Development of a melanin-inclusive reflective pulse oximeter model for equitable performance tested in a large animal model undergoing hypoxia: pilot study

Numerous studies have shown that pulse oximeters are less accurate for individuals with darker skin, which negatively impacts patient outcomes. This underscores the need for more equitable pulse oximetry strategies that account for pigmentation to reduce this bias. Here, we developed a wearable reflective pulse oximeter to gather raw photoplethysmography signals. Conventional and modified pulse oximeter algorithms were applied based on the ratio-of-ratio’s method and a melanin term, derived from quantitative histology of the epidermis. This melanin-inclusive pulse oximetry expression was developed and validated in a Hampshire porcine model (n=4) using adjacent areas of darkly and lightly pigmented skin. The animals were exposed to controlled hypoxia with saturation levels ranging from 100% to 70%. Blood gas analysis was performed and synchronized to the pulse oximeter readings on dark and light sections, with epidermis biopsies sampled and Fontana-Masson stained for pigment quantification. The melanin-inclusive approach reduced the bias in both the 100-85% (from 1.85% to 0.62%) and 84-70% saturation ranges (from 2.70% to 0.16%). This was a marked improvement over conventional pulse oximetry and reference medical-grade devices, which exhibited higher biases (3.08% to 4.98%). This study suggests that the bias in oximeter readings may be correlated with physical quantities of melanin in the epidermis. Future work will entail obtaining a melanin coefficient from the wearable device itself for a complete on-board non-invasive solution. This melanin-inclusive method is a promising strategy to reduce pulse oximeter bias and improve the accuracy of a widely-used medical device, potentially enhancing care across diverse patient populations.