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BLOOD ALCOHOL TESTS



W hy is Breath used to Test for Alcohol Concentrations in the Body? Alcohol is a drug that effects the central nervous system. Impairment from alcohol poisoning was originally defined by blood alcohol levels. It was observed that most people showed measurable mental impairment at around 0.05% blood alcohol concentration (BAC). Above this level it has been found that motor functions deteriorate progressively with increased blood alcohol concentrations. For the average person, unconsciousness results by 0.4% BAC. Above 0.5% (BAC), basic body functions such as the breathing or the beating action of the heart can be depressed to the point that death can occur.

Blood was the medium originally used to measure alcohol concentrations in the human body. Blood tests offer the ability to accurately test the same sample several times, if the sample is maintained properly. The disadvantages with blood analysis is that the collection process requires trained medical personnel, the sample collection is invasive, the analysis requires precise procedures by trained lab technicians , the results are not immediately available and the overall process is costly.

In the 1930's the pioneers in the development of breath alcohol testing took advantage of the fact that alcohol was found in the deep lung breath in proportion the alcohol found in the blood. Breath testing instruments were manufactured to capture a sample of alveolar breath for analyses. Some of the early instruments were crude, but today breath analytical instruments have evolved into low cost, highly accurate, rapid analytical systems that simply and painlessly collect a sample and calculate a result. Although a trained operator is still required, the collection and analysis process is simple. Additionally, many jurisdictions have defined alcohol in terms of breath instead of blood so that an extrapolation to blood in order to determine impairment is no longer necessary.

What is the Science Behind Breath Alcohol Analyzers?

A variety of technologies have been used to test a breath sample for alcohol. They include the following: Wet Chemistry, Photo Spectroscopy, Gas Chromatography, Infra Red Spectroscopy, Semi-Conductor Sensors (Tin Oxide Sensors),and Electro Chemical Analysis (Fuel Cell)

Interesting Historical Note:

The terms Breathalyzer ™ and Breathalyser ™ have become synonymous with breath alcohol testing equipment. Both are trademarked names not owned by Intoximeters, Inc. In fact the term Breathalyzer originated from an instrument invented by R.F. Borkenstein that utilized Chemical Oxidation and Photometry to determine alcohol concentration. The instrument was originally introduced in 1954 and was widely utilized for more than 20 years.





History of Alcohol Testing Breath Alcohol Breath Testing Instruments Portable Breath Testers (PBT) Approved Method Admissibility of Chemical Test Refusals Blood Alcohol 


The path of alcohol in the blood:

Liver Heart  Lungs

"It is in the lungs that the respiratory system bridges with the circulatory system so that oxygen can enter the blood and carbon dioxide can leave it... It is at the surface of the alveolar sacs that blood flowing through the capillaries comes in contact with fresh oxygenated air in the sacs... If, while this exchange is taking place, alcohol or any other volatile substance happens to be in the blood, it too will pass into the alveoli... (Criminalistics 262). "

HENRY'S LAW

In a closed container, at a given temperature and pressure a material in solution will be in equilbrium with air in the space above. Ethanol at 34° C, is in equilibrium with blood at a ration of 2100: 1.

Alcohol's distribution between blood and breath from the deepest part of the lung obeys Henry's Law. This means that  2100 ml of alveolar air will contain the same amount of alcohol that is present in 1 ml of the blood with which it has come to equilibrium.

Instruments

Scientific Basis on Breath Testing Instruments: Breath Tests for Blood Alcohol Determination Partition Ratios. By: Srikumaran K. Melethil, Ph.D., Professor of Pharmacology, University of Missouri at Kansas City. Forensic-Evidence.com.

BAC DATAMASTER: National Patent Analytical Systems Home

The BAC Datamaster is the only evidentiary breath test instrument in the State of Indiana. The Datamaster is certified and inspected according to the Indiana Administrative Code 260. A required by statue 9-30-6-5, all operators and instruments must be certified by the Indiana Department of Toxicology. Instruments are required to be calibrated every 180 days and operators must successfully complete the initial two-day Breath Test School an be recertified every two years.

Datamasters employ the technology of infrared spectroscopy and calculate Breath Alcohol Concentration or BrAC.

Infrared Light:

Not visible to the human eye

Electromagnetic radiation.

The amount of radiant energy of a particular wavelength can be measured by a detector as a decrease in the original power of transmittance of that wavelength.

The following is an explanation of the science behind the Datamaster:

The BAC DataMaster measures alcohol content in a breath sample by absorbance of infrared radiation at two wavelengths: 3.37 and 3.44 mm.  The sample is introduced into a sample chamber that is kept warm enough to prevent condensation.  The principle of infrared absorbance is well known, and is linear through a very wide range.  Data published by NHTSA demonstrate linearity in at least the range 0.04 to 0.16 g/210 L.  The result is calculated in comparison to the concentration of a standard, having a known concentration of ethanol vapor.

The two wavelength values allow the instrument to determine a ratio of absorbances which is unique to ethanol.  If the ratio for a sample is different from that of the ethanol standard, INTERFERENT is printed instead of an ethanol concentration.

Sample collection involves measuring instantaneous ethanol concentration as the breath is blown through the chamber.  Once several absorbance and flow criteria are met, the instrument closes the sample chamber and measures that ethanol concentration of the sample, which is alveolar (deep lung) air.  If the criteria are not met, a result is not given.  Instead either INVALID or INSUFFICIENT is printed.

BAC DATAMASTERS ARE CALIBRATED TO BENEFIT THE DEFENDANT!

1.  Datamasters truncate or eliminate the 3rd digit of every sample. For example: a reading of 0.07% could have been anywhere from a 0.070 to 0.079 percent. The instrument does not round!

2. Calibrated to a ration of 2100:1, when the actual ratio is closer to 2400:1 in humans. This causes an underestimation of BAC.

3. Calibrated to read below the true value of the calibration sample. Instruments calibrated with a 0.08 standard ethanol solution are adjusted to read between a .076 and 0.077. Therefore, an individual that has a BAC of 0.08 would produced a breath alcohol result of .077 on the Datamaster.

These factors combined allow for a 20% or more underestimation of Blood Alcohol Content.

Portable Breath Testers used in Indiana are not evidentiary and employ a fuel-cell technology. Several of the reasons why PBTs are not evidentiary include:

1. No more than 5 positive tests should be run in an hour.

2. Results are dependant upon the temperature at which the test is performed.

3. PBTs should be calibrated frequently.

However, PBTs help to determine if a person's impaired behavior is caused by something other than alcohol, such as a medical condition or through drug use.

FUEL CELL DESIGN:

An instrument using a fuel cell absorbs the alcohol from the breath sample, oxidizes it, and produces an electrical current proportional to the quantity of alcohol present in the breath.

Fuel Cell Technology:

History:

1800's - the fuel cell effect was discovered. Platinum electrodes in sulfuric acid supplied hydrogen at one electrode and oxygen at the other. The resulting reaction created a current flow between the electrodes.

1960s- a fuel cell that can be specific for alcohol

1970s to present- Fuel cell breath analyzers used commercially.

Consists of a porous, chemically inert layer coated with finely divided platinum (platinum black). The porous layer contains an acidic electrolyte solution, with platinum wire connections to the platinum black surfaces. The assembly is encased in plastic, with a gas inlet allowing breath sample delivery.

 

Link to the Indiana  Department of Toxicology webpage with step-by-step photos of the approved method for the administration of a breath test according to IAC 260. 

Factors that Influence Breath Testing Results

Use of the Approved Method.

Residual Mouth Alcohol

Truncation of last digit.

Calibration and maintenance of instrument.

Admissibility of Chemical Test Refusals: American Prosecutors Research Institute. Updated: 5/1/01.

v

Serum is the water component of whole blood. It is what is achieved when the cells and clotting factors are removed from the blood. 

What is the difference between blood and serum alcohol concentrations?

  It has been well established that substantial differences exist in ethanol content between serum and whole blood. This is due to the fact that ethanol distributes within the aqueous fraction of body tissues. Whole blood contains blood cells, lipids, and proteins, and has a water content of approximately 86%. Removal of the cells yields plasma, and further elimination of proteinaceous clotting factors yields serum. The water content of both plasma and serum is approximately 98%. Because of this higher percentage, ethanol levels will be higher in these fractions than in whole blood. The ratio of ethanol in serum to ethanol in whole blood ranges from 1.09:1 to 1.18:1, indicating that ethanol levels will be 9-18% higher in serum.

    Legal statutes in the State of Indiana regarding blood alcohol testing refer simply to "blood", and have been interpreted to refer to whole blood (Indiana Code sections 9-30-5-1, 9-30-6-6, 9-30-6-15 and 9-30-7-4). The State Department of Toxicology uses whole blood for alcohol testing. However, many medical centers perform such tests on the serum fraction only. In such cases, results may need to be converted into the corresponding values for whole blood. It has been established that reducing serum ethanol concentrations by 15-18% is a valid method for calculating whole blood ethanol levels. We recommend a value of 20%, which is at the upper limit of what has been reported by investigators to be the average serum: whole blood ethanol ratio, and thus should be valid for essentially all individuals. The higher percentage is favorable to the defendant, returning a lower blood ethanol concentration and precluding legal challenges that serum ethanol results overstate corresponding whole blood values.

Therefore, when converting between serum and whole blood ethanol concentrations, we recommend using the following formulas:

serum ethanol x 0.8 = whole blood ethanol

whole blood ethanol/0.8 = serum ethanol

Further information regarding ethanol concentrations in whole blood and blood fractions may be found in the following sources:

1.  Winek, C.L. and Carfagna, M. Comparison of Plasma, Serum and Whole Blood Ethanol Concentrations.  J. Analytical Toxicology. 11, 267-268, 1987.

2.  Montgomery,M. R. and Reasor, M J. Retrograde Extrapolation of Blood Alcohol   An Applied Approach. J. Toxicology and Environmental Health. 36,381-392,1992.

3.  Caplan, Y. H. in Medicolegal Aspects of Alcohol (J. C. Garriott, ed.), Lawyers &Judges Publishing Co., Tuscon, AZ, 1996, pp. 137-150.

Blood Alcohol Conversion:

Blood: Serum 1: 1.20
Blood: Plasma 1: 1.20

Police officers use portable breath-testing machines like this one to find out if a driver has a blood alcohol level above the legal limit.
We hear and read about drivers involved in an accident who are later charged with drunken driving, and usually a news report on the accident will say what the driver's blood alcohol level was and what the legal limit for blood alcohol is. A driver might be found to have a level of 0.15, for example, and the legal limit is 0.08. But what do those figures mean? And how do police officers find out if a driver they suspect has been drinking is actually legally drunk? You have probably heard about the Breathalyzer, but may wonder exactly how a person's breath can show how much that person has had to drink.

It is important for public safety that drunken drivers be taken off the roads. Of the 42,000 traffic deaths in the United States in 1999, about 38 percent were related to alcohol. Drivers who can pass roadside sobriety tests -- they can touch their noses or walk a straight line -- still might be breaking the legal limit for blood alcohol and be a hazard on the road. So police officers use some of the latest technology to detect alcohol levels in suspected drunken drivers and remove them from the streets.

Many officers in the field rely on breath alcohol testing devices (Breathalyzer is one type) to determine the blood alcohol concentration (BAC) in drunken-driving suspects. In this article, we will examine the scientific principles and technology behind these breath alcohol testing devices.

Why Test?
Alcohol intoxication is legally defined by the blood alcohol concentration (BAC) level. However, taking a blood sample in the field for later analysis in the laboratory is not practical or efficient for detaining drivers suspected of driving while impaired (DWI) or driving under the influence (DUI). Urine tests for alcohol proved to be just as impractical in the field as blood sampling. What was needed was a way to measure something related to BAC without invading a suspect's body.

In the 1940s, breath alcohol testing devices were first developed for use by police. In 1954, Dr. Robert Borkenstein of the Indiana State Police invented the Breathalyzer, one type of breath alcohol testing device used by law enforcement agencies today.

Let's take a look at what these tests are based on.

Principle of Testing
Alcohol that a person drinks shows up in the breath because it gets absorbed from the mouth, throat, stomach and intestines into the bloodstream.

Alcohol is not digested upon absorption, nor chemically changed in the bloodstream. As the blood goes through the lungs, some of the alcohol moves across the membranes of the lung's air sacs (alveoli) into the air, because alcohol will evaporate from a solution -- that is, it is volatile. The concentration of the alcohol in the alveolar air is related to the concentration of the alcohol in the blood. As the alcohol in the alveolar air is exhaled, it can be detected by the breath alcohol testing device. Instead of having to draw a driver's blood to test his alcohol level, an officer can test the driver's breath on the spot and instantly know if there is a reason to arrest the driver.

Because the alcohol concentration in the breath is related to that in the blood, you can figure the BAC by measuring alcohol on the breath. The ratio of breath alcohol to blood alcohol is 2,100:1. This means that 2,100 milliliters (ml) of alveolar air will contain the same amount of alcohol as 1 ml of blood.

For many years, the legal standard for drunkenness across the United States was 0.10, but many states have now adopted the 0.08 standard. The federal government has pushed states to lower the legal limit. The American Medical Association says that a person can become impaired when the blood alcohol level hits 0.05. If a person's BAC measures 0.08, it means that there are 0.08 grams of alcohol per 100 ml of blood.

There are several different devices used for measuring BAC.

Types of Devices: Breathalyzer
There are three major types of breath alcohol testing devices, and they're based on different principles:

  Breathalyzer - Uses a chemical reaction involving alcohol that produces a color change

  Intoxilyzer - Detects alcohol by infrared (IR) spectroscopy

  Alcosensor III or IV - Detects a chemical reaction of alcohol in a fuel cell Regardless of the type, each device has a mouthpiece, a tube through which the suspect blows air, and a sample chamber where the air goes. The rest of the device varies with the type.

Breathalyzer
The Breathalyzer device contains:   A system to sample the breath of the suspect   Two glass vials containing the chemical reaction mixture   A system of photocells connected to a meter to measure the color change associated with the chemical reaction To measure alcohol, a suspect breathes into the device. The breath sample is bubbled in one vial through a mixture of sulfuric acid, potassium dichromate, silver nitrate and water. The principle of the measurement is based on the following chemical reaction:

In this reaction:   The sulfuric acid removes the alcohol from the air into a liquid solution.   The alcohol reacts with potassium dichromate to produce:

  • chromium sulfate
  • potassium sulfate
  • acetic acid
  • water
The silver nitrate is a catalyst, a substance that makes a reaction go faster without participating in it. The sulfuric acid, in addition to removing the alcohol from the air, also might provide the acidic condition needed for this reaction.

During this reaction, the reddish-orange dichromate ion changes color to the green chromium ion when it reacts with the alcohol; the degree of the color change is directly related to the level of alcohol in the expelled air. To determine the amount of alcohol in that air, the reacted mixture is compared to a vial of unreacted mixture in the photocell system, which produces an electric current that causes the needle in the meter to move from its resting place. The operator then rotates a knob to bring the needle back to the resting place and reads the level of alcohol from the knob -- the more the operator must turn the knob to return it to rest, the greater the level of alcohol.

The Chemistry of Alcohol

The alcohol found in alcoholic beverages is ethyl alcohol (ethanol). The molecular structure of ethanol looks like this:
H
H 3C - C - O - H
H

where C is carbon, H is hydrogen, O is oxygen and each hyphen is a chemical bond between the atoms. For clarity, the bonds of the three hydrogen atoms to the left carbon atom are not shown.

The OH (O - H) group on the molecule is what makes it an alcohol. There are four types of bonds in this molecule:

  carbon-carbon (C - C)   carbon-hydrogen (C - H)   carbon-oxygen (C - O)   oxygen-hydrogen (O - H)

The chemical bonds between the atoms are shared pairs of electrons. Chemical bonds are much like springs: They can bend and stretch. These properties are important in detecting ethanol in a sample by infrared (IR) spectroscopy.

Types of Devices: Intoxilyzer
This device uses infrared (IR) spectroscopy, which identifies molecules based on the way they absorb IR light.

Molecules are constantly vibrating, and these vibrations change when the molecules absorb IR light. The changes in vibration include the bending and stretching of various bonds. Each type of bond within a molecule absorbs IR at different wavelengths. So, to identify ethanol in a sample, you have to look at the wavelengths of the bonds in ethanol (C-O, O-H, C-H, C-C) and measure the absorption of IR light. The absorbed wavelengths help to identify the substance as ethanol, and the amount of IR absorption tells you how much ethanol is there.

Diagram of the Intoxilyzer

In the Intoxilyzer:   A lamp generates a broadband (multiple-wavelength) IR beam.   The broadband IR beam passes through the sample chamber and is focused by a lens onto a spinning filter wheel.

The filter wheel contains narrow band filters specific for the wavelengths of the bonds in ethanol. The light passing through each filter is detected by the photocell, where it is converted to an electrical pulse.

The electrical pulse is relayed to the microprocessor, which interprets the pulses and calculates the BAC based on the absorption of infrared light.

Types of Devices: Alcosensor III or IV
Modern fuel-cell technology (which may power our cars and even our houses some day) has been applied to breath-alcohol detectors. Devices like the Alcosensor III and IV use fuel cells.

The fuel cell has two platinum electrodes with a porous acid-electrolyte material sandwiched between them. As the exhaled air from the suspect flows past one side of the fuel cell, the platinum oxidizes any alcohol in the air to produce acetic acid, protons and electrons.

Oxidation of Alcohol
If you strip off hydrogens from the right carbon of ethanol in the presence of oxygen, you get acetic acid, the main component in vinegar. The molecular structure of acetic acid looks like this:
O
||
H 3C - C - O - H

where C is carbon, H is hydrogen, O is oxygen, the hyphen is a single chemical bond between the atoms and the || symbol is a double bond between the atoms. For clarity, the bonds of the three hydrogen atoms to the left carbon atom are not shown. When ethanol is oxidized to acetic acid, two protons and two electrons are also produced.

The electrons flow through a wire from the platinum electrode. The wire is connected to an electrical-current meter and to the platinum electrode on the other side. The protons move through the lower portion of the fuel cell and combine with oxygen and the electrons on the other side to form water. The more alcohol that becomes oxidized, the greater the electrical current. A microprocessor measures the electrical current and calculates the BAC.

Mr. Casey has won numerous awards in the field of DUI and heads a premier DUI Defense firm in San Diego, CA, successfully representing San Diego DUI clients and routinely attaining favorable verdicts such as not guilty, hung jury, dismissed cases, and greatly reduced penalties.

Contact Us  right now to achieve the most favorable outcome in your San Diego DUI case.





Mr. Casey has won numerous awards in the field of DUI and heads a premier DUI Defense firm in San Diego, CA, successfully representing San Diego DUI clients and routinely attaining favorable verdicts such as not guilty, hung jury, dismissed cases, and greatly reduced penalties.
Contact Us  Today to achieve the most favorable results in your DUI case.




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