NHS pulse oximeters fail black patients and must be replaced, say doctors  

A patient has her blood oxygen saturation level measured ahead of receiving the coronavirus vaccine in Ukraine

Credit: Valentin Sprinchak /TASS

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Doctors are calling for pulse oximeters used by the NHS to monitor Covid symptoms to be replaced, after a US health agency warned the monitors are less accurate at reading blood oxygen in black patients. 

The NHS has given out 300,000 pulse oximeters to patients in England to use at home to help monitor their oxygen levels and prevent "silent hypoxia", a condition associated with coronavirus where oxygen levels can drop fatally low without symptoms. 

But the US Food and Drug Administration last week warned the technology may be less accurate when used on patients with dark skin tones, citing a study that found black patients were three times more likely to have low blood oxygen levels not detected by pulse oximetry than white patients.

"There is definitely a pool of patients that is at risk," said Dr Joseph Hartland, Lecturer at the University of Bristol’s Centre for Medical Education. 

He added: "In all technology there is always going to be room for error in the measurements that we take. With these, it’s quite a disproportionate measurement error which affects a very particular population so it has to be looked at."

Coronavirus excess deaths — UK-wide

The oxygen readers, which slip onto a person’s middle finger and shine a light into their body to calculate blood oxygen levels, have been branded as "live-saving" in the fight against Covid. 

Coronavirus can cause Covid pneumonia which can strike silently, with patients suffering no symptoms even as their blood oxygen levels fall. That’s why the pulse oximeters have become crucial, so patients can seek medical help when they notice their oxygen level dropping, before they get dangerously low.

"Ideally we would replace [pulse oximeters] with something that was inclusive for all patients and gave accurate measurements for everybody," said Hartland. 

"But for peripheral blood monitoring, as far as I’m aware, there’s not a huge amount of other options which is why I think we have to work with the technology that we have, but have discussions about this," he said. 

Dr Keir Philip, a respiratory doctor working on Covid-19 wards in London, stressed: "Pulse oximeters are extremely valuable and saving lots of people’s lives, whether they’re white or black or any other ethnicity". 

But he had also noticed "sub-optimal accuracy" of pulse oximetry in his Covid-19 patients, coming out of intensive care — 67pc of whom were from black, Asian and minority ethnicities.  

"The issue is that the way in which [pulse oximeters] can be inaccurate isn’t fully understood yet", he said, adding only once more research had been done could manufacturers adjust the technology. 

"The fact that people who develop [and] manufacture pulse oximeters have known about this for a long time and haven’t done large, well-conducted studies to assess the accuracy of their pulse oximeters properly in people with different skin colours, I think that’s a big oversight," he said.  

"The injustice is that relatively straightforward research that could be done and should be being done hasn’t been done, and regulatory authorities haven’t demanded that it’s done."

A NHS spokesperson said they had received no reports of incorrect readings due to the issue. 

They added: "While MHRA monitor the safety and performance of the devices, clinicians are aware of the limitations of pulse oximetry, and use readings alongside their clinical judgement to assess patients for signs of deterioration.” 

Graeme Tunbridge, MHRA Director of Devices, said he was aware of the potential impact of skin colour on pulse oximeter readings but reiterated that health professionals "do not depend entirely upon these readings, instead using them in combination with other diagnostic indicators."

He said: "The MHRA has not received any adverse incidents reporting concern over incorrect results or any information suggesting increased risks in the BAME community relating to this factor, but will continue to monitor this closely."