Prolonged ventilation of the premature newborn rabbit after treatment with natural or apoprotein-based artificial surfactant.

Premature rabbit neonates (gestational age 27 days) were treated at birth with natural surfactant purified from chloroform extracts of porcine lung lipids either by acetone precipitation (Surfactant CK, n = 10) or liquid gel chromatography (Curosurf, n = 22). Another group of animals received artificial surfactant "reconstituted" from isolated low molecular weight (less than or equal to 15 K) apoproteins and synthetic dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) (Aposurf, n = 10). The phospholipid concentrations of the preparations were adjusted to provide the same individual dose of DPPC for each group of treated animals (3 or 4 mg). In comparison with untreated controls from the same litters, there was a 4-7-fold enhancement of lung-thorax compliance in all groups of surfactant-treated animals during a 3-h period of artificial ventilation. The average initial (20 min) compliance value was lower in the Aposurf-treated group than in animals receiving natural surfactant preparations, but the difference between the groups gradually diminished and was no longer statistically significant during the 2nd and 3rd h of artificial ventilation. Judged from the fall in tidal volume during ventilation with a short expiration phase (0.17 instead of 0.75 s), the apoprotein-based artificial surfactant was also less effective in stabilizing the lungs. A similar conclusion could be drawn from data on alveolar expansion in histological sections, evaluated by automated image analysis.(ABSTRACT TRUNCATED AT 250 WORDS)