Breathing Patterns and Breathalyzers
The way a DUI suspect breathes immediately before breath testing may have an effect on the breath alcohol test results in a DUI investigation - often increasing the reading noticeably. A scientist in the Department of Alcohol and Drug Addiction Research at the Karolinska Institute in Stockholm, Sweden, has investigated the phenomenon at some length. In an article appearing in 22(4) Medical Science and the Law 275 (1982), entitled How Breathing Technique Can Influence the Resuits of Breath-Alcohol Analysis, Dr. A. W. Jones reports a series of experiments with a group of men who drank moderate doses of alcohol and whose blood-alcohol levels were then measured by gas chromatographic analysis of their breath. The breathing techniques of the subjects were then varied for the tests that immediately followed.
Dr. Jones found that holding one's breath for 30 seconds before expiration increased the concentration of alcohol by 15.7 percent. Hyperventilating for 20 seconds immediately before the analysis of breath, on the other hand, decreased the blood-alcohol level by 10.6 percent. Keeping the mouth closed for five minutes and using shallow nasal breathing resulted in increasing the ethanol concentration by 7.3 percent, and testing after a slow, 20 second exhalation increased levels by 2 percent.
These results were explained by Dr. Jones partly in terms of the rise or fall in the temperature of the 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. The scientist concluded:
The influence of a person's breathing technique, before or during delivery of a breath sample, should be carefully considered when breath-alcohol instruments are used in medico-legal work for evidentiary testing. My experiments show that the duration of contact between the breath and the mucous membranes covering the respiratory tract is a key factor and that an increase in the time spent in contact increases the expired-ethanol concentration.
For another study coming to similar conclusions, see Ohlsson, et al., Accurate Measurement of Blood Alcohol Concentration with Isothermal Rebreathing, 51(1) Journal of Studies on Alcohol 6 (1990).
Dr. Michael Hlastala, Professor of Physiology, Biophysics, and Medicine at the University of Washington, has gone even further and concluded that by changing breathing technique within normally required guidelines, a subject can change the equivalent BAC as measured by the breath from as little as 50 percent to over 150 percent of the true BAC.
(9(6) The Champion at 16 (1985)). Apparently, the heating and cooling of the breath in breathing causes changes in alcohol concentration during exhalation. As Dr. Hlastala has observed:
By far, the most overlooked error in breath testing for alcohol is the pattern of breathing. All breath testers attempt to take a sample from the end of the breath ... [But] the concentration of alcohol changes considerably during the breath ... The first part of the breath, after discarding the dead space, has an alcohol concentration much lower than the equivalent BAC. Whereas, the last part of the breath has an alcohol concentration that is much higher than the equivalent BAC. The last part of the breath can be over 50 percent above the blood alcohol level... Thus, a breath tester reading of 0.l4g percent taken from the last part of the breath may indicate that the blood level is only 0.09g percent.
Dr. Hlastala explains that this takes place because as the DUI suspect breathes room air in, that air cools the airways. When he then breathes out, some of the alcohol in the expired breath coming from the warm lungs condenses on the surface of the airways. As he continues to breathe out, his airways are warmed by the breath, resulting in evaporation of some of the alcohol on the surface. Thus the latter portion of the DUI suspect's breath picks up additional alcohol from this evaporation. Result: a falsely high reading.
Subsequently, in a June 1997 internet message, Dr. Hlastala elaborated on his explanation of the effects of breathing on BAC readings. He explained how breath machines give higher readings for individuals who exhale greater amounts of breath:
No breath test instrument is able to obtain a sample of alveolar air without it changing. During exhalation, the alcohol level always changes as alcohol deposits on the airway mucous. In fact, the presumption of breath test instrument manufacturers that end-exhalation alcohol concentration is equal to alveolar concentration is absolutely incorrect from a scientific perspective... The machines do not control for the amount of breath exhaled and therefore discriminate against individuals who exhale greater amounts of breath before stopping their exhalation. It is the lack of control of breath that is the primary variable making the breath test very inaccurate.
In other words, the greater the amount of breath exhaled before a sample is captured in a DUI case, the more alcohol deposits on the mucous in the passage to be absorbed by the end-exhalation
(captured sample at the end of the breath).
There have been a number of other studies concerning the effects of breathing methods on breath alcohol analysis since those reported by Jones and Hlastala. In one, for example, the blood alcohol level of three subjects as tested on a breath instrument was decreased 24 percent after those subjects ran up and down stairs. In another, BACs of 39 subjects were raised between 5 percent and 15 percent by having them hold their breath for 20 seconds before breathing into the instrument. And in yet another, hyperventilation among 17 subjects resulted in elevating BAC readings by an average of 15 percent. For a discussion of these studies, see Mulder and Neuteboom, The Effects of Hypo- and Hyperventilation on Breath Alcohol Measurements, 24 Blutalkohol 341 (1987).
