Many people with severe COVID-19 and dangerously low oxygen levels do not have difficulty breathing or shortness of breath, thus the condition was dubbed “silent” hypoxia. To learn what causes silent hypoxia — abnormally low — researchers tested three different scenarios.
As reported by Science Daily, the researchers first looked at how COVID-19 impacts the lungs' ability to regulate where blood is directed, causing the lungs of some patients to lose the ability to restrict blood flow to already damaged tissue. For blood oxygen levels to drop to the levels observed in COVID-19 patients, blood flow needs to be much higher than normal in areas of the lungs that can no longer gather oxygen — which contributes to low oxygen levels throughout the entire body, researchers said.
Secondly, they looked at how blood clotting impacts blood flow in different areas of the lung. They noted that when the lining of blood vessels get inflamed from COVID-19 infection, tiny blood clots too small to be seen on medical scans may form inside the lungs. Researchers found that the tiny blood clots could incite silent hypoxia, but determined that condition alone is not likely to cause oxygen levels to drop as low as the levels seen in documented COVID-19 cases.
Last, the team wanted to find out if COVID-19 interferes with the normal ratio of air-to-blood flow that the lungs need to function normally. The study suggests that for this to be a cause of silent hypoxia, the mismatch must be happening in parts of the lung that don't appear injured or abnormal on lung scans.
SOURCE: ScienceDaily November 19, 2020