Hypoxic pulmonary steady-state diffusing capacity for CO and cardiac output in rats born at a simulated altitude of 3500 m

Summary In rats born in the low pressure chamber from sea level parents a higher hypoxic steady-state pulmonary diffusing capacity for CO was found as compared with controls of similar body weight. This difference could be explained by a difference in age or by an increase of blood O₂ capacity. There was no difference in alveolar ventilation and alveolar-arterial O₂ pressure differences, a lower cardiac output, no difference in arterial O₂ tension, no difference in arterial O₂ content but a decreased mixed-venous O₂ content as compared with control rats measured at hypoxia. A shift of the standard blood O₂ dissociation curve to the right was found in the simulated high altitude exposed rats. Calculated mixed-venous O₂ pressure was not altered in these rats; since arterial O₂ pressure was the same no difference in mean tissue capillary O₂ pressure may be presumed as compared with control animals. The results suggest that the first generation of rats exposed to simulated high altitude for their whole life is not only less adapted than animals exposed in their youth (as described in previous work) but that the ability to promote the O₂ transport in time of need in rats born in the low pressure chamber is probably even inferior to that of the controls.