Publications

@article{Swamy2025-po,

title = {Pulse oximeter bench tests under different simulated skin tones},

author = {Suvvi K Narayana Swamy and Chenyang He and Barrie R Hayes-Gill and Daniel J Clark and Sarah Green and Stephen P Morgan},

doi = {10.1007/s11517-024-03091-2},

year  = {2025},

date = {2025-07-01},

urldate = {2025-07-01},

journal = {Med. Biol. Eng. Comput.},

volume = {63},

number = {7},

pages = {1931\textendash1942},

publisher = {Springer Science and Business Media LLC},

abstract = {Pulse oximeters\' (POs) varying performance based on skin tones 

 has been highly publicised. Compared to arterial blood gas 

 analysis, POs tend to overestimate oxygen saturation (SpO2) 

 values for people with darker skin (occult hypoxemia). The 

 objective is to develop a test bench for assessing commercial 

 home and hospital-based POs in controlled laboratory conditions. 

 A laboratory simulator was used to mimic different SpO2 values 

 (~ 70 to 100%). Different neutral density and synthetic melanin 

 filters were used to reproduce low signal and varying melanin 

 attenuation levels. Six devices consisting of commercial home (Bioligh},

keywords = {Melanin, Occult hypoxemia, oxygen saturation, Pulse oximeter, Racial bias, Skin colour, Transmission-mode},

pubstate = {published},

tppubtype = {article}

}

@article{Narayana_Swamy2024-la,

title = {Exploring the bias: how skin color influences oxygen saturation  readings via Monte Carlo simulations},

author = {Suvvi K Narayana Swamy and Chong Liu and Ricardo Correia and Barrie R Hayes-Gill and Stephen P Morgan},

doi = {10.1117/1.JBO.29.S3.S33308},

year  = {2024},

date = {2024-06-01},

urldate = {2024-06-01},

journal = {J. Biomed. Opt.},

volume = {29},

number = {Suppl 3},

pages = {S33308},

publisher = {SPIE-Intl Soc Optical Eng},

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.},

keywords = {Melanin, Monte Carlo, Occult hypoxemia, oxygen saturation, pulse   oximeter, Racial bias, skin color, transmission mode},

pubstate = {published},

tppubtype = {article}

}