Effect of Nasal CPAP on Cardiopulmonary Exercise Testing in Patients With Overlap Syndrome

Patients presenting to the Oklahoma City VA sleep clinic with obstructive sleep apnea syndrome and a desire to initiate CPAP treatment will be included if they have overlap syndrome. Patients will undergo a spirometry and CPET before being started on CPAP as part of standard clinical care. The CPET will be repeated after 8-12 weeks of CPAP use. Patients will be excluded if they have any contraindication to mild exercise or they cannot perform an exercise test due to limited mobility.