Altered Haem—Haem Interaction and Tissue-Oxygen Supply: A Theoretical Analysis

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Abstract
On the basis of its assumed invariance, the heme-heme interaction or shape of the HbO2 dissociation curve is frequently ignored when considering the potential effect of Hb O2 affinity (as characterized fo the P50 [O2 tension at 50% Hb saturation, pH 7.4, 37.degree. C]) on O2 transport. This report reviews some experimental evidence with respect to this assumption and demonstrates the potential effect of altered heme-heme interaction on tissue O2 supply as distinguished from the effect of P50 or position change. Theoretically, heme-heme interaction values in the range that was reported for apparently healthy human subjects can substantially modify O2 transport to tissues, in some cases equalling or exceeding the effect from a similar range of P50 values. It is not presently clear to what extent this range may represent true variation as opposed to random technical error, but the possible implications for O2 transport indicate that a more systematic evaluation of the problem is desirable.