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A nurse carries a portable oxygen tank in a hospital room.
Figure 18.1 The respiratory system and cardiovascular system together form the cardiopulmonary system. Nurses support patients' respiratory needs in many ways, including by providing them with oxygen, as this critical care nurse is doing for a patient with COVID-19. (credit: "Navy Medical Team Suports Louisiana Hospital" by Mass Communication Specialist 2nd Class Michael H. Lehman/Flickr, Public Domain)

Basic life support training uses the first three letters of the alphabet to quickly refer to the most crucial lifesaving actions for a patient who suffers an arrest situation: assessment of the patient’s airway, breathing, and circulation. Until a few years ago, these were referred to as they appear alphabetically—A-B-C. The 2010 American Heart Association (AHA) guidelines changed the order to reflect circulation as the first response, followed by airway and breathing, so it is now C-A-B (AHA, 2020).

In either order, the respiratory system is associated with two-thirds of the immediate and emergent lifesaving response recommended for cardiac and/or respiratory arrests, which suggests its importance. The cardiovascular system is also critical because it is the adequacy of the heart’s pumping action and vascular circulation that delivers oxygen (O2) and other nutrients. Without adequate perfusion, all body systems and components are at risk for significant compromise and ultimately cell death. Consequently, the first three letters of the alphabet are certainly appropriate as quick and recognizable identifiers of the most necessary immediate lifesaving measures to take in hopes of patient survival.


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