Discrepancies in Cardiac Output Measurements by Two Applications of the Direct Fick Principle

Abstract

Simultaneous cardiac output measurements were made on trained non-narcotized dogs by the direct oxygen Fick method and by the dye T1824 dilution method. Good agreement between both methods was observed when the dogs were breathing air. However when the determinations were made 5 minutes after onset of hypoxia, large discrepancies were noted: 3.1 l./min. for the oxygen Fick against 5.2 l./min. for the dye dilution. The sources of error in one or both methods are discussed.