Usefulness of radiological signs of pulmonary congestion in predicting failed spontaneous breathing trials

Abstract

Inspiratory fall in intrathoracic pressure during a spontaneous breathing trial (SBT) may precipitate cardiac dysfunction and acute pulmonary edema. We aimed to determine the relationship between radiological signs of pulmonary congestion prior to an SBT and weaning outcomes. This was a post hoc analysis of a prospective cohort study involving patients in an adult medical-surgical ICU. All enrolled individuals met the eligibility criteria for liberation from mechanical ventilation. Tracheostomized subjects were excluded. The primary endpoint was SBT failure, defined as the inability to tolerate a T-piece trial for 30-120 min. An attending radiologist applied a radiological score on interpretation of digital chest X-rays performed before the SBT. A total of 170 T-piece trials were carried out; SBT failure occurred in 28 trials (16.4%), and 133 subjects (78.3%) were extubated at first attempt. Radiological scores were similar between SBT-failure and SBT-success groups (median [interquartile range] = 3 [2-4] points vs. 3 [2-4] points; p = 0.15), which, according to the score criteria, represented interstitial lung congestion. The analysis of ROC curves demonstrated poor accuracy (area under the curve = 0.58) of chest x-rays findings of congestion prior to the SBT for discriminating between SBT failure and SBT success. No correlation was found between fluid balance in the 48 h preceding the SBT and radiological score results (ρ = -0.13). Radiological findings of pulmonary congestion should not delay SBT indication, given that they did not predict weaning failure in the medical-surgical critically ill population. (ClinicalTrials.gov identifier: NCT02022839 [http://www.clinicaltrials.gov/]).

Figure 1. In A, a chest X-ray of a 68-year-old female patient shows peribronchial cuffing and opacity in a “bat wing” pattern, revealing edema, compounding a radiological score of 4 points, characterized as interstitial lung congestion. In B, a chest X-ray of a 57-year-old male patient shows a cardiothoracic ratio > 60%, peribronchial cuffing, lung vessel redistribution, Kerley’s A line, and lung opacity, resulting in a score of 5 points, characterized as mild alveolar edema.

Figure 2. A ROC curve of the ability of the radiological score to predict spontaneous breathing trial failure. The area under the curve (AUC) is 0.58 (p = 0.2), revealing poor accuracy.