Novel Endpoints in Cough Challenge Testing

Inclusion Criteria: * Adult subjects aged 18 and over. Meet criteria for subject groups as outlined below: Healthy volunteers: * Must be non smokers. * No history of respiratory disease. Healthy smokers: * Current smokers with at least 10 pack year history of smoking. * Spirometry within normal limits i.e. FEV1 \> 80% predicted and FEV1/FVC ratio of \> 75% predicted. Asthma: * Physician diagnosis of asthma * Stable asthma. * Airway hyperresponsiveness to methacoline; PC20\< 16mg/ml. * Non smokers or ex-smokers with smoking history of less than 10 pack years. COPD: * Physician diagnosis of COPD * Ex smokers with smoking history of at least 20 pack years * Spirometry demonstating evidence of airflow obstruction i.e. FEV1/FVC ratio of \< 70% Chronic cough: * History of dry cough for at least 8 weeks. * Normal chest x ray. * Non smokers or ex smokers of less than 10 pack years history of smoking. Exclusion Criteria: * Symptoms of upper respiratory tract infection within the last 4 weeks. * Participation in another clinical trial of an investigational drug within 4 weeks. * Use of medication likely to alter cough reflex sensitivity i.e. ACE inhibitors, codeine phosphate, morphine sulphate. * Patients with severe respiratory disease i.e. FEV1 \< 1.0 litre. * Use of steroid tablets in previous 2 months or taken more than 3 courses of steroid tablets in the preceding 12 months in subjects with asthma or COPD. * Change in asthma treatment in the preceding 6 weeks in asthma group * Significant medical co-morbidities likely to affect ability to participate in the trial or affect cough reflex sensitivity e.g. diabetes, stroke, Parkinson's disease, multiple sclerosis etc.