To compare the effects of two natural surfactant preparations [term fetal rabbit surfactant (FRS) and adult rabbit surfactant (ARS)] and two commercially available preparations [apoprotein-based Survanta® (S) and totally synthetic Exosurf® (E)] on lung water clearance in preterm rabbits following prolonged ventilation (3 hr), pups were delivered at 27 days gestation, treated with one of the surfactant preparations (FRS, ARS: 1250μg phospholipid per pup; S,E: according to manufacturer's directions), ventilated with 100% oxygen for 180 min, sacrificed and their extravascular lung water (EVLW) (ml H2O per g dry lung) determined. EVLW content was also determined on pups which did not survive the 180 min ventilation period. Untreated, ventilated pups served as controls.

None of the untreated pups survived beyond 60 min and EVLW (9.37 ± 0.68, n = 12) was not significantly different from the unventilated 0 hr controls (9.24 ± 0.80, n = 12). All treated pups survived beyond the first 60 min but not necessarily for the full 3 hr. For all treatment groups, there was no change in EVLW in pups which survived less than 2 hr of ventilation, but significant decreases with all treatments except ARS in those which survived more than 2 but less than 3 hr. In pups which survived to 3 hr EVLW was further decreased in all groups. The lowest value was for the S treatment group (6.43 ± 0.54, n = 4) followed by E (6.57 ± 0.95, n = 5), FRS (7.04 ± 0.78, n = 8), then ARS (7.77 ± 1.12, n = 8).

There were significant differences in the survival rates among the different treatments with less than a 25% survival rate to 3 hr for S and E, 40% for ARS and approximately 60% for FRS.

These results indicate a progressive decrease in EVLW and prolonged survival with each of the surfactants but suggest the greater survival rate with FRS may be due to some superior but as yet identified property of this material which contributes to this response. (Supported by Grace Maternity Hospital Foundation).