This randomized controlled trial will include babies with mild-to-moderate RDS, between 4 to 48 hours of age, with gestational age 29 0/7 to 36 6/7 weeks, treated with NCPAP ≥ 5 cm H2O and FiO2 between 0.30 and 0.60 for at least 2 hours to maintain SpO2 88-95%, and informed consent. Exclusion criteria are weight < 1000 g, airway anomalies, pulmonary air leaks, and craniofacial and cardiothoracic malformations.