Comparison of ethanol concentrations in venous blood and end-expired breath during a controlled drinking study

Concentration-time profiles of ethanol were determined for venous whole blood and end-expired breath during a controlled drinking experiment in which healthy men (n = 9) and women (n = 9) drank 0.40-0.65 g ethanol per kg body weight in 2030 min. Specimens of blood and breath were obtained for analysis of ethanol starting at 50-60 min post-dosing and then every 30-60 min for 3-6 It. This protocol furnished 130 blood-breath pairs for statistical evaluation. Blood-ethanol concentration (BAC, mg/g) was determined by headspace gas chromatography and breath-ethanol concentration (BrAC, mg/2 1) was determined with a quantitative infrared analyzer (Intoxilyzer 5000S), which is the instrument currently used in Sweden for legal purposes. In 18 instances the Intoxilyzer 5000S gave readings of 0.00 mg/2 I whereas the actual BAC was 0.08 mg/g on average (range 0.04-0.15 mg/g). The remaining 112 blood- and breath-alcohol measurements were highly correlated (r = 0.97) and the regression relationship was BAC = 0.10 + 0.91BrAC and the residual standard deviation (S.D.) was 0.042 mg/g (8.4%). The slope (0.91 +/- 0.0217) differed significantly from unity being 9% low and the intercept (0. 10 +/- 0.0101) deviated from zero (t = 10.2, P < 0.001), indicating the presence of both proportional and constant bias, respectively. The mean bias (BAC BrAC) was 0.068 mg/g and the 95% limits of agreement were -0.021 and 0. 156 mg/g. The average BAC/BrAC ratio was 2448 +/- 540 (+/- S.D.) with a median of 2351 and 2.5th and 97.5th percentiles of 1836 and 4082. We found no significant gender-related differences in BAC/BrAC ratios, being 2553 +/- 576 for men and 2417 +/- 494 for women (t = 1.34, P > 0.05). The mean rate of ethanol disappearance from blood was 0.157 +/- 0.021 mg/(g per hour), which was very close to the elimination rate from breath of 0.161 +/- 0.021 mg/(2 I per hour) (P > 0.05). Breath-test results obtained with Intoxilyzer 5000S (mg/2 1) were generally less than the coexisting concentrations of ethanol in venous blood (mg/g), which gives an advantage to the suspect who provides breath compared with blood in cases close to a threshold alcohol limit. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.