Tracheostomy and weaning.

No hypothesis relating to respiratory care in the intensive care unit has proved more difficult to study in an objective fashion than the commonly held belief that tracheostomy hastens weaning from ventilatory support. Tracheostomy might facilitate weaning by reducing dead space and decreasing airway resistance, by improving secretion clearance, by reducing the need for sedation, and by decreasing the risk of aspiration. Available evidence indicates that dead space and airway resistance are in fact reduced, although whether the magnitude of these reductions explains the clinical observation of more rapid weaning after tracheotomy is less certain. Most of the data on this subject come from laboratory experiments and short-term physiologic studies on clinically stable patients, and the available evidence from clinical trials with weaning as a primary end point is scant. One large multicenter trial showed no advantage to early tracheotomy but demonstrated how difficult it is to get clinicians to manage their patients with regimens that go against their strongly held opinions. The most recent clinical trial found that percutaneous dilational tracheotomy performed in the first 2 days in patients projected to need > 14 days of ventilatory support greatly reduced ventilator and intensive care unit days, and decreased both the incidence of pneumonia and overall mortality, in comparison with tracheostomy done after day 14. Conducting such trials is difficult because of investigator and clinician bias, the inability to predict which patients will actually require prolonged mechanical ventilation, and several other factors discussed in this article. Tracheotomy probably does aid in liberating some patients from ventilatory support, but this may be as much from its effect on clinician behavior as from any physiologic impact.