CARDIAC OUTPUT IN THE RAT AT NORMAL AND AT HIGH ALTITUDES AND ITS RELATIONSHIP TO GAS EMBOLISM

Abstract

A method was developed for the determination of cardiac output in the rat at normal and at simulated high altitudes using the Fick principle. The rat is anatomically suitable for this technic since a small metal cannula can be introduced directly into the heart through the jugular vein; this makes it possible to obtain highly reliable samples of mixed venous blood. The cardiac output in the rat at Denver''s altitude was found to be 46.5 ml./min. An increase in altitude caused a decrease in cardiac output, and the magnitude of the decrease appears to have some relationship to the occurrence of gas embolism at high altitudes. There was a significant difference in the cardiac output at high altitudes in rats developing gas embolism as compared with those animals in which no embolism developed. Animals with a cardiac output greater than 20 ml./min. did not develop gas embolism, while those with a cardiac output less than this value did show emboli at autopsy.