MODELING THE CONCENTRATION OF ETHANOL IN THE EXHALED BREATH FOLLOWINGPRETEST BREATHING MANEUVERS

A previously developed mathematical model that describes the relations hip between blood alcohol (ethanol) concentration and the concentratio n of alcohol in the exhaled breath at end-exhalation (BrAC) has been u sed to quantitate the effect of pretest breathing conditions on BrAC. The model was first used to ''condition'' the airways with different b reathing maneuvers prior to simulating a single exhalation maneuver, t he maneuver used in standard breath alcohol testing. On inspiration, t he alcohol in the air reaches local equilibrium with the alcohol in th e bronchial capillary bed prior to entering the alveolar region. On ex piration, approximately 50% of the alcohol absorbed on inspiration is desorbed back to the airways. BrAC correlates with the amount of alcoh ol that is desorbed to the airways. The six pretest breathing conditio ns and the percent change in BrAC relative to the control maneuver wer e: hyperventilation (-4.4%), hypoventilation (3.7%), hot-humid air (-2 .9%), hot-dry air (0.66%), cold-humid air (0.13%), and cold-dry air (0 .53%). The mechanism underlying these responses is not due to changes in breath temperature, but, rather to changes in the axial profile of alcohol content in the mucous lining of the airways.