Physiologic Effects of Nasal High Flow on Exercise Tolerance in COPD

This study is testing whether using a high-flow nasal oxygen device during exercise improves exercise tolerance and reduces breathing difficulty in people with COPD (chronic obstructive pulmonary disease) who use low-flow oxygen or no supplemental oxygen at rest. **You may be eligible if...** - You are 18 years or older - You have a diagnosis of COPD - You are able to walk without physical assistance - You use low-flow nasal oxygen (4 L/min or less) or no supplemental oxygen at all **You may NOT be eligible if...** - You are pregnant - You are on bed rest and cannot walk - You require more than 4 L/min of oxygen, or non-invasive ventilation during the day - You have unstable heart rhythm, very low blood pressure, or other acute illness Talk to your doctor to see if this trial is right for you.