Effects of epidermal pigmentation on the accuracy of hyperspectral versus commercial near-infrared spectroscopy tissue oximeters

The accuracy of pulse and tissue oximeters has been questioned due to potential bias related to skin pigmentation. Current commercial oximeters use a limited number of wavelengths to estimate tissue blood oxygen saturation (StO₂), failing to account for additional light absorption caused by melanin which particularly important in individuals with darker skin. This limitation has resulted in inaccurate readings, missed diagnoses, and delayed treatment for these people. Interestingly, the absorption spectrum of melanin in the near-infrared region decreases quasi-monotonically with wavelength, similar to light scattering, which can be effectively mitigated by applying spectral derivatives to hyperspectral near-infrared spectroscopy (<i>h</i>-NIRS) measurements. Consequently, we hypothesize that <i>h</i>-NIRS can mitigate the confounding effects of melanin, to provide more accurate measurements of StO₂ across diverse skin tones. This study evaluates the accuracy of <i>h</i>-NIRS in comparison to few-wavelength spectroscopy (i.e. simulated commercial tissue oximeters) through simulations and tissue-mimicking phantom experiments. The accuracy of <i>h</i>-NIRS for determining StO₂ was assessed against two “virtual devices”, each mimicking a commercially available tissue oximeter (INVOS-5100c and NIRO- 200NX). Results showed significant skin tone-dependent biases of the simulated commercial devices, while <i>h</i>-NIRS demonstrated consistently low errors (&lt;3%) across all skin tones and oxygenation levels. These findings confirm that <i>h</i>-NIRS can effectively mitigate skin tone biases, achieving superior accuracy compared to these commercial devices. These findings are significant as they offer a viable solution to a major limitation of current tissue oximeters and establish <i>h</i>-NIRS as a promising technique for inclusive assessment of StO₂.