• Slug: BC-CNS Pulse Oximeter Inaccuracies. 1,135 words.
• Photo available (thumbnail, caption below).

By Brenna Gauchat
Cronkite News

PHOENIX – The Food and Drug Administration is considering plans to update its 2013 premarket guidance for pulse oximeter manufacturers as research suggests the devices may provide inaccurate readings for patients with dark skin.

The problem, according to several studies, is that pulse oximeters may overestimate blood oxygen levels for patients with darker skin and these false readings can lead to inaccurate diagnoses and the wrong treatments.

Samia Kadri, a family nurse practitioner at Banner Health Urgent Care, said every patient who enters an urgent care facility should have their blood oxygen levels measured by a pulse oximeter as a part of their initial vital tests.

Kadri said the blood oxygen level for a healthy adult should be 98 to 99%. “Anything at 93 – 94, with a healthy adult, I start thinking, what’s going on with my patient?”

While the use of pulse oximeters is an essential part of her routine, Kadri said she understands the technology has its limitations. Factors such as nail polish and body temperature may lead to inaccurate readings.

Despite being aware of these common obstacles to accurate pulse oximeter readings, Kadri said she did not know that skin tone may also be a factor.

COVID-19 exposes problems

On Nov. 1, 2022, the FDA convened at a meeting of the Anesthesiology Devices Advisory Committee at the Center for Devices and Radiological Health (CDRH) to discuss how the COVID-19 pandemic played a role in exposing this issue.

A year later, unsatisfied with the results of this meeting, attorneys general from 24 states and the District of Columbia, including Arizona Attorney General Kris Mayes, signed a letter urging the FDA to take further action.

The attorneys general proposed that manufacturers and vendors of pulse oximeters include “clear, comprehensible, and evidence-based” labels warning users of reduced effectiveness based on skin tone.

“Since the convening, however, pulse oximeters continue to be sold without clear warning labels or other guidance to protect individuals from harm,” the letter said. “We, the undersigned Attorneys General, write to encourage the FDA to act with urgency to address the inaccuracy of pulse oximetry when used on people with darker toned skin.”

Technology limitations

Pulse oximeters are a quick, painless and affordable way to measure one of the most critical vital signs in emergency and non-emergency situations.

The medical device clips to a patient’s body part, typically the fingertip or earlobe, to measure blood oxygen levels. When the oximeter is placed on the fingertip, it shines beams of infrared and red light through the nail and the detector on the underside of the finger measures how much of each light is being absorbed by the skin, arteries and veins.

While oxygenated blood absorbs more infrared light, deoxygenated blood absorbs more red light. This process provides health professionals insight on whether a patient is experiencing hypoxia, low levels of oxygen in the body’s tissue, or hypoxemia, low levels of oxygen in the blood.

Studies have suggested pulse oximeters may overestimate blood oxygen levels for patients with darker skins, having more melanin to absorb these light rays, and these false readings can lead to misdiagnosis and improper care.

One of the first studies exploring the relationship between skin tone and oximeter accuracy was published in 2005 by Anesthesiology. The study concluded that of the three pulse oximeters tested on a variety of Black and white patients, all had the tendency to overestimate blood oxygen levels during hypoxia in patients with dark skin.

More recently, a group of doctors at University of Michigan Hospital wrote to The New England Journal of Medicine about their study, which tested two groups of Black and white patients for occult hypoxemia, an overestimation of blood saturation levels. The study found that Black patients were nearly three times as likely to have low blood oxygen levels not detected by pulse oximetry than their white counterparts.

According to an October 2023 study cited in the attorneys general letter, “pulse oximeter errors likely led Black COVID-19 patients to face a 4.5 hour delay in access to supplemental oxygen, as well as a reduced likelihood of hospital admission and delays or reduced access to dexamethasone treatment.”

The proposed update

On Feb. 2, the FDA held an anesthesia and respiratory therapy devices panel of the Medical Devices Advisory Committee (MDAC). The panel brought together leaders in the health care field to discuss their concerns about pulse oximeters’ technological limitations.

Dr. Jeff Shuren, the director of the CDRH, and Dr. Christine S. Lee, the acting associate commissioner for minority health and director of the Office of Minority Health and Health Equity at the FDA, opened the panel.

“​​Disparate performance of pulse oximeters across people with different amounts of skin pigmentation, racial and ethnic groups, is of great importance to the public health and the FDA,” Shuren said. “Although pulse oximetry is useful for estimating blood oxygen levels, pulse oximeters have limitations and may be less accurate under certain circumstances.”

“We know that variations associated with race and ethnicity have been correlated with risks for certain diseases, conditions and responses to regulated products,” Lee said in her opening remarks. “Understanding these factors remains important for identifying and addressing health disparities.”

The proposed updates would utilize the Monk Skin Tone Scale, a 10-value skin tone scale that is intended “to capture racial and ethnic diversity in pigmentation,” according to the FDA. The proposed guidelines call for collecting hundreds of data points during premarket tests of new devices from “a minimum of 24 participants that span the entire Monk Skin Tone (MST) scale.”

This is a change to the 2013 recommendation that a “study should have subjects with a range of skin pigmentations, including at least 2 darkly pigmented subjects or 15% of your subject pool, whichever is larger.”

The COVID-19 pandemic exposed the consequences of false readings, showing that patients might be overlooked in the prioritization of care.

“During the pandemic, it led to people not being admitted to the hospital,” Kadri said. “A lot of times (health professionals) were looking at the pulse oximeter to see if they needed to be observed inpatient or discharged with warning signs of worsening hypoxia.”

Until policy change is enacted, Kadri said being aware of a patient’s overall well-being while conducting initial tests provides a clue to whether she should look beyond initial oximeter readings to ensure fair medical treatment for all of her patients.

“I will be more in tune when I see a darker pigmented skin toned patient and look at their other vitals,” Kadri said.

“Ask my patient: How do you feel? Do you feel like you’re having shortness of breath? Are you having shortness of breath when you’re walking up the stairs, when you’re moving around for a long time? I did that before, but now I’m going to be a little more hyper alert.”

For more stories from Cronkite News, visit cronkitenews.azpbs.org.