COMMENTARY
Minimum respiratory function for breath alcohol testing in South Australia AJ CROCKE'IT, D A SCHEMBRI, DJ SMITH, R LASLE'IT and J H ALPERS Respiratory Unit, Flinders Medical Centre, Bedford Park, SA 5042, Australia The aim of this study was to determine if inability to complete a breath alcohol test successfully, using a Lion Alcolmeter SD-2 or Drager Alcotest 7110, was related to any of the standard parameters obtained from the lung function spirometry test. A total of 153 subjects referred to a clinical laboratory for routine lung function testing were tested using the Alcolmeter, 158 using the Alcotest, with 69 subjects completing tests on both instruments. Of the 153 patients who volunteered to use the Alcolmeter, 49 (32%) were unable to produce a valid test effort on this instrument. One subject failed to complete a satisfactory test using the Alcotest, and one was unable to master the technique. There was considerable overlap of the minimum value for each of the lung function parameters of those subjects who could or could not successfully complete the breath alcohol test. It is recommended that changes are made to both of the instruments, the techniques used and the legislation, to minimize the number of breath alcohol testing failures and to reduce the variability of the results. Key Words: Breath alcohol analysis; Spirometry; Forced Vital Capacity; Forced Expiratory Volume in one second. Journal of the Forensic Science Society 1992; 32: 349-356 Revision received 6 February 1992; accepted 11 May 1992
Introduction Failure to provide a roadside breath sample to police on request has been classed as an offence in South Australia since the introduction of random breath alcohol analysis. Previous studies using different types of breath alcohol analysers have suggested lower limits for Forced Vital Capacity (FVC) and Forced Expiratory Volume in one second (FEV,.,) 11-41. The degree of pulmonary disability that would prevent an individual from being able to perform successfully on either of the two roadside breath alcohol analysis units used in South Australia is not known. The aim of this study was to document the minimum flow rates and resistance to breathing in the two standard devices, the Lion Alcolmeter SD-2 and Drager Alcotest 7110, and to determine if inability to complete the test successfully was related to any of the standard parameters obtained JFSS 1992; 32(4): 349-356
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from the lung function spirometry test. The study was undertaken at the request of the Breath Analysis Section of the South Australia Police Department, and was approved by the Clinical Investigation Committee of Flinders Medical Centre.
Experimental Lion Alcolmeter SD-2 The assessment of the Alcolmeter was divided into two parts, the first being to determine the triggering flow, minimum expired volume and the resistance to flow of the instrument. Minimum flow to trigger the device (amber light A) was determined using a Gould Goddart Flow Calibration device which consists of an inclined alcohol manometer and high precision flow tubes. The Alcolmeter with mouthpiece was attached to the flow calibration unit and the flow rate was then increased slowly from zero flow until the amber light A was illuminated. This triggering flow rate was measured ten times with each of ten randomly selected disposable mouthpieces. Resistance to a flow rate of 28.5 litreslmin was measured for each mouthpiece by determining the pressure drop across the mouthpiece (cm H,O) and dividing by the flow rate. The volume required for a satisfactory measurement was calculated by measuring the time to trigger green light B using a laboratory stop-watch, at a present flow of 28.5 litreslmin, and multiplying flow by time in minutes. The second part of the assessment was to investigate which parameters of lung function best predicted a subject's ability to perform the Alcolmeter test satisfactorily. Consecutive subjects (n = 153) referred to the laboratory for routine lung function testing were asked, on satisfactorily completing their pulmonary function tests, to exhale into the Alcolmeter. Excluded were subjects aged between 5 and 15 years, the terminally ill, those subjects who had a physical or medical disability that would, in the short term, preclude them from driving a vehicle and those subjects who refused to participate in the study. The subject's ability to trigger the Alcolmeter correctly was recorded along with their age, sex, forced vital capacity (FVC), forced expiratory volume in one second (FEV,,) and peak expiratory flow rate (PEFR).
Drager Alcotest 7110 The Alcotest is a micro-processor controlled unit. A sufficient breath sample volume is indicated by a row of asterisks which appear one after another on a display. A minimum flow rate through the Alcotest is required to activate the display of asterisks, and in the normal operation mode this flow rate must at least be maintained or exceeded until all 16 asterisks are displayed. The breath sample is considered insufficient if the subject stops exhaling before all 16 asterisks are displayed. However, the analyser can be switched 350
JFSS 1992; 32(4): 349-356
to "override" mode which allows a breath analysis to occur after a minimum of 6 asterisks are displayed. This represents a minimum breath sample. The flow of air through the Alcotest was slowly increased from zero until the asterisks appeared on the display. This attempt to measure the minimum flow to trigger the instrument, in the same way as for the Alcolmeter, was only partially successful due to the very low flow rates needed to achieve a minimum of 6 asterisks. Accurate measurement of flow rates below 3 litreslmin was not possible with the available flow calibration device. However, it is estimated that flow rates of less than 2 litreslmin would be sufficient to complete an acceptable test using the Drager unit. The resistance across the mouthpiece used in conjunction with the Alcotest was determined by measuring the pressure drop from one side to the other and dividing change in pressure by flow rate in litreslsec. Resistance across the instrument and minimum volume required to trigger the asterisks successfully were also measured in a sample of 5 Alcotests routinely used in the field. One proved to have a fault and was not included in the final results. Subjects (n = 158) referred to the laboratory for routine lung function testing were asked, on completion of their tests, to exhale into the Alcotest. The exclusion criteria were identical to those used with the Alcolmeter. The number of asterisks displayed during exhalation through the Alcotest was recorded along with the subject's age, sex, FVC, FEV,,,, forced expiratory and PEFR. Flow volume flow from 25 to 75% of vital capacity (FEF,,,,) curve measurements were performed in accordance with American Thoracic Society guidelines [5], using a Jaeger Masterlab computerized pulmonary function unit which was calibrated twice daily.
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Descriptive statistical analyses were performed using SPSS/PC [6]. The Mann-Whitney U test was used to test whether the successful and unsuccessful groups in activating the amber and green lights on the Alcolmeter had been drawn from the same population [7]. Results A total of 69 consecutive subjects were asked to complete both an Alcolmeter and an Alcotest test. Of the 20 subjects who were unable to complete the Alcolmeter test, all were able to complete the Alcotest test. The remaining 49 subjects successfully completed both. Lion Alcolmeter SD-2 The flow rate required to trigger the Alcolmeter is approximately 28 litrestmin (Table 1) and this flow rate needs to be maintained for approximately 2.0 to 2.2 seconds to illuminate the green light B. These data were used to estimate that a mean expired volume of approximately one litre is required at the minimum flow rate for valid results. The resistance to JFSS 1992; 32(4): 349-356
351
flow measured at 28.5 litreslmin ranged from 14.7 to 16.8cm H,O litresfsec. The age of subjects who performed tests on the Alcolmeter ranged from 16 to 86, with more males than females (80:73). A broad spectrum of pulmonary function data was obtained (Table 2), ranging from normal lung function to patterns consistent with severe obstructive and restrictive disease. There was a highly significant difference (p
Minimum respiratory function for breath alcohol testing in South Australia AJ CROCKE'IT, D A SCHEMBRI, DJ SMITH, R LASLE'IT and J H ALPERS Respiratory Unit, Flinders Medical Centre, Bedford Park, SA 5042, Australia The aim of this study was to determine if inability to complete a breath alcohol test successfully, using a Lion Alcolmeter SD-2 or Drager Alcotest 7110, was related to any of the standard parameters obtained from the lung function spirometry test. A total of 153 subjects referred to a clinical laboratory for routine lung function testing were tested using the Alcolmeter, 158 using the Alcotest, with 69 subjects completing tests on both instruments. Of the 153 patients who volunteered to use the Alcolmeter, 49 (32%) were unable to produce a valid test effort on this instrument. One subject failed to complete a satisfactory test using the Alcotest, and one was unable to master the technique. There was considerable overlap of the minimum value for each of the lung function parameters of those subjects who could or could not successfully complete the breath alcohol test. It is recommended that changes are made to both of the instruments, the techniques used and the legislation, to minimize the number of breath alcohol testing failures and to reduce the variability of the results. Key Words: Breath alcohol analysis; Spirometry; Forced Vital Capacity; Forced Expiratory Volume in one second. Journal of the Forensic Science Society 1992; 32: 349-356 Revision received 6 February 1992; accepted 11 May 1992
Introduction Failure to provide a roadside breath sample to police on request has been classed as an offence in South Australia since the introduction of random breath alcohol analysis. Previous studies using different types of breath alcohol analysers have suggested lower limits for Forced Vital Capacity (FVC) and Forced Expiratory Volume in one second (FEV,.,) 11-41. The degree of pulmonary disability that would prevent an individual from being able to perform successfully on either of the two roadside breath alcohol analysis units used in South Australia is not known. The aim of this study was to document the minimum flow rates and resistance to breathing in the two standard devices, the Lion Alcolmeter SD-2 and Drager Alcotest 7110, and to determine if inability to complete the test successfully was related to any of the standard parameters obtained JFSS 1992; 32(4): 349-356
349
from the lung function spirometry test. The study was undertaken at the request of the Breath Analysis Section of the South Australia Police Department, and was approved by the Clinical Investigation Committee of Flinders Medical Centre.
Experimental Lion Alcolmeter SD-2 The assessment of the Alcolmeter was divided into two parts, the first being to determine the triggering flow, minimum expired volume and the resistance to flow of the instrument. Minimum flow to trigger the device (amber light A) was determined using a Gould Goddart Flow Calibration device which consists of an inclined alcohol manometer and high precision flow tubes. The Alcolmeter with mouthpiece was attached to the flow calibration unit and the flow rate was then increased slowly from zero flow until the amber light A was illuminated. This triggering flow rate was measured ten times with each of ten randomly selected disposable mouthpieces. Resistance to a flow rate of 28.5 litreslmin was measured for each mouthpiece by determining the pressure drop across the mouthpiece (cm H,O) and dividing by the flow rate. The volume required for a satisfactory measurement was calculated by measuring the time to trigger green light B using a laboratory stop-watch, at a present flow of 28.5 litreslmin, and multiplying flow by time in minutes. The second part of the assessment was to investigate which parameters of lung function best predicted a subject's ability to perform the Alcolmeter test satisfactorily. Consecutive subjects (n = 153) referred to the laboratory for routine lung function testing were asked, on satisfactorily completing their pulmonary function tests, to exhale into the Alcolmeter. Excluded were subjects aged between 5 and 15 years, the terminally ill, those subjects who had a physical or medical disability that would, in the short term, preclude them from driving a vehicle and those subjects who refused to participate in the study. The subject's ability to trigger the Alcolmeter correctly was recorded along with their age, sex, forced vital capacity (FVC), forced expiratory volume in one second (FEV,,) and peak expiratory flow rate (PEFR).
Drager Alcotest 7110 The Alcotest is a micro-processor controlled unit. A sufficient breath sample volume is indicated by a row of asterisks which appear one after another on a display. A minimum flow rate through the Alcotest is required to activate the display of asterisks, and in the normal operation mode this flow rate must at least be maintained or exceeded until all 16 asterisks are displayed. The breath sample is considered insufficient if the subject stops exhaling before all 16 asterisks are displayed. However, the analyser can be switched 350
JFSS 1992; 32(4): 349-356
to "override" mode which allows a breath analysis to occur after a minimum of 6 asterisks are displayed. This represents a minimum breath sample. The flow of air through the Alcotest was slowly increased from zero until the asterisks appeared on the display. This attempt to measure the minimum flow to trigger the instrument, in the same way as for the Alcolmeter, was only partially successful due to the very low flow rates needed to achieve a minimum of 6 asterisks. Accurate measurement of flow rates below 3 litreslmin was not possible with the available flow calibration device. However, it is estimated that flow rates of less than 2 litreslmin would be sufficient to complete an acceptable test using the Drager unit. The resistance across the mouthpiece used in conjunction with the Alcotest was determined by measuring the pressure drop from one side to the other and dividing change in pressure by flow rate in litreslsec. Resistance across the instrument and minimum volume required to trigger the asterisks successfully were also measured in a sample of 5 Alcotests routinely used in the field. One proved to have a fault and was not included in the final results. Subjects (n = 158) referred to the laboratory for routine lung function testing were asked, on completion of their tests, to exhale into the Alcotest. The exclusion criteria were identical to those used with the Alcolmeter. The number of asterisks displayed during exhalation through the Alcotest was recorded along with the subject's age, sex, FVC, FEV,,,, forced expiratory and PEFR. Flow volume flow from 25 to 75% of vital capacity (FEF,,,,) curve measurements were performed in accordance with American Thoracic Society guidelines [5], using a Jaeger Masterlab computerized pulmonary function unit which was calibrated twice daily.
+
Descriptive statistical analyses were performed using SPSS/PC [6]. The Mann-Whitney U test was used to test whether the successful and unsuccessful groups in activating the amber and green lights on the Alcolmeter had been drawn from the same population [7]. Results A total of 69 consecutive subjects were asked to complete both an Alcolmeter and an Alcotest test. Of the 20 subjects who were unable to complete the Alcolmeter test, all were able to complete the Alcotest test. The remaining 49 subjects successfully completed both. Lion Alcolmeter SD-2 The flow rate required to trigger the Alcolmeter is approximately 28 litrestmin (Table 1) and this flow rate needs to be maintained for approximately 2.0 to 2.2 seconds to illuminate the green light B. These data were used to estimate that a mean expired volume of approximately one litre is required at the minimum flow rate for valid results. The resistance to JFSS 1992; 32(4): 349-356
351
flow measured at 28.5 litreslmin ranged from 14.7 to 16.8cm H,O litresfsec. The age of subjects who performed tests on the Alcolmeter ranged from 16 to 86, with more males than females (80:73). A broad spectrum of pulmonary function data was obtained (Table 2), ranging from normal lung function to patterns consistent with severe obstructive and restrictive disease. There was a highly significant difference (p
