PULMONARY HYPERTENSION RESULTING FROM OXYGEN EXPOSURE
NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA WARMINSTER
Pagination or Media Count:
Rats exposed to an atmosphere of 95 to 100 oxygen at a partial pressure of 516 mm Hg for periods of 30 days showed no obvious abnormalities. At the end of this exposure they were removed from the system and anaesthetized. Aortic and intratracheal pressures were measured by standard direct procedures in response to breathing air and oxygen and to transient increases in intratracheal pressure. Compared with the results in unexposed rats, the experimental animals showed an increase in pulmonary arterial pressure PAP and a decrease in mean aortic pressure. The increase in aortic pressure caused by breathing oxygen which was present in the unexposed animals could be elicited in the exposed rats. The increase in PAP is attributed to structural changes in the pulmonary vasculature associated with oxygen exposure and it is postulated that an increase in vascular resistance is responsible for a decreased cardiac output, giving rise to the systemic hypotension. Whereas mean aortic pressure fell during increased intratracheal pressure, mean pressure from the right heart did not change, suggesting that the right ventricle empties itself less well against the increased pressure.