Measurement of blood oxygen saturation using a multichannel fiberoptic oximeter–densitometer

Abstract

Design principles and performance of a new fiberoptic oximeter–densitometer for measurement of blood oxygen saturation are described. This instrument is capable of performing measurements using either an intravascular catheter, flow-through cuvette, or earpiece. The operations of the flow-through cuvette and earpiece are based on the principles of light transmission, that of the catheter on the principles of hemoreflection. The system incorporates five interference filters permitting the selection of a particular wavelength or combination of wavelengths to perform different modes of operation. Estimates using both catheter and cuvette appeared to be independent of variations over a wide range in hematocrit and flow rate. In the range from 20 to 100% saturation the standard deviation of the differences between the in vitro estimates by the catheter and (or) cuvette and the Van Slyke analyses were 1.62 and 1.73%, respectively. In 53 children with congenital heart disease (22 cyanotic) values calculated from readings by the earpiece were related to values of arterial oxygen saturation as measured by American Optical Company reflection oximeter at the time of cardiac catheterization. In the range from 50 to 100% saturation, the regression line between the two techniques was linear and the standard deviation of the differences was 2.89% (3.12% in cyanotic children alone).The method provides a high degree of compensation for variations in skin pigmentation.