The Small Statured Test Subject
Breath Sampling Criteria - Part 3
Counterpoint Volume 6: Issue 4 - Article 5 (December 2022; Updated November 2023)
An article for participants in the myCAMprogram
Jan Semenoff, BA, EMA
Forensic Criminalist
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Article information:2200 words (approximately 10-12 minutes)
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What is the ability of a person of very small stature to physically provide a breath sample into an approved screening device or approved instrument?
Terminology & parameters
First, let’s define some values. Keep in mind that these are all statistical values, and will vary by country, region, or ethnicity. As an example, the average height for a North American Caucasian male is 5’ 9” (175 cm) while the average height for males, worldwide, is 5’ 7” (171 cm).
Average human adult weight also varies by continent and are often based upon dietary considerations. In North American males, again as an example, the average weight is 190 lbs (85 kg), while in Asian and African males the average weight is 130 lbs (60 kg).
Typically, males weigh more than females. Let’s focus on North American “averages”.
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Average Height (North America) [1]
Male 5’ 9” 175 cm Female 5’ 4” 162 cm |
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Average Weight (North America) [2]
Male 190 lb 85 kg Female 155 lb 70 kg |
Small Statured Persons
Short stature refers to the height of a person that is below typical. Because of the lack of preciseness of the term short, and wide variance in human height, there is considerable disagreement as to what constitutes being short.
Weight, on the other hand, is often categorized using Body Mass Index (BMI). BMI is a calculated value derived from the height and weight of a person. It is a convenient rule of thumb that broadly categorizes a person as underweight (below 18.5), normal weight (18.5 - 25), and overweight (above 25). When used as a health predictor, it has considerable limitations, and its values should be interpreted with caution.
Certainly, a small statured person has other issues with alcohol absorption and increased BAC levels due to lower body mass.
A Standard Drink is defined as 1.5 ounces (45 mL) of hard liquor (vodka, gin, whisky) at 40% alcohol concentration, 5 ounces (150 mL) of wine at 12% alcohol concentration, and 12 ounces (330 mL) of beer or cider at 5% alcohol concentration.
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As an example, an average height (5’ 9”) and weight (190 lb) male (with a BMI of 28) will receive the equivalent BAC of 0.020 grams/dL per Standard Drink, while an average height (5’ 4”) and weight (155 lb) female (BMI 28) will receive the equivalent BAC of 0.030 g/dL per standard drink. Therefore, statistically on average, a female receives 50% more equivalent BAC per standard drink.
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Compare this to an underweight 125 lb male, who will receive the equivalent BAC of 0.030 g/dL per Standard Drink, while an underweight 100 lb female will receive the equivalent BAC of 0.047 g/dL per standard drink.
So, let’s focus on the ability of a small statured person in their ability to provide a breath sample. For our purposes, we will consider anyone with a BMI below 18.5 to be “small statured”.
Breath Test Requirements
Breath test devices are designed to obtain a sample of deep lung air, analyze it for alcohol, and express the concentration in a specific unit of measure. Most modern units operate on the principle that a person, regardless of their size, must exhale with sufficient force to activate a pressure sensor or transducer of some sort. This action in turn activates a timing circuit.
The test subject must maintain an even exhalation with sufficient force to maintain the minimum pressure set for the pressure transducer. If 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 time, pressure and volume are required to obtain a sample that can be analyzed by the instrument.
To achieve the desired target goal of a deep-lung air sample, the minimum exhalation time required for most breath test instruments is set at five to six seconds duration. The minimum exhalation force required is typically set at a pressure equivalent to a 15 cm (6”) column of water. The target volume for exhalation is typically set at between 1.1 – 1.5 litres of breath.
Establishing a instrumentation standard
It is interesting to note that the minimum requirement of pressure, time and volume have been, for the most part, the standards used for measurement of a sample to determine its suitability. An Intoximeter Alco-Sensor FST, as an example, has similar sample provision requirements as an Intoxilyzer 5000C, an Intoximeter EC/IR II, or an older ALERT Model J3A. This is in part due to new instruments being compared to older ones currently permitted for use as Approved Screening Devices or Evidentiary Instruments during the certification and review process. In short, older devices were based on these parameters. Newer devices are compared to these approved parameters to see if the new device provides equivalent readings, under similar sample provision situations. The status quo has therefore been maintained regarding sample provision for quite some time.
It is interesting to note that the minimum requirement of pressure, time and volume have been, for the most part, the standards used for measurement of a sample to determine its suitability. An Intoximeter Alco-Sensor FST, as an example, has similar sample provision requirements as an Intoxilyzer 5000C, an Intoximeter EC/IR II, or an older ALERT Model J3A. This is in part due to new instruments being compared to older ones currently permitted for use as Approved Screening Devices or Evidentiary Instruments during the certification and review process. In short, older devices were based on these parameters. Newer devices are compared to these approved parameters to see if the new device provides equivalent readings, under similar sample provision situations. The status quo has therefore been maintained regarding sample provision for quite some time.
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This is in sharp contrast with devices such as the Breathalyzer Model 900 or 900A. When I was first qualified on these instruments in the early 1990’s, it was up to the operator to determine the suitability of the sample being provided and assess whether deep-lung air samples were being properly provided to be analyzed for the presence and quantity of alcohol they contained. Qualified Technicians are still responsible to determine that the breath sample is truly a deep lung air sample. As a result, persons of very large stature might be required to provide samples beyond the minimum five-second, 1.1 – 1.5 L requirement. As an example, a large, male, football-linebacker might be required to exhale 12-15 seconds AND 3.5 – 4.0 litres to obtain the desired sample of deep-lung air.
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Conversely, a smaller statured person would provide a true sample of deep-lung air far quicker than the above example. However, the units employing a pressure/time/volume algorithm are not capable of determining the actual lung capacity of the individual being tested. Therefore, they are designed or programmed to obtain samples given certain assumptions. The five-second, 15cm water column pressure, 1.1 – 1.5 litre minimum volume are based on persons of normal stature. Some persons will be able to exceed these requirements, while other persons may not be able to achieve the minimums mandated by instrument design.
It should be noted that in a typical spirometry test, the person is required to inhale to the fullest possible capacity. This is not necessarily done during a breath alcohol test. Therefore, the measured breath exhalation may represent a volume not deliverable during a complete exhalation.
The Effect of Lung Volume and Exhalation Ability on the Breath Test
Of course, remember 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 measured breath exhalation 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.” [3]
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.
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Additionally, the type of disposable mouthpiece used during a spirometry test is typically a wide-bore tube, similar in size and shape to a toilet paper roll tube. An alcohol breath test instrument employs a tube similar in diameter to that of a drinking straw. 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. [4] These were normal, healthy women. None were identified as diminutive in stature.
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.”[1] 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. [5]
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Our 1990 study, published in Chest [6], also found that 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 litre 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.
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). [7]
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 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. [8] [9]
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. By their findings, many test subjects would not be expected to provide a suitable 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. Many small statured persons have a measured PEF well under that threshold.
In 2023, Ives et al published their findings on the ability of healthy adults to provide a breath sample. They looked at the spirometry records of healthy, non-smoking individuals (281,210) with no history of lung disease or respiratory problems and concluded that:
- A "significant minority" (a little more than 2%) "cannot use existing evidential breath analysis machines."
- Females were three times more likely to be unable to provide a breath sample compared with males (1.64 % vs 0.54%)
- Short stature was also identified with 2.6% of males and 308% of females below the 2nd percentile of height unable to provide a breath sample.
- Age was also a factor. Comparing the youngest group with the oldest (40s versus 70s), the risk of not being able to provide a sample increased tenfold for males (0.16% vs 1.63%) and sixfold for females (0.65% to 3.83%).
- They concluded overall that 1 male in 186 and 1 female in 61 "would be physiologically incapable of providing an evidential breath sample".
All the other studies here, including my own, 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.
Perhaps a table of finding is easier to understand:
Practice Tip: |
Final thoughts:
Size matters. The ability to provide a breath sample suitable for analysis depends, in part, on the ability to physically exhale enough breath to meet the pressure/time/volume parameters of the instrument used.
- Persons with a history of pulmonary disorders may not be able to meet these parameters
- Small statured persons may not be able to meet these parameters
- By their design, it is easier to exhale into a spirometer than it is to provide a sample into a typical breath alcohol testing device.
Send me your questions or comments:
Comments and questions will be posted here with their responses:
Comments and questions will be posted here with their responses:
For further study:
- Taken from https://en.wikipedia.org/wiki/Average_human_height_by_country on 12 December 2022.
- Taken from https://en.wikipedia.org/wiki/Human_body_weight on 12 December 2022.
- Hlastala, M.P. and Anderson, J.C., The Impact of Breathing Pattern and Lung Size on the Breath Alcohol Test, Annals of Biomedical Engineering, Volume 35, No. 2, February 2007, page 268.
- 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, 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.
- 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, D., Moore, A.J., Butterfield, A.K. and Azzan, L., A Study to Investigate the Ability of Subjects with Chronic Lung Disease s to Provide Evidential Breath Samples Using the Lion Intoxilyzer 6000UK Breath Alcohol Testing Device, Respiratory Medicine (2000), Volume 94, pages 684-688.
- Ives, G., Sbaffi, L., and Bath, P. A., Can all healthy adults use the current evidential breath alcohol analysers? An investigation using a large spirometry database, Medico-Legal Journal 0 (0) 1-6, 2023.
- 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.
- Crockett, A.J., Schembri D.A., Smith, D.J. Laslett, and Alpers, R., Minimum Respiratory Function for Breath Alcohol Testing in South Australia, Journal of the Forensic J.H. Science Society, Volume 32, Issue 4, 1992, Pages 349-356.
