Falta de acurácia dos índices ventilatórios para predizer sucesso de extubação em crianças submetidas a ventilação mecânica

Abstract

OBJECTIVES: Between 10 percent and 20 percent of children submitted to mechanical ventilation in the pediatric intensive care unit present extubation failure. Several ventilatory indexes have been proposed to predict extubation failure. The aim of this study was to analyze the accuracy of these indices in predicting successful extubation in children and to evaluate these variables according to the age of the patient and the specific disease. METHODS: A prospective observational study including all children submitted to mechanical ventilation in a Brazilian referral pediatric intensive care unit was conducted between August 2007 and August 2008. The tidal volume, maximal negative inspiratory pressure, rapid shallow breathing index and other ventilatory indexes were measured before extubation. These variables were analyzed according to the extubation outcome (success or failure) as well as age and specific disease (post cardiac surgery and acute viral bronchiolitis). RESULTS: A total of 100 patients were included (median age of 2.1 years old). Extubation failure was observed in 13 percent and was associated with lower weight (10.3+8.1 Kg vs. 5.5+2.4 Kg; p=0.01). We also evaluated the relationship between extubation failure and the main cause indicating mechanical ventilation: children who had received cardiac surgery (n=17) presented an extubation failure rate of 29.4 percent with a relative risk of 4.6 (1.2-17.2) when compared to children with acute viral bronchiolitis (n=47, extubation failure rate of 6.4 percent). The maximal inspiratory pressure was the only physiologic variable independently associated with the outcome. However, this variable showed a wide dispersion and lack of accuracy for predicting extubation success (sensitivity of 82 percent and specificity of 55 percent for a cut point of -37.5 cmH2O predicting successful extubation). The same wide dispersion was observed with other ventilatory indexes. CONCLUSION: The indexes ...