Pulse oximeter performance and skin pigment: comparison of 34 oximeters using current and emerging regulatory frameworks
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Background
The International Organization for Standardization (ISO) and US Food and Drug Administration (FDA) are updating standards and guidance for pulse oximeters to reduce performance disparities linked to skin pigment. We tested common oximeters with current and anticipated regulatory frameworks. We hypothesized that most oximeters would show more positive bias in darkly vs lightly pigmented participants and that fewer oximeters would ‘pass’ anticipated regulations.
Methods
We used a controlled desaturation protocol to test 34 oximeters across arterial oxygen saturations (SaO2) 70–100% in healthy adults. Based on what FDA and ISO had shared at the time of study design, we studied cohort sizes of > 24 with > 25% of participants being darkly pigmented. We used the subjective Monk Skin Tone (MST) scale and the objective individual typology angle (ITA) derived from a spectrophotometer to characterize skin pigment. The root mean square error (ARMS), bias (mean of SpO2 - SaO2 error), and skin pigment differential bias were calculated. Monte Carlo simulation explored potential impacts of participant selection on device passing.
Results
For cohorts of 24 participants, 28/34 oximeters passed 2017 ISO Standard ARMS < 4%, 22/34 passed 2013 FDA guidance ARMS < 3%, 21/34 oximeters passed both ARMS and differential bias criteria for anticipated ISO standards, and 1/34 passed anticipated FDA criteria. More devices passed with cohorts > 24. Eleven oximeters had more positive bias in participants with dark vs. light (dorsal finger) pigmentation across 70– 100% SaO2. Eighteen devices could pass or fail depending on cohorts selected for analysis.
Conclusions
Pulse oximeters show variable performance across manufacturers and models, with only some devices showing more positive bias in people with darker skin. Anticipated updates to ISO and FDA frameworks yield strikingly different assessments and require refinement. Whether they will translate into improved real-world performance or reduced health disparities is yet to be determined.
