Current Issue

Vehicles are becoming increasingly important for travel, commuting, logistics, etc. However, as the number of automobiles has increased, road traffic safety has become a worldwide problem for reducing road traffic accidents and fatalities. Sweden declared a Vision Zero slogan to eliminate any victims from road traffic accidents [1]. Among road traffic accidents, alcohol-related accidents and fatalities are primary concerns worldwide in terms of improving safety in road traffic situations. To alleviate alcohol-related accidents, most nations use alcohol sensing apparatus for screening drunken drivers, which measures BrAC using optical components or fuel-cell type devices [2-4].

Currently, breathalyzers for monitoring BrAC are widely used to screen impaired drivers at roadsides. The legal limit for impairment is 0.08% in the U.S. and 0.05% in most European countries. Although Sweden adopted a 0.05% BAC limit in the 1950s, the legal BAC limit was recently lowered to 0.02% to further improve traffic safety. James and Robert reported that fatal crashes and severe personal injuries have decreased by lowering legal limits, leading to safer road traffic situations [5]. In 1962, the Korean government legitimized road traffic laws to enforce alcohol-impaired driving. Four decades later, BrAC analysis for road traffic offences was regulated in 2006, with a legal BAC limit of 0.05% for driving. In addition, several trials have been conducted to decrease the legal limit of BAC to 0.03% for road traffic safety and reduce alcohol-related fatalities. Finally, the Korean government settled its legal limit to 0.03% in 2019.

Because consumed alcohol is eliminated from the body through the exhaled air that comes from the deep lungs [6,7], the measurement of BrAC has been used to analyze BAC for decades. The relationship between BAC and BrAC has been studied for a long time; therefore, BAC is currently converted from BrAC by multiplying with the ratio of BAC to BrAC, known as the partition ratio or conversion factor, Q. The US National Highway Traffic Safety Administration (NHTSA) uses a Q-factor of 2,100 [8], which was also adopted for converting BrAC to BAC in Korea. However, Jones and Andersson reported that most countries adopt a conversion factor of 2,000–2,300 [9]. Furthermore, a recent study showed that the conversion factor could range from 2,225 to 2,650; Jones and Andersson reported an average conversion factor of 2,448 in their article [10]. Pavlic et al. presented the time dependency of Q ranging from 2,225 to 2,650 [11]. Lindberg et al. showed that the BAC/BrAC ratio was 2,251 in Swedish subjects [1].

The Q-factor is relevant to the BAC determined by the breathalyzer and varies from country to country. Therefore, the primary objective of this study is to identify the BAC/BrAC ratio of healthy Koreans and identify alternative BAC measurement methods to estimate BACs and screen drunken drivers correctly.

Arranging the results of BACs according to the ellapsed times, healthy Korean women also show three characteristic alcohol metabolisim patterns as shown in Fig. 1: early-saturation, saturation, and non-saturation patterns. It is quite similar to the results of Korean males reported previously[12]. As can be seen in Table 1, Korean women show around 44% of non-saturation pattern. It means that Korean women digest the alcohol more easily than the males. As suggested in Fig. 1 and Table 1, the alcohol metabolism of Korean adults could be confirmed with three characteristic patterns.

Fig. 1. 
Three characteristic patterns of BACs: (a) early saturation, (b) saturation, (c) non-saturation.

Fig. 2 shows the relationship between BACs and BrACs measured using two different apparatuses: a multi-gas analyzer and a portable breathalyzer with an assumed partition ratio Q=2,100. In the case of Korean males and women, BACs were overestimated using the multigas analyzer, as depicted in Fig. 2; regression lines y=1.032x+0.0042 with R²=0.849 for males and y=1.003x+0.0047 with R²=0.892 for women. However, when breath alcohol concentrations were measured with a portable breathalyzer, the BACs were underestimated, as shown in Fig. 2; regression lines y=0.749x-0.0007 wih R²=0.802 for males and y=0.7885x+0.0001 wih R²=0.859 for females. From the BACs and BrAC analyses, the partition ratio should be lowered in a multi-gas analyzer and increased in a portable breathalyzer for correct BAC measurements.

Fig. 2. 
Relationship between BACs and BrACs measured by two different analyzers: (a) male, (b) female.

Although the results of the multi-gas analyzer were similar to the blood alcohol concentrations for all subjects, the BrACs and BACs results did not exactly match in both measurement methods, as shown in Fig. 1 and Fig. 2. A small bias of approximately 10% of the error (± 0.005%) exists with the measurement of the multi-gas analyzer; however, the data measured by the breathalyzer showed a slightly higher offset value in the BAC measurements. Furthermore, although the BACs had meaningful values, the breathalyzer didn’t monitor the actual BACs in some subjects. Therefore, the partition ratio was calculated according to the sex, elapsed time, and the average value at all time intervals.

The partition ratios as functions of BACs are shown in Fig. 3. In these figures, the partition ratio is divided into two regions–before and after 60 min of alcohol intake and their average values are listed in Table 2. The average value of T_max, which is the average time that BACs reach the highest value after consuming alcohol in this study, was 55 min [13]; therefore, the partition ratios were calculated with this time reference.

Fig. 3. 
Partition ratios (Q-factor) as a function of BACs: (a) male, (b) female.

During the absorption time of alcohol (less than 60 min after consuming alcohol), the averages of the Q-factor were small compared to the value used in the screening of drunken drivers. The average partition ratio was slightly higher in females than in males. The standard deviation in each group showed a large distribution: approximately 300 in the male group and 300–600 in the female group. Therefore, the Q-factor and the standard deviation of the Q-factor were small in the Korean women. However, when entire data were calculated without time limitations, the average partition ratio of healthy Korean males and women were calculated as 1,913 and 1991, respectively.

The partition ratio (Q=2,011 or 2109 after 60 min) is an important factor in calculating the estimated BACs when the extrapolated BAC is needed to evaluate the initial BAC value by the police. In addition, the average partition ratio, after drinking alcohol without a time limit, would be essential to the manufacturers of BAIIDs because the user of BAIIDs would be required to pass the rolling retest while driving [14,15]. Therefore, it would be valuable to determine the relationship between BACs and BrACs as a parameter of the partition ratio; this relationship is presented in Fig. 4. As shown in Fig. 4 (a), when Q=2,100 was adopted to calculate the BACs, the actual BACs were overestimated by the exhaled breath samples. The regression line was y= 0.8615x+0.0023 with R²=0.892 (Q=2,100). It is certain that the measurement results would not be favorable for healthy Korean males. However, when the partition ratio was less than 2,100, as noted by Q=1,913, the BrAC product by Q-factor showed more favorable matches than the previous results with the regression line y= 0.9457x+0.0023, with R²=0.891. For Korean women, the Q-factor (Q=1991) suggested in Fig. 3(b) is more reasonable, as shown in Fig. 4(b).

Fig. 4. 
BACs vs. BrACs according to the partition ratio, Q: (a) male, (b) female.

To ensure the replacement of invasive BACs measurements, Bland–Altman plots [16] according to the partition ratios (Q=1,913 for males and Q=1,991 for women) are presented in Fig. 5. If there is no or a small bias in the Bland–Altman plot, it is well known that a new experimental apparatus or method could be replaceable in medical checkups. As described in a previous report [12], when the partition ratio Q was 2100, there was a bias of –0.0052 and its 95% CI ranged from –0.0059 to –0.0045. However, when the Q-factor of 1913 was multiplied by BrACs to calculate BACs, the bias was –0.0004 for males and –0.0017 for women. Because the limit of agreement was offset toward negative values in the case of Q=2,100, the measured values from the multi-gas analyzer clearly exaggerated the BACs, as shown in Fig. 4. From the results shown in Fig. 4 and 5, it is clear that the average value of the partition ratio calculated with the whole interval BAC/BrAC ratio is more reasonable than the value of Q (=2,100) used in the current breathalyzer for healthy Koreans.

Fig. 5. 
Bland-Altman plots of healthy Korean; (a) male (Q=1913), (b) female (Q=1991).

Table 3 lists the ethanol concentration versus CO₂ concentration as a function of time interval intaking alcohol. Ethanol concentrations peaked in both cases; however, the concentrations of exhaled carbon dioxide show a relatively uniform distribution in this study. It can be inferred from Table 3 that the ethanol and carbon dioxide should be measured simultaneously to assure the screening procedures of drunken drivers.

To reveal the relationship between BACs and BrACs in healthy Koreans, extensive medical tests were performed for the first time. Healthy Koreans showed three characteristic BAC patterns of alcohol metabolism; however, more than 50% of the participants showed saturation patterns with BACs peaks at less than 60 min. As the BACs are underestimated by using conventional value (Q=2,100), it would be better to consider new values (Q=1,913 for males and Q=1,991 for women) or execute more profound research to reveal the exact partition ratio for healthy Koreans. In addition, to prevent false drinkers, it is recommended that alcohol and carbon dioxide concentrations be analyzed simultaneously.