Mechanical vs. reflex effects of diffuse pulmonary embolism in anesthetized dogs.

The effects of repeated pulmonary embolisms with glass spheres on systemic and right intracavitary pressures and on arterial oxygen saturation of anesthetized dogs are described. The results of studies of intact dogs and of the isolated perfused left lower lobe indicate that the hemodynamic effects were due to mechanical obstruction to the flow of blood through the lungs eventually followed by right heart failure. Evidence for reflex effects on the blood vessels or heart was lacking. The systemic arterial unsaturation which eventually developed after repeated embolisms was completely overcome by the inspiration of oxygen and was attributed to a reduction of the diffusing capacity of the lung.