Spatial distribution of pulmonary blood flow in dogs in left decubitus position

Spatial distributions of pulmonary blood flow (SDPBF) were measured in 6 dogs by injecting radioactive microspheres (15 μm diameter) into the right ventricle and by computer controlled scintiscanning of the surfaces of each cross section obtained by sectioning the entire excised fixed lungs into 1 cm thick slices. SDPBF measured in the excised lungs was mathematically corrected to the in vivo parenchymal distribution at the time of the microsphere injection. Relative alveolar volume increased with height along the left to right axis as well as in the apical region along the caudad cephalad isogravitational axis of the thorax in the left decubitus position. Likewise, flow fraction per unit alveolus increased from apex to base. SDPBF generally was decreased in the periphery relative to the interior of individual lobes. SDPBF was decreased in the most dependent regions of the lobes of the superior as well as of the dependent lung. Fractions of total blood flow and of volume in the dependent left lung were found to be 49.3 and 40.8%, respectively.