rendered before treatment of less serious injuries. ABC stands for AIRWAYS, BREATHING and CIRCULATION. The same mnemonic is used by all emergency health professionals. Attention must first be brought to the airway to ensure it is clear. Obstruction (choking) is a life threatening emergency. Following evaluation of the airway, a first aid attendant would determine adequacy of breathing and provide rescue breathing if necessary. Assessment of circulation is not usually carried out for patients who are not breathing, with first aiders now trained to go straight to chest compressions (and thus providing artificial circulation) but pulse checks may be done on less serious patients.
Some organisations add a fourth step of D for Deadly Bleeding or Defibrillation, while others consider this as part of the Circulation step. Variations on techniques to evaluate and maintain the ABCs depend on the skill level of the first aider. Once the ABCs are secured, first aiders can begin additional treatments, as required. Some organisations teach the same order of priority using the 3Bs – Breathing, Bleeding and Bones or 4Bs – Breathing, Bleeding, Brain and Bones. While the ABCs and 3Bs are taught to be performed sequentially, certain conditions may require the consideration of two steps simultaneously. This includes the provision of both artificial respiration and chest compressions to someone who is not breathing and has no pulse, and the consideration of cervical spine injuries when ensuring an open airway.