[Pulmonary hypertension of chronic respiratory disease]

Pulmonary hypertension of chronic respiratory disease is defined as elevation of the mean resting pulmonary artery pressure to over 20 mm Hg. It is the commonest cause of pre-capillary pulmonary hypertension on account of the high prevalence of chronic obstructive pulmonary disease. It is primarily due to alveolar hypoxia that leads to remodelling of the distal pulmonary vasculature and consequently to an increase in pulmonary resistance. It is not as severe as idiopathic pulmonary hypertension. The mean pulmonary artery pressure is usually moderately increased (20-35 mm Hg) when patients are seen during a stable period of the disease. There are, however, more severe cases of pulmonary hypertension called, in some cases, disproportionate but these are uncommon. Increased right ventricular afterload can lead to the development of right ventricular failure that is a definite prognostic factor. The clinical symptoms of pulmonary hypertension are at a secondary level compared with those of the causal disease. Non-invasive diagnosis depends on Doppler echocardiography. Currently the most effective treatment is long term oxygen therapy (16-18 hr/24 hr). This improves or, at least stabilises, the pulmonary hypertension.