ABSTRACT
The physiologic aberration that causes abnormal alveolar surface tension in the lungs of infants with RDS was investigated by measuring relative quantities of surfactant-related phospholipids in tracheal effluent from infants with RDS. A preliminary study in premature lambs demonstrated that the percent DSPC (molar ratio of DSPC to total phospholipid) is similar in tracheal effluent and lung lavagate. The percent DSPC in tracheal effluent from human infants with RDS was similar to the percent DSPC in effluent from non-RDS infants on the first day of life (47.4% ± 2.9 vs 46.7% ± 1.2), and remained constant during the first 8 days of life. Phosphatidylglycerol (PG) was universally absent in effluent from RDS infants on the first and second day of life but appeared by the eighth day of life in all infants who remained intubated. PG was present in tracheal effluent from only 10 of 16 non-RDS infants on the first day of life. These findings suggest that, in regard to the surface-active lecithin content, surfactant from RDS infants is qualitatively normal and that the absence of RDS is not dependent on the presence of PG.
