The accuracy, likelihood ratio, probability of weaning success when test is positive and probability of weaning success selleck chem Romidepsin when test is negative of the indexes utilized to predict the weaning outcome in the prospective-validation data set are shown in Table Table2.2. IWI presented the highest SE (0.97), SP (0.94), PPV (0.99), NPV (0.86), DA (0.97) and likelihood ratio of positive test (16.05) besides the lowest likelihood ratio of negative test (0.03). Moreover, IWI presented the highest probability of weaning success when the test is positive (0.99) and the lowest probability of weaning success when the test is negative (0.14).

Table 2Accuracy, likelihood ratio, probability for weaning success when test is positive and probability for weaning success when test is negative of the indexes used to predict the weaning outcome in the prospective-validation data setThe area under the ROC curves for IWI was significantly higher than the corresponding area for the f/Vt ratio (0.96 �� 0.02 �� 0.85 �� 0.04 respectively; P = 0.003) and also significantly higher than the other indexes. The area under the ROC curves for all the indexes are shown in Table Table33 and the comparisons among the area under the ROC curves for all the indexes in the prospective-validation data set are shown in Table Table4.4. Selected most significant ROC curves, that is, for IWI, f/Vt ratio, Cst,rs and Vt, are shown in Figure Figure11.Figure 1Receiver operator characteristic curves for the indexes evaluated in the prospective validation data set. f/Vt ratio = frequency to tidal volume ratio; IWI = integrative weaning index; Vt = tidal volume.

Table 3Area under the receiver operator characteristic curves and standard error for each index in the prospective-validation data setTable 4Comparison of the areas under the receiver operator characteristic curves (P value for the two-tailed test)DiscussionThe purpose of weaning indexes is to identify patients who can be successfully weaned. Clinical judgment is not enough to predict weaning outcome accurately [5,8] (50% PPV and 67% NPV) [5,22]. The search for better indexes or parameters that can best predict weaning outcome has been attempted by most international weaning researchers. SBT were introduced lately showing a positive weaning predictive value of 85% [5]. However, 15% of the patients who can complete an SBT require reintubation in the following 48 hours after extubation.

This indicates that there are patients that tolerate short SBTs but not longer ones. Although SBT represented an advancement, it is not totally satisfying. In the study by Frutos-Vivar and colleagues [23], extubation failure occurred in 121 of the 900 patients GSK-3 (13.4%) that completed the SBT. Among the routinely measured clinical variables, f/Vt ratio, positive fluid balance 24 hours prior to extubation, and the presence of pneumonia at the beginning of mechanical ventilation were the best predictors of extubation failure [23].