#WhatTheFAQ: How do oximeters exacerbate the issue of racial bias in medicine?

The COVID-19 pandemic brought the Pulse Oximeter into all our homes. We anxiously watched the readings on this small device to deduce the impact that the COVID-19 virus was having on us and our loved ones. However, alarming studies have now come to light that point out that the oximeters were not designed to work properly on people with darker skin tones. What is the fallout?

How does a Pulse Oximeter work?
The device became ubiquitous during the COVID-19 pandemic, with people using it to measure the level of oxygen saturation levels in their blood. This is because the COVID-19 virus impacted the lungs of the infected people and that can impact the level of oxygen in the blood. The device is placed on a fingertip and it uses light beams to measure the oxygen saturation levels in the blood. This removes the need to draw blood samples to measure the saturation levels. According to the United States Food and Drug Administration, the ideal oxygen saturation levels or SpO2 levels range between 95-100%. For individuals whose lungs have been infected, these levels could drop significantly, leading to severe health issues. Oximeter readings at home were often crucial in determining the severity of the COVID-19 infection in patients.

What are its limitations, as warned by the US FDA?
For a device so critical, the oximeter has several limitations as listed by the FDA. "Be aware that multiple factors can affect the accuracy of a pulse oximeter reading, such as poor circulation, skin pigmentation, skin thickness, skin temperature, current tobacco use, and use of fingernail polish," says the FDA on oximeters. The FDA's take on the matter supports a host of other research on the efficacy of oximeters on people with darker skin colour. Among these reports is a recent one published in Nature News, which states that oximeters overestimate the oxygen saturation levels in the blood of people with darker skin tones.

How do oximeters err when it comes to people with darker skin tones?
The infrared light emitted by the oximeters is absorbed better by oxygenated haemoglobin in the blood. In darker skin tones the presence of Melanosomes in larger quantities than in lighter skin tones disrupts the passage of the infrared light, thus, impacting the reading. 

What impact did these limitations have during the pandemic?
With the oximeters overestimating the oxygen saturation levels in the blood of infected patients, studies have reported that crucial time has been lost relying on those readings, even as the patient's health deteriorated, and were possibly in hypoxemia, which is the stage when oxygen saturation levels in the blood are dangerously low. The Nature News article reported that in the US, Black people were three times more likely to not be diagnosed with hypoxemia, when compared to white people, due to the incorrect readings on oximeters. Other studies have also found similar issues for Asian and Hispanic and mixed-race individuals as well. 

What are other instances of bias or discrimination in medical science?
The US employs an algorithm to assign healthcare to individuals with complex medical needs. Now, a study by Ziad Obermeyer of the University of California, Berkeley, and his team, has found that people who identified as Black were assigned lower risk scores when compared to equally sick white people. As per a report on Nature News on the study, scientists speculate that reduced access to care is due to the effects of systemic racism, ranging from distrust of the healthcare system to direct racial discrimination by healthcare providers. 

One of the areas where this discrimination is reflected is the high maternal mortality rate among Black women in the US. As per a report in the US Department of Labour Blog, "the likelihood of dying from a pregnancy-related cause is 2.5 times higher for a Black woman in this country than for a white woman."