Surface tensions in the lungs of hypoxic guinea pig fetuses aspirating amniotic fluid

Eighty guinea pig fetuses, with gestational ages between 53 and 65 days were randomly assigned to 4 experimental categories, 2 of which underwent hypoxic stress in utero at each age level. An air-breathing and a non-air-breathing specimen aspirated quantities of amniotic fluid. There were an air-breathing and an apneic premature fetus which had never aspirated amniotic fluid. One would expect aspirators to demonstrate increased surface tensions in extracted surfactant and the nonaspirators would not. Likewise, one should find differences in respiratory distress and longevity between the 2 air-breathing groups. Previous studies16 have shown clear anatomical differences in each of these fetal lung types in terms of alveolar mensuration and many other histological characteristics. Significant changes were not seen in fetal lung surface tension values as a result of the experimentally induced “intrauterine lung lavage.” Even short episodes of intrauterine stress had deleterious effects upon extrauterine longevity and respiratory function following delivery of the air-breathing groups.