Species differences in upper respiratory tract deposition of XXXX and @entity1068 vapors.

@entity1 @entity4774 @entity840 @entity1324 @entity35 @entity1068
Regional deposition patterns determine the dose of inhaled gaseous toxicant received by various areas of the respiratory tract. To study potential species differences in upper respiratory tract (URT) deposition of @entity1324 and @entity1068 vapors, and to determine if deposition of these vapors could be described by a ventilation-perfusion (V-P) model, URT deposition efficiencies of these vapors were measured over a 12- to 18-min period at selected flow rates in the surgically isolated URT of @entity4774 -anesthetized Fischer @entity35 and Hartley @entity840 . For both gases in both species, deposition efficiencies were significantly dependent upon inspiratory flow rate (p less than 0.0005). The V-P model predicts a linear relationship will exist between the ratio of the deposited to the nondeposited fraction and the inverse of the inspiratory flow rate. Such relationships were observed for deposition of @entity1324 (r = 0.93, p less than 0.0005) and @entity1068 vapors (r = 0.95, p less than 0.0005) in the @entity840 and for deposition of @entity1324 vapor (r = 0.95, p less than 0.0005) in the @entity35 . In contrast, a linear relationship was not observed for @entity1068 in the @entity35 suggesting that deposition mechanism(s) differ for this vapor in this species. Despite the fact that the surface area of the URT of the @entity840 is greater than that of the @entity35 , URT deposition of these vapors was as much as twice as efficient in the @entity35 as in the @entity840 (p less than 0.0005). This effect was not due to different blood:air partition coefficients as they were identical in both species. In toto, these results suggest there may be important anatomic and/or physiologic differences in the URT of the Hartley @entity840 and Fischer @entity35 . Such differences may have to be considered when comparing the response(s) of these species to toxic gases or when extrapolating data obtained from these species to the @entity1 .
