Neonatal chronic lung disease in the post-surfactant era.

This is a brief review of neonatal chronic lung disease, sometimes called the 'new bronchopulmonary dysplasia (BPD)'. The clinical, radiographic and pathological features of this condition have changed considerably in recent years because of major advances in perinatal care, including widespread use of antenatal glucocorticoid therapy, postnatal surfactant replacement and improved respiratory and nutritional support. Authentic animal models, featuring lengthy mechanical ventilation of surfactant-treated, premature neonatal baboons and lambs, have provided important insights on the pathophysiology and treatment of this disease. Lung histopathology after 2-4 weeks of positive-pressure ventilation with oxygen-rich gas results in failed formation of alveoli and lung capillaries, excess disordered elastin accumulation, smooth muscle overgrowth in small pulmonary arteries and airways, chronic inflammation and interstitial edema. Treatment interventions that have been tested in these animal models include nasal application of continuous positive airway pressure, high-frequency mechanical ventilation, inhaled nitric oxide and retinol. The challenge now is to improve understanding of the molecular mechanisms that regulate normal lung growth and development, and to clarify the dysregulation of lung structure and function that occurs with injury and subsequent repair so that effective treatment or prevention strategies can be devised and implemented.