Breath Alcohol Analysis and the Blood: Breath Ratio

Abstract

The history of breath alcohol analysis and of the concept of a blood: breath ratio is briefly reviewed and it is suggested that the ratio is always lower and more variable than predicted by accepted theory. Using gas liquid chromatography for both breath and blood it has been shown that the blood: breath ratio falls during expiration and only reaches its presently accepted value of 2100: 1, predicted from in vitro studies, after prolonged rebreathing. It is suggested that this is due to alcohol being absorbed from the breath during expiration by the mucosa of the upper respiratory tract, to replace that lost during inspiration. Proposals are made for further studies and for modifications in present breath sampling procedures which could make breath analysis an acceptable substitute for blood analysis in all except marginal cases.