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Pulse oximeters are crucial in fighting Covid.They may not be suitable for dark skin



The US Food and Drug Administration warned on Friday that oximeters used during the pandemic may produce inaccurate results.
Earlier this week, the US Centers for Disease Control and Prevention also updated its coronavirus clinical guidelines to warn doctors and nurses that some research data indicated that skin pigmentation can affect the accuracy of the device.

Dr. William Maisel, Director of the Office of Product Evaluation and Quality of the FDA’s Center for Devices and Radiological Health, said: “Although pulse oximeters can be used to estimate blood oxygen levels, these devices have limitations that may cause inaccurate readings.”

; In a statement.

The pulse oximeter is a small clamp-like device that can be attached to the patient’s finger painlessly and constantly monitors the amount of oxygen in the blood. Covid-19 is a respiratory disease, which means that it attacks the lungs first, so low oxygen levels indicate that the patient may get worse. CDC data shows that blacks, Latinos and American Indians are four times more likely to be hospitalized due to Covid-19.
The most recent warning came after a study published in the New England Journal of Medicine last December. Dr. Michael Sjoding and several colleagues at the University of Michigan analyzed data from more than 10,000 patients. For each patient, they compared the oxygen level recorded by the pulse oximeter with the oxygen level measured by the arterial blood gas, which is a more accurate but painful and invasive procedure.

Researchers want to know that when a pulse oximeter should record more relevant things, it will often show relatively normal oxygen levels.

Among white patients, the misleading rate of pulse oximeter was 3.6%. Among black patients, this proportion is 11.7%.

Dr. Sjoding said that the conclusion reached is that in black patients, the pulse oximeter is three times more likely to miss significant hypoxia or hypoxemia. The study showed that 1 in 10 black patients had deceptive results.

Why the reading is not accurate

There is a relatively simple explanation. The pulse oximeter works by emitting two types of red light from the fingers. The sensor on the other side of the device picks up this light and uses it to detect the color of your blood. Bright red blood has high oxygen content, while blue or purple blood has less. If the device is not calibrated for dark skin, pigmentation may affect the way light is absorbed. Dark nail polish can cause a similar effect.

Dr. Michel Woogon, director of the Department of Intensive Care Medicine and director of the Department of Pulmonary Medicine at Montefiore Medical Center in New York, said that experienced doctors do not rely solely on pulse oximeters for diagnosis or treatment of patients.

Dr. Gong said: “As long as this number is okay, they won’t tell patients that I don’t care how you feel, don’t worry.” “This is a tool. As a tool, we need to be able to be correct in the context of other information. use it.”

However, Dr. Gong said that during the pandemic, hospitals are overwhelmed, and doctors who are usually not in the emergency room are taken to visit and triage patients. Pulse oximeter numbers may increase weight. If the patient’s oxygen level is critical, inaccurate readings may be particularly problematic.

Dr. Gong said that doctors also need to be aware of their unconscious biases. For example, research shows that when African Americans complain of pain, they are less likely to take analgesics than whites. If the patient says they have difficulty breathing, the doctor should not dissolve them just because the pulse oximeter reading is normal.

Dr. Gong said: “The only way to reduce the health gap is if we deal with it from multiple aspects, from greater contributions and our personal interactions, that is.”

It’s not just a doctor with a pulse oximeter. When the hospital reached its limit during the pandemic, some Covid-19 patients with mild symptoms were sent home to monitor their progress. According to market research, the sales of household pulse oximeters have increased by 500% since the new coronavirus entered the United States.

Amy Moran-Thomas, an anthropology professor at the Massachusetts Institute of Technology, started studying pulse oximeters when he was sent home with her husband last year.

Discovery is not new

Moran-Thomas discovered a study dating back to the 1990s that showed problems with pulse oximeters in patients with darker skin.

In 2005, a study conducted at the Hypoxia Laboratory at the University of California, San Francisco found that three different pulse oximeter models overestimated the oxygen content of dark-skinned patients. They conducted a follow-up study in 2007 with similar results.

Moran said: “Reading 77 like my husband might conceal the true saturation as low as 69-or even greater immediate danger. But EMT or training nurses may not be able to detect these differences. The number seems objective and correct. Racially neutral,” Moran-Thomas wrote in the Boston Review.

Moran-Thomas wants to know why the problems discovered decades ago have not been solved.

Dr. Sjoding said: “I am a pulmonary and intensive care physician.” He started his research after reading Moran-Thomas’ article. “One of our co-authors is a famous black doctor at the University of Michigan. None of us knows. Since the mid-2000s, none of us knows about these studies. This is not part of our training.”

The public’s attention seems to be increasing. On January 25, several U.S. senators A letter urged them to study this problem. The FDA is responsible for approving the pre-market approval of any medical pulse oximeter. The agency currently requires pulse oximeters to be tested on various skin tones, which means “at least 2 dark pigments (test subjects) or 15% of the subject pool, whichever is greater.”
The FDA said it is carefully reviewing available data to determine if additional guidance or research from the agency is needed. Recently, it approved a smartphone pulse oximeter that claims to work on all skin tones, using an automatic calibration period of 10 to 20 seconds to accurately measure the way light moves in the user’s skin.

In an interview with CNN on Wednesday, Dr. Meisser said: “These devices are not just for the primary or primary purpose of information, but can be used to make clinical diagnosis or treatment decisions.” “Even if it is the most accurate product, Nor should you rely too much on pulse oximeter readings.”

Dr. Sjoding said: “Just make sure you are aware of this when making decisions.” “The pulse oximeter readings may differ by two points. If this is the case, would you take care of this patient in other ways?”


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