The study is based on the theory of a "unified airway" that considers the nose and paranasal sinuses together with lower airways as one integrated unit. The upper and lower respiratory tracts function as an interdependent physiologic mechanism, and stimuli that trigger changes in one portion of the airway, can provoke similar changes throughout the airway. This is well documented in asthmatic patients but documented poorly in patients suffering from chronic obstructive lung disease (COPD).