COPD is the fourth leading cause of death in the United States, with more than 12 million people currently diagnosed with the disease. Risk factors for COPD include smoking, environmental exposure to lung irritants, and genetic predisposition. People with COPD often experience symptoms of chronic cough, shortness of breath, excess mucus production, and wheezing. In COPD, the airways in the lungs are chronically obstructed, and if left untreated, this obstruction can cause significant damage to the lungs and lasting disability. The quality of life of a person with COPD decreases as the disease progresses, making treating and managing COPD in the moderate stages important. Long-term oxygen therapy has been shown to help people with severe COPD that is characterized by very low blood oxygen levels at rest to live longer and healthier lives. This study will determine whether supplemental oxygen therapy is helpful for people with COPD that is characterized by moderately low blood oxygen levels at rest or normal oxygen levels at rest and low or very low levels during exercise.

Participation in this study will last at least one year and up to 7 years. Potential participants will first undergo a screening visit that will include questionnaires, a breathing test, measurements of resting and walking blood oxygen levels, a brief physical exam, and a blood draw. Eligible participants will then return for a second screening visit, during which they will complete more questionnaires. At the end of the second visit, eligible participants will be assigned randomly to supplemental oxygen therapy or no oxygen therapy.

Participants assigned to supplemental oxygen therapy will receive stationary and portable oxygen systems. Shortly after receiving the portable oxygen system, participants will return for a 1-hour visit to determine how much oxygen to use while walking and to learn how to use the equipment. Participants who have low blood oxygen levels during rest will be instructed to use supplemental oxygen 24 hours per day. Patients with normal resting blood oxygen levels, but low or very low blood oxygen levels during exercise will be instructed to use it during physical activity and sleep. Throughout the treatment period, participants will be asked to keep records of the number of oxygen tanks emptied or pounds of oxygen delivered, meter readings, and changes in equipment. Study officials will contact participants weekly for the first month, monthly for the next 5 months, and then every 2 months until the Year 1 study visit. Participants will also complete a form about their oxygen equipment and usage every 2 months. Participants assigned to receive no oxygen treatment will be contacted 1 week after study group assignment for a check-up.

All participants will return for study visits once a year for up to 7 years. At each of these visits, participants will complete some of the same tests and questionnaires from the screening visit. At the Year 1 visit, participants will also undergo a blood draw. Both treatment groups will receive two phone calls each year to check on status and use of oxygen. Participants in both groups will be asked to complete a quality of life questionnaire by mail at 4 months and 16 months. Participants will also sign a release of medical records form each year and will have their Medicare claims collected for the time they are in the study.