In our study, 18% of the patients that completed the SBT were reintubated. Interestingly, our new index IWI predicted extubation failure in 9 out of 10 patients that presented extubation failure. Our results showed that IWI was useful to detect those patients who passed the SBT but needed reintubation http://www.selleckchem.com/products/Bicalutamide(Casodex).html afterwards. Further studies are needed to better understand why IWI can detect this population that fails SBT in a late phase. The IWI presented the highest probability of weaning success when the test was positive (0.99) and the lowest probability of weaning success when the test was negative (0.14). The likelihood ratios of positive test and negative test of the IWI were 16.05 and 0.03 respectively, being correlated with great changes in probability [21].

The area under the ROC curves for IWI was significantly higher than the area of f/Vt ratio (0.96 �� 0.02 �� 0.85 �� 0.04 respectively; P = 0.003), and also significantly higher than the other indexes, being considered highly accurate, according to the guideline proposed by Swets [20].Some physiological measurements such as MIP, which generally present the area under the ROC curves considered less accurate [11,21], can be helpful when their values are more than -15 to -10 cmH2O, indicating that the patient probably will not be able to breathe spontaneously for a long time. Weaning indexes that evaluate one single function have generally presented poor accuracy [8,11]. For this reason, an integrative index that can evaluate multiple essential functions, such as f/Vt ratio and the compliance, rate, oxygenation and pressure (CROP) index [11] have been introduced in the literature.

Unfortunately, the CROP index did not present the same accuracy as f/Vt ratio and its area under the ROC curves was no more than 0.78 [11]. In our study, the new integrative IWI presented the area under the ROC curve of 0.96 and f/Vt of 0.85. Our hypothesis to justify the difference between the accuracy of CROP index and that of IWI is that in the first one, the MIP (a criterion that is considered to be less accurate) [11,21] was included, and in IWI, f/Vt ratio (an index that is considered to be one of the most accurate) [11,16] was included. We think that MIP inclusion in CROP index impairs its accuracy.In a prospective study by Aboussouan and colleagues [12] the time to weaning evaluated in 113 consecutive patients was shorter in those that presented the Cst,rs of more than 20 ml/cmH2O, a normal creatinine level (0.

6 to 1.4 mg/dl) and a f/Vt ratio of 105 breaths/min/liter or less. Our results corroborated the findings of Entinostat the study by Aboussouan and colleagues [12], once Cst,rs and f/Vt ratio are included in the IWI equation and presented the second and the third largest areas under the ROC curves (0.85 and 0.83, respectively).