Carboxyhemoglobin formation due to carbon monoxide exposure in rats.

The Coburn-Forster-Kane equation (CFKE) is a well-tested model for prediction of carboxyhemoglobin (COHb) formation due to carbon monoxide (CO) exposure in humans. There have been few and relatively poorly tested attempts to implement a CFKE for rats. Such an implementation is of interest because many experiments on the effects of CO in rats were done without measuring COHb. To extrapolate from rats to humans requires a rat version of the CFKE. Rats were exposed to 150, 250, 500, and 1000 ppm CO for up to 240 min. Blood gases and COHb were measured. A CFKE was implemented for rats by using parameters found in the literature and estimating them from the data. It was deduced from the blood-gas data that rats hyperventilate slightly as COHb increases. The blood-gas data were used to estimate ventilation and alveolar capillary oxygen partial pressure. The hyperventilation required an iterative solution to the CFKE. The iterative CFKE predictions were found to differ statistically from observations, but in explainable ways and/or in small amounts.