How Skin Tone Influences Pulse Oximeter Accuracy
By Ariqa Everett. Ariqa has degrees in biological sciences and African American studies and currently works as a program assistant for a Global Health organization.
Medical review by Diane B. Francis, PhD
Vital signs are an excellent way for providers to get to know you and to detect when something in your body is outside the normal range. However, detecting irregularities can be difficult when our medical devices are biased toward darker skin. Recent evidence shows that pulse oximeter, a small device that measures oxygen, inaccurately measures low blood oxygen levels in patients with darker skin. Yet, the same device is still used as a standard of care today.
The Fifth Vital Sign
At the start of most doctor visits, a healthcare provider will ask to check your vital signs to gain insight into your well-being. The four main vital signs are body temperature, heart rate, breathing rate, and blood pressure. Since COVID-19, providers have been routinely checking blood oxygen saturation levels using a pulse oximeter. This is happening so much that one’s oxygen level is considered the fifth vital sign.
Oxygen saturation is the amount of oxygen you have in your blood. Once oxygen enters the body, it flows into your bloodstream and acts as an energy source for your body's processes. Low oxygen levels can lead to severe conditions that damage organ systems, including your brain and heart. Pre-existing conditions such as heart and lung disease can increase the risk of poor oxygen levels. During COVID-19, poor oxygen flow was a primary symptom that emphasized the importance of monitoring oxygen saturation levels. Healthcare and public health leaders encouraged people to monitor their vitals at home using pulse oximeters. COVID-19 also highlighted health disparities between skin tone and pulse oximeter accuracy.
The Importance of Accurate Oxygen Readings
Pulse oximetry was first designed in 1974. Unfortunately, researchers failed to include people with a range of skin tones in the study. This omission has led to bias toward patients with darker complexions. Today the FDA requires all medical testing to include diverse participants. Still,their definition of diversity is "at least two darkly pigmented people in the sample" Having such little variety has contributed to the racial bias we see today. Researchers tested the accuracy of currently available pulse oximeters in over 30 patients and found that the oxygen levels in patients with dark skin were being overestimated. This inaccurate assessment can lead to delayed care and poor health outcomes.
Pulse oximetry is noninvasive and painless. The pulse oximeter’s blood oxygen sensor measures the amount of red light that passes through the finger. Many factors can block the amount of light passing through and cause errors, such as nail polish, skin thickness, and darker skin tones. A person's oxygen saturation level is a key element in clinical decision-making. Saturation levels between 95 percent and 100 percent are considered normal. Levels that drop below 92 percent can be a sign that there is a lack of oxygen reaching the body's tissues. Being unable to depend on a pulse oximeter for accurate readings leads to darker skin patients being subjected to invasive options such as an Arterial Blood Gas (ABG) test. ABG test samples blood from the arteries, typically in the wrist for adults or heel for babies.
Something New, Something Blue
New research by a team of bioengineers at the University of Texas explored the potential of using blue-green light instead of red-infrared light on more melanated skin. The proposed solution is to use blue-green light so sensors will measure the reflection off of the skin rather than the light passing through it. This new pulse oximeter device, the Shani, was also adjusted for melanin using an algorithm. Researchers tested 16 healthy adults, ages 20-40. Six of the volunteers had brown skin, five had dark skin, and the remaining fair skin. The Shani has been successfully tested in preclinical and clinical studies on a range of skin tones. Moving forward, the team strives to create a wearable device that accurately reads blood oxygen levels on any skin color.
Technology can improve how we interact with healthcare. Wearable devices like smartwatches and activity trackers have changed how we monitor our health. During our daily flow of life, a wearable device could continuously monitor our vital signs in and out of the doctor's office. These devices have increased interest in one's health status with their user-friendly features, placing patients at the center of their healthcare. At home, work, or exercising, wearables could capture vital data that helps in faster diagnosis, increased access to care, and improved patient experiences.
Innovative ideas like the Shani pulse oximeter can only provide solutions to bias in diagnostic tools if there is more diversity in medical device clinical trials. Consider getting involved. Diversity in clinical trials benefits everyone. Clinical trials can seem scary or overwhelming, but they are an opportunity for you to be a part of something revolutionizing healthcare.
How Do You Get Involved?
Step 1: Consult your physician. Start by talking to your doctor about joining clinical trials.
Step 2: Confirm eligibility. Clinical trials have guidelines, so make sure it is the right one for you.
Step 3: Review the study description and develop questions. Go over these questions with your physician and the organizers of the study.
Step 4: Informed Consent. Understand what informed consent means and your rights as a voluntary participant.
Call to Action
DHH is expanding and amplifying research on inequities in diagnostic testing. We believe this topic impacts EVERYONE, as tests are the baseline for care and treatment of any health issue or disease. Stay tuned to learn with us, as we continue to report on what you need to know to advocate for yourself and others. Subscribe for the latest.
Sources
Team, A. by our C. (2021, January 29). Pulse oximeters and how to use them. LloydsPharmacy. https://lloydspharmacy.com/blogs/coronavirus/how-to-use-a-pulse-oximeter
National Institute on Minority Health and Health Disparities Accessed August 1, 2023. https://www.nimhd.nih.gov/resources/understanding-health-disparities/diversity-and-inclusion-in-clinica
Sanjay G Gokhale, Vinoop Daggubati, Georgios Alexandrakis. Innovative technology to eliminate the racial bias in non-invasive, point-of-care (POC) haemoglobin and pulse oximetry measurements. BMJ Innovations, 2022; bmjinnov-2022-001018 DOI: 10.1136/bmjinnov-2022-001018
Blood Oxygen Level. Cleveland Clinic website. Accessed August 1, 2023. https://my.clevelandclinic.org/health/diagnostics/22447-blood-oxygen-level
Dias, D., & Paulo Silva Cunha, J. (2018). Wearable Health Devices-Vital Sign Monitoring, Systems and Technologies. Sensors (Basel, Switzerland), 18(8), 2414. https://doi.org/10.3390/s18082414
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