Alcohol Countermeasure Systems
Contents
Alcohol and the Physiology of the Human Body
Absorption
Distribution
Elimination
Breath - Blood Alcohol Ratio
Behavior as a Result of Alcohol Consumption
Effects of Alcohol on Driving Performance
The Physiology of Breath Testing
Alcohol and the
Physiology of the Human Body Alcohol is a drug and must be handled
with care. Knowing its uses and abuses is just as important as reading
the instructions on a bottle of pills. It is basic preventive medicine
to know how your body handles alcohol, how much is safe to drink and, finally,
how your body gets rid of it.
When you have a drink, a small
amount of alcohol enters the bloodstream directly through the tissues of
the mouth and throat. When it reaches the stomach 30 - 40 percent of the
alcohol can be absorbed in 20 minutes if the outlet valve of the stomach
is closed. When the outlet is open, however, the alcohol passes into the
small intestine, where rapid absorption takes place. The bloodstream then
distributes the alcohol uniformly throughout the body. In this manner,
the alcohol reaches the brain.
Alcohol is an anesthetic. Its effects
are similar to ether or chloroform. As a central nervous system depressant,
it affects all parts of your body controlled by the brain. Your ability
to make appropriate judgments and to exercise self-control is affected.
This means that you cannot control the effects of alcohol by an act of
will.
Alcohol does not simply pass through
you. Like most things we eat or drink, it must be broken down and eliminated.
Moreover, alcohol affects the body fairly rapidly, although its impact
can be decreased according to a number of factors.
Disposing of alcohol is much more
time consuming than drinking. Most alcohol is eliminated by a process called
oxidation, which breaks it down into carbon dioxide and water. More than
90 percent of the alcohol is oxidized in the liver and the remainder is
discharged unchanged through the lungs and kidneys. Only a negligible proportion
is eliminated through tears, saliva and perspiration. You cannot dance,
jog, sing, or cry away alcohol. Frequent urination does not help. Nor is
the rate of elimination affected by a person's weight or tolerance to alcohol.
It takes as long for the experienced drinker to eliminate alcohol as it
does for the inexperienced drinker.
Absorption
Alcohol is a small molecule which readily mixes with water. It can be taken into the body by any of the common routes of administration for drugs. The most practical and effective route is oral ingestion.As soon as alcohol comes into contact with the tissues of the mouth and throat, absorption begins. Alcohol quickly passes through these tissues and enters the rich blood supply of the blood vessels in this area, by a process of simple diffusion. Unlike other complex substances, such as fats, carbohydrates and proteins, alcohol does not require preliminary digestion or breakdown for absorption, and no carrier is needed for its passage into the bloodstream. Alcoholic beverages are retained in the stomach for a period of time prior to transfer into the small intestine.
The absorption of alcohol into the bloodstream can also occur directly at the stomach wall, but most rapid absorption occurs through the wall of the small intestine, a highly specialized tissue for the uptake of nutrients into the body. It has a large surface area, one thousand times greater than the stomach, and has thinner walls and a greater blood supply.
Regardless of the alcohol concentration of a beverage consumed, the concentration of alcohol in the small intestine rarely exceeds 1 to 2% v/v. Only the mouth, the throat and the stomach come into contact with high concentrations of alcohol, and only in the stomach is this contact prolonged.
Anything which will retain alcohol in the stomach will prolong absorption, while conditions which allow rapid passage of alcohol into the small intestine will hasten the rate of absorption. Typically about 30% of all consumed alcohol is absorbed from the stomach whereas 70% is absorbed from the small intestine. Factors which may effect the total rate of absorption include the type and nature of alcoholic beverages, the concentration of the alcoholic beverage itself, the type of food and quantity of food consumed, sex of the individual, body weight, body water content, experience with alcohol, metabolic disposition and other physical, biological, and physiological factors. These parameters taken together define consumption tolerance for a given individual.
Distribution
Once alcohol has been absorbed into the bloodstream it is circulated throughout the body diffusing into the body tissues and fluids mixing and equilibrating with total body water. Immediately after absorption and distribution, alcohol is distributed into the blood throughout the body in the cardiovascular system to the various organs of body fluids. Differences are seen between body fluids and body organs, however, a relatively constant ration between them exists. The most important single factor which influences the alcohol concentration in an organ or fluid is its water content, since alcohol is soluble in water.The alcohol that is absorbed from the stomach and small intestine enters the portal vein which leads directly to the liver, the major detoxifying organ of the body. The blood of the body, prior entering the right side of the heart. The blood is then pumped through the lungs where oxygen is taken up, carbon dioxide and other volatile compounds such as ethyl alcohol are given off. This process takes place in the alveolar sacs in the deep lung region. The lung contains approximately 300 million alveoli. Surrounding the alveoli is a fine network of capillary blood vessels. In the respiratory system air moves back and forth through the same set of tubules and there is continuous mixing of inspired and expired air. The blood on returning from our lungs enters the left side of the heart from which it is pumped into the arterial system throughout the body. About 1/3 of the total blood volume pumped out of the left heart, goes to the brain whereas the remaining 2/3 goes to the rest of the body. The larger portion is passed through the kidneys where it is filtered and purified.
Elimination
The elimination of alcohol from the body begins shortly after it is present in the body and continues until it has been totally removed. Elimination proceeds by two (2) separate means: Metabolism and Excretion. About 90 - 98% of the total amount of alcohol consumed is removed by metabolism. Metabolism which occurs chiefly in the liver effectively removes alcohol from the body by changing it to other compounds. An enzyme, alcohol dehydrogenase, brings about this reaction . The end products of this reaction, carbon dioxide and water, are non-toxic and excreted from the body by natural means.The combination of metabolism and excretion leads to total amount of alcohol eliminated from the body. For a given individual, this amount is relatively constant. The actual amount is dependent upon a persons weight and amount of fatty tissue. For a 150 pound man, the amount of alcohol that can be eliminated from the body in one (1) hour is approximately 25 ml of 40% v/v liquor (about 1 ounce) or 10 ml of pure alcohol. It is obvious therefore that the sum of the amount of alcohol eliminated from the body since the time drinking started should provide a fairly accurate estimate of the total amount of alcohol, a given individual may have consumed.
The body removes alcohol at a constant rate. Once absorption is completed, the blood alcohol concentration should decrease until all the alcohol is removed. The rate of elimination is determined by monitoring the decreasing blood alcohol levels with time.
If this rate of elimination were measured in all people, it would be observed that regardless of height, weight, sex, or amount of fatty tissue, the average rate is about the same for all people: 15 mg% per hour. The normal range for values of this rate is 10 - 20 mg% per hour. However, the average value of 15 mg% per hour will be used. It is possible then to calculate with a fair degree of certainty what a person's BAC would have been at some time previous, or what it will be, given the BAC at a particular time. If no additional alcohol was consumed in the interval and the BAC of the subject has been declining over the time interval, a reasonable prediction can be made.
Breath - Blood Alcohol Ratio
When alcohol leaves the blood stream and enters the breath it reaches
a point of equilibrium in the "deep lung" or alveolar region. The relationship
between the concentration of alcohol in the arterial blood region of the
lungs and the concentration of alcohol in the breath from the deep lung
region (alveoli) at the end expiratory breath temperature (34 C) is known
as the breath-blood ratio. This ratio has been experimentally determined
by a number of research groups since Widmarks's historic work in this field
and at present the most commonly accepted ratio is 2100:1. That is, 2100
parts of deep lung air contain the same amount of alcohol as 1 part of
blood.
Others have found the factor of 2320-2370 to
1 can be established using re-breathed air as a means of breath alcohol
determination and have therefore proposed the adoption of 2300:1 as the
international standard. While this more closely approximates the value
to be predicted from Henry's Law, it does not take into consideration the
practical limits of the design of breath testing instruments commonly being
used for evidential and screening purposes. Thus, while the ratio of 2100:1
generally results in an under-estimation of blood alcohol concentration
from a breath alcohol analysis, this is preferred to an over-estimation
when the results of the analysis are to be used to establish a criminal
charge or other sanction.
To ensure that a proper sample of breath from
the deep lung region has been analyzed for alcohol content, a variety of
techniques have been adopted which require a controlled and uninterrupted
flow of breath until near complete expiration has occurred. It is the breath
from the deep lung region (end expiratory) that contains the highest concentration
of alcohol which is in equilibrium with the alcohol concentration of the
blood.
Mixed expired breath has a lower alcohol concentration
since it is not in equilibrium with the blood. Thus, the means to sample
breath for alcohol analysis must ensure that all of the mixed expired air
is exhaled first before a sample of breath from the deep lung region is
captured for analysis.
Further, to ensure that the alcohol in the breath
sample is representative of the alcohol concentration of the blood, one
must ensure that there is no concentration of the breath sample from residual
alcohol in the mouth and throat from a recent drink. This is accomplished
by waiting fifteen (15) minutes after a last drink or rinsing the mouth
and swallowing water before conducting a breath test.
Behavior as a Result
of Alcohol Consumption Alcohol affects everyone. It does so, however,
in different ways, depending on your mood, physical condition, personality
and the company you keep. If you are just recovering from a cold or have
had little sleep, the effects of alcohol will be magnified. If you are
worried about your job or your love life, drinking will only compound your
feelings of anxiety and possibly lead to aggressive or hostile behavior.
Your reaction to alcohol will also vary according to the social demands
placed upon you. A few drinks with your friend will make you feel drunker
than a few drinks with the family.
You may learn to compensate for
some of the more obvious symptoms of drinking. Researchers call this behavioral
tolerance and everyone calls it "holding your liquor". While experienced
drinkers can learn the act normally when talking or walking, they cannot
control the effects of alcohol on skills demanding fine motor coordination
or precise judgment.
Some drinkers develop physical
tolerance to alcohol. As a result of prolonged regular drinking, the liver
becomes more efficient in breaking down alcohol. In addition, some cells
in the brain can become less sensitive to the effects of alcohol. As a
result of both of these factors, progressively more alcohol may be needed
to produce the mode-altering effects experienced in earlier stages of drinking.
Whatever the individual variations,
there is an established sequence of symptoms which correspond to different
degrees of intoxication. The first mental processes to be affected are
those connected with training or previous experience. One skill impaired
at the initial stages of intoxication is driving ability, particularly
for individuals who have not been driving very long.
After a few more drinks, the ability
to perform familiar and habitual tasks requiring relatively little thought,
attention or skill is impaired. At this stage, you may find you have to
concentrate on opening a bottle of wine. Simply moving around in a crowd
of people at a party may require your full attention. You may drop things
and conversations may be difficult to follow.
As the alcohol level rises in the
blood, muscular coordination is further affected and basic reflexes become
progressively depressed. There is reduced hand steadiness, difficulty in
standing and emotional outbursts. The drinker may become aggressive or
hostile.
Beyond this stage, the drinker
risks falling into a stupor and eventual coma. If the coma persists for
more than 10 hours, a person usually dies of asphyxiation due to paralysis
of the respiratory center of the brain. Alcohol poisoning usually occurs
at BAC's above 400 mg%.
Effects of Alcohol
on Driving Performance The driving task has been described as a
complex divided attention task involving; 1) a central visual task (tracking
or maintaining the vehicle's lane position) and 2) a peripheral visual
task (scanning the environment, for objects, e.g. other traffic or potential
driving hazards). When these two activities are combined into a time-shared
or divided attention task, alcohol impairs driving performance at BAC's
as low as 50 mg%. Neither of the two activities appear to be impaired by
alcohol when performed alone. However, when combined, performance is generally
poorer on the peripheral visual task.
Alcohol impairment of performance
in divided attention tasks is most likely due to an impairment of the information
processing. It appears that alcohol has less effect on the processing of
information from a single source than on that coming from several sources.
Drivers who are under the influence of alcohol tend to concentrate on one
task and neglect others in a divided attention task.
Driving an automobile is usually
taken for granted as being a relatively easy task, not requiring much conscious
effort or critical judgment. Yet the sensory functions of the body bombard
the brain with required information which must be assimilated and processed
such that smooth, controlled operation of the automobile results. The brain
makes decisions and regulates motor activity based upon training and previous
experiences. Thus, the many complete maneuvers that one makes while driving
occurs "automatically" and one does not have to be consciously aware of
it.
Because alcohol acts to depress
the reticular activating system, several things occur. The altering mechanism
is depressed such that a person does not become aware of potentially hazardous
or dangerous situations that the sensory functions detect. The sensory
functions themselves are deteriorated and may not be supplying complete
or correct information to the brain. A person's motor of functions are
impaired; yet, because of alcohol's depressant effect that person will
feel less inhibited and more self confident about his driving skills. As
a result a person, after having consumed alcohol, is more likely to speed
into high risk situations which would normally be avoided or treated cautiously.
The Physiology of
Breath Testing Following oral consumption, alcohol is absorbed from
the gastro-intestinal tract and distributed throughout the body by the
circulatory system. Alcohol diffuses freely and is found in relative concentrations
according to the water content of the various tissues. By processes of
metabolism and simple excretion, including its passage into the breath,
alcohol is removed from the body.
The relative concentration of alcohol
in the various tissues, including blood, urine, lachrymal fluid and saliva,
can be predicted and correlated on the basis of their respective water
contents. Alcohol passes unchanged from the blood stream into the breath
and, therefore, the alcohol concentration of the blood may be calculated
from a breath alcohol determination.
The process of respiration takes
place at the juncture of the blood and the breath within the alveolar sacs,
deep in the lungs. Blood coming from the right side of the heart is pumped
through the pulmonary arteries which circulate through the alveolar region
and carries with it carbon dioxide and other volatile gases which are produced
in the body as a result of metabolism. These gases pass freely through
the walls of the blood vessels in the alveoli. At the same time, oxygen
from the breath diffuses through the alveolar walls to the blood stream.
This process is concentration dependent, the gases diffuse from an area
of higher concentration to an area of lower concentration. The pulmonary
veins then carry the oxygen enriched blood from the lungs back to the left
side of the heart where it is distributed throughout the body.
To conduct a proper breath analysis
for alcohol content, it is necessary to sample breath from the deep lung
region. A variety of techniques have been employed for this purpose but,
generally, try to mimic the respiratory profile.
A variety of techniques have been
employed to ensure the collection of a proper sample of breath, some of
which rely upon operator judgment and training, while other techniques
are completely automatic in their nature. One of the techniques is to provide
a continuous and uninterrupted flow of breath above a minimum threshold
pressure and for a minimum duration of time to a breath alcohol detector.
This protocol ensures the sampling of deep lung air for the alcohol concentration
necessary to the accuracy of of the breath testing instrument.
