A study concerning the blood/breath alcohol conversion factor Q: concentration dependency and its applicability in daily routine.
The conversion factor Q, obtained by division of blood alcohol concentration (BAC) by breath alcohol concentration (BrAC) is a widely discussed topic due to its great variance. By Austrian law, regulations frequently require an estimation of a corresponding BAC by a measured BrAC. It is known that Q depends among other things, on the alcohol kinetic state of the person being tested, which mathematically can be transformed to a dependency on the BrAC. Theoretically calculated Q values per BrAC level form a hyperbola shaped curve, thus decreasing with increasing BrAC values. Applying Austrian forensic standards for BAC and BrAC measurements, these calculations were verified in a study under practical conditions with BAC and BrAC data of 390 individuals. Q decreases from 2629 (+/- 455) for BrAC levels < 0.1 mg/l to 2229 (+/- 160) for a BrAC range of 0.4-0.5 mg/l and increases again to 2428 (+/- 124) for BrAC levels > 0.6 mg/l. Since these results were obtained under realistic practical conditions they can be directly applied in routine forensic expert opinion and can eliminate avoidable variances in the calculation of Q.
Pavlic
M
M
Institute of Legal Medicine, Department of Forensic Toxicology, Innsbruck Medical University, Muellerstrasse 44, A-6020 Innsbruck, Austria. marion.pavlic@uibk.ac.at
Grubwieser
P
P
Brandstätter
A
A
Libiseller
K
K
Rabl
W
W
D000328:Adult; D001944:Breath Tests; D002492:Central Nervous System Depressants / Q000032:analysis / Q000493:pharmacokinetics*; D000431:Ethanol / Q000032:analysis / Q000493:pharmacokinetics*; D005260:Female; D005554:Forensic Medicine; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological
D002492:Central Nervous System Depressants; D000431:Ethanol