Neurohemodynamics of Pulmonary Edema. III. Estimated Changes in Pulmonary Blood Volume Accompanying Systemic Vasoconstriction and Vasodilation

Abstract

A simple gravimetric technic has been presented by means of which it is possible to estimate changes in pulmonary blood volume. The pulmonary vascular bed seems to behave passively its volume depending for the most part on the volume changes of the systemic circulation. The systemic vasoconstriction induced by the intracisternal injn. of thrombin and fibrinogen is accompanied by an increase in pulmonary blood volume as well as an elevation of pulmonary vascular pressures. Systemic vasodilation produces the reverse effect, namely, a shift of blood from pulmonary to systemic circulation in addition to lowering pulmonary vascular pressures. When pulmonary venous pressure is markedly elevated, slight to moderate systemic vasodilation can greatly reduce that pressure. The general shape of the in vivo pressure-volume curve of the pulmonary vascular bed was detd. and was found to conform in contour to previously obtained curves from the isolated lung prepn. The obtained data also indicate that stress relaxation is a phenomenon of some importance in the pulmonary vascular bed in vivo as well as in the isolated lung.