HYPEROXIA-INDUCED AIRWAY HYPERREACTIVITY IN NEONATAL GUINEA-PIGS IS NOT INFLAMMATION DEPENDENT

A high percentage of neonatal human infants exposed to prolonged assis ted ventilation with supplemental oxygen develop airway hyperreactivit y. In order to demonstrate that this effect could be replicated in gui nea pigs, 4-day-old pups were exposed either to air or 70% oxygen for 4 days. Nine days later each group was subjected to a histamine challe nge and differences in respiratory mechanics were determined. The airw ay pressure response oi the hyperoxia group was significantly greater and the respiratory compliance was significantly less than those of th e air-exposed pups. The role of inflammation was assessed both by anal ysis of bronchoalveolar lavage fluid (BAL) and by histopathology on an imals I day after discontinuation of the exposures. There were no diff erences between the two groups in BAL protein, total cell count, or th e white blood cell (WBC) differential. Histology did not show any evid ence of a difference between the two groups in inflammation or in airw ay remodeling.