The term bronchopulmonary dysplasia (BPD) was initially introduced to describe chronic pulmonary changes that occurred in certain premature infants following respiratory distress syndrome (RDS).1 Subsequently, BPD has been recognized as a sequela of other forms of severe lung disease in newborn infants. Bronchopulmonary dysplasia currently is responsible for the prolonged hospitalization of 10% to 20% of neonates who survive with the aid of mechanical ventilatory support.2,3 Lung pathology in this condition consists of multiple emphysematous areas alternating with atelectasis, bronchiolar mucosal hyperplasia and metaplasia, peribronchial smooth-muscle hypertrophy, and interstitial fibroblast proliferation.1 Clinically, BPD is characterized by chronic respiratory failure and persistent pulmonary roentgenographic abnormalities. The latter may vary from faint, diffuse opacification to cystic emphysematous changes with air trapping, while functional impairment varies from mild carbon dioxide retention to the need for months of mechanical ventilatory support and Proposed Pathogenesis Factors Involved Susceptible Host Acute Lung Injury