Characterization of oxygen-hemoglobin equilibrium curves using nonlinear regression of the Hill equation: parameter...

Measurements of oxygen concentration versus PO2 in blood from 33 normal adults were fitted, using a special nonlinear regression analysis, to the Hill equation to obtain the parameters describing the position (P50) and shape (n) of each oxygen-hemoglobin equilibrium curve (OHEC). Data between 20% and 97% saturation were described well by this empirical two-parameter model. The mean (+/- SD) P50 and n were found to be 26.2 (+/- 0.8) torr and 2.50 (+/- 0.07), respectively, in good agreement with previously published values. Some normal individuals, however, deviated markedly from the averages indicating that the published values cannot be applied to everyone.