AN INQUIRY INTO THE BASIS OF THE ACETYLENE METHOD OF DETERMINING THE CARDIAC OUTPUT

Abstract

An attempt is made to evaluate the acetylene method of determining the cardiac output. The method requires the rebreathing of a gas mixture and taking of samples over a period of 20 to 25 sec. Data are presented which indicate that the total circulation time of normal man averages about 14 sec. After ventilating one lung of a dog with acetylene and the other with O for 8 sec., it is found that acetylene has been carried from one lung to the other through the circulation. Thus the first circulation can be expected to carry acetylene back to the lungs. Since the theory of the acetylene method involves the assumption that the samples are taken before return of acetylene to the lungs in the venous blood, it is concluded that the procedure must be revised.