title: Evaluation of a new index of mechanical ventilation weaning: the timed inspiratory effort.
abstract: OBJECTIVE
  The performance of most indices used to predict ventilator weaning outcomes remains below expectation. The purpose of this study was to evaluate a new weaning index, the timed inspiratory effort (TIE) index, which is based on the maximal inspiratory pressure and the occlusion time required to reach it.
  
  
  METHODS
  This observational prospective study included patients undergoing mechanical ventilation. Patients ready to be weaned had their TIE index and 6 previously reported indices recorded. The primary end point was the overall predictive performance of the studied weaning indices (area under the receiver operating characteristic curves [AUCs]). The secondary end points were sensitivity, specificity, positive predictive value, and negative predictive value. P values <.05 were considered significant.
  
  
  RESULTS
  From the 128 initially screened patients, the 103 patients selected for the study included 45 women and 58 men (mean age 60.8 ± 19.8 years). In all, 60 patients were weaned, 43 were not weaned, and 32 died during the study period. Tracheotomy was necessary in 61 patients. The mean duration of mechanical ventilation was 17.5 ± 17.3 days. The AUC of 3 weaning predictors (the TIE index, the integrative weaning index, and the frequency-to-tidal volume [f/Vt] ratio index) was higher than the other indices. The TIE index had the largest AUC.
  
  
  CONCLUSIONS
  The TIE index performed better than the best weaning indices used in clinical practice.
authors.affiliation: Medical Science Post-graduation Program, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil leonardo.uti@gmail.com.
authors.forename: Leonardo Cordeiro
authors.initials: LC
authors.lastname: de Souza
authors.affiliation: Physiotherapy School, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Fernando Silva
authors.initials: FS
authors.lastname: Guimarães
authors.affiliation: Nephrology Division, Department of Medicine, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil.
authors.forename: Jocemir Ronaldo
authors.initials: JR
authors.lastname: Lugon
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001938:Brazil; D003422:Critical Care; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012121:Respiration, Artificial; D012132:Respiratory Muscles; D013990:Tidal Volume; D013997:Time Factors; D015300:Ventilator Weaning / Q000379:methods*; D014939:Work of Breathing
keywords: ICU; ROC curves; maximal inspiratory pressure; mechanical ventilation; respiratory drive; weaning