Research

Does taking endurance into account improve the prediction of weaning outcome in mechanically ventilated children?

Odile Noizet¹ , Francis Leclerc¹ , Ahmed Sadik¹, Bruno Grandbastien², Yvon Riou³, Aimée Dorkenoo¹, Catherine Fourier¹, Robin Cremer¹ and Stephane Leteurtre¹

¹Paediatric Intensive Care Unit, University Hospital of Lille, Rue Eugène Avinée, 59037 Lille Cedex, France

²Department of Epidemiology, University Hospital of Lille, Rue Eugène Avinée, 59037 Lille Cedex, France

³Department of Respiratory Physiology, University Hospital of Lille, Rue Eugène Avinée, 59037 Lille Cedex, France

author email corresponding author email

Critical Care 2005, 9:R798-R807doi:10.1186/cc3898

Published:	16 November 2005

See related commentary http://ccforum.com/content/9/6/651

Abstract

Introduction

We conducted the present study to determine whether a combination of the mechanical ventilation weaning predictors proposed by the collective Task Force of the American College of Chest Physicians (TF) and weaning endurance indices enhance prediction of weaning success.

Method

Conducted in a tertiary paediatric intensive care unit at a university hospital, this prospective study included 54 children receiving mechanical ventilation (≥6 hours) who underwent 57 episodes of weaning. We calculated the indices proposed by the TF (spontaneous respiratory rate, paediatric rapid shallow breathing, rapid shallow breathing occlusion pressure [ROP] and maximal inspiratory pressure during an occlusion test [Pi_max]) and weaning endurance indices (pressure-time index, tension-time index obtained from P_0.1 [TTI₁] and from airway pressure [TTI₂]) during spontaneous breathing. Performances of each TF index and combinations of them were calculated, and the best single index and combination were identified. Weaning endurance parameters (TTI₁ and TTI₂) were calculated and the best index was determined using a logistic regression model. Regression coefficients were estimated using the maximum likelihood ratio (LR) method. Hosmer–Lemeshow test was used to estimate goodness-of-fit of the model. An equation was constructed to predict weaning success. Finally, we calculated the performances of combinations of best TF indices and best endurance index.

Results

The best single TF index was ROP, the best TF combination was represented by the expression (0.66 × ROP) + (0.34 × Pi_max), and the best endurance index was the TTI₂, although their performance was poor. The best model resulting from the combination of these indices was defined by the following expression: (0.6 × ROP) – (0.1 × Pi_max) + (0.5 × TTI₂). This integrated index was a good weaning predictor (P < 0.01), with a LR⁺ of 6.4 and LR⁺/LR^- ratio of 12.5. However, at a threshold value <1.3 it was only predictive of weaning success (LR^- = 0.5).

Conclusion

The proposed combined index, incorporating endurance, was of modest value in predicting weaning outcome. This is the first report of the value of endurance parameters in predicting weaning success in children. Currently, clinical judgement associated with spontaneous breathing trials apparently remain superior.