Inclusion Criteria:  Infants born equal or earlier than 32 weeks of gestational age admitted in the Neonatal Intensive Care Unit. Parental consent signed. Less than or equal to 48 hours postnatal age.  Exclusion Criteria:  Infants with known major congenital anomalies (eg. congenital upper airwayobstruction, congenital lung anomaly, severe pulmonary hypoplasia, hydrops,neuromuscular diseases, chromosomopaties) Infants with poor prognosis and risk of imminent death Infants who have received the first dose of surfactant before of the enrolment to the study.