Practical and physiological aspects of breath alcohol analysis

Abstract: Breath alcohol analysis constitutes sufficient material for the prosecution of drunk driving without the need for blood analysis. However, the prevailing method used for breath analysis lacks standardization of several physiological variables that cause a variation of the breath alcohol concentration (BrAC). In this thesis, a novel analyzer which standardizes the BrAC to the water vapour concentration was used to investigate different aspects of breath analysis. In study I the BrAC-profile and elimination rate of mouth alcohol (MA), a potential source of error, was investigated. It was concluded that the BrAC-profile is an unreliable means to detect MA and that the elimination rate is independent of blood alcohol. In study II the precision of breath and blood analysis was compared and the relationship between breath and blood alcohol concentrations was investigated. It was shown that the precision of breath and blood analysis was equally good and that there was a stable relationship between the breath and blood alcohol concentrations from 30 minutes and onward after alcohol administration. In study III the mechanisms of alcohol exchange within the lungs were investigated. The results implied that there is a significant exchange of alcohol with the conducting airways and that this exchange causes a relatively low BrAC in the early absorption phase. In study IV the analytical performance of BrAC-measurements by standardization to water vapour was determined. The method complies with standards for evidential breath testing and allows analysis without mouth piece with a nearly intact accuracy and precision.