Department of Critical Care Medicine, Nanjing Zhong-Da Hospital, Southeast University School of Medicine, China; Department of Critical Care Medicine St. Michaels's Hospital, University of Toronto, Canada

Patients, mechanically ventilated for > 24 h, were included when they met criteria for their first spontaneous breathing trial (SBT) on continuous positive airway pressure (CPAP) (5-6 cmH2O) for 30 minutes. Patients who did not fulfill the criteria for successful SBT, or required assist, or deceased within 48h post-extubation were considered extubation failure (F). Patients who completed the SBT and remained extubated > 48 h were considered successfully extubated (S). Before and during the SBT, arterial blood gases, heart, rate, blood pressure, and EAdi, flow, Vt, f, and, airway pressure (Paw) were measured. At 0, 5, 10, 15 and 30 minutes of the SBT, f/Vt, diaphragm electrical activity (EAdi), NME, and NVE were calculated. NME was calculated as Paw/EAdi during inspiratory occlusion. NVE was calculated as Vt/EAdi during unassisted inspirations.Arterial blood gases, heart rate, and blood pressure were measured. The receiver operating characteristic (ROC) curve was calculated to evaluate the predictive performance of each index.