Near-infrared spectroscopy (NIRS) and skin tone in children: A prospective cohort study

Background: Retrospective studies suggest that pulse oximetry overestimates saturation in children from races that may be associated with darker skin tone. Near-infrared spectroscopy (NIRS) relies on similar optical technology, but less is known about the effect of skin tone on NIRS. We aimed to quantify the effect of skin tone on NIRS performance. Methods: Consecutive patients under 21 years undergoing cardiac catheterization were enrolled (N=110). Skin tone was measured using spectrophotometry. Regional oxygen saturation was recorded from a Medtronic INVOS 5100C NIRS device placed on the forehead and was compared to the mixed venous saturation. Multivariable linear regressions were used to determine the effect of skin tone measured by individual typology angle (ITA). Results: Mean bias was larger for patients with darker skin in ITA categories 5-6 at -12.8% compared to ITA 3-4 at -2.5% with a difference of 10.3% (95%CI[4.4, 16.3], p<0.001) and ITA 1-2 at 0.3% with a difference of 13.1% (95%CI[7.5, 18.7], p<0.001). ITA was associated with NIRS bias in multivariable regression analysis (coefficient 0.173, p<0.001). Conclusions: Darker skin tone is associated with worse NIRS performance and lower NIRS values compared to mixed venous saturation for the INVOS 5100C system. This may lead to differences in care and contribute to inequities in outcomes. Better validation guidelines are needed to ensure equity in performance across varying skin tones.