ABSTRACT
In order to obtain reliable results in breath-alcohol analysis it is necessary to consider alveolar air. In former examinations of the question, which part of expired air contains almost pure alveolar air, a separation between the influence of temperature and volume had not been made. Only after a temperature correction has been performed the influence of volume can clearly be seen in drinking experiments. Measurements undertaken with the ALCOMAT clearly show the influence of varied breathing techniques on the results of breath-alcohol determinations. The demand of a minimum volume in the breath test is not sufficient by itself. In order to get a correct result the expiration volume should be more than 70% of the subject's vital capacity. In case of an expired volume remarkably below 50% of the vital capacity the measured values can be more than 10% below the expected values. Such big deviations can only be the result of a deliberate inspiration and expiration technique of the subject.
Subject(s)
Accidents, Traffic/legislation & jurisprudence , Alcoholic Intoxication/diagnosis , Breath Tests/instrumentation , Ethanol/pharmacokinetics , Lung Volume Measurements , Adult , Alcoholic Intoxication/blood , Humans , MaleABSTRACT
Breath-alcohol concentration determined in expired alveolar air depends even at equal blood concentration on the temperature of the breath while leaving the subject's mouth. By using a two-stage simulator it is possible to simulate the physiological reality and to examine the measuring conditions of the temperature. The results show the essential influence of the mouthpieces and the environmental temperature on the measured values. Deviations especially appear at low environmental temperature. To reduce systematic deviations an electrically heated support of the temperature probe was developed which diminishes the influence of the mouthpieces to -0.3 degree centigrade. This device almost eliminates the influence of temperature of the environment.
Subject(s)
Alcoholic Intoxication/diagnosis , Body Temperature , Breath Tests/instrumentation , Ethanol/pharmacokinetics , Alcoholic Intoxication/blood , Body Temperature/drug effects , HumansABSTRACT
To describe the reliability of breath-alcohol testers, values are measured which characterize precision, accuracy, analytical sensitivity, drift, and hysteresis. The instruments tested were two infrared devices (Alcomat, Alcotest 7110) and one device equipped with a fuel cell (Alcolmeter EBA). Criteria of acceptability are the limits from the first preliminary draft of recommendations by the Organisation Internationale de Métrologie Légale (OIML). The results of measurements clearly show the level of reliability of modern instruments which largely attain the OIML requirements. All measurements were performed with a simulator at 34 degrees C. Therefore the definite influence of breath temperature on the alcohol concentration could be neglected.
