The Diffusing Characteristics and Pressure-Volume Relationships of the Pulmonary Capillary Bed in Mitral Valve Disease*

In 1957, Forster, Roughton, and their associates reported a method of estimating pulmonary capillary blood volume (Vc) and diffusing capacity of the alveolar-capillary membrane (DM) by measuring the diffusing capacity of the lung for carbon monoxide (DL) at varying levels of alveolar oxygen tension (1, 2).1 Since then there hlave been a number of reports on the behavior of membrane diffusion and pulmonary capillary blood volume under physiological and pharmacological stresses (3-7) and in certain disease states (8-17). The purpose of this study was to measure the pulmonary capillary blood volume in normal subjects and in patients with mitral valve disease and to relate the findings to intravascular pressure and flows^ data obtained by cardiac catheterization.