Lung compliance and alveolar expansion in the artificially ventilated premature newborn rabbit after maternal treatment with ambroxol.

Premature newborn rabbits were delivered on day 27 of gestation, with or without antenatal treatment with ambroxol (50 mg/kg/day in maternal injections, on days 24-26). The animals were tracheostomized, kept in body plethysmographs at 35 degrees C, and ventilated artificially for 10 min with 100% oxygen, insufflation pressure 30 cm H2O, frequency 40/min, and varying inspiration time (20, 40, 60, or 80%). Lung-thorax compliance increased with inspiration time in both ambroxol-treated animals and controls, but there was no difference in compliance between treated and non-treated litters. Alveolar expansion, evaluated morphometrically in histological sections, was enhanced in ambroxol-treated animals ventilated with prolonged inspiration phase (60 or 80%); such a difference was not found in the on-treated group. This suggests that antenatal treatment with ambroxol might have a stimulating effect on the synthesis and/or release of factors improving alveolar stability in the premature lung.