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ALCOHOL IN THE HUMAN BODY The Alcolizer instrument measures the blood alcohol concentration (BAC) simply by breath analysis. When a person consumes an alcoholic drink (beer, wine, spirits, etc.,) the liquid passes quickly from the mouth into the stomach and, ultimately into the small intestine. However, the alcoholic fluid can only pass from the stomach through to the small intestine when the stomach valve opens. This process is known as gastric emptying. Alcohol, particularly in strong solution, is able to delay the opening of this valve and this may explain the fact that a person may sometimes consume two or three straight spirits and yet show a low BAC for some appreciable time afterwards. It is in the upper part of the small intestine, the duodenum, that the alcohol is absorbed into the blood stream. As the blood flows from the duodenum it eventually passes through the liver, where a certain small quantity of alcohol is constantly removed. This elimination process proceeds at a fixed rate, but is fairly slow, so that only a small quantity of alcohol can be removed at any time. Eventually, however, about 90% of the ingested alcohol will have been removed by the liver as the blood flows back through it from the body, with the remainder being removed through urine, breath and the skin with sweat. In the liver, the alcohol is broken down chemically to produce, eventually, carbon dioxide. This is carried by the blood and excreted from the body via the breath from the lungs. The concentration of alcohol for most rapid absorption is about 20% by volume, which corresponds to scotch and water 50/50, or sherry. Because strong solutions of alcohol depress the rate of opening of the valve connecting the stomach to the duodenum, drinks like neat sprits (typically 40% alcohol by volume) have a slower rate of absorption. Beers, because of their low concentration (typically 4% alcohol by volume), are also more slowly absorbed. Carbon dioxide, as in soda water, dry ginger or champagne, hastens the passage of alcohol into the blood and hence increases the maximum BAC. In general, the slower the rate of absorption, the lower the maximum BAC will be, all other factors being equal. All the time a person is drinking, alcohol is being absorbed into the bloodstream, so that they are increasing their BAC. Even when they have finished actual consumption, alcohol is still present in the stomach and intestine so that the alcohol absorption phase is not actually completed until some time later. If the intestine and stomach are empty of solid food then absorption of alcohol is unimpeded and may take only 30 minutes to reach completion after the last drink has been swallowed. However, if the stomach is relatively full of food from a recent, or current meal, then the absorption of alcohol into the blood is slowed and may take 90 minutes, or even longer, to reach completion. The presence of food in the stomach will also influence the maximum BAC that can be attained after the consumption of a certain quantity of alcohol. If the alcohol is consumed over a long period of time, then the rate of increase in the BAC due to its absorption may be close to the simultaneous breakdown rate in the liver. This breakdown rate is roughly equivalent to removing the alcohol from 285mL or a single measure of spirits every hour. Body Weight Nearly two thirds of body weight is water. Absorbed alcohol is distributed by the blood and mixes evenly throughout this water. The larger the body, the more water contained, and so the lower the final alcohol concentration. The larger the person, the lower the BAC after drinking a certain quantity of alcohol. ALCOLIZER TECHNOLOGY PO Box 1856 Cleveland DC Unit 8 132-140 Ross Court Queensland 4165 Australia Cleveland QLD 4163 Australia Phone 617 3821 1606 Fax 617 3821 1633 Web Site www.alcolizer.com Deep Lung Air A true measurement of the blood alcohol concentration can only be obtained by analysing deep lung air since only this has been in close contact with the blood. See Fig 1. Air from the mouth and the upper parts of the respiratory tract has not been in close contact with the blood and so is low in alcohol. In most people, deep lung air is reached after the first 1 litre of breath has been expired. Shallow Lung Air Deep Lung Air Blood in closest contact with air at end of the lungs Fig. 1 Alcohol and the lungs Mouth Alcohol The concentration of alcohol in the mouth is much higher than would ever be present in the blood so that, if a breath sample were analyzed soon after the subject had consumed his or her drink, the reading would be very high due to residual alcohol remaining in the mouth. Some of this mouth alcohol would evaporate into the expired air but this breath alcohol reading would not reflect the true blood alcohol concentration. It is important therefore that a period of at least 15 minutes has elapsed since the subject had his or her last drink. This fifteen minute period allows for any mouth alcohol to be dispersed, so that a valid breath alcohol analysis can be carried out to determine the blood alcohol concentration. It should always be remembered that, breath analysis looks to measure the representative portion of alcohol coming from the blood and not alcohol remaining from the last drink. Effects of Alcohol the Human Body Alcohol is a central nervous system depressant. This means that it slows down the processes occurring in the higher centres of the brain resulting in the classical symptoms of alcohol intoxication. These symptoms include, among others, loss of balance, poor coordination of the eyes and limbs, tunnel vision and the inability to make self criticism, with the result that the drunken driver genuinely believes himself to be driving better and mores safely than he really is. The common though mistaken idea that alcohol is a stimulant stems from the appearance and behaviour of a person under its influence. This behaviour is caused by the depression or removal of shyness or those normal restraints imposed on the sober individual by society or the environment. ALCOLIZER TECHNOLOGY PO Box 1856 Cleveland DC Unit 8 132-140 Ross Court Queensland 4165 Australia Cleveland QLD 4163 Australia Phone 617 3821 1606 Fax 617 3821 1633 Web Site www.alcolizer.com