Perioperative monitoring of the oxygen reserve: where do we stand?

The Oxygen Reserve Index (ORi) is an advanced plethysmography-derived variable that may help to quantify the degree of hyperoxia in patients receiving supplemental oxygen administration. ORi is a (relative) indicator of the actual partial pressure of oxygen dissolved in arterial blood (PaO 2 ). As such, it may help in the titration of oxygen administration or it may help to warn the clinician of a deterioration of oxygen status of the patient. In this issue of the journal, Fadel et al. provide a ‘classical’ clinical validation study by assessing the correlation between ORi and PaO 2 in patients about to undergo open-heart surgery. Within the moderate hyperoxic range (100–200 mmHg PaO 2 ), there is a sound correlation between ORi and PaO 2 . This editorial discusses the clinical implications of this validation study and elaborates on the possible role of ORi monitoring in addition to SpO 2 (peripheral arterial oxygen saturation) monitoring alone.