Gastro-esophageal reflux and aspiration is a common problem in premature infants receiving mechanical ventilation. Pepsin measured in tracheal aspirate (TA) emerged as a specific marker for aspiration. The objective of this study is to examine if TA pepsin will change when ventilated premature infants are positioned in two different positions; on their back vs. on their right side.

Inclusion Criteria:

• Infants born between 28 and 32 weeks gestational age
• postnatal age > 72 hours
• tracheally intubated and receiving conventional mechanical ventilation
• feeding enterally more than 20 ml per day.

Exclusion Criteria:

• neurological insult in the form of perinatal asphyxia (pH <7, base deficit more than 12, Apgar score at < 3 at 5 minutes of life), intracranial hemorrhage grades 3 or 4 at 72 hours of age or periventricular leucomalacia
• major congenital anomalies, or gastrointestinal anomalies such as tracheoesophageal fistula, or necrotizing enterocolitis ,
• receiving xanthine derivatives, H2 blockers, prokinetics, proton pump inhibitors or sedation