Pulmonary perfusion is more uniform in the prone than in the supine position: scintigraphy in healthy humans

The main purpose of this study was to find out whether the dominant dorsal lung perfusion while supine changes to a dominant ventral lung perfusion wh ile prone. Regional distribution of pulmonary blood flow was determined in 10 healthy volunteers. The subjects were studied in both prone and supine p ositions with and without lung distension caused by 10 cmH(2)O of continuou s positive airway pressure (CPAP). Radiolabeled macroaggregates of albumin, rapidly trapped by pulmonary capillaries in proportion to blood flow, were injected intravenously. Tomographic gamma camera examinations (single-phot on-emission computed tomography) were performed after injections in the dif ferent positions. All data acquisitions were made with the subject in the s upine position. CPAP enhanced perfusion differences along the gravitational axis, which was more pronounced in the supine than prone position. Diaphra gmatic sections of the lung had a more uniform pulmonary blood flow distrib ution in the prone than supine position during both normal and CPAP breathi ng. It was concluded that the dominant dorsal lung perfusion observed when the subjects were supine was not changed into a dominant ventral lung perfu sion when the subjects were prone. Lung perfusion was more uniformly distri buted in the prone compared with in the supine position, a difference that was more marked during total lung distension (CPAP) than during normal brea thing.