The main purpose of this study is to evaluate the sensitivity of a new oxygen enhanced magnetic resonance imaging (OE-MRI) method in detecting changes in the lungs of patients with moderate to severe chronic obstructive pulmonary disease (COPD) following treatment with either Oxis Turbuhaler or Symbicort Turbuhaler.

Inclusion Criteria:

• Age greater than or equal to 40 years
• Male and female
• Clinical diagnosis of moderate to severe COPD according GOLD guidelines
• Current or ex smoker with a smoking history equivalent to at least 20 cigarettes smoked per day for 10 years
• A Modified Medical Research Council (MMRC) dyspnoea scale score of ≥2.
• FEV1/FVC < 0.7 (post-bronchodilator)
• FEV1 > 40 % PN and < 70 % PN (post-bronchodilator)

Clinical Study Protocol Local Amendment affects UK:

- FEV1 > 30 % PN and < 80 % PN (post-bronchodilator)

Exclusion Criteria:

• Current diagnosis of asthma according to GINA guidelines
• Pregnancy, breast-feeding or planned pregnancy during the study. Fertile women not using acceptable contraceptive measures as judged by the investigator
• Significant upper or lower respiratory tract infection not fully recovered in the 4 weeks prior to visit 1
• Participation in or scheduled for an intensive COPD rehabilitation program
• Claustrophobia, pacemaker, clips within the brain, previous brain or heart surgery, history of metal in the eye or other MRI contraindication such as obesity or inability to stay in the supine position for 60 minutes