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Biomedical subjects

R G Gullberg

Publications and source records attributed to R G Gullberg.

At least 19 recordsLinked to original sources
PubMed1996

Simple versus sophisticated models of breath alcohol exhalation profiles.

For medicolegal purposes, breath alcohol content is typically determined from an end-expiratory sample. Measurements obtained by this method necessarily underestimate the alveolar breath alcohol content, and therefore underestimate the blood alcohol content. We suggest and analyse an improved paradigm which uses the entire time-series of breath alcohol measurements during exhalation, not simply the last recorded value. We present two mathematical models for the exhaling lung, and discuss the implications of each for more accurate and therefore more reliable breath alcohol measurement.

Adult↗
PubMed1994

Guidelines for estimating the amount of alcohol consumed from a single measurement of blood alcohol concentration: re-evaluation of Widmark's equation.

This article deals with the pharmacokinetics of ethanol and the reliability of estimating the amount of alcohol ingested from a single measurement of a person's blood alcohol concentration (BAC). Blood alcohol curves were plotted for 108 male subjects after they drank various doses of ethanol (0.51-0.85 g/kg body weight). The rate of disappearance of ethanol from the blood (beta-slope) and the apparent volume of distribution of ethanol (Widmark's rho factor, rho) were calculated for each subject; the mean beta-slope was 13.3 mg/dl/h (SD = 2.0), and the mean rho factor was 0.689 l/kg (SD = 0.061). The value of beta increased slightly with increasing dose of alcohol (P < 0.05). The blood alcohol parameters beta and rho were negatively correlated (r = -0.135). The BACs measured at 2 h and 5 h post-drinking were used to estimate the amount of alcohol each subject had consumed according to the method proposed by Widmark [1]. The mean differences (estimated-actual) and the +/- 95% limits of agreement were -0.72 g (+/- 12), and 2.2 (+/- 15), for the 2 h and 5 h BAC values, respectively. A method based on error propagation was used to derive the 95% limits of uncertainty in the amount of alcohol ingested. On the basis of a single measurement of BAC, we could estimate the amount of alcohol ingested within +/- 20%.

Adult↗
PubMed1994

The frequency of apparent acetone in a group of breath alcohol data: statistical treatment and forensic implications.

The potential presence of interfering substances (specifically acetone) is a concern in the forensic reporting of evidential breath alcohol analysis. As a result, manufacturers have designed instruments to monitor its occurrence through various hardware and software features. This paper is a retrospective study where 35,945 duplicate breath samples from BAC Verifier DataMaster instruments are evaluated for the frequency of 'interferant' values > or = 0.010 g per 210 l ethanol equivalent. A total of 264 (0.74%) of the duplicate samples had an interferant value on the first sample only, while 235 (0.66%) had interferant values on the second samples only. A total of 77 (0.21%) of the duplicate samples had in interferant values on both breath samples and only in these cases could the presence of measurable acetone even be considered. The occurrence of interferant results appeared also to be instrument-dependent with 55.7% of the interferant values on the first breath sample occurring on nine (13%) of the instruments displaying such results. The occurrences of interferant values on the first breath sample did not conform to the Poisson distribution (P < 0.0001) for the instrument with the largest number of occurrences, while there was conformance for other instruments evaluated. Finally, approximately 23 cases (0.064%) remained where the presence of acetone is a possible consideration. Several issues are presented that the forensic scientist should consider when attempting to explain an apparent interferant result in an individual case. It should be remembered that measurement results need to be interpreted in their context, and data analysis concerning an instrument's performance should be considered.

Acetone↗
PubMed1994

Employing simulated data to illustrate an important cause of the 'steepling' effect in breath alcohol analysis.

The 'steepling' effect (large excursions in analytical data over time) is a debated issue in forensic breath alcohol analysis with various explanations being postulated. Simulated breath alcohol data was generated according to a hypothetical kinetic model where single random samples as well as means of duplicate random samples were plotted with respect to time at 0.2 hour intervals. In addition, the simulated data was compared when both two or more digit treatment was employed. Results showed the occurrence of significant noise or 'steepling' when single, two-digit breath alcohol samples were employed as compared to a four-digit mean computed from three-digit duplicates. The magnitude of variability was quantified by means of nonlinear regression resulting in the residual sum of squares (RSS) = 0.00202 for the single analysis and RSS = 0.00053 for the mean of duplicates. The method of data collection and treatment appears to contribute significantly to the 'steepling' phenomenon. Intuitively, replicate analyses reduce variability and allow for more accurate kinetic modelling employing breath alcohol analysis.

Alcoholic Intoxication↗
PubMed1994

Isopropanol interference with breath alcohol analysis: a case report.

The presence of interfering substances, particularly acetone, has historically been a concern in the forensic measurement of ethanol in human breath. Although modern infrared instruments employ methods for distinguishing between ethanol and acetone, false-positive interferant results can arise from instrumental or procedural problems. The case described gives the analytical results of an individual arrested for driving while intoxicated and subsequently providing breath samples in two different BAC Verifier Datamaster infrared breath alcohol instruments. The instruments recorded ethanol results ranging from 0.09 to 0.17 g/210 L with corresponding interferant results of 0.02 to 0.06 g/210 L over approximately three hours. Breath and venous blood specimens collected later were analyzed by gas chromatography and revealed in the blood: isopropanol 0.023 g/100 mL, acetone 0.057 g/100 mL and ethanol 0.076g/100 mL. Qualitative analysis of the breath sample by GCMS also showed the presence of all three compounds. This individual had apparently consumed both ethanol and isopropanol with acetone resulting from the metabolism of isopropanol. An important observation is that the breath test instruments detected the interfering substances on each breath sample and yet they did not show tendencies to report false interferences when compared with statewide interferant data.

1-Propanol↗
PubMed1993

The application of control charts in breath alcohol measurement systems.

Measurement provides numerical information, usually to assist in some decision process. Quality control is fundamental to the measurement process if the results are to provide confidence to the decision maker. The degree of quality control required depends on the context and purpose of the measurements. Quality control is particularly important in the forensic measurement of breath alcohol in light of the significant consequences involved. Control charts are an important and widely used tool in quality control for both measuring and manufacturing processes. They help evaluate measurement variability and provide a visual assessment of the system's state of statistical control. Control charts can be developed and applied in a variety of different ways. Several examples are illustrated that apply control charts to breath alcohol measuring systems. Application of these methods should result in improved process monitoring in addition to improved confidence for forensic purposes.

Breath Tests↗
PubMed1993

Evaluating the variability of duplicate breath alcohol analyses as a function of subject age.

The influence of the person's age upon reproducibility in duplicate breath alcohol analyses is investigated. A total of n = 30,324 duplicate results (with both > or = 0.01 g/210L) were selected and divided into eight age groups from 10-19, 20-29, and up through 80+. Two duplicate agreement criteria, +/- 10% of the mean and +/- 0.02 g/210L, were evaluated according to age. A X2 trend analysis was employed and resulted in: +/- 10% of mean criteria, P < 0.001 and +/- 0.02 g/210L criteria, P > 0.05. The proportions of duplicates not conforming to the two agreement standards along with 95% confidence intervals were: +/- 10% of mean, 0.026 (0.024 to 0.028) and +/- 0.02 g/210L, 0.052 (0.050 to 0.054). Depending on the agreement criteria selected there will be proportional differences, but neither appears to be importantly influenced by the subject's age. The breath sampling criteria employed in the instrument studied does not appear to inhibit acceptable agreement, even in elderly subjects where the risk of respiratory disfunction increases.

Adolescent↗
PubMed1992

Comparing roadside with subsequent breath alcohol analyses and their relevance to the issue of retrograde extrapolation.

Driving while intoxicated (DWI) legislation requires proving the critical breath alcohol concentration (BrAC) at the time of driving. With time delayed analysis, retrograde extrapolation is occasionally employed but has several uncertainties associated with it. The present study attempts to address whether subjects actually arrested for DWI are likely to have BrAC values near the time of driving differing largely from those performed at a subsequent time. Selected officers arrested n = 161 subjects where roadside BrAC was determined with Pre-Arrest Breath Test (PBT) devices along with subsequent duplicate evidential analyses followed by an additional PBT analysis. These two sets of duplicates, one with large time interval (mean = 63.5 min.) and one with a 2-3 min difference, were then compared by several statistical methods. The results showing duplicate variability did not differ when the long time interval existed (F = 1.0, P > 0.05). A small but significant decrease in BrAC with respect to time appeared for the duplicate PBT data. Retrograde extrapolation applied to the data employing an assumed 0.015 g/210 l/h yielded a small but significant overestimate of the actual roadside PBT result. Finally, evidentiary analyses performed within 2 h of driving will provide good estimates and certainly not overestimates, of the BrAC existing at the time of driving and it appears that extrapolation may be unwarranted in these cases.

Alcoholic Intoxication↗
PubMed1992

The elimination rate of mouth alcohol: mathematical modeling and implications in breath alcohol analysis.

Mouth alcohol, if present in high enough concentrations, can falsely bias the accurate measurement of end-expiratory breath alcohol. Mouth alcohol will be eliminated over time, however, and can be modeled with a single term decaying exponential of the form: B0e-kt + C. It is important, however, to determine the model and its parameters when alcohol is already present within the biologic system. Using three individuals as their own controls, mouth alcohol was administered both before and after alcohol consumption followed by breath alcohol analysis performed at approximately 0.5 min intervals. The results showed that both model parameters (B0 and k) are effected and that the asymptotic value (C) is reached much sooner when alcohol already exists in the end-expiratory breath. Considering only three individuals were involved, the forensic-science importance appears to be that, as the end-expiratory breath alcohol concentration increases, the time necessary for the mouth alcohol to decrease to unbiased levels is decreased. Fifteen min of observation time prior to breath alcohol analysis appears to be more than adequate at forensically relevant concentrations.

Breath Tests↗
PubMed1991

Duplicate breath alcohol analysis: some further parameters for evaluation.

An individual exhaling into a breath alcohol instrument produces a breath alcohol concentration (BrAC) profile which is a continuous function of time. Microprocessor based breath alcohol instruments provide the capability to collect and store the BrAC profile data in discrete format. The present study collected duplicate BrAC profile data arrays on 11 field tested subjects and 16 experimentally tested subjects. The field subjects provided duplicate breath samples under normal field conditions. The experimental group provided one sample following normal breathing and one following breath holding. Each profile was subjected to ten different mathematical procedures. The duplicate results were then evaluated by a t-test for paired data. The experimental group showed statistical significance (P less than 0.01) for all but one mathematical parameter evaluated. The field group showed no statistical significance on any of the mathematical parameters. The results showed that BrAC profiles can be evaluated in a variety of ways and provide an index for detecting differences in breathing pattern prior to breath exhalation. The field data showed remarkable reproducibility by all mathematical indices. The results have forensic as well as physiological implications.

Breath Tests↗
PubMed1991

Differences between roadside and subsequent evidential breath alcohol results and their forensic significance.

Breath alcohol measurements for forensic purposes are typically not made at the time of a driving incident but at some later time. Therefore, the magnitude of variation in breath alcohol concentration (BrAC) following the time of arrest is of concern. The use of roadside preliminary breath test (PBT) instruments can provide data on BrAC closer to the time of a driving incident and allow for comparison with later evidential analysis. This retrospective study evaluates two distributions (N = 968): differences between PBT results and the first evidential breath test (PBT-BrAC1) and differences between two (duplicate) evidential breath alcohol tests (BrAC1-BrAC2). The two distributions were shown to vary from each other and from the normal with statistical significance (p less than .05). The PBT-BrAC1 distribution had greater variability (SD = .025) than the BrAC1-BrAC2 distribution (SD = .010). An important result was that the PBT was equal to (within duplicate sampling variability) or greater than BrAC1 in approximately 85.5% of the cases. The remaining 14.5% could not be explained by sampling variability within the duplicate test distribution. The variability in both distributions typically exceeds the normally accepted alcohol elimination rates. The conclusion is that differences between roadside and subsequent evidential breath results cannot be attributed solely to absorption or elimination kinetics. Intra-individual breath sample differences can be large and thus obscure the accurate evaluation of absorption and elimination rates. Breath tests conducted within approximately 2 hours of driving will reflect, within experimental uncertainty, the BrAC at the time of driving.

Accidents, Traffic↗
PubMed1990

An application of probability theory to a group of breath-alcohol and blood-alcohol data.

Many jurisdictions have "per se" driving-while-intoxicated (DWI) status expressed in terms of a blood-alcohol concentration (BAC) standard (in grams per 100 mL or the equivalent). Since breath-alcohol (BrAC) analysis is typically employed to determine BAC, there is often challenge to the use of an assumed 2100:1 conversion ratio. This concern may be relevant in light of considerable data that show a low percentage of cases in which BrAC greater than BAC, and this concern increases when the BrAC is used to predict BAC in the context of "per se" legislation. Probability theory provides a basis for estimating the likelihood of an individual having a BrAC greater than or equal to g/210 L with a corresponding BAC less than 0.10 g/100 mL. Actual field data from the state of Wisconsin (n = 404) were evaluated to determine the probability of this occurrence. The probability for this occurrence involves the multiplication law for independent events. The computed probability from the data was 0.018. The actual number of occurrences where BrAC greater than or equal to 0.10 g/210 L and BAC less than 0.10 g/100 mL was 5, resulting in a probability of 0.012. The concern of having BrAC greater than BAC at the critical "per se" level has a very low probability of occurrence, which thus supports the reasonableness of "per se" DWI legislation based upon a blood-alcohol standard determined by breath-alcohol analysis.

Alcoholic Intoxication↗
PubMed1989

Breath alcohol test precision: an in vivo vs. in vitro evaluation.

Random error is associated with breath alcohol measurements, as with all analytical methods. The total random uncertainty of a group of n measurements is typically determined by computing the standard deviation and requiring it to be less than some appropriate level (i.e., +/- 0.0042 g/210 l). The total random uncertainty has two primary sources; the instrumental method and the sample source. These are typically inseparable values. In breath alcohol testing the two primary sample sources are simulators and human breath. The present study evaluates ten groups of simulator samples consisting of ten measurements each on BAC Verifier Datamaster instruments. The data also includes ten breath alcohol measurements from each of 21 individuals following alcohol consumption. The range of standard deviations for the simulator samples was 0.0003-0.0022 g/210 l. The range of standard deviations for the human breath samples was 0.0015-0.0089 g/210 l. Two statistics that test for homogeneity for variances were applied. The simulator samples resulted in a Cochran's C test of 0.5000 and an Fmax test of 48.9. The human breath samples resulted in a Cochran's C test of 0.1519 and an Fmax test of 27.3. All were significant at P less than 0.001. The statistical tests demonstrated that the intragroup variability among the human subjects was comparable to the intragroup variability among the simulator samples. The data also demonstrates that the sample source (simulator or human) is probably the largest contributor to total random uncertainty. Therefore, when duplicate breath alcohol testing from individuals shows variability in the second decimal place the cause is differences in breath samples provided and not instrumental imprecision.

Alcohol Drinking↗