Widmark factors for local Chinese in Hong Kong

Experimental study of the temporal profile of breath alcohol concentration in a Chinese population after a light meal

In forensic science, the Widmark equation is widely used to deduce the blood alcohol concentration (BAC) at different time points. But the linear model specified by Widmark might be deficient in predicting the breath alcohol concentration (BrAC) at different time points, and extrapolating the peak and the corresponding time. In order to establish the temporal profile of alcohol concentration which captures the effects of non-linear nature of alcohol absorption, elimination, and peak, in particular of Chinese population after a light meal, a drinking experiment was conducted in this study. To achieve this, a double-blind drinking experiment was conducted to measure the BrAC of 52 Chinese participants after a light meal in this study. Prior to the experiment, all participants were required to abstain from food for 4 hours, more importantly, from alcohol and sedatives for 24 hours. A standard light meal was provided about 30 minutes prior to the alcohol intake in the experiment. The BrAC was measured at a 10-minute interval during the absorption phase and 30-minute interval during the elimination phase respectively. The measurements were stopped when the BrAC fell to 0.010 mg/100 ml or below, or more than 8 hours after the alcohol intake. Then, the temporal profiles of BrAC, assuming linear and non-linear relationships, were established using Full Bayesian approach. The linear component indicated the alcohol impairment in normal social function, with which a light meal is usually accompanied with drinking. On the other hand, the non-linear (gamma distribution) part replicated the absorption phase, elimination phase, and the peak of alcohol concentration. The proposed model well performed than the conventional regression model. Additionally, the confounding factors including gender, body weight, and dosage were controlled for. Results should be useful for the development of cost-effective enforcement measures that could deter against drink driving.

Do Objective Measures of Blood Alcohol Concentrations Make More Sense than Self-reports in Emergency Department Studies?

PURPOSE

: Concerns about self-reports have led to calls for objective measures of blood alcohol concentration (BAC). The present study compared objective measures with self-reports.

METHODS

: BAC from breath or blood samples were obtained from 272 randomly sampled injured patients who were admitted to a Swiss emergency department (ED). Self-reports were compared a) between those providing and refusing a BAC test, and b) to estimated peak BAC (EPBAC) values based on BACs using the Widmark formula.

RESULTS

: Those providing BACs were significantly (P < 0.05) younger, more often male, and less often reported alcohol consumption before injury, but consumed higher quantities when drinking. Eighty-eight percent of those with BAC measures gave consistent reports (positive or negative). Significantly more patients reported consumption with negative BAC measures (N = 29) than vice versa (N = 3). Duration of consumption and times between injury and BAC measurement predicted EPBAC better than did the objective BAC measure.

CONCLUSIONS

: There is little evidence that patients who provide objective BAC measures deliberately conceal consumption. ED studies must rely on self-reports, eg, take the time period between injury and ED admission into account. Clearly, objective measures are of clinical relevance, eg, to provide optimal treatment in the ED. However, they may be less relevant to establishing effects in an epidemiologic sense, such as estimating risk relationships. In this respect, efforts to increase the validity and reliability of self-reports should be preferred over the collection of additional objective measures.

Alcohol study on blood concentration estimation: reliability and applicability of Widmark formula on Chinese male population

Widmark formula suggests estimating blood alcohol concentration level (BAC) on a given amount of alcohol administrated with knowledge of subject's body weight and sex. The idea has been referenced extensively in forensic science with application in drink driving prosecution. A sample of Chinese subjects was collected in the drinking experiment, and in this study we mainly focus on the verification of the validity of Widmark formula on Chinese male population. A promising result is obtained where the extrapolated BAC measurement is directly proportional to the amount of alcohol administrated, and inversely to the subject's body weight. The results noted in the general linear model is further supported by the nonlinear regression analysis and a concordant argument reaches by deploying the concept to the BAC level attained at peak.

A controlled study of the time-course of breath alcohol concentration after moderate ingestion of ethanol following a social drinking session

This paper evaluates the breath alcohol concentration (BrAC), nausea (feeling of being slightly intoxicated) and subjective driving performance after ingesting a moderate dose of alcohol in the presence of a light meal, which intends to approach a social drinking setting. 119 healthy individuals (69 males and 50 females, aged 21.7+/-3.0) ingested three glasses of wine (95mL each) and their BrAC was determined by an Alcotest 7410 at 15, 30, 45, 60, 90 and 120min post-drinking. 46% of females and no male subjects exceeded a BrAC of 0.25mg/L, the legal limit for driving fixed by some Western countries. 53% of the study population felt nausea during the experimental session and 20% self-reported impairment of their driving skills. In both cases these subjective effects were more pronounced in females. The major determinants of mean BrAC were time post-drinking, gender (male) and body mass index (BMI), all these variables being inversely associated. Females and individuals with a BMI lower than 22.5kg/m(2) were at an increased risk of exceeding the legal limit of BrAC. The feeling of nausea was significantly associated with gender (females), the ingestion of up to 2 drinks on weekdays, and having exceeded a BrAC of 0.25mg/L during the experimental study. The main predictor of self-perception of impaired driving skills was the feeling of nausea, followed by a BrAC in excess of 0.25mg/L. In conclusion, both females and subjects with lower BMI are at an increased risk of exceeding the legal limit of BrAC after moderate alcohol consumption resembling a social drinking setting.

Estimating the uncertainty associated with Widmark's equation as commonly applied in forensic toxicology

No computation is performed more frequently by forensic toxicologists than that involving Widmark's equation. The equation is employed to estimate either the number of drinks consumed or the corresponding blood or breath alcohol concentration. Despite the wide use of Widmark's equation, rarely is an uncertainty estimate also provided. Estimates from Widmark's equation involve at least seven uncertain random variables. Uncertainty estimates are presented that rely on methods of general error propagation compared to a method developed by Widmark. Assuming reasonable variable and uncertainty estimates, the error propagation method yielded for N=10.4 drinks, a combined uncertainty (standard deviation) of 1.3 drinks (CV=12.3%). Similarly, estimating the blood alcohol concentration yielded for 0.120 g/100 ml, an uncertainty of 0.0255 g/100 ml (CV=21.2%). Widmark's uncertainty method yielded 1.6 drinks (CV=15.4%). The derivation of Widmark's uncertainty estimate is also presented, showing that he considered only rho and beta to be uncertain. Widmark estimates for the number of drinks should include a 2CV estimate of approximately 25% while the blood alcohol concentration estimate should include a 2CV estimate of approximately 42%. Including valid estimates of uncertainty should enhance the legal admissibility and confidence for Widmark estimations.

Impact of Alcohol on Vestibular Function in Relation to the Legal Limit of 0.25 mg/l Breath Alcohol Concentration

The aim of this study was to investigate the effect of alcohol on sacculocollic and vestibulo-ocular reflex systems, when the breath alcohol concentration (BrAC) is close to the legal limit of 0.25 mg/l. Twenty healthy male volunteers underwent vestibular evoked myogenic potential and caloric coupled with visual suppression tests. These tests were conducted prior to imbibing alcohol at a dosage of 0.5 g/kg to achieve a peak BrAC of around 0.25 mg/l. Once the peak BrAC was reached, these tests were performed again. Predosing and postdosing analytical results were compared, as were those with BrAC levels > or = 0.25 mg/l and <0.25 mg/l. After ingesting alcohol, 36 ears (90%) showed vestibular evoked myogenic potential responses, with a significantly increased latency of peak p13. The mean slow-phase velocity of caloric nystagmus in 40 ears after dosing was significantly reduced, and that with BrAC > or =0.25 mg/l was significantly less than that with BrAC <0.25 mg/l. Likewise, the visual suppression index decreased considerably after alcohol ingestion. In conclusion, from the perspective of vestibular function, the 0.25-mg/l BrAC limit gains clinical significance, because the vestibulo-ocular reflex performance deteriorates further, when the BrAC exceeds 0.25 mg/l. However, impaired performance of sacculocollic reflex and vestibulocerebellar interaction has occurred, when the BrAC was <0.25 mg/l, suggesting that a lower legal threshold is appropriate.