Modification of Oximeter Ratio to Reduce Pigmentation Bias in Pulse Oximetry

Pulse oximeters are widely used in healthcare systems to estimate blood oxygen saturation level (SpO2) using red and infrared light. Recent clinical and simulation studies reported that in darkly pigmented subjects oximeter over-estimates SpO2 which could lead to higher rates of occult hypoxemia in highly pigmented subjects. The probable solutions to solve this over-estimation bias could be modification of the current oximeter design, calibration enrollment or modification of oximeter ratio (R). In this study, a modification of the current oximeter ratio (R) was presented by using different combinations of currently estimated oximeter parameters. Simulation results showed that modified oximeter ratio reduces over-estimation bias in highly pigmented subjects compared to the conventional oximeter ratio. In the regions near hypoxemia threshold (90% oxygenation level), the over-estimation bias in the simulated test cohort could reduce from 1.36% to -0.01% if modified oximeter ratio is used. Results show that modification of oximeter ratio could be used in future to improve oximeter accuracy and produce pigmentation independent outcomes.