1. Pediatrician, Pediatric Intensive Care Unit, Hospital de Clínicas, Faculdade

Objective: To evaluate the association between time on mechanical ventilation and anthropometric, clinical and pulmonary function variables, measured early, in infants on invasive mechanical ventilation with acute respiratory failure due to viral bronchiolitis, and the temporal progression of variables with significant correlations. Methods: Twenty-nine infants admitted to the pediatric intensive care unit of UNICAMP university hospital were studied. Acute viral bronchiolitis was defined according to clinical and radiological criteria. Children with chronic diseases and those that were hemodynamically unstable were excluded. All measurements were taken after 24 to 72 hours mechanical ventilation, using volumetric capnography and blood gas analysis. Mechanical ventilation time was divided into: < 7 days and> 7 days. Association between time on mechanical ventilation and the variables analyzed was determined by Spearmans Correlation Coefficient (rs). Results: Time on mechanical ventilation showed a significant positive correlation with PaCO2 (rs = 0.45, p = 0.01) and ventilation index (rs = 0.51, p = 0.005), and a negative correlation with pH (rs = -0.40, p = 0.03). Ventilation indices of 37, measured between day one and day five, was associated with a progressively increased risk of more than 7 days on mechanical ventilation (OR = 4.2 on the first day to 15.71 on the fourth day). Conclusions: Ventilation index, PaCO2 and pH, measured early, were associated with prolonged mechanica