1. Exploring the bias: how skin color influences oxygen saturation readings via Monte Carlo simulations.
- Author
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Narayana Swamy SK, Liu C, Correia R, Hayes-Gill BR, and Morgan SP
- Subjects
- Humans, Oxygen blood, Computer Simulation, Skin blood supply, Skin chemistry, Skin diagnostic imaging, Models, Biological, Fingers physiology, Fingers blood supply, Monte Carlo Method, Skin Pigmentation physiology, Oximetry methods, Oxygen Saturation physiology
- Abstract
Significance: Our goal is to understand the root cause of reported oxygen saturation ( SpO 2 ) overestimation in heavily pigmented skin types to devise solutions toward enabling equity in pulse oximeter designs., Aim: We aim to gain theoretical insights into the effect of skin tone on SpO 2 - R curves using a three-dimensional, four-layer tissue model representing a finger., Approach: A finger tissue model, comprising the epidermis, dermis, two arteries, and a bone, was developed using a Monte Carlo-based approach in the MCmatlab software. Two skin tones-light and dark-were simulated by adjusting the absorption and scattering properties within the epidermal layer. Following this, SpO 2 - R curves were generated in various tissue configurations, including transmission and reflection modes using red and infrared wavelengths. In addition, the influence of source-detector (SD) separation distances on both light and dark skin tissue models was studied., Results: In transmission mode, SpO 2 - R curves did not deviate with changes in skin tones because both pulsatile and non-pulsatile terms experienced equal attenuation at red and infrared wavelengths. However, in reflection mode, measurable variations in SpO 2 - R curves were evident. This was due to differential attenuation of the red components, which resulted in a lower perfusion index at the red wavelength in darker skin. As the SD separation increased, the effect of skin tone on SpO 2 - R curves in reflection mode became less pronounced, with the largest SD separation exhibiting effects similar to those observed in transmission mode., Conclusions: Monte Carlo simulations have demonstrated that different light pathlengths within the tissue contribute to the overestimation of SpO 2 in people with darker skin in reflection mode pulse oximetry. Increasing the SD separation may mitigate the effect of skin tone on SpO 2 readings. These trends were not observed in transmission mode; however, further planned research using more complex models of the tissue is essential., (© 2024 The Authors.)
- Published
- 2024
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