Simulation of continuous blood O2 equilibrium curve over the physiologic pH, DPG and pCO2 range

We analyzed 56 O 2 equilibrium curves of fresh human blood, each from 0 to 150 Torr PO 2. The data were collected over ranges of values for the 2,3-diphosphoglyceric acid-to-hemoglobin concentrations ratio [DPG]/[Hb] of 0.2-2.7, for pH of 7.0-7.8, and for PCO 2 of 7-70 Torr. Each curve was characterized according to the Adair scheme for the stepwise oxygenation of Hb, and the resulting constants (α 1, α 2, α 3, α 4) were analyzed to allow the simulation of the entire O 2 equilibrium curve under any conditions of [DPG]/[Hb], pH, and PCO 2 in the specific range. This analysis provides a powerful tool to study the affinity of Hb for O 2 within the red blood cell and to predict the shape of the O 2 equilibrium curve in various physiological and pathological states. Other attempts to predict blood O 2 affinity have considered only P 50 (the PO 2 at one-half saturation with O 2) or have provided too little data for continuous simulations.