Impact of epidermal melanin on peripheral pulse oximetry measurements
Authors: Rice James , Dixon Jalan , Renfrew Ethan , Nemeth Denise , Finkelstein Akiva , Gernhofer Yan , Hinckley Sam , Chaparro Rafael , Samson Teresa , Pizano Cristina , Hildebrand Bernard , Mifflin Steven 
Published: September 2024

Importance

Pulse oximetry is used widely to assess oxygen saturation in nearly all healthcare institutions.

Objective

This 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, Participants

This 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.

Exposure

Participants 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. SpO2was measured using the Masimo MightyStat®Rx Fingertip Pulse Oximeter, and ABG samples were analyzed using the i-STAT®1 blood analyzer.

Main Outcome(s) and Measure(s)

The primary outcome was the difference between SpO2and SaO2across varying melanin concentrations, hypothesized before data collection.

Results

Analysis revealed a significant difference between SaO2and SpO2with 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). PO2emerged as the leading predictor in two regression models, explaining 50.5% of the variance when combined with melanin.

Conclusion and Relevance

Taken 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 Points

Question

How does epidermal melanin concentration affect the accuracy of pulse oximetry measurements compared to arterial blood gas results?

Findings

This 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.

Meaning

Higher 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.