Comparison of Effectiveness of Nasal CPAP and Nasal IMV in Early Rescue Surfactant Treatment in Preterm Infants

Inclusion Criteria: \- Gestational age 26-32 weeks The criteria for failure were met by at least 1 of the following: * pH: 7.10 and PaCO2: 70 mm Hg * Recurrent apnea with \>3 episodes (Prophylactic caffeine were used in all infants) * Single episode of apnea that required bag-and-mask ventilation * PaO2: 50 mmHg with a fraction of inspired oxygen of \>0.5. Exclusion Criteria: * Major congenital anomalies * Presence of cardiovascular instability * Intubation at admission to the NICU * Consent not provided or refused