Those low oxygen levels can irreparably damage vital organs if gone undetected for too long.

More than six months since COVID-19 began spreading in the US, scientists are still solving the many puzzling aspects of how the novel coronavirus attacks the lungs and other parts of the body.

Despite experiencing dangerously low levels of oxygen, many people infected with severe cases of COVID-19 sometimes show no symptoms of shortness of breath or difficulty breathing.

Hypoxia’s ability to quietly inflict damage is why health experts call it “silent.” In coronavirus patients, researchers think the infection first damages the lungs, rendering parts of them incapable of functioning properly. Those tissues lose oxygen and stop working, no longer infusing the blood stream with oxygen, causing silent hypoxia. But exactly how that domino effect occurs has not been clear until now.

“We didn’t know [how this] was physiologically possible,” says Bela Suki, professor of biomedical engineering and of materials science and engineering at Boston University and one of the coauthors of the study in Nature Communications.

Some coronavirus patients have experienced what some experts have described as levels of blood oxygen that are “incompatible with life.” Disturbingly, Suki says that many of these patients showed little to no signs of abnormalities when they underwent lung scans.

To help get to the bottom of what causes silent hypoxia, biomedical engineers used computer modeling to test out three different scenarios that help explain how and why the lungs stop providing oxygen to the bloodstream.

They found that silent hypoxia is likely caused by a combination of biological mechanisms that may occur simultaneously in the lungs of COVID-19 patients, says lead author Jacob Herrmann, a biomedical engineer and research postdoctoral associate in Suki’s lab.

Read the full article about COVID-19's silent hypoxia by Jessica Colarossi at Futurity.