50 - Weaning from Mechanical Ventilation

Weaning from mechanical ventilation represents the period of transition from total ventilatory support to spontaneous breathing. About 70% of intubated mechanically ventilated patients are extubated on the first spontaneous breathing trial (SBT) attempt, whether by disconnection from the ventilator or after breathing at low levels of pressure support for short periods of time, such as 30 to 120 minutes. This pattern has recently been categorized as “simple weaning,” and the prognosis for such patients is good. The remaining patients, about 30%, need progressive withdrawal from artificial ventilatory support. These patients can be classified either as “difficult weaning” when they require up to three SBTs to achieve successful weaning, or “prolonged weaning” if they fail at least three weaning attempts or require more than 7 days of ventilatory support from the first SBT. The mortality rate for patients not simple/easy to wean is approximately 25%. Early liberation from mechanical ventilation and removal of the endotracheal tube is clinically important. Unnecessary prolongation of mechanical ventilation increases the risks of complications including infections (particularly of bronchopulmonary origin), barotrauma, cardiovascular compromise, tracheal injuries, and muscle deconditioning. To optimize patient outcomes, clinicians should hasten the process that ultimately leads to removal of the endotracheal tube. Liberation and extubation are different issues. Liberation refers to weaning from mechanical ventilation and means that a patient no longer requires ventilatory support. When this step is achieved, the clinician has to consider a different question: Is the patient able to breathe spontaneously without the endotracheal tube? Removal of the endotracheal tube is referred to as extubation. In terms of magnitude, the extubation failure rate—that is, the need to replace the endotracheal tube and reinstitute mechanical ventilation—is variable and ranges from 5% to 20% of extubated patients.