The advances in intensive care have enabled more patients to survive an acute critical illness. However, these advances have also created a large and growing population of patients with prolonged dependence on mechanical ventilation (MV) and other intensive care therapies. Most patients require short periods of respiratory support, but a minority requires prolonged MV (PMV), which has been defined as a period of 21 days for ≥6 hours/day on MV. The requirement for a period of MV usually mandates admission to an ICU, and PMV is included in the term ‘‘chronically critically ill’’ described in a 1985 study by Girard and Raffin et al. that focused on patients who survived an initial episode of critical illness but remained dependent on intensive care; in other words, they were patients who neither died in the acute period of intensive care unit (ICU) treatment nor recovered.