Absorption Force of the Capillaries of the Visceral Pleura in Determination of the Intrapleural Pressure

Abstract

A method is described for the measurement of the net absorption pressure of the capillaries at the level of the visceral pleura. This pressure was found to be about 15 mm Hg and due to the difference between the plasma colloid osmotic pressure and the hydrostatic pressure in the pulmonary capillaries; such a difference does not exist in the parietal pleura. The hydrostatic pressure of the pulmonary capillaries estimated by this method has the same value as that observed by cardiac catheterization. From the results and theoretical considerations it appears that the negative intrapleural pressure is the result of the net absorption pressure of the visceral pleura. This force is higher than the elastic retraction force of the lung and therefore it holds the visceral and the parietal pleura together.