Breath Sampling Criteria - Part 3
Obtaining a suitable sample from a breath test subject
Counterpoint Volume 2: Issue 3 - Article 3 (November 2017)
An article for participants in the myCAMprogram
Jan Semenoff, BA, EMA
Forensic Criminalist
You should refer to the following articles:
COPD & Breath Alcohol Testing Counterpoint Volume 2, Issue 1
COPD & Breath Alcohol Testing Counterpoint Volume 2, Issue 1
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One of the most important considerations in a breath alcohol test is the physical ability of the test subject to provide the necessary breath samples, regardless of ethanol content. We’ve discussed in the previous articles (referenced above) the breath test device’s requirements for pressure, volume and exhalation time. Remember that breath alcohol testing is predicated on averages in determining those minimum sample requirements – average lung volume, average ability to exhale hard enough and long enough, etc. Obviously, you need to know if your client can meet those minimum sampling requirements. These averages play an important role, particularly in refuse breath test cases.
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A refresher on instrument requirements:
Most modern breath test devices are designed to obtain a sample of deep lung air, analyze it for ethanol, and express the concentration obtained in a given unit of measure. The general principle is that a test subject must exhale with a sufficient force to activate a pressure transducer or sensor of some sort. This action will activate a timing circuit.
The test subject must then maintain an even exhalation with sufficient force to exceed the minimum pressure set for the pressure transducer. As long as this minimum pressure is maintained, the timing circuit continues, and the sample will then be received, and subsequently analyzed, at the end of expiration. Specific parameters for all three conditions; exhalation time, minimum exhalation pressure and volume of breath delivered are required to obtain a sample that can be analyzed by the instrument.
In order to achieve the desired target goal of a deep-lung air sample, the minimum requirements for most breath test instruments is set at:
The test subject must then maintain an even exhalation with sufficient force to exceed the minimum pressure set for the pressure transducer. As long as this minimum pressure is maintained, the timing circuit continues, and the sample will then be received, and subsequently analyzed, at the end of expiration. Specific parameters for all three conditions; exhalation time, minimum exhalation pressure and volume of breath delivered are required to obtain a sample that can be analyzed by the instrument.
In order to achieve the desired target goal of a deep-lung air sample, the minimum requirements for most breath test instruments is set at:
- LONG ENOUGH - An exhalation of five to six seconds duration.
- HARD ENOUGH - A minimum exhalation force required is typically set at a pressure equivalent to a 15 cm (6”) column of water.
- EXHALED VOLUME - The target volume for exhalation is typically set at between 1.1 – 1.5 litres of breath.
Determining lung function
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Establishing “Normal”
Typically, establishing “normal” lung function involves establishing the person’s lung volume and lung capacities associated with different phases of the breathing cycle. In this case, normal really means the ability to meet the minimum requirements described above. How much air can you fully inhale? How much air can you completely exhale? How forcefully can you exhale the air? I guarantee that your measurements will be different than mine. There are a number of variables at play… How tall are you? Are you acclimatized to living at altitude? Are you in good physical condition? Do you exercise? Do you smoke? (Did you ever smoke?) What is your Body Mass Index? |
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Some important terms:
FEV - Forced Expiratory Volume
Forced Expiratory Volume (FEV) measures the volume of air a person can exhale during a forced breath.
VC - Vital Capacity
Vital capacity (VC) is the maximum amount of air a person can exhale from the lungs after a completely full inhalation.
FVC - Forced Vital Capacity
Forced Vital Capacity (FVC) is the total volume of air exhaled during the FEV test.
Forced Expiratory Volume (FEV) measures the volume of air a person can exhale during a forced breath.
- The amount of air forcefully exhaled during the first (FEV1), second (FEV2), and/or third seconds (FEV3) of the forced breath.
- A person with asthma or COPD will have a lower FEV1 test compared to a healthy person.
VC - Vital Capacity
Vital capacity (VC) is the maximum amount of air a person can exhale from the lungs after a completely full inhalation.
FVC - Forced Vital Capacity
Forced Vital Capacity (FVC) is the total volume of air exhaled during the FEV test.
- In general, it is common in healthy individuals to be able to expel 75% - 80 % of their vital capacity in the first second of the FVC test.
- Establishing a “normal” FVC is not as simple as it seems, as it combines age, gender, predicted values, allowances for history of smoking, etc. In simple terms, a “normal” person will have a FVC between 3-5 litres, as a rule of thumb
The effect of lung volume and exhalation ability on the breath test
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We have already discussed the effects of COPD on a breath test (Counterpoint Volume 2, Issue 1- Article 1). In essence, a test subject’s ability to provide a breath sample may, under certain conditions, be compromised to the point that no suitable sample can be obtained for a proper ethanol analysis. However, this may be considered a rare event that only occurs in extreme cases. But, what about an otherwise healthy individual, free from lung function abnormalities. Can size and lung volume also offer an impediment to the provision of a sample suitable for analysis? Again, we look at average lung volume, then compare that to extremes found in normal healthy individuals.
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Size Matters
The size of the test subject is a limiting factor, and therefore an important consideration. I’ve observed a number of small-statured people struggle with the instrument sampling requirements while honestly attempting to provide a breath sample (and I’m referring here mainly to training exercises, where the will to provide the sample was probably higher than a custodial event, where the motivation to provide the sample might be somewhat lower.)
Of course, know that full expiration of the entire inhaled lung volume is impossible – the lungs would collapse. Some residual air must remain, even with a full exhalation. In effect, the minimum volume of Forced Inspirational Vital Capacity may be inadequate to provide a breath sample volume requirement of 1.1 – 1.5 litres under normal breath testing procedures. Anderson and Hlastala comment, “For lungs with vital capacities less than 2.0 L, it is often difficult for the subject to fulfill the 1.5 litre minimum exhalation volume.” [1]
[1] Hlastala, M.P. and Anderson, J.C., “The Impact of Breathing Pattern and Lund Size on the Breath Alcohol Test”, Annals of Biomedical Engineering, Volume 35, No. 2, February 2007, page 268. Provided by the author.
Hlastala and Anderson add, on page 271:
The size of the test subject is a limiting factor, and therefore an important consideration. I’ve observed a number of small-statured people struggle with the instrument sampling requirements while honestly attempting to provide a breath sample (and I’m referring here mainly to training exercises, where the will to provide the sample was probably higher than a custodial event, where the motivation to provide the sample might be somewhat lower.)
Of course, know that full expiration of the entire inhaled lung volume is impossible – the lungs would collapse. Some residual air must remain, even with a full exhalation. In effect, the minimum volume of Forced Inspirational Vital Capacity may be inadequate to provide a breath sample volume requirement of 1.1 – 1.5 litres under normal breath testing procedures. Anderson and Hlastala comment, “For lungs with vital capacities less than 2.0 L, it is often difficult for the subject to fulfill the 1.5 litre minimum exhalation volume.” [1]
[1] Hlastala, M.P. and Anderson, J.C., “The Impact of Breathing Pattern and Lund Size on the Breath Alcohol Test”, Annals of Biomedical Engineering, Volume 35, No. 2, February 2007, page 268. Provided by the author.
Hlastala and Anderson add, on page 271:
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The ability to fulfill the minimum exhalation criteria for a breath test instrument is limited in individuals with smaller lungs and less than full inhalations. Figure 5 illustrates the combined impact lung size and inspiratory volume have on the ability to provide a minimum sample volume. As the size of the individual’s lungs decrease, it becomes more important to inspire a greater volume before exhalation. This finding is consistent with the observations of Jones and Andersson showing the probability of failing to provide a minimum sample is greater in females than males. Both genders show an increase in the probability of an insufficient sample with increasing age.[2]
[2] Ibid, page 271 |
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Additionally, the type of disposable mouthpiece used during a medical spirometry test is typically a wide-bore tube, similar in size and shape to a toilet paper roll tube. They are shown on the left in the image above. An alcohol breath test instrument employs a tube similar in diameter to that of a drinking straw (as shown in the image to the right). The decreased diameter of the mouthpiece tube causes increased resistance during sample provision due to backpressure. This in turn reduces the full volume of air that can be exhaled.
Jones and Andersson also reported that about 5% of women between 15-24 years of age, and about 8% of women between 25-34 years of age were unable to provide a sufficient sample into an Intoxilyzer 5000S. [3] These were normal, healthy women. None were identified as diminutive in stature.
[3] Jones, A.W. and Andersson, L., Variability of the Blood/Breath Alcohol ratio in Drinking Drivers, Journal of Forensic Science, 1996; 41(6), page 917.
Odell, et al, concluded in their 1998 study, Breath Testing in Patients with Respiratory Disability, that:
[3] Jones, A.W. and Andersson, L., Variability of the Blood/Breath Alcohol ratio in Drinking Drivers, Journal of Forensic Science, 1996; 41(6), page 917.
Odell, et al, concluded in their 1998 study, Breath Testing in Patients with Respiratory Disability, that:
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“Three of the five subjects had restrictive respiratory disease raising the possibility that it is the absolute lung volume rather than the respiratory flow rates which is the parameter.”[4] They found that, in some cases, a person with an FEV1 greater than 1.5 and an FVC greater than 1.75 was able to provide a sample. However, often the person could not complete the sampling requirements as they ran out of exhaled breath. 45% of the patients tested could not maintain the exhalation flow sufficient to provide a sample suitable for analysis.
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[4] Odell, M.S., McDonald, C.F., Farrar, J, Natsis, J.S., and Pretto, J.F., “Breath Testing in Patients with Respiratory Distress”, Journal of Clinical Forensic Medicine (1998) 5, page 48.
I participated in a yearlong study, published in Chest [5], that also found it was lung volume that presented an obstacle to providing a suitable sample. In short, some test subjects were able to blow hard enough to activate the pressure transducer, but not long enough to meet the minimum 5-second exhalation requirement. They simply ran out of breath as their lungs were too small to deliver the necessary 5-second, 1.1 – 1.5 litres of breath required. We found that most persons with an FEV1 greater than 1.5 and an FVC greater than 1.43 could provide a suitable sample under most circumstances.
[5] Prabhu, M.B., Hurst, T.S., Cockcroft, D.W., Baule, C. and Semenoff, J., “Airflow Obstruction and Roadside Breath Alcohol Testing”, Chest 1991: Volume 100, pages 585-586.
[5] Prabhu, M.B., Hurst, T.S., Cockcroft, D.W., Baule, C. and Semenoff, J., “Airflow Obstruction and Roadside Breath Alcohol Testing”, Chest 1991: Volume 100, pages 585-586.
Honeybourne, et al, concluded that a person needed an FEV1 greater than 1.1 to provide a sample. However, they also noted than 8/9 patients with an FVC greater than 1.5 could NOT successfully provide a sample onto a police breath test device (the Intoxilyzer 6000).
Gomm, et al, conducted two studies in 1991 and 1993 that dealt with the ability of persons with COPD or persons of very small stature to provide breath samples into police breath test devices. Both studies concluded that the test subject had to have an FEV1 greater than 2.0 – 2.3 and an FVC greater than 2.6 in order to successfully provide a breath sample. It should be noted that they defined small statured people as being 5’ 5” (166 cm.) or less in height.
Gomm, et al, conducted two studies in 1991 and 1993 that dealt with the ability of persons with COPD or persons of very small stature to provide breath samples into police breath test devices. Both studies concluded that the test subject had to have an FEV1 greater than 2.0 – 2.3 and an FVC greater than 2.6 in order to successfully provide a breath sample. It should be noted that they defined small statured people as being 5’ 5” (166 cm.) or less in height.
The 1993 Gomm, et al, study is perhaps the most instructive, as it is the only one to address the ability of small statured people to provide a sample. This study added an additional element – PEF, or Peak Expiratory Flow, measured in litres per minute. They concluded that the person would have to provide a PEF of at least 330 L/min to meet the sampling requirements.
All the other studies here, including the one I participated in, refer to patients with Chronic Obstructive Pulmonary Disorder to provide a reading. Although FEV1 and FVC are reliable measurands to assess the suitability to provide a sample, there were some people in all the studies who had the minimum lung functions but still were not able to keep the time and pressure necessary to provide a suitable sample.
All the other studies here, including the one I participated in, refer to patients with Chronic Obstructive Pulmonary Disorder to provide a reading. Although FEV1 and FVC are reliable measurands to assess the suitability to provide a sample, there were some people in all the studies who had the minimum lung functions but still were not able to keep the time and pressure necessary to provide a suitable sample.
Where does this leave your client?
This information is useful under circumstances where a person, particularly one that is small statured, is charged with refusing to provide a breath sample. Ideally, there are no outward indicia of impairment or intoxication, nor evidence to support a charge of impaired driving. The only issue in these ideal cases is the ability to provide a breath sample. Have your client’s lung volume and lung function assessed, and compare these results with the minimum, requirements here to see if they were even capable of providing a breath sample. Obviously, an expert (or two) may have to be retained.
Case study:
I was asked to prepare a letter of opinion on a refuse breath test case involving a 26-year old female, 127 cm (3’10”) in height, 41 kg (90 lbs.) in weight with a body mass index of 25.4. Her FEV1 (Forced Expiratory Volume over 1 second) was about 1.85 litres. Her FVC (Forced Vital Capacity) was about 2.1 litres.
She was stopped at a roadside sobriety check point after being observed leaving a licensed establishment. She operated her specially-equipped vehicle in a normal fashion with no indication of impaired driving. No indicia of impairment or intoxication were observed on her physically. She passed sobriety tests with flying colors. The testing officer noted in his report that she seemed to be complying with instructions to provide the sample, but just couldn’t blow long enough to provide a breath sample. Regardless, the officers elected to charge her with refusal.
The charges were ultimately stayed.
Look again at her height and weight and consider their implications. Wonders never cease…
She was stopped at a roadside sobriety check point after being observed leaving a licensed establishment. She operated her specially-equipped vehicle in a normal fashion with no indication of impaired driving. No indicia of impairment or intoxication were observed on her physically. She passed sobriety tests with flying colors. The testing officer noted in his report that she seemed to be complying with instructions to provide the sample, but just couldn’t blow long enough to provide a breath sample. Regardless, the officers elected to charge her with refusal.
The charges were ultimately stayed.
Look again at her height and weight and consider their implications. Wonders never cease…
Final thoughts:
The size of the test subject matters:
- They may be charged with refusing a breath test due to their inability to physically provide a sample.
- Their lung function and volume may play a part - Have them medically assessed.
- In general, a person needs an FEV1 greater than 1.5 - 2.3 litres, and an FVC greater than 1.4 - 2.6 litres to provide an adequate breath sample
- The probability of an insufficient sample is greater in females than males
Send me your questions or comments:
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Comments and questions will be posted here with their responses:
For further study:
- Dubowski, K.M. Absorption, Distribution and Elimination of Alcohol: Highway Safety Aspects, 10 J. Stud. Alcohol Suppl. (1985).
- Gomm, P.J. and Broster, C.G., Study into the Ability of Healthy People of Small Stature to Satisfy the Sampling Requirements of Breath Alcohol Testing Instruments, Med. Sci. Law, Volume 33, No. 4, pages 311-314.
- Gomm, P.J., Osselton, M.D. and Broster, C.G., Study into the Ability of Patients with Impaired Lung Function to Use Breath Alcohol Testing Devices, Med. Sci. Law, Volume31, pages 221-225.
- Honeybourne, D., Moore, A.J., Butterfield, A.K. and Azzan, L., A Study to Investigate the Ability of Subjects with Chronic Lund Disease s to Provide Evidential Breath Samples Using the Lion Intoxilyzer 6000UK Breath Alcohol Testing Device, Respiratory Medicine (2000), Volume 94, pages 684-688.
- Hlastala, M.P. and Anderson, J.C., The Impact of Breathing Pattern and Lund Size on the Breath Alcohol Test, Annals of Biomedical Engineering, Volume 35, No. 2, February 2007, pp. 264-272.
- Jones, A.W. and Andersson, L., Variability of the Blood/Breath Alcohol ratio in Drinking Drivers, Journal of Forensic Science, 1996; 41(6): 916-921.
- Odell, M.S., McDonald, C.F., Farrar, J, Natsis, J.S., and Pretto, J.F., Breath Testing in Patients with Respiratory Distress, Journal of Clinical Forensic Medicine (1998) 5, pages 45-48.
- Prabhu, M.B., Hurst, T.S., Cockcroft, D.W., Baule, C. and Semenoff, J., Airflow Obstruction and Roadside Breath Alcohol Testing, Chest 1991: Volume 100, pages 585-586.
