Effects of shifts in hemoglobin-oxygen affinity during hypoxia

To investigate the possibility that the influence of hemoglobin-oxygen affinity on tissue oxygenation may be reversed in severe hypoxia, 16 anesthetized rabbits with chronically-implanted tissue oxygen electrodes were ventilated with 12% oxygen and subjected to 100 ml exchange transfusions with high, low, or normal affinity rabbit blood. Despite the widely divergent in vivo P50 values produced, significant differences in tissue oxygen levels were not observed among the three groups following exchange transfusions. During subsequent normoxia, more complete recovery of tissue oxygen was apparent in the low affinity group. This study emphasizes the need for further definition of the influence of hemoglobin-oxygen affinity on the functions of individual organs.