Relationship between blood-oxygen affinity and blood volume.

The hypothesis was tested that total blood volume (TBV) is correlated with hemoglobin oxygen affinity. Intraspecifically Hb-O2 affinity was manipulated in rats using NaOCN. Interspecifically the hypothesis was evaluated using data gathered from the literature. Both intra- and interspecifically TBV increased with increasing hemoglobin oxygen affinity (delta TBV/delta P50 = -1.18). Intraspecifically decreases in P50 were associated with an increase in red blood cell mass and hematocrit. Interspecifically plasma volume had an inverse relationship with Hb-O2 affinity (delta TBV/delta P50 = -1.10) and hematocrit showed no changes. These data suggest that an increased blood volume may be part of the mechanism explaining the inverse correlation between P50 and hypoxic tolerance.