A Study to Evaluate the 24 Hour Spirometric Effect (FEV1) of Fluticasone Furoate/Vilanterol Inhalation Powder (100mcg Fluticasone Furoate (FF)/25mcg Vilanterol (VI)) Compared With Salmeterol/Fluticasone Propionate Inhalation Powder (50mcg Salmeterol/500mcg Fluticasone Propionate (FP))

Inclusion Criteria: * Signed and dated written informed consent * Male or females ≥ 40 years of age * Established clinical history of COPD by ATS/ERS definition * Females are eligible to enter and participate if of non-childbearing potential, or if of child bearing potential, has a negative serum pregnancy test at screening, and agrees to one of the acceptable contraceptive methods listed in protocol, used consistently and correctly * Former or current smoker \> 10 pack years * Post-albuterol spirometry criteria: FEV1/FVC ratio ≤ 0.70 and FEV1 ≤ 70% of predicted normal (NHANES III) * have been hospitalised or have been treated with oral corticosteroids or antibiotics for their COPD within the last 3 years prior to Screening (Visit 1) Exclusion Criteria: * Current diagnosis of asthma * Subjects with other respiratory disorders including active tuberculosis, α1-antitrypsin deficiency, lung cancer, bronchiectasis, sarcoidosis, lung fibrosis, pulmonary hypertension, interstitial lung diseases or other active pulmonary diseases * Lung volume reduction surgery within previous 12 months * Clinically significant abnormalities not due to COPD by chest x-ray * Hospitalized for poorly controlled COPD within 12 weeks of Screening * Poorly controlled COPD 6 weeks prior to Screening, defined as acute worsening of COPD that is managed by the subject with corticosteroids or antibiotics or that requires treatment prescribed by a physician * Lower respiratory infection requiring antibiotics 6 weeks prior to Screening * Uncontrolled or clinically significant (in opinion of PI) cardiovascular, hypertension, neurological, psychiatric, renal, hepatic, immunological, endocrine, peptic ulcer disease, or hematological abnormalities * Carcinoma not in complete remission for at least 5 years * Subjects with history of hypersensitivity to study medications (e.g., beta-agonists, corticosteroid) or components of inhalation powder (e.g., lactose, magnesium stearate) * Subjects with history of severe milk protein allergy that, in opinion of study physician, contraindicates subject's participation - Known/suspected history of alcohol or drug abuse in the last 2 years * Women who are pregnant or lactating or plan to become pregnant * Subjects medically unable to withhold albuterol and/or ipratropium 4 hours prior to spirometry testing at each study visit * Use of certain medications such as bronchodilators and corticosteroids for the protocol-specific times prior to Visit 1 (the Investigator will discuss the specific medications) * Long Term Oxygen Therapy (LTOT) or nocturnal oxygen therapy \>12 hours a day * Participation in the acute phase of a pulmonary rehabilitation program within 4 weeks prior to Screening or during the study - Non-compliance or inability to comply with study procedures or scheduled visits * Affiliation with investigator site