Tissue oxygenation and splenic erythropoiesis during chronic hypoxia and hypercapnia.

Tissue (gas pocket) oxygen levels and erythropoietic activity were monitored in groups of rats chronically exposed to hypoxia (70 Torr PIO2), hypercapnia (60 Torr PICO2), or a combination of the two conditions. Arterial gas tensions and pH were also measured. Overall condition of the animals was assessed by comparison of growth rates with pair-fed controls. Hypoxic-hypercapnic pocket PO2 values (24-40 Torr) were similar to normoxic-normocapnic values (28-37 Torr), but greater than in hypoxia-normocapnia, and less than in normoxia-hypercapnia. Erythropoietic activity during hypoxia-hypercapnia ceased and the rats had a growth rate significantly below that of other groups. While chronic CO2 does increase tissue (pocket) oxygenation to near normal levels, probably due to increased ventilation and subsequently PaO2, the hypoxic-hypercapnic rats evidenced greater detrimental effects than did rats in hypoxic or hypercapnic environments.