Dual-ratio approach to pulse oximetry and the effect of skin tone

For the models and methods considered here, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mi>SpO</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> measurements are strongly impacted by heterogeneous pulsatile hemodynamics. This variability may be larger than the skin tone bias, which is a known confound in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mi>SpO</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> measurements. The partial suppression of variability in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mi>SpO</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> recovered by DR suggests the promise of DR for pulse oximetry.