Low oxygen exposure does not cause pulmonary injury in the newborn rat

Background: Two recent studies have suggested that low levels of supplemental inspired oxygen may cause lung injury in preterm infants. Aims: To assess lung injury of newborn rats exposed to 14 days of low-level variation of oxygen. Study design: Four groups were compared with 12 animals per group and 4 lung sections per animal. These were, a control group raised in room air and three groups raised in levels of inspired oxygen fluctuating around the following mean values: group Lo (mean FiO₂ 0.179), group N (mean FiO₂ 0.213), and group Hi (mean FiO₂ 0.247). The degree of oxygen variability was identical for each group. Lungs were inflated at 20 cm H₂O, fixed and stained with H and E and Millers Elastin. Subjects: Sprague Dawley albino newborn rats. Outcome measures: Random alveolar areas were studied and analysed using imaging software to assess total amount of tissue and elastin, number of secondary septa, and mean linear intercept. Results: There were no significant differences between the three experimental oxygen groups and the control group in terms of lung / body weight ratio and the measured markers of lung development. Conclusion: We conclude that low-level oxygen supplementation during early lung development does not affect alveolar development in the newborn rat.