Scoring of surface parameters of physiological relevance to surfactant therapy in respiratory distress syndrome

The Wilhelmy balance was used for in vitro testing of surface parameters of surfactants used for respiratory distress syndrome therapy. Two commercial protein-free surfactants, ALEC and Exosurf, were compared with pure forms of the three main phospholipids in natural surfactants, dipalmitoyl phospha tidylcholine (PC), phosphatidylglycerol (PG), and phosphatidylethanolamine (PE), and their binary mixtures, PC with PE and PG each in the ratio 2:3. S urface excess films (15 Angstrom (2)/molecule) were compressed at 1.2 cycle s/min past collapse to a compression ratio of 4:1. The maximum surface pres sure, spreading time, compressibility, respreading ratio, recruitment index , and hysteresis area were compared. A consolidated list of criteria for se lection of suitable surfactants was compiled from the literature. A relativ e scoring system was devised for comparison based on these criteria. PC/PG (2:3) performed the best as it fulfilled all the criteria and obtained the highest relative score. Exosurf also performed well, except on the respread ing criterion. ALEC and PC/PE were equivalent in their performance and perf ormed well, except on two criteria: hysteresis area and recruitment index. Thus the scoring system proposed here proved valuable to rate the overall e fficacy as well as relative merits of surfactant formulations.