Aridol Challenge as a Tool to Predict Treatment Response to Inhaled Corticosteroids in COPD

Inclusion Criteria: * Diagnosis of COPD (history, spirometry, symptoms including chronic cough and/or shortness of breath that is worse on exertion and/or excess sputum production) * Aged 45 - 80 years * Have pre-bronchodilator FEV1 \> 1.4 litres and at least 60% of predicted for height, age and gender and a post-bronchodilator FEV1 \<80% of predicted for height, age and gender * Post-bronchodilator FEV1/FVC \< 70 % * ≥ 10 pack years smoking history * As determined by the investigator, are capable and willing to: * perform all of the techniques necessary to measure lung function; * administer the dry powder mannitol. * Are capable of, and have given informed consent to, participating in this study in accordance with local regulations. * The subject must be in stable clinical condition at the time of, and for a period of 14 days prior to, their recruitment into the study. Stable clinical condition is defined as lack of: * change in sputum production (volume, colour, consistency); * increased cough; * worsening dyspnoea; * increased malaise, fatigue or lethargy; * reduction in exercise tolerance; * fever; * antibiotic treatment (for respiratory infection). Exclusion Criteria: * Investigators, site personnel directly affiliated with this study, and their immediate families. Immediate family is defined as a spouse, parent, child or sibling, whether biologically or legally adopted. * Subjects receiving treatment with inhaled corticosteroids (including combination therapies, e.g. Seretide®, Symbicort®) or oral corticosteroids within the last 6 weeks. * Subjects who have had an exacerbation or a chest infection within the 2 weeks prior to the study. * Subjects receiving antibiotic treatment for respiratory infection. * Known diagnosis of asthma or allergic rhinitis. * Myocardial infarction in the six months prior to enrolment. * Cerebral vascular accident in the six months prior to enrolment. * Ocular surgery in the three months prior to enrolment. * Abdominal surgery in the three months prior to enrolment. * Active tuberculosis (TB). * Lung cancer or any other malignancies, which are considered by the investigator as a contraindication to participating in the study. * Lung disease other than COPD (e.g. bronchiectasis). * Uncontrolled insulin-dependant or non-insulin dependant diabetes, i.e. \>10% HbA1c. * Female subjects of reproductive capability, not using a reliable form of contraception * Inability to obtain informed consent from the subject or subject's authorised representative. * Subjects who have participated in another investigative drug study parallel to, or within 4 weeks of, study entry. * Known intolerance to mannitol. * Uncontrolled hypertension - systolic blood pressure (BP) \> 200 mmHg and or diastolic BP \> 100 mmHg. * Planned pulmonary rehabilitation. * Have had major abdominal, chest or brain surgery in the three months prior to enrolment. * Have known cerebral, aortic or abdominal aneurysm.