Significance
Pulsatile blood oxygen saturation (SpO2) via pulse oximetry is a valuable clinical metric for assessing oxygen delivery. Individual anatomical features, including skin tone, may affect current optical pulse oximetry methods.
Aim
We developed an optical pulse oximetry method based on dual-ratio (DR) measurements to suppress individual anatomical confounds on SpO2.
Approach
We designed a DR-based finger pulse oximeter, hypothesizing that DR would suppress confounds from optical coupling and superficial tissue absorption. This method is tested using Monte Carlo simulations and in vivo experiments.
Results
Different melanosome volume fractions in the epidermis, a surrogate for skin tone, cause changes in the recovered SpO2 on the order of 1% in simulation and in vivo. Different heterogeneous pulsatile hemodynamics cause greater changes on the order of 10% in simulations. SpO2 recovered with DR measurements showed less variability than the traditional single-distance (SD) transmission method.
Conclusions
For the models and methods considered here, SpO2 measurements are strongly impacted by heterogeneous pulsatile hemodynamics. This variability may be larger than the skin tone bias, which is a known confound in SpO2 measurements. The partial suppression of variability in the SpO2 recovered by DR suggests the promise of DR for pulse oximetry.
