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Melanin bias in pulse oximetry explained by light source spectral bandwidth
Andrew Bierman1, Kevin Benner2, Mark S Rea2
1Namreiba LLC, Albany, NY, USA.
British Journal of Anaesthesia
|March 5, 2024
Summary
Pulse oximetry (SpO2) overestimates oxygen levels in individuals with dark skin due to melanin. Narrower spectral bandwidths in pulse oximeters can eliminate this bias.
Area of Science:
- Biomedical optics
- Medical device technology
- Physiological monitoring
Background:
- Pulse oximetry (SpO2) noninvasively measures blood oxygen saturation (SaO2) using optical light transmission.
- Current SpO2 devices exhibit a bias, overestimating oxygen levels in individuals with darker skin tones.
- This bias is attributed to differences in light absorption by melanin in the skin.
Purpose of the Study:
- To investigate the impact of spectral bandwidth on pulse oximetry accuracy.
- To determine if melanin concentration affects SpO2 readings across different spectral bandwidths.
- To develop a method for mitigating bias in SpO2 measurements for diverse skin tones.
Main Methods:
- Developed spectrally resolved photoplethysmography (srPPG) to analyze light transmission through fingertips.
- Recorded spectral transmission changes with varying oxygen levels and applied narrow and broad digital spectral filters.
- Quantified fractional melanin content and analyzed its effect on SpO2 readings between bandwidths.
Main Results:
- Experimental results confirmed the Beer-Lambert law prediction of SpO2 bias in darker skin tones.
- Light-emitting diode spectra in commercial pulse oximeters contribute to erroneously high SpO2 readings with increased melanin.
- A systematic variation in SpO2 readings was observed between narrow and broad spectral bandwidths.
Conclusions:
- Melanin bias in pulse oximetry can be eliminated by using narrower spectral bandwidths.
- Current pulse oximeter designs require modification to improve accuracy across all skin tones.
- Future pulse oximeter development should prioritize spectral characteristics to ensure equitable performance.
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