Impact of epidermal melanin on peripheral pulse oximetry measurements

ImportancePulse oximetry is used widely to assess oxygen saturation in nearly all healthcare institutions. ObjectiveThis study aimed to investigate the relationship between epidermal melanin concentrations, determined by colorimetry, and discrepancies between arterial blood saturation (SaO2), determined by arterial blood gas (ABG), and peripheral oxygen saturation (SpO2) determined by pulse oximetry. Design, Setting, ParticipantsThis observational, correlational study was conducted over a one-week period in 2024 at the University of the Incarnate Word School of Osteopathic Medicine. Twenty-eight healthy adult volunteers (14 male; 14 female) with varying skin pigmentation were recruited via convenience sampling. Participants with conditions affecting oxygen saturation were excluded. ExposureParticipants underwent non-invasive pulse oximetry to measure peripheral oxygen saturation (SpO2) and invasive arterial blood gas (ABG) analysis to measure arterial oxygen saturation (SaO2). Melanin concentrations were measured using DSM III ColorMeter on the dorsal and palmar aspects of the hand. SpO2 was measured using the Masimo MightyStat(R) Rx Fingertip Pulse Oximeter, and ABG samples were analyzed using the i-STAT(R) 1 blood analyzer. Main Outcome(s) and Measure(s)The primary outcome was the difference between SpO2 and SaO2 across varying melanin concentrations, hypothesized before data collection. ResultsAnalysis revealed a significant difference between SaO2 and SpO2 with a moderately positive correlation with average epidermal melanin concentrations (r = 0.432; 95% CI, 0.07 to 0.693; P = 0.022) and a moderately inverse correlation with average luminance (r = -0.492; 95% CI,- 0.731 to -0.145; P = 0.008). A strong inverse relationship was found between melanin and luminance (r = -0.85; 95% CI -0.928 to -0.698; P <0.001). PO2 emerged as the leading predictor in two regression models, explaining 50.5% of the variance when combined with melanin. Conclusion and RelevanceTaken together, these data suggest that pulse oximetry overestimates oxygen saturation in individuals with comparatively high epidermal melanin concentrations. Future investigations that include a broader age range and participants with various comorbidities may provide a more comprehensive understanding of the impact of epidermal melanin on the accuracy of pulse oximetry readings. Key PointsO_ST_ABSQuestionC_ST_ABSHow does epidermal melanin concentration affect the accuracy of pulse oximetry measurements compared to arterial blood gas results? FindingsThis study found that higher epidermal melanin concentrations were associated with greater discrepancies between pulse oximetry and arterial oxygen saturation readings, suggesting that pulse oximeters may overestimate oxygen levels in individuals with darker skin tones. MeaningHigher epidermal melanin concentrations may result in less accurate pulse oximetry measurements, potentially leading to misinterpretations of oxygen saturation in patients with darker skin tones, raising concerns about the accuracy of these devices across diverse populations.