NHFOV vs NIPPV vs nCPAP in Preterm Infants With Respiratory Distress Syndrome

This will be a prospective, multi-center, three-arms,parallel, randomized, controlled trial with a superiority design,conducted in China. The investigators conduct this multi-centre, randomized, controlled trial to test the hypothesis that NHFOV is more effective than nCPAP or NIPPV in the treatment of respiratory distress syndrome (RDS) in infants with a gestational age of less than 30 weeks or a birth weight of less than 1500g when used as a primary noninvasive ventilation (NIV) mode.