PURPOSE: Our objective was to assess whether SpO₂/FiO₂ (SF) ratio could be a useful NIV outcome predictor in children with acute respiratory failure (ARF) and tried to develop a predictive model of NIV failure. METHODS: Prospective, observational, multicenter study. Episodes of ARF-fulfilling inclusion criteria from 15 January 2010 to 14 January 2011 were treated with NIV according to a pre-established protocol...