 The purpose of study is to evaluate the physiologic effects of pulmonary tissuestructural changes associated with COPD and upper airway inflammation on upper airway collapsibility. Upper airway collapsibility is closely associated with development of obstructive sleep apnea OSA, which is a common disease characterized by repetitive collapse of upper airway during sleep, leading to hypoxemia and arousal. OSA has important neurocognitive and cardiovascular consequences, especially in patients with COPD. 