Modification of alveolar hyperoxia induced pulmonary vasodilatation by indomethacin

Decrease in pulmonary vascular resistance was observed in neonatal minature pigs breathing 100% O2 or 95% O2:5% CO2. The pulmonary vasodilator response to hyperoxia ventilation was reduced by indomethacin in the intact animal and in the isolated perfused lung preparation. In the isolated perfused lung preparation, it was also shown that lung alveolar pO2 rather than pulmonary arterial pO2 was responsible for the pulmonary vasodilation. The study suggests that alveolar hyperoxia induced decrease in pulmonary vascular resistance may be mediated in part by release of prostaglandins. The relevance of this study with oxygen therapy in newborn infants is also discussed.