Broad-linewidth sources result in a skin-tone bias in noninvasive optical measurement of oxygen saturation

Pulse oximeters overestimate arterial oxygen saturation in patients with darker skin tones, potentially increasing rates of occult hypoxemia. The emission of broad-linewidth light-emitting diodes (LEDs) has been proposed as a possible cause for this melanin-dependent bias.

This letter utilizes a physics-based model to investigate if the spectral bandwidth of light sources contributes to melanin-dependent measurement biases.

Pulse oximetry measurements were simulated across varying melanin concentrations and source bandwidths using a hybrid diffusion theory and Monte Carlo model. Epidermal melanin absorption was modeled with transmissive filters on the surfaces of an infinite slab representing bulk tissue.

Simulations demonstrate that pulse oximeter calibration curves depend on melanin concentration when broad-linewidth LEDs are utilized. Conversely, calibration curves remain independent of melanin when employing monochromatic laser diodes (LDs).

Spectral coloring from broad-linewidth LEDs contributes to the skin-tone bias observed in pulse oximetry. Although updating calibration methods for different skin tones is a potential approach, adopting monochromatic LDs could alternatively eliminate this spectral-coloring contribution to the bias.