Name (BAC) for the amount of alcohol contained in venous blood, expressed in milligrams per gram or per milliliters (1 per mille = 1 gram of alcohol in 1 kilogram of blood or 1 mg / gram). The measurement is carried out in serum (blood without blood cells and coagulation factors) and is converted to blood content. For the determination of blood alcohol, the enzyme ADH (Alcohol dehydrogenase) used. The Swedish chemist Univ. Prof. Erik Widmark (1889-1945) developed in 1922 the named after him "Widmark's formula" for the determination of the BAK. In addition to the Widmark formula, there are other also named after the "inventors" calculation method (Seidel, Ullrich, Watson), which take into account body weight and gender and body length and age. The Widmark formula is used as the basis for electronic BAK terminals.
With the help of Widmark's formula, the blood alcohol content can be calculated with an accuracy of plus / minus 0.1 per thousand: c = A / (r * G)
There alcohol is water-soluble, it is not distributed in the bones and fat tissue, therefore, this body mass fraction is not available. The factor is lower for women, as they have on average a higher body fat percentage. Men should also assume a correspondingly lower weight G if they are overweight, since body fat is beneficial neither in distribution nor in the breakdown of alcohol.
Ingested amount of alcohol in grams = V * e * p
For the calculation of the mass of alcohol (A) in a liquid (beer, wine, brandy), the volume (V) of the beverage must be measured in deciliters with the alcoholic strength by volume (e) and the density (specific gravity) of alcohol (p = 0.8 kg / l or 0.08 g / cc). For one liter of wine (100 cl) with 12% alcohol by volume, the 12 cl alcohol present in this case corresponds to a weight of 96 g. With three glasses cognac with 4 cl each yield 12 cl Cognac (slightly less than "a Achterl"), these are at 40% vol alcohol content 4.8 cl alcohol with a weight of 38.4 g. For the calculation of the blood alcohol concentration, therefore, multiply the amount of the beverage in cc by the alcohol content by volume and then by 0,08. Two calculation examples:
A man of 85 kg and a woman of 70 kg each enjoy three eighths of wine (0.375 l = 37.5 cl) with 12% vol alcohol content: 37.5 * 12 * 0.08 = 36 g alcohol
reduced body weight = body weight in kg * distribution factor:
Man with 85 kg: 0.7 * 85 = 59.5 kg
Woman with 70 kg: 0.6 * 70 = 42.0 kg
Alcohol level = alcohol / reduced body weight
Man 36 g / 59.5 kg = 0.60 ‰ - best assumption 0.38 ‰
Woman 36 g / 42.0 kg = 0.86 ‰ - best assumption 0.59 ‰
A possible alcohol degradation is not taken into account in the first value. Neither is the fact that 10% and 30% (20% on average) can be deducted as the alcohol is not fully absorbed by the body. Assuming this 20% and a reduction of 0.1 ‰, the "best guess" results.
The alcohol consumed passes from the stomach (20%) and the small intestine (80%) first into the bloodstream and then into the body tissue (resorption). The division depends on the amount of blood (about 5 to 7l) and the body size or body area, the more extensive, the better the alcohol is distributed. However, as already mentioned, fatty tissue can not absorb alcohol. Therefore, in a tall, lean person alcohol is more distributed and there is relatively less concentration of alcohol in the blood compared to a small, fat person. The intake is relatively slow and, depending on the contents of the stomach, is not complete until one or two hours after the drinker has finished.
The liver is the only organ that can break down the alcohol up to 90%, the rest is eliminated through the kidneys with the urine or sweat. The organ begins with the loss of alcohol at the earliest 15 minutes "after the first sip" and continues to linear it continuously, regardless of further consumption. The more someone is used to alcohol, the higher the elimination rate. The human body degrades 0.1 to 0.2 ‰ per hour. A thumb formula: Half a liter of beer (5% vol) or one eighth of wine (12% vol) with ~ 12 mg of alcohol each are broken down in one to two hours. See further information under health,