A Large‐Scale Study of the Relationship Between Blood and Breath Alcohol Concentrations in New Zealand Drinking Drivers^*

Abstract

Blood alcohol concentrations (BAC) and corresponding breath alcohol concentrations (BrAC) were determined for 21,582 drivers apprehended by New Zealand police. BAC was measured using headspace gas chromatography, and BrAC was determined with Intoxilyzer 5000 or Seres Ethylometre infrared analysers. The delay (DEL) between breath testing and blood sampling ranged from 0.03 to 5.4 h. BAC/BrAC ratios were calculated before and after BAC values were corrected for DEL using 19 mg/dL/h as an estimate of the blood alcohol clearance rate. Calculations were performed for single and duplicate breath samples obtained using the Intoxilyzer (groups I-1 and I-2) and Seres devices (groups S-1 and S-2). Before correction for DEL, BAC/BrAC ratios for groups I-1, I-2, S-1, and S-2 were (mean+/-SD) 2320+/-260, 2180+/-242, 2330+/-276, and 2250+/-259, respectively. After BAC values were adjusted for DEL, BAC/BrAC ratios for these groups were (mean+/-SD) 2510+/-256, 2370+/-240, 2520+/-280, and 2440+/-260, respectively. Our results indicate that in New Zealand the mean BAC/BrAC ratio is 19-26% higher than the ratio of the respective legal limits (2000).

Breath Analyzer Screening of Emergency Department Patients Suspected of Alcohol Intoxication

“…This breath-to-venousblood ratio measured in the ED setting is 30% higher than the coefficient recommended by the manufacturer and legally accepted in France (2000), with a 95% CI of 2509-2714, excluding legal conversion coefficients in use worldwide (2000, 2100). A study based on more than 21,500 arrested drivers reported a mean BAC/BrAC ratio 19-26% higher than the ratio of the corresponding legal limit (11). Numerous studies have shown great interand intra-individual variability for the BAC/BrAC ratio.…”

“…Breath alcohol testing is widely used in law enforcement procedures for road safety. Many studies, mostly conducted on drivers suspected of driving under the influence of alcohol, show a high correlation between BAC and breath alcohol concentration (BrAC) measurements (9)(10)(11).…”

New Zealand's Breath and Blood Alcohol Testing Programs: Further data analysis and forensic implications

“…In order to estimate the BAC along with the corresponding BAC/BrAC ratios at the time of breath alcohol analyses, a linear BAC elimination rate of 0.019 g/dL/h was assumed [8], and the mean BAC values were increased by a factor of 0.019 times the delay (in hours) between breath testing and blood sampling [2,6]. Cases where the mean BrAC exceeded the time-adjusted mean BAC were classified as false-positives.…”

“…Blood alcohol analysis was performed using automated headspace-gas chromatography as described previously [6,7] and breath analysis was performed using instruments calibrated as described previously [6]. The Intoxilyzer 5000 employs analytical wavelengths of 3.48 and 3.39 mm (with a reference wavelength of 3.80 mm), and both Seres instruments employ a single analytical wavelength of 9.5 mm.…”

“…Prior to that date, drivers had the right to a blood test only if their evidential breath test result was 600 mg/L (0.126 g/210 L) and over the legal limit of 400 mg/L (0.084 g/210 L) for drivers 20 or more years of age, or over the legal limit of 150 mg/L (0.0315 g/210 L) for drivers under 20 years of age. These laws have allowed the establishment of a large database of paired breath and blood alcohol results and a preliminary study of this data, focusing on the variability of the BAC/BrAC ratio, has been published [6].…”