Beyond the Surface: Pulse Oximetry Accuracy in Darkly Pigmented Skin Tones

A Persistent Problem Hidden in Plain Sight 

For decades, pulse oximetry has served as a cornerstone of clinical monitoring—offering a quick, noninvasive estimate of blood oxygen saturation (SpO₂). Yet, the COVID-19 pandemic exposed a long-standing and underappreciated flaw: pulse oximeters can overestimate oxygen levels in individuals with darker skin pigmentation. 

Inaccurate SpO₂ readings may mask hypoxemia, delay treatment decisions, and contribute to existing health disparities. The issue has prompted renewed scrutiny from regulators, researchers, and manufacturers alike. 

At Parameters Research Laboratory (PRL), we help device developers understand and address this challenge through controlled desaturation studies, diverse participant recruitment, and regulatory-grade validation protocols that quantify accuracy across all skin tones. 

Why Skin Tone Affects Pulse Oximetry Accuracy 

Pulse oximeters work by transmitting red and infrared light through tissue, measuring how much is absorbed by oxygenated and deoxygenated hemoglobin. However, melanin—the pigment that determines skin tone—also absorbs light, particularly in the spectrum used by these devices. 

When oximeter algorithms fail to account for this additional absorption, the device may interpret less light as higher oxygenation, artificially inflating SpO₂ values. 

In practice, this means that: 

• A person with lighter skin and a person with darker skin may have identical arterial oxygen saturation (SaO₂), but the pulse oximeter might display a higher SpO₂ in the darker-skinned individual. 

• This systematic overestimation can result in occult hypoxemia, where true desaturation goes undetected. 

Evidence of Bias Across Populations 

A growing body of evidence highlights this discrepancy: 

• NEJM (2020) – Black patients were nearly three times more likely than White patients to have occult hypoxemia (SaO₂ < 88% with SpO₂ 92–96%). 

• JAMA Network Open (2023) – Among 24,000+ COVID-19 patients, pulse oximeters overestimated SaO₂ by nearly 1% on average in Black patients, leading to delays in therapy initiation. 

• FDA Safety Communication (2021) – The FDA acknowledged that pulse oximeter accuracy can vary by skin pigmentation, emphasizing the need for diverse validation datasets. 

• Anesthesia & Analgesia (2022) - Darker skin pigmentation amplifies oximeter error, especially under conditions of low perfusion conducted in a laboratory setting. 

  
  

Many retrospective studies are limited by timing mismatches, inconsistent reference methods, and the use of self-reported race instead of skin tone. As pulse oximetry remains an essential clinical tool, understanding and addressing these sources of bias—particularly in darker skin tones—is a vital next step.  

The Regulatory Shift Toward Inclusivity 

In response to these findings, regulatory agencies are updating expectations for device validation: 

• FDA guidance now recommends that pulse oximetry studies include a minimum of 25% of participants with darkly pigmented skin (based on the Monk scales 8-10). 

• Standards organizations such as the International Standards Organization (ISO) are revisiting test methods to ensure optical performance is evaluated across diverse skin tones and perfusion states. 

• The Open Oximetry Project advocates for open-source datasets that promote equity and transparency in oximeter design and verification. 

For MedTech developers, this means that inclusive validation is no longer optional; it’s a regulatory necessity. 

How PRL Supports Inclusive Device Verification  

At PRL, we specialize in regulatory-grade verification of pulse oximetry and physiological monitoring technologies, with a focus on inclusivity and precision. 

1. Controlled Desaturation in a Dedicated Hypoxia Lab 

Our controlled desaturation laboratory allows safe, reproducible simulation of oxygen saturation levels from normoxia to hypoxia. By collecting simultaneous arterial blood gas (ABG) and SpO₂ data, PRL can quantify bias across all saturation levels. 

2. Inclusive Participant Recruitment 

Through structured recruitment across the Monk skin tone scale, we ensure that verification datasets capture the full diversity of human skin pigmentation. This approach enables: 

• Non-Disparate Performance Evaluation. 

• Stratified analysis per Monk Skin tone and Individual Typology Angle (ITA). 

• Regulator-ready reporting for FDA, CE mark, and ISO 14155 compliance. 

  
  

3. Data Integrity and Regulatory Alignment 

PRL designs studies that adhere to Good Clinical Practice (GCP) and ISO 80601-2-61 principles, ensuring transparent, reproducible, and regulator-ready data packages. Our emphasis on Clinical Research Service Provider (formerly known as Clinical Research Organization or “CRO” transparency, trial protocol alignment, and risk mitigation helps developers avoid costly FDA submission delays. 

Looking Ahead: Building Trust Through Transparency 

Pulse oximetry has become synonymous with modern monitoring, but its limitations must be acknowledged and addressed. As the MedTech industry evolves, inclusive testing practices will define the credibility of next-generation monitoring devices. 

Clinical studies are essential to demonstrate the safety and effectiveness of pulse oximeter systems and to ensure consistent, equitable performance across patients with diverse skin pigmentation.  PRL’s dedication to diverse recruitment, rigorous desaturation testing, and collaborative partnerships ensures that every device validated in our lab delivers accurate performance—for every user. 

Partner with PRL 

If your organization is developing or validating pulse oximetry or wearable monitoring devices, partner with PRL to: 

• Conduct controlled desaturation studies with gold-standard arterial reference data. 

• Demonstrate inclusive performance across skin tones for FDA and CE submissions. 

• Strengthen regulator-ready documentation aligned with ISO and GCP standards. 

Contact us today!

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