The advantages of standardizing exhaled breath-alcohol concentration to a reference respiratory gas—water vapor

• Published in: Journal of breath research Vol. 17; no. 1; pp. 14002 - 14016
• Main Authors: Lindberg, Lars, Jones, Alan Wayne
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.01.2023
• Subjects: Alcohol; Anestesi och intensivvård; Anesthesiology and Intensive Care; Breath tests; breath-alcohol; Clinical Medicine; ethanol; infrared technology; Klinisk medicin; Medical and Health Sciences; Medicin och hälsovetenskap; Physiology; respiratory gases; standardization; water-vapor; alcohol; infrared technology; breath-alcohol; standardization; respiratory gases; water-vapor; ethanol
• ISSN: 1752-7155; 1752-7163; 1752-7163
• DOI: 10.1088/1752-7163/aca21b

Measuring the concentration of alcohol (ethanol) in exhaled breath (BrAC) provides a rapid and non-invasive way to determine the co-existing concentration in arterial blood (A-BAC). The results of breath-alcohol testing are used worldwide as evidence of excessive drinking, such as when traffic offenders are prosecuted. Two types of breath-alcohol analyzer are in common use; hand-held instruments used as preliminary screening tests of sobriety and more sophisticated evidential instruments, the results of which are accepted as evidence for prosecution of drunken drivers. Most evidential breath-alcohol analyzers are designed to capture the last portion of a prolonged exhalation, which is thought to reflect the alcohol concentration in substantially alveolar air. The basic premise of breath-alcohol analysis is that there is a physiological relationship between A-BAC and BrAC and close agreement between the two analytical methods. This article reviews the principles and practice of breath-alcohol analysis and introduces the concept of standardizing the results to a secondary physiological gas (water vapor), which therefore serves as an internal standard. The measured BrAC is thus adjusted to an alveolar air water content of 43.95 mg l −1 at 37 °C. This has several advantages, and means that a sample of breath can be captured without the person having to blow directly into the instrument. Adjusting the breath-alcohol concentration to water vapor concentration also compensates for variations in temperature of the expired air. The contact-free method of sampling breath means that a mouthpiece is unnecessary and the test subject does not need to make a continuous end exhalation.