Tracheal aspirate lecithin/sphingomyelin ratios as predictors of recovery from respiratory distress syndrome.

In thirty infants with severe respiratory distress syndrome who required endotracheal intubation, serial tracheal aspirate lecithin/sphingomyelin ratios were determined. There was 19 survivors and 11 nonsurvivors. The L/S ratios were plotted as a function of postnatal age; the ratios of the survivors demonstrated a significant increase between 24 and 96 hours. Nonsurvivors did not show this change. There was a significant difference on Days 3, 4, and 5 between survivors and nonsurvivors in the percentage of L/S ratios greater than 2.5. Daily mean L/S ratios correctly identified the outcome of 23 of 24 infants alive on Days 4 and/or 5 and were a more accurate prediction of survival than a single L/S ratio. The changes in the L/S ratios of the tracheal aspirates were not related to gestational age.