A subject who fails to provide an adequate breath sample for a breath alcohol measuring device under the provisions of Road Traffic Act 1988 may be charged with refusing to supply a sample unless the police officer believes the person is genuinely unable to do so. Subjects who are confronted with this situation may approach their general practitioner or chest physician for advice on whether they are medically able to provide adequate breath samples to satisfy the breath testing devices. There is currently no guidance available for medical practitioners concerning respiratory performance or lung function which will impair the use of such breath testing devices. This paper describes experiments with human volunteers suffering from respiratory illnesses and their ability to provide adequate breath samples to satisfy the requirements of the breath alcohol testing devices used in Great Britain. It was found that the most suitable parameters for determining whether a subject was capable of using a breath alcohol testing device were spirometry measurements of Forced Expired Volume in one second (FEV1) and Forced Vital Capacity (FVC). In this study subjects with a FEV1 less than 2.0 litres and a FVC less than 2.6 litres were generally unable to use all the devices.

Subjects suffering from respiratory diseases occasionally experience difficulty when attempting to provide breath samples to satisfy the requirements of breath alcohol testing devices. In order to assist ventilation, such subjects may resort to the use of an aerosol inhaler. Twenty aerosol inhalers containing drugs which exhibit an effect on the respiratory system and five nasal sprays used to relieve the symptoms of hay fever, have been tested for interference on the range of breath alcohol measuring devices used by the police in Great Britain. No interference attributable to the contents of any of the aerosol inhalers or nasal sprays tested was observed on any of the instruments in police use.

Subjects suffering from asthma can occasionally experience difficulty in providing adequate breath samples for evidential breath alcohol testing devices and may therefore resort to the use of bronchodilators such as salbutamol to improve their respiration. Experiments showed that although salbutamol caused bronchodilation it did not affect breath alcohol levels of asthmatics who have been drinking. The blood:breath alcohol ratios obtained from asthmatics were within the normally recorded range before and after use of salbutamol. We conclude that the use of salbutamol by asthmatics does not affect the reliability of measurements made by evidential breath alcohol testing devices.

In a previous study (Gomm et al., 1991) people with a variety of respiratory diseases were tested and criteria defined for assessing their ability to provide samples for Breath Alcohol Testing Instruments. This study investigated the possible problems which may be encountered by healthy people of small stature--5ft 5in (166cm) or less--who do not suffer from a respiratory disease. This study followed the same pattern as the earlier work in that lung function (Forced Expiration Volume in One Second (FEV1) and Forced Vital Capacity (FVC)) was measured by spirometry, and Peak Expiration Flow Rate (PEFR) was measured using a Wright peak flow meter. Following the lung function measurements the subjects were requested to provide samples for Breath Alcohol Testing Instruments used by the Police in Great Britain. As with the previously reported work (Gomm et al., 1991), this study found that the FEV1 and FVC gave the most reliable indication of a person's capability of satisfying the sampling requirements of Breath Alcohol Testing Instruments, but on this occasion the PEFR also provided a good confirmatory indication. Because there were no subjects with interstitial lung diseases the values determined by this study on 48 healthy adults indicate that a healthy person of small stature should be capable of supplying a suitable breath sample if their FEV1, FVC and PEFR are greater than 2.31, 2.61 and 330 l/min respectively.

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