Oxygen Reserve Index: A Novel Noninvasive Measure of Oxygen Reserve--A Pilot Study.

Background: Pulse oximetry provides no indication of downward trends in PaO2 until saturation begins to decrease. The Oxygen Reserve Index (ORI) is a novel pulse oximeter-based nondimensional index that ranges from 1 to 0 as PaO2 decreases from about 200 to 80 mmHg and is measured by optically detecting changes in SvO2 after SaO2 saturates to the maximum. The authors tested the hypothesis that the ORI provides a clinically important warning of impending desaturation in pediatric patients during induction of anesthesia.