Effect of Continuous Positive Airway Pressure Delivered by Two Different Modalities on Breathing Pattern in Preterm Infants

Inclusion Criteria: * Birth weights ≤ 1500g * Gestational age less than 32 week * Stable on nasal continuous positive airway pressure (CPAP) of 5-6cmH20 support for at least 48 hours * Treated with methylxanthines for apnea of prematurity * In less than 35% oxygen Exclusion Criteria: * Congenital and acquired problem of the gastrointestinal tract * Phrenic nerve injury and/or diaphragm paralysis * Esophageal perforation/tracheoesophageal fistula * Congenital/acquired neurological deficit and/or seizures * Hemodynamic instability * Congenital heart disease (including symptomatic patent ductus arteriosus) * Undergoing treatment for sepsis or pneumonia * Use of muscle relaxants, narcotic analgesics, or gastric motility agents * Congenital anomalies of respiratory tract (e.g. CCAM) * Infants requiring more than 35% oxygen * Infants with facial anomalies * Infants with pneumothorax and/or pneumomediatinum * Infants in the immediate postoperative period * Infants with significant gastric residues and vomiting