Lung Ultrasound Prior to Spontaneous Breathing Trial Is Not Helpful in the Decision to Wean

Lung ultrasound is increasingly becoming a diagnostic tool in the critical care setting. B-pattern on a lung ultrasound is an artifact composed of multiple B-lines and correlates with interstitial edema. A randomized controlled trial concluded that bedside thoracic ultrasound could predict postextubation distress through changes in lung aeration during a weaning procedure; however, it could not screen patients before performance of a spontaneous breathing trial (SBT).

We conducted a 2-year, prospective, multicenter, observational study in 2 adult medical-surgical ICUs in southern Brazil. All enrolled subjects met eligibility criteria for ventilation liberation. Patients with tracheostomy were excluded. Lung ultrasound was performed immediately before SBT. B-predominance was defined as any profile with anterior bilateral B-pattern. The primary outcome was SBT failure, defined as the inability to tolerate a T-piece trial of 30-120 min, in which case subjects were not extubated.

From 2011 to 2013, 250 subjects undergoing weaning procedures were evaluated. SBT failure occurred in 51 (20.4%) subjects. Subjects with a successful SBT were extubated on the first attempt in 75.6% of cases. B-predominance was a very weak predictor for SBT outcome, showing 47% sensitivity, 64% specificity, 25% positive predictive value, and 82% negative predictive value.

B-pattern detected by a simplified lung ultrasound protocol should not preclude hemodynamically stable, sufficiently oxygenated patients from performing an SBT.