Hyperoxia Effects on Pulmonary Pressure: Volume Characteristics and Lavage Surfactant Phospholipid in the Newborn Rabbit

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Abstract
The effect of hyperoxia (> 95%) on surfactant phospholipid recovered by lavage and pulmonary pressure:volume characteristics was studied in rabbits exposed from birth through 4 days of life. Decreased surfactant phospholipid (μg/mg dry lung weight) in the airways was observed as early as 6 h and persisted through 96 h of life in hyperoxiaexposed animals. The composition of lavage phospholipids and fatty acid profile of phosphatidylcholine was not altered by hyperoxia. Pressure:volume analysis revealed a decrease in maximum lung distensibility (V30, volume at 30 cm pressure) at 48 and 96 h and a decrease in inflation compliance (P30i, pressure on inflation to 30% V30) at 48 h of life in newborn pups exposed to hyperoxia. Pressure:volume changes in both male and female newborns were observed with hyperoxia exposure. However, only female pups exhibited a decrease in lavage phospholipid content as measured at 48 h. These data suggest that the newborn rabbit surfactant system is susceptible to oxygen toxicity. In addition to age-related differences, sex differences may exist with regard to susceptibility to hyperoxia. Subtle alterations in the surfactant system at this critical time of rapid lung development could have long lasting effects on lung function.