Pulmonary ‘Capillary’ Pressure in Man

Abstract

A venous catheter was introduced into the pulmonary artery of man and wedged into a distal ramification so as to obstruct its lumen. Blood samples withdrawn through this catheter in individuals with systemic arterial oxygen unsaturation were fully saturated with O2, indicating the lack of any significant pre-capillary admixture of bronchial with pulmonary arterial blood. Pressures recorded through the catheter in the position described were identical with those recorded through a catheter wedged into a pulmonary vein in 2 patients with atrial septal defects. It is therefore believed that both pressures are close approximations of the true pulmonary capillary pressure. The pulmonary "capillary" pressure averaged 10 mm. Hg with a variation between 7 and 15 in 13 normal patients. The mean pulmonary artery pressure in these individuals averaged 16 mm. Hg with variations between 11 and 21. The gradient of pressure between Pulmonary artery and pulmonary "capillaries" varied between 3 and 9 mm. Hg with an avg. of 6.