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in collaboration with
Dr Gérald Kierzek (Medical Director of Doctissimo)
Medical validation:
July 22, 2022
These devices, used to measure the blood oxygen saturation of patients with respiratory failure, seem to work less well in people with dark skin. A “worrying” finding according to the researchers.
At the start of the pandemic, many “skewed” pulse oximeter readings had already been pointed out in patients of color. On July 6, a new study published in the journal British Medical Journal, supported this hypothesis. It reveals that pulse oximeters are more likely to be inaccurate in black patients than in white patients.
The rate of occult hypoxemia is higher in black patients
To determine the extent of the problem, a group of researchers led by Dr. Valeria Valbuena examined data from hospitalized patients within the network.”United States Veterans Health Administration”the largest integrated health system in the country.
More than 30,000 veterans – tested using a pulse oximeter (a small clip that is placed on a finger, a toe or the lobe of an ear) and a blood gas test – have observed from 2013 to 2019.
The primary endpoint was occult hypoxemia – that is, arterial blood oxygen saturation below 88% despite a pulse oximetry reading above 92%.
After this battery of tests, the scientists found that the probability of occult hypoxemia in white veterans was 15.6%, 19.6% in black veterans and 16.2% in Hispanic or Latino veterans. .
A significant difference in pulse oximeter performance based on ethnicity.
Higher mortality
Also according to the study, an incorrect reading of the pulse oximeter can lead to a loss of luck in patients who are oxygen deficient. A completely “worrying” discovery according to Dr. Valeria Valbuena.
“The problem of ‘biased’ pulse oximetry is truly serious and could affect a large number of patients. Our results suggest that in the Veterans Health Administration alone, there could be over 75,000 cases per year where a lack of oxygen in the blood in a black veteran would have been detected if the pulse oximeters worked as well as in white veterans”.
This “missed” hypoxemia is indeed linked to “poorer health outcomes, higher mortality and more severe disability”.
A “doubly interesting” study, for Dr. Kierzek.
“Firstly, it shows that the pulse oximeter does not offer the same results for everyone, an important fact for the ambulatory follow-up of patients, and secondly it raises the fact that in France, we do not have the right to carry out ethnic research, when it is useful. Adapting the saturometer on a case-by-case basis would indeed be necessary. It is also necessary, to avoid distorted results, to position the sensor correctly, to read the instructions, to take the measurement again …”.
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Pulse oximeter: why the measurements can be distorted?
According to the scientists, the lack of reliable results in oximetry could be attributed to the measurement noise inherent in the device (interfering signals) which would be more present in black patients.
Improper oximeter position, hand tremors, poor patient circulation, and even wearing nail polish can also bias results.
There “awareness of clinicians” and an “extra caution” are therefore necessary. No clinical decision should be based on a single pulse oximeter reading.