ABC is a medical abbreviation for Airway, Breathing, and Circulation. It's the sequence to follow in Basic Life Support (BLS), although this order is sometimes changed to Circulation, Airway, Breating (C-A-B) depending on the scenario.
ABC was derived from Maslow’s hierarchy of needs in which airway, breathing, and circulation (ABC), are physiological elements that are needed for the body to survive and help determine one’s level of health.