Up to 40 patients will be enrolled into the study, ranging in age from 40 to 75 years of age. Patients will be medically assessed before participation to ensure their suitability. The study will take place in one centre in the UK over five sessions; at each session one dose (2 puffs) of GB or one dose (2 puffs) of placebo will be administered from a simple inhaler device. Neither staff nor patients will know which dose, or if placebo, is being taken. Lung function will be measured for up to 26 hours after the administration of each dose using standard spirometry equipment. Blood samples will be taken over a 24-hour period to check the blood levels of GB. There will be a period of about a week between each dosing session. Patients will be medically reviewed after the study to confirm that no untoward effects are present.