CALCULATION AND DIGITAL DISPLAY OF WHOLE BLOOD OXYGEN SATURATION BY ANALOG TECHNIQUES

An electronic analog system has been developed which performs the double scale calculation from the Wood oximeter and gives a single output as a log ratio and also gives a digital display of oxygen saturation, with simultaneous recording of these parameters if desired. This system, built of commercially available analog components, consists of operational amplifiers to amplify the output of the red and infrared photocells, logarithmic devices to calculate the optical density as sensed by these two photocells, a division circuit to calculate the log ratio, a scaling circuit to facilitate digital display in percent oxygen saturation, and a digital voltmeter. The theory of operation, methods for calibrating the components, and the complete system are discussed. Comparison between the oxygen saturation of whole blood as determined by Van Slyke analysis, the computed log ratio, and that observed on the digital display is given. The system proved to be easy to use, virtually drift free, and nearly as accurate as the more time consuming manual methods. Copyright © 1969 by The Institute of Electrical and Electronics Engineers, Inc.