Clinical utility of ORi™, Masimo Oxygen Reserve Index™ in obese patients

Masimo has announced the findings of an abstract presented at the annual meeting of the Society for Technology in Anesthesia (STA) in Miami, Florida.

In the study, researchers at the UC Davis School of Medicine evaluated the potential clinical utility of Masimo Oxygen Reserve Index™ (ORi™) as an early warning of impending arterial haemoglobin desaturation in obese patients.¹ This is the first published research investigating the utility of ORi in this particular population group.

ORi is a relative indicator of a patient’s oxygen reserve in the moderate hyperoxic region (partial pressure of oxygen in arterial blood [PaO₂] in the range of 100 to 200 mmHg). As an “index” parameter with a unit-less scale between 0 and 1, ORi can be trended and has optional alarms to notify clinicians of changes in a patient’s oxygen reserve.

In the prospective, observational study, Dr. Ayala and colleagues analysed data from 36 adult patients with BMI between 30 and 40 kg/m² who were scheduled for elective surgical procedures requiring general anesthesia and endotracheal intubation. The patients’ ORi values were measured using a Masimo Root^® Patient Monitoring and Connectivity Platform with Radical-7^® Pulse CO-Oximeter^®. The researchers recorded the time elapsed from the start of ORi alarming (triggered by decrease in the absolute value and rate of change in ORi) to 98% oxygen saturation, and considered this interval to be the average increase in warning time provided by ORi.

The researchers found that among the patients, the average time from the start of ORi alarming to 98% oxygen saturation was 42 ± 49 seconds (ranging from 5 to 255 seconds). Excluding two outliers, the average increase in warning time provided by ORi was 33 ± 23 seconds (ranging from 5 to 107 seconds).

The researchers concluded that the study “demonstrates the ability of ORi to provide advanced warning of arterial desaturation as an adjunct to SpO₂ in this high risk patient population. This additional warning time can potentially translate to improved patient safety by allowing earlier calls for help, assistance from a more experienced person, or modification of airway management. For this analysis we defined the advance warning to end at 98% SpO2, with a defined trigger for intervention at 94% SpO₂.”

In another study, researchers at Children’s Medical Center in Dallas, Texas concluded that ORi could provide clinicians with a median of 31.5 seconds advanced warning of impending desaturation in pediatric patients with induced apnoea after pre-oxygenation.²

UC Davis received funding from Masimo for the ORi study.

References

1. Ayala S, Singh A, Applegate R, and Fleming N. Oxygen Reserve Index: Utility as Early Warning of Desaturation in Morbidly Obese Patients. Proceedings from the 2018 STA Annual Meeting, Miami, FL.
2. Szmuk P et al. Oxygen Reserve Index A Novel Noninvasive Measure of Oxygen Reserve–A Pilot Study. Anesthesiology. 4 2016, Vol. 124, 779-784. doi:10.1097/ALN.0000000000001009.