ABSTRACT
While it may be most satisfying to draw a clear distinction between the short-tenn and long-tenn use of mechanical assistance to ventilation, there is no universally accepted delineation of when the use of ventilation becomes long-tenn. Rather, multiple factors need to be considered before ventilation can be classified as chronic (Table I) and the patient as unweanable from mechanical assistance to ventilation. Two scenarios illustrate the broad range of situations that must be included in any definition of long-tenn mechanical assistance to ventilation. In the first case, ventilatory assistance can clearly be considered long-tenn when instituted on a nonurgent basis for symptoms of daytime hypersomnolence and severe hypercapnia. Such a circumstance may occur in a patient with a chronic neurologic condition such as muscular dystrophy. The most appropriate method of initiating ventilatory assistance may be noninvasively using positive pressure ventilation via a nasal mask. On the other hand, the situation may be less clear in a patient with severe chronic obstructive pulmonary disease (COPD) intubated for an acute pneumonia. After three weeks of mechanical ventilation via an endotracheal tube and when the pneumonia has resolved, weaning may be progressing very slowly. Although the patient is off the ventilator for 8 hr each day, it may be unclear if the patient will wean completely or will require chronic ventilatory assistance.
