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Critical Care

Open Access

Lung ultrasound findings predict weaning failure from mechanical ventilation

  • AC Pecanha Antonio1,
  • P Souza Castro1,
  • LF Schulz1,
  • J Maccari1,
  • R Oliveira1,
  • C Teixeira1 and
  • M Knorst2
Critical Care201418(Suppl 1):P298

Published: 17 March 2014


Lung ultrasound is increasingly becoming a diagnostic tool in the critical care setting. The B-line is an artifact that correlates with interstitial edema. Decreases in intrathoracic pressure during a spontaneous breathing trial (SBT) will augment venous return and impede left ventricular ejection, increasing intrathoracic blood volume. Therefore, the presence of cardiovascular dysfunction can contribute to weaning failure (WF). A randomized trial concluded that bedside lung ultrasound could predict post-extubation distress through changes in aeration during a T-tube test; however, it could not screen patients before submission to a SBT [1]. We aim to assess the reliability of lung ultrasound as a predictor of weaning outcomes.


We conducted a prospective, multicenter, observational study in two adult medical-surgical ICUs. Lung ultrasound was performed immediately before SBT. Three or more B-lines in a single view were called a B-pattern. B-predominance was defined as a B-pattern on at least one of the four anterior chest wall zones. All enrolled patients met eligibility criteria for ventilation liberation. Patients with tracheostomy were excluded.


During 2 years, 250 SBTs were analyzed. WF, defined as an inability to tolerate a T-tube trial during 30 to 120 minutes, occurred in 51 (20.4%). There was a higher prevalence of chronic obstructive pulmonary disease in the WF group as well as higher duration of mechanical ventilation. WF patients were also younger. Patients succeed at SBT and were extubated at first time in 75.9% of cases. We observed a significant association between B-predominance prior to submission to SBT and WF (OR = 1.99 (1.04 to 3.84)). For diagnosing WF, B-predominance showed 69% sensitivity, 48% specificity, 25% positive predictive value, and 86% negative predictive value.


The finding of B-predominance at bedside lung ultrasound performed before SBT predicts WF, although it shows low accuracy.

Authors’ Affiliations

Hospital Moinhos de Vento, Porto Alegre, Brazil
UFRGS, Porto Alegre, Brazil


  1. Soummer A, Perbet S, Brisson H, Arbelot C, Constantin JM, Lu Q, Rouby JJ, et al.: Lung Ultrasound Study Group: Ultrasound assessment of lung aeration loss during a successful weaning trial predicts postextubation distress. Crit Care Med 2012, 40: 2064-2072. 10.1097/CCM.0b013e31824e68aeView ArticlePubMedGoogle Scholar


© Pecanha Antonio et al.; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.