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Happy hypoxia: A mysterious COVID-19 symptom that has left doctors baffled

Hypoxia may be due to clotting in the small blood vessels of the lungs, say some doctors.

Some COVID-19 infected patients with extraordinarily low blood-oxygen levels, or hypoxia, describe themselves as comfortable. Baffled doctors call them happy hypoxics. Read to know more about this mysterious COVID-19 symptom.

Written by Longjam Dineshwori |Updated : May 1, 2020 9:03 AM IST

The deadly COVID-19 disease, which has shaken the world, continues to surprise doctors and researchers with many mysterious symptoms. One of which is extraordinarily low oxygen levels, or hypoxia. In some cases of COVID-19, the blood oxygen levels of infected patients dropped alarmingly low, but they can't sense it at all. Doctors called this group happy hypoxics.

The mismatch between what they see on the monitor and what the patient looks like in front of them, has left many doctors confused as to when and how to treat the mysterious condition.

Why they don't feel their falling oxygen levels?

According to experts, this is because low oxygen saturation doesn't always come along with obvious respiratory difficulties in the early stages of the COVID-19 disease.

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Lung diseases, such as pneumonia, may cause many changes in the body such falling saturations, stiff or fluid-filled lungs, and rising levels of carbon dioxide as the lungs can't expel it efficiently. And doctors say these features that make patients feeling short of breath and not the low oxygen saturation itself. Critically ill COVID-19 patients struggle to breathe due to damaged lungs, but such obvious respiratory difficulties may not occur in early stages of the disease.

Happy hypoxics may have very low blood-oxygen levels, but since their carbon dioxide levels is normal, they don't experience problem in breathing. This is the reason why they feel OK - the doctors explained.

What causes hypoxia in COVID patients?

A normal blood-oxygen saturation is at least 95%. In many COVID-19 cases, it dropped to 70s, 60s, or 50s or even lower. The blood-oxygen level is usually measured by a device clipped to a finger or blood tests. There are many hypotheses about what causes of hypoxia in COVID patients. Clotting is recognised as a major feature of severe COVID-19.

Some experts think subtle clotting might begin early in the lungs, due to an inflammatory reaction in their blood vessels, preventing it from getting properly oxygenated. They developed this idea after observing that some patients with breathing troubles also had circulatory problems in their toes. When these patients were given heparin, a common blood thinner, both their toes and breathing improved or recovered.

Some doctors are now trying to find out whether heparin can boost COVID-19 patients' low oxygen levels regardless of whether they were struggling to breathe. Several clinical trials are also underway in different counties to test whether blood thinners can prevent or treat complications of severe COVID-19, including respiratory problems.

However, it is not confirmed yet that happy hypoxia emerges because of clotting in the small blood vessels of the lungs.

Treatment of COVID-19 hypoxia

While the occurrence of happy hypoxia has left many doctors baffled, concerns have been raised over the use of aggressive treatment to treat the condition.

Some doctors are apparently trying to inflate lungs with ventilators or high-pressure oxygen even when patients seem comfortable. Such measures have been criticised, calling it as Pavlovian response" to COVID-19 hypoxia. Some experts are of the opinion that it could harm the lungs that are inflating on their own, suggesting that it can done if patients aren't helped by noninvasive treatment.

Can early hypoxia progress to pneumonia and death?

So far, no study has appeared on whether early detection of hypoxia might head off bad outcomes. But hypoxemic respiratory failure and hypotension were found to be the most common precursors of mortality in critically ill patients with coronavirus 2019 (COVID-19) during the first 3 weeks of the COVID-19 outbreak in Seattle, Washington. The findings were published in the New England Journal of Medicine.

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