Physiology Of Breath Testing - Dräger Alcotest 7410 GLC Operator's Manual

Alcotest 7410 GLC User's Manual
knowledge of the GLC before using it to
obtain grounds for an approved instrument
demand. The following material will
describe the operation, some theoretical

Physiology of Breath Testing

This brief chapter is included to explain
how breath samples are used to determine
the blood alcohol concentration.
When a person consumes an alcoholic
beverage, it passes from the mouth and
esophagus to the stomach and small
intestine where it is absorbed into the blood
stream. The absorption of alcohol is quite
rapid, generally taking 20 to 30 minutes
after consumption to reach the maximum
reading. The absorption time is affected by
the type and amount of food in the stomach
and the type of beverage consumed. Once in
the blood stream, the alcohol is distributed
to all parts of the body including the lungs,
brain and liver. It is the depressant action of
alcohol in the brain that causes impairment
and intoxication.
Elimination of the alcohol begins
immediately after it has entered the blood.
Most of the alcohol (90 – 98%) is
eliminated by metabolism in the liver. The
remainder (2 – 10%) is eliminated
considerations, and law and policy
concerning the use of the
Alcotest 7410 GLC.
unchanged through urine, sweat, breath and
other body fluids. Unlike absorption, the
elimination process is slow. The average
elimination rate is 15 mg% per hour.
The basis for all breath test instruments is
that alcohol is eliminated unchanged in the
breath. There is a fixed and known
relationship between the amount of alcohol
in the breath and the amount of alcohol in
the blood. This relationship (essentially the
principle of breath testing) is:
2100 parts of deep lung air contain the
same amount of alcohol as one part
of blood.
Because this ratio has been well established
in scientific experiments, it is possible to
collect a measured volume of breath,
analyze it for alcohol and convert the result
to a blood alcohol content. This principle is
used by all breath test instruments,
including the GLC.
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