Interpretation of Breathalyser Results for Medico-Legal Purposes

Interpretation of Breathalyser Results for Medico-Legal Purposes - AN INVESTIGATION OF THE BLOOD ALCOHOL CONCENTRATION OF SUBJECTS MONITORED IN A SERIES OF CONTROLLED DRINKING EXPERIMENTS I. E. C. Cameron3 and P. A. Donkin It is now generally accepted that driving after consumption of alcoholic beverages is a major contributing factor in road traffic accidents and infringements. Statistics of the New South Wales Police Departm ent show that from January to N ovem ber 1976, there were approxim ately 7000 drivers apprehended with blood alcohol concentrations between 0.08% and 0.15% and a further 8000 with concentrations over 0.15%. W hen such cases involve the giving of evidence by professional experts in Court, their function is to assist the Court in determining the degree to which alcohol may have contributed to the accident or incident. This assistance may fall into a num ber o f categories, including: (a) Relating a particular blood alcohol concentration to the degree of impairment in driving ability. (b) Estimating the likely blood alcohol concentration at an earlier time than that at which the test was perform ed (i.e. at the time o f the incident leading to apprehension). (c) Relating the concentration to the am ount of intoxicating liquor that would have to be consum ed to reach that concentration. (d) Relating the blood alcohol concentration determ ined indirectly by analysis o f a person s breath to that determ ined by a direct analysis o f a blood sample. In regard to (a), the concentration of alcohol in the blood which is necessary in order to im pair driving ability has been investigated by various workers, and has involved: (i) m easurem ent o f visual and m anual skills o f subjects during drinking experim ents1; (ii) the testing of actual driving performance (usually on a closed road circuit) before and after the consum ption o f various am ounts o f alcoholic beverages.2 As a result o f such studies it is now widely accepted that all drivers with a blood alcohol concentration of 0.1% will have some degree of im pairm ent of their driving ability, while even at lower levels, down to 0.04% to 0.05%, many drivers will exhibit im pairm ent. In regard to (d) above, the validity of breath analysis for forensic purposes has also been extensively investigated. In Australia, the Breathalyser is the only instrument used for these purposes at present. Much work has been done to compare the results of analyses made with the Breathalyser with results of direct blood analyses. Our experience confirms the opinions of other workers in this field that once the phase of rapid absorption of alcohol into the blood has passed, the Breathalyser figure almost invariably understates the figure from direct blood analysis.3 The work on which this paper is based was undertaken primarily to investigate some of the factors involved in answering questions raised by (b) and (c) above. In 1959 McCallum a Breath Analysis Section, New South Wales Police Department 206

Interpretation o f Breathalyser Results fo r Medico-Legal Purposes 207 and Scroggie4, and Bayly and M ccallum5, made an extensive study of these problems using blood samples, and their work is now the basis o f such determ inations in Australia. In this work the intention was to conduct a num ber of controlled drinking experiments to study: (a) the relationship between the quantity of alcohol ingested and the maximum blood alcohol concentration reached; and (b) the time taken after completion of drinking to reach the maxim um concentration. It was decided to use the Breathalyser for determining blood alcohol concentrations in these experiments, together with occasional concurrent analyses o f venous blood. Although the Breathalyser has been criticised as an instrument for research purposes, because of its tendency to understate the results of direct blood analysis, it does have the advantage of providing a convenient method for collection and analysis of a large number of samples from one subject over a short period of time. It might also be noted in passing that these criticisms do not have the same validity in its application as a forensic instrum ent. These experiments were divided into three parts as follows: E xperim ent 1 (see Table II) 20 subjects drank 284 ml measures of beer (4.7% v/v) on an empty stomach at their m axim um rate for 1 hour. Experiment 2 (see Table III) 42 subjects drank 284 ml measures of beer (4.7% v/v) over a three-hour period. These were consumed several hours after a light breakfast and at the subject s own rate. E xp erim ent 3 (see Table IV) Drinking conditions were the same as in Experiment 2 except that some subjects drank 114 ml measures of table wine (12% v/v) and others drank 27 ml measures o f whisky (39.5% v/v) diluted with ginger ale. In each experiment a num ber of subjects vomited, and these were of course, excluded from the final results. It will be noted that the greater part of this work was done with beer as the beverage consumed, this being by far the most popular alcoholic beverage in Australia. However, it is of interest to note that the actual am ount of alcohol contained in a standard measure o f many popular beverages is com parable (see Table I). TABLE I Alcohol content o f various beverages Beverage A Icohol content v/v Standard measure (N.S.W.) Alcohol content of standard measure (approx.) *> Beer 4.7% 10 fl. oz. 13 ml Table wine 12% 4 fl. oz. 13.5 ml Fortified wine 25% 2 fl. oz. 14.2 ml Whisky 40% 1 fl. oz. 11.5 ml Other factors will of course affect the rate of absorption of different liquors, e.g. the concentration of alcohol in the beverage, as consumed, and the question of whether the beverage (or diluent) is carbonated.

208 I. & C. Cameron and P. A. Donkin In the tables below, cm ax represents the m axim um concentration reached after drinking ceased, as determ ined by breath analysis; /m ax is the time taken after the cessation o f drinking to reach cmax; E represents the glass equivalent, or rise in blood alcohol concentration for each glass o f beverage consum ed and D represents the elim ination rate at a period between 2Vi-3V2 hours after drinking ceased. In calculating E, w e have the num ber o f consum ed by deducting one drink for each hour during which drinking continued, in order to com pensate for elim ination occurring during the drinking period. W e endeavoured to have our subjects drink at a regular rate throughout each drinking session. The blood alcohol concentration at the tim e o f cessation o f drinking (Co) was determ ined from a blood sam ple, as it is not possible to use a breath analysis at this time, due to mouth alcohol. Further blood sam ples were taken at approxim ately cm ax and during the elim ination phase. It was found that it was not possible to obtain the second blood sam ple close enough to cmax, and for this reason it was not possible to calculate the rise in blood alcohol concentration after drinking ceased (cmax Co) on blood sam ples alone as this would involve a great deal o f interpolation. On com paring Co, as determ ined from blood, with cm ax, as determ ined from breath, it w as fou n d that cmax> was in m any cases equal to or less than Co. For these reasons it was decided to abandon any attem pt to calculate the rate and extent o f the rise in b loo d alcoh ol concentration after cessation o f drinking. TABLE II E xperim ent 1 Subject Age Wt (kg) Cmax breath tmax E D 1 34 82 12 11 0.095 75 0.0086 0.015 2 39 84 8 7 0.075 25 0.0107 0.020 3 29 98 12 11 0.130 85 0.0118 0.015 4 20 67 7 6 <&090 65 0.0150 0.020 5 30 S2 8 7 0.095 75 0.0135 0.010 It 30 82 9 8 0.095 80 0.0119 0.025 8 33 79 9 8 0.100 60 0.0125 9 19 102 10 9 0.115 40 0.0128 0.015 10 32 84 9 8 0.085 50 0.0106 0.015 11 22 108 9 8 0.105 70 0.0131 0.015 12 24 102 13 12 0.130 85 0.0108 13 26 67 7 6 0.120 40 0.0200 0.015 14 28 81 10 9 0.110 40 0.0122 0.015 15 24 73 13 12 0.175 75 0.0146 0.020 17 22 76 11 10 0.125 50 0.0125 0.015 19 27 98 15 14 0.185 65 0.0132 20 27 86 11 10 0.130 40 0.0130 Average 9 60 0.013

Interpretation o f Breathalyser Results fo r Medico-Legal Purposes 209 TABLE III Experiment 2 Subject no Age Wt (kg) no. cmax breath tmax E D Al 24 92 14 11 0.135 35 0.0122 A2 37 89 16 13 0.170 40 0.0131 0.020 0.015 A4 39 86 10 7 0.080 30 0.0114 0.010 A5 27 78 17 14 0.160 50 0.0114 0.015 A3 28 73 14 11 0.180 80 0.0164 A6 31 92 23 20 0.245 65 0.0123 A 8 22 101 18 15 0.165 75 0.0110 0.020 A9 29 92 17 14 0.185 75 0.0132 0.020 A 10 24 94 17 14 0.145 55 0.0104 0.010 A15 24 54 10 7 0.135 50 0.0193 A I6 30 86 15 12 0.170 40 0.0142 0.020 A18 42 79 14 11 0.100 45 0.0091 0.020 A19 28 86 14 11 0.145 40 0.0132 0.010 A20 24 99 12 9 0.110 45 0.0122 0.025 B1 34 91 11 8 0.095 50 0.0119 B2 28 83 14 11 0.145 38 0.0132 B3 44 85 17 14 0.150 46 0.0107 B4 30 72 12 9 0.130 40 0.0144 B5 32 78 14 11 0.145 25 0.0132 B6 33 74 12 9 0.130 64 0.0144 B7 33 92 10 7 0.100 15 0.0143 B8 29 96 19 16 0.210 38 0.0131 B9 31 94 19 16 0.180 32 0.0113 BIO 47 76 20 17 0.200 73 0.0118 B ll 28 86 20 17 0.175 56 0.0103 B12 27 87 11 1 1 0.120 22 0.0141 B13 24 76 18 P I 0.190 28 0.0123 B14 28 105 10 m 0.070 22 0.0093 BI5 48 111 26 23 0.215 57 0.0094 B16 22 86 16 13 0.170 44 0.0131 B17 22 70 12 9 0.160 29 0.0178 B18 30 95 13 10 0.120 42 0.0120 B19 21 99 13 10 0.110 21 0.0110 B20 51 86 22 19 0.230 45 0.0121 B21 30 86 13 10 /2 0.115 24 0.0110 B22 23 95 15 12 0.150 25 0.0120 Average \2Vi 43 0.013 TABLE TV Experim ent 3 Liquor no. of of cmax breath tmax E Wine 17 14>/2 0.215 60 0.0148 Wine 11 m 0.155 55 00182 Wine 14 1 V/i 0.185 55 0.0161 Wine 14 WVi 0.185 35 0.0161 Wine 12 9lA 0.185 45 0.0195 Whisky 17 14'/2 0.125 45 0.0086 Whisky 16 13V4 0.140 40 0.0104 Average 12 48 0.015

210 I. E. C. Cameron and P. A. Donkin CONCLUSIONS As shown in the tables, the average glass equivalent value obtained in both the one-hour and three-hour beer drinking experiments was 0.013% per glass. In the one-hour experiment the range was from 0.009%-0.020% per glass, while in the three-hour experiment the range was from 0.009%-0.019% per glass. It is evident that these two experiments produced almost identical results as to the value o f E. O f the 53 subjects involved in the beer drinking experiments, only two subject A 15 (Table III), a 54 Kg male, and subject 13 (Table II), a female had a glass equivalent above 0.018%. Accordingly, we would consider 0.018% to represent the maximum amount of alcohol added to the blood for each 10 oz glass of beer consumed by a person of average weight and build; and 0.013% to be the average figure. The time taken to reach cmax after drinking ceased varied in Experiment I (one-hour) from 25 to 85 minutes, with an average of 60 minutes. In Experiment 2 (three-hour) the range was from 15 to 80 minutes, with an average o f 43 minutes. The rate of elimination (removal of alcohol from the blood) was determined for a number of subjects in this study. As these results were in close agreement with those obtained by other workers in this field, averaging 0.020% per hour, this figure was not calculated for subjects tested in the later sessions. We offer no com ment on the results of Experiment 3, as the numbers involved are too small to be significant. However, the results are included, as comparison of these with the results o f the beer drinking experiments is o f some interest. REFERENCES 1. Teo, R. Alcohol, Drugs and Accident Risk Traffic Accident Research Unit, Dept, of Motor Transport, N.S.W 1975. 2. Lovibond, S. H. The Warwick Farm Project-Danger Level Road Safety, 6, 1970. 3. Preston, W. L. K. The Validity of the Breathalyzer Medical Journal of Australia, 1968. 4. McCallum N. E. W. and Scroggie, J. G., Some Aspects of Alcohol Concentration in Body Fluids, Part 1; Correlation Between Blood Alcohol Concentration and Alcohol Consumption, Medical Journal o f Australia 2: 169, 1959. 5. Bayly, R. C. and McCallum N. E. W. Some Aspects of Alcohol in Body Fluids. Part II The Change in Blood Alcohol Concentration Following Alcohol Consumption, Medical Journal of Australia 2: 173, 1959.