Comparing solutions to the linear and nonlinear CFK equations for predicting COHb formation

The Coburn, Forster, Kane model of COHb formation as a result of exposure to CO exists in two forms: the linear CFK equation that assumes a constant level of oxyhemoglobin; and the nonlinear CFK equation that allows the oxyhemoglobin level to vary with the carboxyhemoglobin level. Although both equations are currently used, no rigorous analysis exists to show under what conditions the two models determine substantially different solutions. This paper provides such an analysis and shows that the linear model may be used as a reasonable approximation over a much wider range of carboxyhemoglobin levels than had been supposed on physiological grounds.