se known as bronchopulmonary dysplasia. This pulmonary complication ranks as a leading cause of mortality. During the 1980s, approximately 3,500 deaths were annually attributed to RDS in the United States alone (Morris, 1990, pp. 547-549). Indeed, RDS is responsible for about one fourth of all neonatal mortality (Cosmi, 1992, pp. 283-286).
Pulmonary surfactant is produced in the lungs' alveoli by type II pneumocytes. This liquid normally forms a 1-10 (m thick layer coating the pulmonary airways and air spaces (Espinosa, Shapiro, Fredberg, & Kamm, 1993, pp. 2028-2037). Its composition by weight is 85 percent phospholipid, 10 percent protein, and 5 percent neutral lipids. Approximately 40 percent of pulmonary surfactant phospholipid consists of saturated dipalmitoyl phosphatidylcholine; whereas, 20 percent is unsaturated phosphatidylcholine. The remaining 20 percent includes phosphatidylglycerol, phosphatidylinositol, phosphatidlyserine, sphingomyelin, and phosphatidylethanolamine (Morris, 1990, pp. 547-549).
Within the type II pneumocyte, these components assemble complexly in specialized vesicles known as lamellar bodies. Specific hormonal and physiologic signals cause lamellar body secretion into the airway. Their lipid layers then unravel to form tubular myelin. This produces a lattice of phospholipid and protein which adsorbs and spreads to form a "monolayer at the alveolar hypophase-air interface" (Morris, 1990, pp. 547-549). Dipalmitoyl phosphatidylcholine is the phospholipid most responsible for surfactant's ability to reduce surface tension. However, by itself, dipalmitoyl phosphatidylcholine cannot respread and adsorb after compression. Such actions require certain apopro
...