An influential report released in 1983 defined life-sustaining therapies as “all health care interventions that have the effect of increasing the life span of the patient.”1 This definition is highly inclusive: aspirin for stable coronary artery disease, intravenous antibiotics for osteomyelitis, and mechanical ventilation for respiratory failure all qualify. However, when considering withholding or withdrawing life-sustaining interventions, clinicians commonly refer to a more discrete group of therapies intended to forestall impending death by augmenting or replacing a vital bodily function. A hallmark of life-sustaining therapies, therefore, is that withholding or withdrawing them leads to physiologic decompensation foreseeably to cardiac arrest.