A new integrative weaning index of discontinuation from mechanical ventilation

Abstract

IntroductionIndexes predicting weaning outcome are frequently inaccurate. We developed a new integrative weaning index aimed at improving the accuracy of the traditional indexes.MethodsThree hundred and thirty-one patients mechanically-ventilated for more than 24 hours were evaluated. Initially, the threshold values of each index that best discriminate between a successful and an unsuccessful weaning outcome were determined in 115 patients. In the second phase, the predictive performance of these values was tested prospectively in the other 216 patients. Frequency/tidal volume ratio (f/Vt ratio), tidal volume (Vt), tracheal airway occlusion pressure 0.1 s (P 0.1), the product of P 0.1 and f/Vt (P 0.1 × f/Vt), respiratory rate (f), static compliance of the respiratory system (Cst,rs), ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2 ratio) and the new integrative weaning index IWI (Cst,rs × arterial oxygen saturation/f/Vt ratio) were evaluated in all patients. The readiness for weaning and the decision to return to mechanical ventilation was made by the physician in charge, based on the signs of poor tolerance. The receiver operating characteristic (ROC) curves were calculated in order to evaluate the predictive performance of each index. The Bayes' theorem was used to assess the probability of each test of predicting weaning.ResultsIn the prospective-validation set, successful weaning was observed in 183 patients (84.7%) and weaning failure in 33 (15.27%). IWI presented the highest accuracy, with the area under the ROC curves larger than that under the curves for the f/Vt ratio (0.96 × 0.85 respectively; P = 0.003), and also larger than that under the curves for the other indexes. IWI presented a higher probability of successful weaning when the test was positive (0.99) and a lower probability when the test was negative (0.14). Measurement of Cst,rs during the weaning process was considered one of the study limitations.ConclusionsIWI was the best predictive performance index of weaning outcome and can be used in the intensive care unit setting.Trial Registrationcontrolled-trials.com ISRCTN92117906

Ultrasound assessment of lung aeration loss during a successful weaning trial predicts postextubation distress*

“…In these 22 patients, the ultrasound analysis of lung derecruitment following extubation appeared helpful to predict postextubation distress. The seven patients with postextubation distress had a higher LUS score 4 hrs after extubation than patients with postextubation success: 19 [15][16][17][18][19] vs. 15 [14][15][16][17][18][19], p = .07.…”

“…Identifying patients definitively weaned from mechanical ventilation following extubation remains a difficult issue (12)(13)(14). Most proposed predictors of postextubation distress either require special equipment, are too complex for bedside use, or have a limited predictive value (4,14,15).…”

“…Most proposed predictors of postextubation distress either require special equipment, are too complex for bedside use, or have a limited predictive value (4,14,15). Therefore, to date, there are no simple clinical indices known to be powerful predictors of postextubation distress.…”

Utility of the dead space fraction (Vd/Vt) as a predictor of extubation success

“…In turn, the IWI, studied by Nemer et al and calculated as the product of static compliance and SaO 2 divided by the Fr/Vt ratio, with a cutoff point of 25 ml/cmH 2 O/FiO 2 yielded a sensitivity of 0.97% and a specificity of 0.94% in predicting extubation failure. 28,29 Undoubtedly, these values imply a very high level of success, though when extubation failure predictors are compared, not only the numerical values of the statistical analyses must be taken into account. In this field a very important consideration is the complexity of application, integration and interpretation of the values obtained.…”

Modified Rapid Shallow Breathing Index Adjusted With Anthropometric Parameters Increases Predictive Power for Extubation Failure Compared With the Unmodified Index in Postcardiac Surgery Patients

“…The predictive value of the RSBI has been estimated to be 0.85, which means that this index fails in a considerable number of patients. 8 However, this useful predictive value also has a significant false positive rate. Therefore, clinicians should improve accuracy of predictive value for extubation.…”