Pulmonary Hypertension Associated with Chronic Obstructive Pulmonary Disease

Pulmonary hypertension (PH) is likely to complicate chronic obstructive pulmonary disease (COPD) in a large proportion of patients, especially those with severe disease. Majority of patients have a mild to moderate elevation in the pulmonary artery pressure that usually does not require specific treatment. A small subset of patients, however, develops severe PH that is "out-of-proportion" to the severity of COPD. Generally considered a consequence of chronic hypoxaemia, endothelial dysfunction has now been recognised to play an important role in the pathogenesis of PH in COPD. Pulmonary vessels remodelling characterised by intimal enlargement with proliferating smooth muscle cells, medial hypertrophy, arteriolar muscularisation and endothelial cell proliferation, especially affecting the small arterioles and arteries, leads to permanent changes in the vascular structure and function. Clinical recognition of PH is difficult. Echocardiography is used for screening while right heart catheterisation is the gold standard for diagnosis. In patients who have a moderate degree of chronic hypoxaemia, long term oxygen therapy is indicated and is the only therapeutic measure so far known to retard the progress of PH. Newer therapies targeting the specific abnormalities of vasoconstrictor-vasodilator balance, arising as a consequence of endothelial dysfunction, are under investigation and may offer a management option especially in severe PH associated with COPD.