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As I’ve indicated with numerous examples in earlier posts, these breath machines which determine guilt or innocence in drunk driving cases are not exactly the reliable devices that law enforcement would have us believe. Yet another example of that unreliability is the fact that the results will vary depending upon the breathing pattern of the person being tested. This has been confirmed in a number of scientific studies.

In one, for example, a group of men drank moderate doses of alcohol and their blood-alcohol levels were then measured by gas chromatographic analysis of their breath. The breathing techniques were then varied. 

The results indicated that holding your breath for 30 seconds before exhaling increased the blood-alcohol concentration (BAC) by 15.7%. Hyperventilating for 20 seconds immediately before the analyses of breath, on the other hand, decreased the blood-alcohol level by 10.6%. Keeping the mouth closed for five minutes and using shallow nasal breathing resulted in increasing the BAC by 7.3%, and testing after a slow, 20-second exhalation increased levels by 2%. “How Breathing Techniques Can Influence the Results of Breath-Alcohol Analyses”, 22(4) Medical Science and the Law 275.

For another study with similar findings, see “Accurate Measurement of Blood Alcohol Concentration with Isothermal Breathing”, 51(1) Journal of Studies on Alcohol 6.

Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington, has gone farther and concluded:

By far, the most overlooked error in breath testing for alcohol is the pattern of breathing….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% above the alcohol level….Thus, a breath tester reading of 0.14% taken from the last part of the breath may indicate that the blood level is only 0.09%.” 9(6) The Champion 16 (1985).

Many police officers know this. They also know that if the breath alcohol test contradicts their judgement that the person they arrested is intoxicated, they won’t look good. So when they tell the arrestee to blow into the machine’s mouthpiece, they’ll yell at him, “Breathe harder! Harder! Keep breathing until I tell you to stop!” As Professor Hlastala has found, this method of breathing ensures that the breath captured by the machine will be from the bottom of the lungs, near the alveolar sacs, which will be richest in alcohol — giving a higher (but inaccurate) reading.
 

DUI BLOG

If you are arrested for DUI and a breath test shows a blood alcohol concentration (BAC) of .08% or higher, you are guilty. It does not matter, of course, whether you are a man or a women: the laws do not discriminate.

Maybe they should…

Researchers at the University School of Medicine in Trieste, Italy, found that the stomach lining contains an enzyme called gastric alcohol dehydrogenase that breaks down alcohol — and that women have less than men. To determine the relative effects of the enzyme, they gave alcohol both orally and intravenously to groups of alcoholic and non-alcoholic men and women. They found that women reached the same levels of blood alcohol as men after drinking only half as much; with weight differences taken into account, they found that women reached BAC levels illegal in a DUI case after drinking 20 to 30 percent less alcohol than men.

The scientists’ conclusion: legislatures may need to consider sex differences in drunk driving laws when defining safe levels of drinking for driving motor vehicles. Frezza and Lieber, "High Blood Alcohol Levels in Women: The Role of Decreased Gastric Alcohol Dehydrogenase Activity and First-Pass Metabolism", 322(2) New England Journal of Medicine 95 (1990).

Yet another study has found that women have lower "partition ratios" of blood to breath. What kind of ratios? Well, all breath machines in DUI cases measure the amount of alcohol in a person’s breath. But the what we really want to know is the amount of alcohol in the person’s blood. So how do we get that? Simple: a small computer in the breathalyzer multiplies the amount of alcohol it detects in the breath sample by 2100 times.

This is based upon the theory that, on average, there are 2100 units of alcohol in the blood for every unit of alcohol in the breath. (Note: that’s an average — but it varies from person to person.) According to the study, women have a significantly lower partition ratio. Jones, "Determination of Liquid/Air Partition Coefficients for Dilute Solutions of Ethanol in Water, Whole Blood and Plasma", Analytical Toxicology 193 (July/August 1983). And the lower the ratio, the higher the reading — even though the true BAC does not vary. Example: a woman with a true BAC of .06% and a ratio of 1500:1 (rather than the presumed 2100:1) will get a reading on the machine of .09% — above the legal limit. Put another way, the breath machine will show an average man accused of drunk driving to be innocent — but a woman with the same blood alcohol level to be guilty.

And then there’s the problem of birth control….

Scientists in Canada have found that "women taking oral contraceptive steroids (O.C.S.) appeared to eliminate ethanol significantly faster than women not taking O.C.S." Papple, "The Effects of Oral Contraceptive Steroids on the Rate of Post-Absorptive Phase Decline of Blood Alcohol Concentration in the Adult Woman, 15(1) Canadian Society of Forensic Science Journal 17 (1982). That means that women will reach peak BAC faster, and return to lower levels more quickly. This, of course, can create serious problems in a DUI case when attempting to estimate BAC at the time of driving based upon a breath test administered one hour later. Making the problem worse, researchers have also discovered that women who were taking birth control pills or who were pregnant had higher levels of acetaldehyde on their breath, due to the decreased ability to metabolize the enzyme as the level of sex steroids increases.

So what?

Well, most breath machines use infrared analysis in measuring the breath sample of a DUI suspect. But these machines don’t really measure alcohol, rather they measure any compound which contains the "methyl group" in its molecular structure. And acetaldehyde is one of these compounds. Result: a higher "blood alcohol" reading on the breathalyzer. Jeavons and Zeiner, "Effects of Elevated Female Sex Steroids on Ethanol and Acetaldehyde Metabolism in Humans", 8(4) Alcoholism: Clinical and Experimental Research 352 (1984).

It’s always a problem when the law, in its infinite wisdom, assumes that all of us are exactly the same.
 

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I have mentioned that a primary problem with blood alcohol analysis is that the no two individuals are alike in their physiology and metabolism of alcohol (see, for example, Convicting the Average Person, Racial Differences in the Metabolism of Alcohol and High Blood Alcohol – or a Zinc Deficiency?. Further, many foreign compounds can influence attempts to measure blood alcohol levels (see, for example, Under the Influence…Gasoline?, Asthma Inhalers Can Cause High Breathalyzer Results and Driving Under the Influence of…Paint?.

One of many other factors that render attempts to estimate an individual’s blood alcohol concentration at a given point in time is smoking.

A scientific study has found that cigarette smoking can influence absorption by the body of alcohol – and thus, among other things, attempts to estimate earlier blood alcohol levels when driving based upon tested levels. Johnson et al., "Cigarette Smoking and Rate of Gastric Emptying: Effect on Alcohol Absorption", 302 British Medical Journal 20 (1991).

The researchers reported testing blood samples of a group of smokers for blood alcohol levels both after smoking and after prolonged abstinence. The result was that "areas under the venous blood alcohol concentration-time curves between zero and 30 minutes and 60 minutes and the peak blood alcohol concentrations were significantly less during the smoking period compared with the non-smoking period". (Emphasis added) Gastric emptying was also found to be slower during the smoking evaluation.

The scientists concluded that the effect of smoking on alcohol absorption has "considerable social and medicolegal relevance", and that the ingestion of nicotine should be taken into when dealing with alcohol metabolism.

Non-specific analysis is another problem causing breath machines to give false readings when the subject is a smoker. As I mentioned in an earlier post, Why Breathalyzers Don’t Measure Alcohol, breath machines are actually designed to report the presence of any compound containing the methyl group in its molecular structure, not just alcohol. They cannot distinguish the difference between alcohol and, say, acetaldehyde.

Acetaldehyde? That’s a compound produced in the liver in small amounts as a by-product in the metabolism of alcohol. Unfortunately, alcohol moving from the blood into the lungs has been found to metabolize there as well – and, thus, to produce acetaldehyde there. The amount of acetaldehyde produced in the lungs varies from person to person. However, scientists have found one interesting fact: acetaldehyde concentrations in the lungs of smokers are greater than for non-smokers – far greater. Translated: smokers are more likely to have falsely high readings on a Breathalyzer. "Origin of Breath Acetaldehyde During Ethanol Oxidation: Effect of Long-Term Cigarette Smoking", 100 Journal of Laboratory Clinical Medicine 908.

End result: because breathalyzers can’t tell the difference between alcohol and acetaldehyde, a higher blood-alcohol reading. And if you are a smoker, a much higher reading.
 

DUI BLOG

Want to trick that breathalyzer into a false reading? Not that difficult: just change your breathing pattern.

As I’ve indicated in literally hundreds of earlier posts, these breath machines which determine guilt or innocence in DUI cases are not exactly the reliable devices that law enforcement would have us believe. (See, for example, How Breathalyzers Work – and Why They Don’t, Why Breathalyzers Don’t Measure Alcohol and How Accurate Are Breathalyzers?.)  Yet another example of that unreliability is the fact that the results will vary depending upon the breathing pattern of the person being tested.

This has been confirmed in a number of scientific studies.

In one, for example, a group of men drank moderate doses of alcohol and their blood-alcohol levels were then measured by gas chromatographic analysis of their breath. The breathing techniques were then varied.The results indicated that holding your breath for 30 seconds before exhaling increased the blood-alcohol concentration (BAC) by 15.7%. Hyperventilating for 20 seconds immediately before the analyses of breath, on the other hand, decreased the blood-alcohol level by 10.6%. Keeping the mouth closed for five minutes and using shallow nasal breathing resulted in increasing the BAC by 7.3%, and testing after a slow, 20-second exhalation increased levels by 2%. "How Breathing Techniques Can Influence the Results of Breath-Alcohol Analyses", 22(4) Medical Science and the Law275.For another study with similar findings, see "Accurate Measurement of Blood Alcohol Concentration with Isothermal Breathing", 51(1) Journal of Studies on Alcohol 6.

Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington has gone farther and concluded:

"By far, the most overlooked error in breath testing for alcohol is the pattern of breathing….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% above the alcohol level….Thus, a breath tester reading of 0.14% taken from the last part of the breath may indicate that the blood level is only 0.09%." 9(6) The Champion 16 (1985).

Many police officers know this. They also know that if the machine contradicts their judgement that the person they arrested is intoxicated, they won’t look good. So when they tell the suspect to blow into the machine’s mouthpiece, they’ll yell at him, "Keep breathing! Breathe harder! Harder!" As Professor Hlastala has found, this ensures that the breath captured by the machine will be from the bottom of the lungs, near the alveolar sacs, which will be richest in alcohol. With the higher alcohol concentration, the machine will give a higher — but inaccurate — reading.
 

DUI BLOG

As I have said in earlier posts, law enforcement investigation techniques depend largely upon the fictitious premise that all humans are physiologically identical (see “Convicting the Average DUI Suspect"). Without that presumption, field sobriety and breath alcohol tests would not be possible. I have previously discussed many examples of physiological differences — from person to person and within one person from moment to moment — which will directly alter breath or blood alcohol testing (see, for example, “Diabetes and the Counterfeit DUI”, “GERD, Acid Reflux and False Breathalyzer Results" and "The Effect of Anemia on Breath Tests").

Yet another example of variability is body temperature. Put simply, an individual’s body temperature will have a direct effect on the results of a breath test. The effects of changes in body temeprature from the norm of 98.6 degrees on breath testing has been discussed in an article entitled “Body Temperature and the Breathalyzer Boobytrap”, 721 Michigan Bar Journal (September 1982). If because of illness, for example, the body temperature is elevated by only 1 degree Centrigrade (1.8 degrees Fahrenheit), the 1:2100 breath-to-blood partition ratio will be affected so as to produce a 7 percent higher test result. Higher body temperatures will, of course, result in greater errors.

You don’t have to be sick to have a higher body temperature. Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington, confirms this — and the effects on breath test results. In an article entitled “Physiological Errors Associated with Alcohol Breath Testing”, 9(6) The Champion 18 (1985), he comments that even the average body temperature of a normal, healthy person “may vary by as much as 1 degree Centigrade above or below the normal mean value of 37 degrees Centigrade — or 1.8 degrees from the mean value of 98.6 degrees Fahrenheit”.

Not only can the normal mean body temperature of an individual vary from that of other persons, but the “temperature of any individual may vary from time to time during the day by as much as 1 degree Centigrade”. Result? The partition ratio for alcohol in blood is altered — meaning, according to Professor Hlastala, a 6.3 percent error for every 1 degree Centigrade increase or decrease from the presumed normal body temperature.

Yet another example of how breathalyzers are not actually testing you, but rather an “average” person who does not exist.
 

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