Positive airway pressure (PAP) therapy is generally offered to patients with obstructive sleep apnea. The investigators suggest that beneficial effects of PAP therapy is by preventing apneas and therefore reducing cardiac and pulmonary morbidities. The investigators sought to verify this by assessing cardiac and pulmonary function during exercise.

Inclusion Criteria:

• obstructive sleep apnea diagnosed by polysomnography
• CPAP therapy indicated

Exclusion Criteria:

• obstructive or restrictive lung disease
• cardiac failure
• acute coronary syndrome
• inability to cycle

All consecutive patients newly diasgnosed with obstructive sleep apnea in whom CPAP therapy was indicated