RecruitingDevice studyPEP Buddy in Pulmonary RehabilitationIn this study, the investigators will test Veterans with COPD in Pulmonary Rehabilitation. Between two groups, the investigators will give one group a device that assists with breathing and symptoms and the other receives a 'sham' device which does not provide these benefits. The investigators will test to see if the symptoms and exercise capacity of the group who receives this device improves faster in Pulmonary Rehabilitation and has longer lasting benefits after the end of Pulmonary Rehabilitation.