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Serial Weekly Measurements of the Timed Inspiratory Effort Index Can Predict Successful Prolonged Weaning
Bruno Leonardo da Silva Guimarães1, Leonardo Cordeiro de Souza2, Fernando Silva Guimarães3
1Medical Science Post-graduation Program, Universidade Federal Fluminense, Niteroi, Brazil.
Background:
Patients who require prolonged weaning from mechanical ventilation represent a major challenge in intensive care, and the timed inspiratory effort (TIE) index has been shown to be a clinically valuable tool to predict weaning success.
Objective:
To evaluate whether weekly serial measurements of the TIE index can predict the success in prolonged weaning.
Methods:
A prospective observational study in which the subjects who started the weaning process off mechanical ventilation underwent weekly measurements of the TIE index. The area under the receiver operating characteristic curve was used to evaluate the accuracy of the TIE index as a predictor of weaning success. A multivariate Cox regression model was developed to test the association of TIE index values of ≥1.0 cm H2O/s with a failure of weaning.
Results:
Seventy subjects were selected. Their median (IQR) age was 72 (62-78) y, the median (IQR) duration of mechanical ventilation was 17.5 (14-28) d, and the median (IQR) APACHE II (Acute Physiology and Chronic Health Evaluation) II score was 28 (24-31). Thirty-five of the 70 subjects (50%) died, 22 of them after successful weaning. A total of 224 tests were performed over 56 d. The area under the receiver operating characteristic curve of the TIE index was 0.93. In the analysis of the probability of success during the follow-up (Kaplan-Meier method), a significant difference was obtained in favor of those with a TIE index of ≥ 1.0 cm H2O/s (53% vs 32%, P = .030). In the multivariate Cox regression analysis, values of the TIE index ≥ 1.0 cm H2O/s revealed an inverse, strong, and independent association with failure (hazard ratio 0.36, 95% CI 0.15-0.91; P = .030). The following variables were also found to have an independent but direct association with failure: age and length of time before weaning.
Conclusions:
When measured weekly, a TIE index of ≥1.0 cm H2O/s was a good predictor of success in subjects who required prolonged weaning in our hospital.
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