Measurement of Cardiac Output Using the Photoelectric Earpiece: A Comparison with Simultaneous Fick Measurements

Abstract
Comparison of resting earpiece dye dilution cardiac outputs using the Cambridge Mark II amplifier-recorder with simultaneous Fick determinations has shown a satisfactory correlation in 27 patients (r =0.93). The correlation has proved to be comparable to that of cuvette densitometer-Fick studies previously reported. Modified techniques for injection of Coomassie Blue dye and calibration by the end-tail method without the need for dye extraction from the serum have simplified the procedure greatly. The Cambridge earpiece has been shown to be a reliable quantitative tool having the advantages of simplicity and ease of performance without the need of an arterial puncture, and making possible a wider usage of the technique.