The procedures include: Enrollment of 10 patients, who are randomized to either exercise with their oxygen prescription followed by exercise with the RDS, or exercise with the RDS followed by exercise on their oxygen prescription. Randomization will occur on a 1:1 basis. Each set of exercise will be separated by a 30 minute recovery session. Subjects will be adults who are on supplemental oxygen and are able to exercise on a treadmill. Subjects will be above 18 years of age. Subject participation will last approximately 1 month. Subjects will be recruited from the Loma Linda pulmonary clinic and the pulmonary rehabilitation program. Consent will take place in the pulmonary clinic, pulmonary function lab or pulmonary rehabilitation by trained study physicians. If Multi-center: N/A (single center) If Single center or investigator-initiated: 10 subjects will participate in the study.