It is now possible to make continuous in vivo measurements of the oxygen saturation and total cardiac output of a patient on a real time basis by using the recently developed technique of fiber optics spectrophotometry. This paper describes instrumental features of a fiber optics oximeter-densitometer which has been used on experimental animals as well as on human beings for the measurement of oxygen saturation and dye concentration. The in vivo measurement made possible with this remote spectrophotometer has shown significant advantages over the in vitro method, which in the past has required withdrawal of blood samples and subsequent measurements with attendant time delays and inaccuracies. This instrument allows the correlation of oxygen saturation variations in various regions within the heart with intercardiac, ECG, and pressure measurements. The clinical data on this instrument have demonstrated its value in the diagnosis of heart defects.
N. S. Kapany, D. C. Harrison, N. Silbertrust, R. P. Drake, T. McLaughlin, and H. A. Miller, "Fiber Optics Oximeter-Densitometer for Cardiovascular Studies," Appl. Opt. 6, 565-570 (1967)