Information About Breath Tests and Their Accuracy. Is Breath Testing for Ethanol Accurate?
Like any computerized or mechanical machine, errors occur. I attended a demonstration of a breath testing machine where the expert giving the demonstration had beakers of different hydrocarbon liquids-acetate, methanol, isopropyl alcohol and ethanol. When each was tested the machine treated all of them as ethanol. The machine did not filter out the non-ethanol solutions as it should have. There are times when people have interferents in their mouth, i.e. mouthwash, and the machine does not register that.. This means the test score was higher than it should have been. In these examples, the filter did not work to separate out the non-ethanol hydrocarbon.
Another example is where noise-sound waves-can affect the motor that spins the filters-noises like the police walkie talkies can affect the results. There is supposed to be a mechanism that should have filtered out the sound waves at certain frequencies. On some machines there is an escape valve on the back of the machine when if covered does not allow the chambered breath alcohol to be fully exhausted and thus contaminates a test with alcohol that does not belong to the person being tested or the newly tested sample, which brings on a higher reading.
The breath machine has a computer chip and when it malfunctions the test results are inaccurate.
Many individuals and scientists who are experts in this type of testing steadfastly indicate that body temperature affects the testing process, which is not accounted for by the machine. To counter this the manufacturers say that the tube through which you blow is kept at a certain temperature. However, it is the person’s body temperature that is important and what if his normal temp is above the average or he has a fever.
These factors could raise your breath test scores. There are instances when the machine itself does not self- calibrate accurately. The machine before and after each test must self-calibrate against the machine’s known quantity sample. If it fails to do so accurately then the machine that analyzed your sample could be inaccurate and invalid. But what if the self- calibration is within the margin of error-Connecticut allows 5% either way-does this mean the machine was accurate? No. If you get the machine’s repair history you may pick up a machine with a long repair history of various kinds of problems that can affect the accuracy of the sample or at least bring into question the issue of accuracy.
Dr. Michael Hlastala claims that Alcohol Breath Testing does not allow for racial and gender bias. He claims that “small or larger lung volume has an effect on the test results.” He goes on to say that,” Inherent in the justification of the Alcohol Breath Test(ABT) is the presumed equality between end-exhaled alcohol concentration and alveolar alcohol concentration that is directly related to the blood alcohol concentration (BAC). Thus the ABT (Alcohol Breath Test) has been viewed as an accurate indirect measure of BAC. However, recent literature has shown that such a relationship between breath and blood is not necessarily identical for all individuals. An assumption used in the development of the ABT is that the last part of the exhaled breath has a concentration that is equal to that in the alveolar gas. This long-held assumption is the basis for justifying the ABT as an accurate measure of BAC. However, it has recently been shown that end-exhaled alcohol concentration (EEAC) is less than alveolar alcohol concentration (AAC) due to the exchange of alcohol in the airways with the bronchial circulation during both inspiration and expiration 2-4. The relative difference between AAC and EEAC varies with alterations in the breathing pattern.” Dr. Hlastala is indicating that you just cannot say that the breath machine takes into consideration all people because weights of individuals are different as is the size of lungs in each person and race and gender and lung volume. The testing that he refers to indicates that in cases where lung volume is lower the BAC could be higher. He believes that the old assumptions do not hold up in view of these more recent studies.
Many lawyers believe that the breath machine is not the most accurate method and that it is fraught with numerous mechanical breakdowns as well and many other types of problems some of which I have tried to explain in the preceding paragraphs. Then there is the computer program the processes the results and what that program consists of and the argument that it does not take into consideration the issues of lung volume, race and gender.
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