Distribution of ethanol between blood and dorsal subcutaneous air of the rat and the feasibility of using this distribution coefficient to estimate blood ethanol.

Equilibration of ethanol between dorsal subcutaneous air and blood is rapid, a steady state being already present in 60 seconds after air injection in the rat. The mean in vivo partition coefficient (blood/air) is 2,875, the linear regression coefficient having a standard error of 112, the high F value of this regression indicating the linearity and reliability of the estimates of calculated blood ethanol; the variance arises mainly from temperature variance of the air bleb. Although the concentration of alcohol in the blood must remain the standard of comparison, the production of the air bleb and its subsequent serial sampling is a virtually noninvasive technique which yields an almost immediate result at a sensitivity and specificity greater than that from the usual enzymatic determination of ethanol in blood.