Pulmonary fluid balance in the human newborn infant

At birth, the infant's lungs must be cleared of fetal lung fluid. This process is mediated through the activation of airway epithelial sodium channels (ENaC). In animals, ENaC is considered crucial for postnatal pulmonary adaptation. In humans, postnatal ENaC expression is gestational age dependent and its activity, measured as nasal potential difference, correlates with lung compliance. It is therefore likely that in the human newborn infant ENaC is also important for physiologic postnatal adaptation. Low pulmonary expression or activity of ENaC in the perinatal period may cause delayed clearance of lung fluid and thereby contribute to development of respiratory distress in both term and preterm infants.