Measurement of Cardiac Output in Man by Dye Dilution Curves Using Simultaneous Ear Oximeter and Whole Blood Cuvette Techniques

Abstract

In 10 subjects, dye dilution curves were performed on 31 occasions by intravenous in jection of Coomassie blue dye. The curves were recorded by a conventional whole blood cuvette technique using arterial blood with drawn from the brachial artery, and by an ear oximetric technique. Comparison was made of the time contponents of the two curves and of the cardiac output values derived from them. The differences in time components were frequently considerable. It was con cluded that the ear curves were thus unsuit able for estimation of indices such as the "central blood volume." By contrast there was no systematic difference between the car diac output values computed by the two methods. The standard deviation of the differ ences between the two methods was 11.7 per cent of the average cardiac index observed. It was concluded that the ear oximetric tech nique employed offered a satisfactory method of studying the cardiac output in man.