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A study concerning the blood/breath alcohol conversion factor Q: Concentration dependency and its applicability in daily routine

2005; Elsevier BV; Volume: 158; Issue: 2-3 Linguagem: Inglês

10.1016/j.forsciint.2005.05.004

1872-6283

M. Pavlic, Petra Grubwieser, Anita Kloss‐Brandstätter, Kathrin Libiseller, Walter Rabl,

Pesticide Residue Analysis and Safety

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.