2. Respiratory Assessments Forced Expiratory Volume per second (FEVI) will be measured using a dry wedge spirometer (Vitalograph, Buckingham, UK) and expressed as a percent of predicted value. Subjects will be trained in the use of the apparatus before beginning the study. The baseline value at each visit will be measured after at least fifteen minutes of quiet rest, and will be taken as the highest of three readings made at one minute intervals. 400 microg ventolin administered via a metered dose inhaler will be given if initial spirometry shows an obstructive picture (FEV1 <80% predicted, FEV1 /FVC<70%) in order to distinguish between the presence of asthma or COPD.