Utility of skin tone on pulse oximetry in critically ill patients: a prospective cohort study
Authors: Hao Sicheng , Dempsey Katelyn , Matos João , Cox Christopher E. , Rotemberg Veronica , Gichoya Judy W. , Kibbe Warren , Hong Chuan , Wong Ian 
Published: February 2024

Importance

Pulse oximetry, a ubiquitous vital sign in modern medicine, has inequitable accuracy that disproportionately affects Black and Hispanic patients, with associated increases in mortality, organ dysfunction, and oxygen therapy. Although the root cause of these clinical performance discrepancies is believed to be skin tone, previous retrospective studies used self-reported race or ethnicity as a surrogate for skin tone.

Objective

To determine the utility of objectively measured skin tone in explaining pulse oximetry discrepancies.

Design, Setting, and Participants

Admitted hospital patients at Duke University Hospital were eligible for this prospective cohort study if they had pulse oximetry recorded up to 5 minutes prior to arterial blood gas (ABG) measurements. Skin tone was measured across sixteen body locations using administered visual scales (Fitzpatrick Skin Type, Monk Skin Tone, and Von Luschan), reflectance colorimetry (Delfin SkinColorCatch [L*, individual typology angle {ITA}, Melanin Index {MI}]), and reflectance spectrophotometry (Konica Minolta CM-700D [L*], Variable Spectro 1 [L*]).

Main Outcomes and Measures

Mean directional bias, variability of bias, and accuracy root mean square (ARMS), comparing pulse oximetry and ABG measurements. Linear mixed-effects models were fitted to estimate mean directional bias while accounting for clinical confounders.

Results

128 patients (57 Black, 56 White) with 521 ABG–pulse oximetry pairs were recruited, none with hidden hypoxemia. Skin tone data was prospectively collected using 6 measurement methods, generating 8 measurements. The collected skin tone measurements were shown to yield differences among each other and overlap with self-reported racial groups, suggesting that skin tone could potentially provide information beyond self-reported race. Among the eight skin tone measurements in this study, and compared to self-reported race, the Monk Scale had the best relationship with differences in pulse oximetry bias (point estimate: −2.40%; 95% CI: −4.32%, - 0.48%;p=0.01) when comparing patients with lighter and dark skin tones.

Conclusions and relevance

We found clinical performance differences in pulse oximetry, especially in darker skin tones. Additional studies are needed to determine the relative contributions of skin tone measures and other potential factors on pulse oximetry discrepancies.

Key Points

Question

Can skin tone capture information beyond race to help explain pulse oximetry discrepancies?

Findings

Pulse oximetry bias across races seems to persist across skin tone when measured using administered visual scales, reflectance colorimetry, or reflectance spectrophotometry. Among the eight skin tone measurements in this study, and compared to self-reported race, the Monk Scale seemed to best correlate with pulse oximetry bias when comparing patients with lighter and dark skin tones.

Meaning

Compared to self-reported race, skin tone is associated with some pulse oximetry discrepancies; we recommend using skin tone to assist the regulatory clearance of equitable pulse oximeters.