Impact of intracellular Hb concentration on oxygen dissociation curve and delivery of single SS red cells in vivo. Calculated ODCs for single red cells exposed to a linear decrease in oxygen pressure from 100 torr to 0 torr at 40 torr/s, similar to the rate in vivo.^43,60,61 For a 40-g/dL cell, after polymerization has occurred there is a large decrease in saturation because of the low affinity of polymerized hemoglobin (p50 = 170 torr) and a concomitant large increase in oxygen delivery. The fraction of oxygen delivered is indicated by the double-headed vertical arrow and the dotted horizontal lines.