Detection and Quantitation of Intracardiac Left-to-Right Shunts by an Oximetric Inert Gas Technic

Abstract

A method is described for detecting and quantitating small left-to-right shunts by recording continuously and simultaneously the changes in blood oxygen saturation at a systemic artery and at selected sites in the right heart chambers or great vessels produced by a few breaths of an inert gas such as helium or nitrogen.The advantages of this technic for detecting and quantitating left-to-right shunts are (1) the same instrument, namely, the cuvette oximeter, used to determine blood oxygen saturation and indicator-dilution curves in conjunction with routine diagnostic catheterization procedures, also is used to record the inert gas curves, (2) only one right heart catheter is needed, (3) the method is relatively simple, (4) the shunt can be quantitated, and (5) shunts of less than 10 per cent of pulmonary flow can be detected.It is concluded that the technic is of considerable practical value as a means of excluding the presence of or demonstrating and determining the magnitude of small left-to-right shunts.