Blood HbO2 and HbCO2 Dissociation Curves at Varied O2, CO2, pH, 2,3-DPG and Temperature Levels (vol 32, pg 1676, 2004)

New mathematical model equations for O-2 and CO2 saturations of hemoglobin (S-HbO2 and S-HbCO2) are developed here from the equilibrium binding of O-2 and CO2 with hemoglobin inside RBCs. They are in the form of an invertible Hill-type equation with the apparent Hill coefficients K-HbO2 and K-HbCO2 in the expressions for SHbO(2) and SHbCO(2) dependent on the levels of O-2 and CO2 partial pressures (P-O2 and P-CO2), pH, 2,3-DPG concentration, and temperature in blood. The invertibility of these new equations allows P-O2 and P-CO2 to be computed efficiently from S-HbO2 and S-HbCO2 and vice versa. The oxyhemoglobin (HbO(2)) and carbamino-hemoglobin (HbCO(2)) dissociation curves computed from these equations are in good agreement with the published experimental and theoretical curves in the literature. The model solutions describe that, at standard physiological conditions, the hemoglobin is about 97.2% saturated by O-2 and the amino group of hemoglobin is about 13.1% saturated by CO2. The O-2 and CO2 content in whole blood are also calculated here from the gas solubilities, hematocrits, and the new formulas for S-HbO2 and S-HbCO2. Because of the mathematical simplicity and invertibility, these new formulas can be conveniently used in the modeling of simultaneous transport and exchange of O-2 and CO2 in the alveoli-blood and blood-tissue exchange systems.