ABC and its variations are initialism mnemonics for essential steps used by both medical professionals and lay persons (such as first aiders) when dealing with a patient. In its original form it stands for Airway, Breathing, and Circulation. The protocol was originally developed as a memory aid for rescuers performing cardiopulmonary resuscitation, and the most widely known use of the initialism is in the care of the unconscious or unresponsive patient, although it is also used as a reminder of the priorities for assessment and treatment of patients in many acute medical and trauma situations, from first-aid to hospital medical treatment. Airway, breathing, and circulation are all vital for life, and each is required, in that order, for the next to be effective. Since its development, the mnemonic has been extended and modified to fit the different areas in which it is used, with different versions changing the meaning of letters (such as from the original 'Circulation' to 'Compressions') or adding other letters (such as an optional "D" step for Disability or Defibrillation).
In 2010, the American Heart Association and International Liaison Committee on Resuscitation changed the recommended order of CPR interventions for most cases of cardiac arrest to chest compressions, airway, breathing or CAB.
The 'ABC' method of remembering the correct protocol for CPR is almost as old as the procedure itself, and is an important part of the history of cardiopulmonary resuscitation. Throughout history, a variety of differing methods of resuscitation had been attempted and documented, although most yielded very poor outcomes. In 1957, Peter Safar wrote the book ABC of Resuscitation, which established the basis for mass training of CPR. This new concept was distributed in a 1962 training video called "The Pulse of Life" created by James Jude, Guy Knickerbocker and Peter Safar. Jude and Knickerbocker, along with William Kouwenhouen developed the method of external chest compressions, while Safar worked with James Elam to prove the effectiveness of artificial respiration. Their combined findings were presented at annual Maryland Medical Society meeting on September 16, 1960 in Ocean City, and gained rapid and widespread acceptance over the following decade, helped by the video and speaking tour the men undertook. The ABC system for CPR training was later adopted by the American Heart Association, which promulgated standards for CPR in 1973.