Citation

Haffner HT, Graw M, Jeske A, Schmitt G, Goll M, Dietz K. Blutalkohol 2002; 39(6): 397-406.

Affiliation

Verkehrsmedizin/Verkehrspsychologie, Inst. fur Rechts-/Verkehrsmedizin, 69115 Heidelberg, Germany.

Copyright

(Copyright © 2002, International Committee on Alcohol, Drugs and Traffic Safety and Bund gegen Alkohol und Drogen im Straßenverkehr, Publisher Steintor Verlag)

DOI

unavailable

PMID

unavailable

Abstract

For a comparative study of the precision of the breath alcohol concentrations determined with the Draeger Alcotest 7110 Evidential and the precision of forensically determined blood alcohol concentrations, 6 volunteers received 2 parenteral doses of ethanol each, until their BrAC reached a level of approximately 0.65 mg/l. After a short waiting period in order to exclude diffusion delays, the BrAC was determined at short intervals until a BrAC of 0.20 mg/l was reached. Blood samples were taken simultaneously to determine the blood alcohol concentrations. Linear elimination functions were calculated from the BrAC and from BAC. Residual values of the concentrations, determined at identical times, were compared. With regard to the entire concentration range (= 344) almost identical coefficients of variation were obtained for both BrAC (CV: 2.86%) and BAC (CV: 2.58%). However, they varied considerably in different BrAC intervals. No differences in the coefficients of variation were observed (BrAC - CV: 3.59% and 2.44%; BAC - CV: 3.53% and 2.29%) in BrAC ranges between 0.20 and 0.30 mg/l (n=101) and between 0.35 - 0.45 mg/l (n = 93). On the other hand, highly significant differences could be observed when the BrAC ranged between 0.50 and 0.60 mg/l (n = 96) (BrAC - CV: 2.29%; BAC - CV: 1.35%). Therefore drawing a comparison with BAC an extra 25% of the basic BrAC value must be added to the respective threshold values, which denote the inability to drive (BrAC: 0.20 mg/l + 0.05 mg/l (identical to) BAC: 0.40(per mille) + 0.10(per mille)). This safety margin allows us to assume identical conditions with regard to precision of the measures breath and blood alcohol concentrations. In analogy to the BAC threshold values, where an extra 10% of the basic BAC value is added, it would be necessary to add a safety margin of approximately 17% of a basic BrAC that is to be determined in order to create a BrAC threshold value that would account for absolute driving inability. These safety margins are necessary in order to even out the different degrees of precision obtained with the different methods that are employed for determining BrAC and BAC. It cannot be concluded that a BAC will most likely exceed this threshold value purely on the basis of alcohol concentrations measures in breath alcohol.