How breathing technique can influence the results of breath-alcohol analysis.

Abstract

This paper reports experiments to test how a person's breathing technique can influence the concentration of ethanol and the temperature of end-expired breath samples. The experiments were performed with healthy men after they drank a moderate dose of ethanol and the concentration of ethanol in breath was determined by gas chromatography. The results were compared with control breaths, which were deep inspirations and forced expirations of room air, analysed within 2–3 minutes of the test-breath sample. With breath-holding (30 seconds) before expiration, the concentration of ethanol increased by 15.7 ± 2.24 per cent (mean ± SE) and the temperature of breath rose by 0.6 ± 0.09°C. Hyperventilating for 20 seconds, immediately before the analysis of breath, decreased the concentrations of ethanol by 10.6 ± 1.37 per cent and the breath temperature dropped by 1.0 ± 0.22°C. Keeping the mouth closed for 5 minutes (shallow breathing) increased expired ethanol concentration by 7.3 ± 1.2 per cent and the breath temperature rose by 0.7 ± 0.14°C. After a slow (20 second) exhalation expired ethanol increased by 2.0 ± 0.71 per cent but breath temperatures remained unchanged from control tests. My results suggest that the changes in expired-ethanol concentrations are partly caused by the rise or fall in the temperature of breath. But an equally important factor is the amount of time the breath spends in contact with the mucous membranes of the upper respiratory tract. A long contact time increases the concentration of ethanol and rapid ventilation lowers it. Regardless of the breathing technique tested, the results recovered to control values immediately the subjects began breathing normally again.