A Study to Evaluate the Effects of BGF and GFF on Specific Image Based Airway Volumes and Resistance in Subjects With Moderate to Severe COPD

This is a randomised, controlled, two period cross-over, 4 weeks chronic dosing, study to evaluate the effects of Budesonide/Glycopyrronium/Formoterol Fumarate (BGF), and Glycopyrronium/Formoterol Fumarate (GFF), on specific image based airway volumes and resistance in subjects with moderate to severe Chronic Obstructive Pulmonary Disease. In this study, airway dimension parameters will be calculated for each of the active compounds. This imaging methodology will allow an assessment of the extent of airway changes using a triple combination of Budesonide/Glycopyrronium/Formoterol Fumarate (BGF) and the dual combination Glycopyrronium/Formoterol Fumarate (GFF).