In vivo studies with an intravascular and intracardiac reflection oximeter

¹ Department of Medicine, Columbia University College of Physicians and Surgeons, and Cardio-Pulmonary Laboratory, First Medical and Chest Services, Bellevue Hospital, New York City

An oximeter is described which employs two bundles of flexible glass fibers to conduct appropriately filtered light into, and that light diffusely reflected by the blood out of, the blood stream for the determination of oxygen saturation or dye concentration within blood flowing past the tip of either an arterial needle or a cardiac catheter which contains both bundles. The ratio of intensities of the reflected light at two wavelengths is linearly related to oxygen saturation (I_RR805/ I_RR660) and dye concentration (I_RR900/I_RR805). Data is reported in vivo and in vitro with respect to accuracy of the determinations (± 1.9%). The effect of patient-to-patient variation in hematocrit and other factors, and of pulsatile blood flow, is described. Application of the technique to physiologic study is illustrated, and theoretical aspects of reflection oximetry, as they apply to the instrument, are discussed.

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