LISA vs INSURE in the Treatment of Respiratory Distress Syndrome in Preterm Infants

Inclusion Criteria: * Gestational age (GA) less than 32 weeks * diagnosis of RDS. The diagnosis of RDS will be based on clinical manifestations (Progressive dyspnea, nasal flaring and or grunting), chest X-ray findings and need for noninvasive ventilation support(fraction of inspired oxygen\>40％) in 6 hours after birth * informed parental consent has been obtained Exclusion Criteria: * severe RDS have been treated with endotracheal intubation,surfactant and mechanical ventilation * major congenital malformations or complex congenital heart disease * Pulmonary hemorrhage * Cardiopulmonary failure * septicemia, Intraventricular Hemorrhage (IVH, ≥ Grade Ⅲ), and Congenital genetic metabolic disease * transferred out of the NICUs(neonatal intensive care units) with surgical treatment or other intervention