Regional pulmonary blood volume in patients with abnormal blood pressure or flow in the pulmonary circulation.

We studied the effects of a chronic increase in flow and of chronic hypertension on regional pulmonary blood volume and extravascular lung density (lung tissue and interstitial water per unit thoracic volume) in one group of patients with intracardiac, left-to-right shunt and in another group with Eisenmenger's syndrome or primary pulmonary hypertension. We used positron computerized tomography to measure regional lung density (transmission scans) and blood volume (labelling with 11CO). The distribution of pulmonary blood volume was more uniform in patients with a chronic increase in pulmonary blood flow than in normal subjects. There were also indications of an absolute increase in intrapulmonary blood volume. In patients with chronic pulmonary arterial hypertension, the regional distribution of blood volume was abnormally uniform, but there were no indications of substantial abnormalities in overall intrapulmonary blood volume.