Managing the apparent and hidden difficulties of weaning from mechanical ventilation.

BACKGROUND: In anaesthetized patients scheduled for surgery, tracheal intubation is performed with the expectation of subsequent smooth extubation. In critically ill patients, separation from the ventilator is often gradual and the time chosen for extubation may be either delayed or premature. Thus, weaning is challenging, represents a large part of the ventilation period and concerns all mechanically ventilated patients surviving their stay. DEFINITIONS AND MANAGEMENT: Weaning may be stratified in three groups according to its difficulty and duration. In simple weaning the main issue is to detect the soonest time to start separation from the ventilator; this is frequently impeded by poor sedation management and excessive ventilator assistance. A two-step diagnostic approach is the most efficacious: screening for ascertained readiness to wean is confirmed by a diagnostic test simulating the post-extubation period, best performed by unassisted breathing (no PEEP). In case of test failure (difficult weaning), a structured and thorough diagnostic work-up regarding potentially reversible pathologies is required with a focus on cardiovascular dysfunction or fluid overload at the time of separation from the ventilator, respiratory or global muscle weakness and underlying infection. Prolonged weaning is exceptionally time- and resource-consuming, needs to properly appraise psychological problems, sleep and nutrition, and is probably best performed in specialized units.
CONCLUSIONS: Adequately managing simple and difficult weaning requires one to think about ICU policies in terms of sedation, fluid balance and having a systematic screening strategy; it also needs an individualized approach to understand and treat the failing patients. Prolonged weaning requires a holistic approach.