Helmet Continuous Positive Airway Pressure Support for Severe Bronchiolitis in PICUs

Binary randomized peep level of Helmet CPAP (1-0). The first patient enrolled will be assign to treatment 1 (10 cmH2O peep level), independently from its BSS. The following patients enrolled will be assign to treatment 0 (5 cmH2O peep level), and consecutively up to 25 patients at least. * 10 cmH2O peep, 50 L/min gas flow, fraction of inspired oxygen (FiO2) 0.5 on PICU admission (random 1) * 5 cmH2O peep, 50 L/min gas flow, FiO2 0.5 on PICU admission (random 0) If clinical and respiratory worsening, reduction of pH or partial oxygen arterial pressure (PaO2)/FiO2 occurs in the following first hour after Helmet CPAP treatment start, patients enrolled will receive endotracheal intubation, full face mask non invasive ventilation or higher peep level treatment (7.5-10 cmH2O) according to clinical evaluation, if necessary. In investigator\'s experience, early worsening of severe bronchiolitis in PICU in the first hour of Helmet CPAP treatment with 10 cmH2O peep level leads to endotracheal intubation.