Pulmonary arterial hypertension and emphysema.

Pulmonary artery pressures were estimated by an indirect method using echocardiography (Boyd et al. 1980), in a group of patients with chronic airflow obstruction, in order to investigate the degree of pulmonary hypertension in patients with emphysema. We found a positive correlation between the estimated pulmonary artery end diastolic pressure (PAEDP) and the radiological emphysema score (r = 0.58, P less than 0.005), and between the estimated PAEDP and the transfer constant for carbon monoxide (KCO) (r = 0.66, P less than 0.002). There was no correlation between the PAEDP and the arterial partial pressure of oxygen (PaO2) before exercise, between the PAEDP and the change in oxygen partial pressure after exercise, or between the KCO and the PaO2. It is suggested that emphysema does predispose to pulmonary arterial hypertension and that the relationship is probably secondary to vessel destruction rather than hypoxia.