Effect of posture and anaesthesia on the distribution of pulmonary perfusion and lung configuration in beagle dogs.

To investigate the effect of posture and anaesthesia on the topographical distribution of pulmonary perfusion in canine lungs, the changes in lung shape, configuration and regional perfusion were assessed in healthy beagle dogs, using a repeated 99mTc perfusion scintigraphic procedure. The general shape of the lung images was similar in standing and prone postures, except for a relative increase of the more ventral zone in the prone posture, ascribed to vertical flattening of the lung associated with enlargement of the ventral zones. Configuration changes revealed a shift of the parenchyma towards the more caudal parts in the prone posture, which suggests a parenchymal compression of the paradiaphragmatic lung zones. The prone posture induced a decreased perfusion to the caudal third of the lung. Anaesthesia induced significant changes in lung shape without an obvious direction. The perfusion to the more ventral as well as to the more cranial zones was reduced. Differences in the perfusion distribution are thought to be mainly due to the pressure exerted by the abdominal content through the diaphragm and to the shift of the blood towards better ventilated lung regions.