Myth #3: Breath Test — Absorptive Phase Test is Okay
A number of articles report a huge disparity between measurements of breath alcohol and venal blood alcohol content when the person being tested is still absorbing the alcohol into his or her body, or is in the absorptive phase of alcohol metabolism. One study showed that the breath result can be as much as 100 percent higher than the blood level during the absorptive phase. E. Martin, W. Moll, P. Schmid, L. Dettli, The Pharmacokinetics of Alcohol in Human Breath, Venous and Arterial Blood After Oral Ingestion, 26 (5) Eur. J. Clin. Pharmacol., 619 (1984).
Defending against DUI / DWIOther studies also report unacceptably high differences between breath and blood results obtained during the absorptive phase. E.g., G. Simpson, Accuracy and Precision of Breath Alcohol Measurements for Subjects in the Absorptive State, 33(6) Clin. Chem. 753 (June, 1987); G. Simpson, Corrections to a Report, 33(11) Clin Chem 2130 (Nov. 1987) (erratum to the June article); G. Simpson, Do Breath Tests Really Underestimate Blood Alcohol Concentration? 13(2) Journal of Analytical Toxicology, 120 (Mar.-Apr. 1989). Dr. Simpson’s conclusions speak for themselves. Simultaneous measurements of breath alcohol concentration (BrAC) and venous blood alcohol concentration (VBAC) show that actual VBAC can be overestimated by more than 100% for a significant amount of time after drinking stops. The maximum error for four individual subjects is +230%, +190%, +60%, and +30%. The magnitude of these errors indicates that results from quantitative evidential breath alcohol analyzers are far less accurate for the absorptive state than the postabsorptive state, but the specifications for accuracy and precision given by manufacturers of these instruments do not reflect this. Effective DUI / DWI DefenseG. Simpson, Accuracy and Precision of Alcohol Measurements for Subjects in the Absorptive State, 33 (6) Clin. Chem. 753, 753 (1987). He continues: The results also indicate that there is a significant likelihood that subjects will be in the absorptive state when tested under field conditions. I conclude that estimates of BAC based on BrAC measurements are not reliable in the absorptive state and that the uncertainty associated with such estimates should be accounted for, particularly when the results are used in connection with law enforcement. Id. at 753.Next article: Index: |
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