An improved algorithm for reflective and transmissive pulse oximetry across different skin pigmentation

While pulse oximeters are used ubiquitously in different clinical settings, numerous studies have noted differences in performance across individuals with different skin tones. In a study of 11 participants spanning the Monk Skin Tone scale, we observed a bias of 1.38% and ARMS of 1.31% in transmissive mode and a bias of 3.91% and an ARMS of 2.35% in reflective mode when applying the conventional ratio-of-ratios expression. Adding a red/infrared ratio to the fit reduced the bias and ARMS to -0.17% and 1.11%, respectively in transmissive mode and 0.28% and 1.64%, respectively in reflective mode. This work introduces a readily available optical platform for future investigation and improvement of pulse oximeter accuracy, avoiding the confounder of proprietary signal processing and enabling open science.