A Convenient Method for the Determination of the Approximate Cardiac Output in Man.

Although the ethyl iodide method of Starr and Gamble (1) and the acetylene method of Grollman (2) give useful results in the determination of the cardiac output in man, they require special apparatus and a time consuming technique not easy to master. It appeared that if the determination of the cardiac output is to become a practical procedure for the clinic a further simplification of methods is necessary, and with this end in view the possibilities of using oxygen and carbon dioxide for this purpose were reinvestigated. The plan was to devise the simplest possible procedure, to make the necessary assumptions, and then to compare the results with the values secured by means of ethyl iodide and acetylene. A method has been developed 1 by which the cardiac output may be estimated from a determination of metabolism and the analysis of the oxygen and carbon dioxide contents of only two samples, collected during a single rebreathing procedure much like that used in Grollman's acetylene method. The results obtained by this new oxygen method have been found to be in reasonably good agreement with those secured by the use of ethyl iodide and acetylene.