A mystery coronavirus effect dubbed "happy hypoxia" found in patients suffering coronavirus is baffling doctors.
Several doctors have reported witnessing patients chatting to people, scrolling on their phone and acting normally despite having dangerously low oxygen levels.
A normal blood-oxygen saturation is at least 95 per cent.
Patients can feel short of breath or delirious if this drops - with most losing consciousness if it falls below 75 per cent.
But doctors are reporting A&E coronavirus patients with extremely low oxygen - some cases below 50 per cent - that are still awake and sitting up in bed.
The "happy hypoxia" phenomenon is now raising questions about how coronavirus attacks the lungs.
Speaking to the Guardian, Dr Mike Charlesworth, an anaesthetist at Wythenshawe hospital in Manchester, said severe hypoxia would normally cause these patients to appear extremely ill.
He said: “With pneumonia or a pulmonary embolism they wouldn’t be sat up in bed talking to you.
"We just don’t understand it. We don’t know if it’s causing organ damage that we’re not able to detect. We don’t understand if the body’s compensating.”
The reason for the "happy hypoxia" syndrome still remains unclear, but scientists suggest coronavirus could cause clotting in the lungs that prevents blood from getting enough oxygen.
Clinical trials are looking at whether blood thinners could treat complications of the virus, including low blood oxygen.
Doctors have even suggested patients should be given readers to detect oxygen levels at home incase they fall dangerously low.
Based on the findings, scientists are urging doctors to avoid aggressive treatments including ventilators unless completely necessary.
For example, a study last month found that flipping patients onto their stomachs could improve their oxygen levels without the need for a ventilator.
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