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Infectious Diseases

11 May 2020

How do some Covid-19 patients not realise they have dangerously low oxygen levels?

Hypoxia (or low levels of blood oxygen levels) are frequently reported in Covid-19 patients. But some don’t realise this, baffling experts.

As the novel coronavirus slowly reveals itself to science, there is one phenomenon that is truly mystifying.

Many patients who have Covid-19 seem to feel fine and comfortable while having alarmingly low blood oxygen levels. This condition, called hypoxia, is usually associated with serious respiratory distress, such as pneumonia, when the lungs can’t expel carbon dioxide efficiently or when they become filled with fluid.

In these cases, it’s the compromised lungs that leave patients feeling out of breath – not the low oxygen levels. According to experts, normal blood-oxygen levels should be at least 95%.

Some hypotheses emerging

Early in Covid-19, when the lungs are not damaged, patients often don’t realise their blood-oxygen levels are dropping dangerously low. “The lungs are inflating so they feel OK,” Elnara Marcia Negri, a pulmonologist at Hospital Sírio-Libanês in São Paulo said in an article. Reuben Strayer, an emergency physician and Maimonides Medical Center in New York City stated that their clinicians are also baffled by this.

“There is a mismatch [between] what we see on the monitor and what the patient looks like in front of us,” he said. 

No-one is truly sure why this is, but some hypotheses are emerging among medical professionals and researchers. Negri believes that blood clotting as an early inflammation response may be the reason why blood oxygen levels drop lower.

Other professionals also believe the clotting hypothesis and have started to test admitted Covid-19 patients for clotting and start administering blood thinners as a treatment. But they do say that this is simply not the only explanation. 

Would at-home oxygen testing help? Oximeters are relatively inexpensive devices that can be used at home, which could serve as an indication that your blood oxygen levels are low before you start experiencing serious complications.

However, experts don’t believe that that is the simplest solution to avoid bad outcomes from Covid-19. Doctors are also not sure whether diagnosing hypoxia early enough would be enough to alleviate serious complications from Covid-19, as it hasn’t been studied enough. 

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