PLATYPNEA RELATED TO ORTHODEOXIA CAUSED BY TRUE VASCULAR LUNG SHUNTS

The term platypnea is used to describe dyspnea produced by the assumption of an erect position and relieved by a recumbent one. The term orthodeoxia is suggested to describe accentuated arterial O2 unsaturation in the erect position improved by a recumbent one. Three patients were described in which orthodeoxia and platypnea, caused by the gravitational effects of an erect thorax, produced increased pulmonary blood flow through true vascular communications (right to left) in the lung bases. Recognition of orthodeoxia may have important diagnostic and therapeutic implications and, when present, should raise the etiologic possibility of true vascular lung shunts. Two of the 3 patients studied had true vascular shunting in the lung related to chronic liver disease and the 3rd had congenital multiple pulmonary arteriovenous fistulas.