Concentration dependency of the BAC/BrAC (blood alcohol concentration/breath alcohol concentration) conversion factor during the linear elimination phase

Abstract

According to the theoretical pharmacokinetical considerations put forward by Wehner et al. the BAC(ven)/BrAC conversion factor Q is not a constant value and varies depending on the pharmacokinetic phase deduced from the alcohol concentration curve. Based on these considerations we propose that Q must be inversely proportional to the BrAC during the postabsorptive linear elimination phase, expressed as the hyperbola Q=1/kappa+(CT)/BrAC. The constants kappa or 1/kappa and (CT)--where (CT) consists of different parameters which remain constant during the linear elimination phase--can be experimentally determined from the linear relationship BrAC = kappaBAC(ven)-kappa(CT). To test this hypothesis 12 human volunteers received parenteral doses of ethanol. During the elimination phase, BAC and BrAC of each volunteer were measured between 18 and 34 times in a BrAC range between 0.65 mg/l and 0.12 mg/l. The conversion factor Q was either expressed in the form of the hyperbola Q=1/kappa+(CT)/BrAC or directly calculated from the ratio BAC(ven)/BrAC and the results obtained using both methods were found to be very similar. The values of 1/kappa of the hyperbolic functions varied between 1.808 and 2.165 and those of (CT) between 0.004 and 0.127. For a BrAC of 0.25 mg/l, an average value of 2.308+/-0.080 could be calculated for the conversion factor Q(0.25). On average, the value of Q(0.40) amounted to 2.207+/-0.048 and that of Q(0.55) to 2.160+/-0.056.

Comments on the paper entitled ?Concentration dependency of the BAC/BrAC (blood alcohol concentration/breath alcohol concentration) conversion factor during the linear elimination phase? by H.-T. Haffner et al.

“…We commend the authors of this study for their extensive and detailed work in this area (Haffner et al 2003). The authors have demonstrated that 1) Q is inversely proportional to the BrAC, 2) as BrAC increases, the closer Q approaches asymptotically the value of 1/κ, and 3) because in the majority of cases (11/12) the Q/ BrAC relation was fit best by a hyperbolic function, it was suggested that the determination of BAC from low BrACs would be affected disproportionately if a dose-specific value of Q was not utilized.…”

The Prevalence of Alcohol Use among Road Users and Its Impact on Traffic Crash Severity in Ghana

“…In total, 2,736 drivers were randomly stopped and their BrAC measured with the breathalyser; Alco-sensor V. BrAc figures were converted to BAC using the principle of Henry's law based on the established partition ratio between blood and breath alcohol concentration ratio of 2,300:1 in the UK (Cowan et al, 2010;Haffner et al, 2003; University of Dundee, 2011). Among those drivers whose BrAC were tested, 8.7% had detectable alcohol in their breath whilst 5.5% exceeded the legal alcohol BAC limit of 80 mg/dl (0.08%) in the country.…”

“…In regards to the estimation of alcohol-impaired driving, the measured breath alcohol concentration was first converted into Blood Alcohol Concentration (BAC) using the principle of Henry's Law, which is based on the partition ratio between blood and breath alcohol concentration ratios of 2,300:1 developed in the U.K. (Cowan et al, 2010;Haffner et al, 2003). Descriptive statistics were used to present the distribution of BAC by the various covariates.…”

“…Measured Breath Alcohol Concentrations (BrACs) were converted into Blood Alcohol Concentrations (BACs) using the partition ratio between blood and breath alcohol concentration ratios of 2,300:1 (Cowan et al, 2010;Haffner et al, 2003).…”

“…The Breath Alcohol Concentration measurements on the field with the alcosensor V were converted into their equivalent Blood Alcohol Concentrations (BAC) using the converting factor of 1:2,300 (breath to blood ratio) (Cowan, Burris, Hughes, & Cunningham, 2010;Haffner, Graw, Dettling, Schmitt, & Schuff, 2003). Research has established that the level of blood alcohol concentration (BAC in milligrams alcohol per 100 ml blood) is 2,300 times higher than the level of breath alcohol concentration (BrAc in micrograms per 100 ml breath).…”