Methods: Patients with stable, severe COPD and healthy, age-matched subjects (H) perform semi supine echocardiography with PAPs measurement. COPD patients perform ramp protocol with gas exchange detection. Serum hsCRP level is also determined in COPD patients. All of the subjects perform complete lung function with body pletysmography and diffusion capacity measurement. Endothel dysfunction is detected by flow mediated vasodilation measurement after arm strangulation with Doppler ultrasonography.