Silent Hypoxia caused by Wuhan Virus (excrept)
Hypoxia's ability to quietly inflict damage is why it's been coined "silent." In coronavirus patients, it's thought that the infection first damages the lungs, rendering parts of them incapable of functioning properly. Those tissues loose oxygen and stop working, no longer infusing the blood stream with oxygen, causing silent hypoxia.
Silent hypoxia is likely caused by a combination of biological mechanisms that may occur simultaneously in the lungs of COVID-19 patients. Healthy lungs keep the blood oxygenated at a level between 95 and 100 percent -- if it dips below 92 percent, it's a cause for concern and a doctor might decide to intervene with supplemental oxygen.
Opening up Blood vessels in the Infected Area
Normally, if areas of the lung aren't gathering much oxygen due to damage from infection, the blood vessels will constrict in those areas. This is actually a good thing that our lungs have evolved to do, because it forces blood to instead flow through lung tissue replete with oxygen, which is then circulated throughout the rest of the body. The lungs of some COVID-19 patients had lost the ability of restricting blood flow to already damaged tissue, and in contrast, were potentially opening up those blood vessels even more -- something that is hard to see or measure on a CT scan. For blood oxygen levels to drop to the levels observed in COVID-19 patients, blood flow would indeed have to be much higher than normal in areas of the lungs that can no longer gather oxygen -- contributing to low levels of oxygen throughout the entire body.
Tiny Blood Clots
When the lining of blood vessels get inflamed from COVID-19 infection, tiny blood clots too small to be seen on medical scans can form inside the lungs. Using computer modelling of the lungs, that this could incite silent hypoxia, but alone it is likely not enough to cause oxygen levels to drop as low as the levels seen in patient data.
Air-to-blood ratio
Last, the researchers used their computer model to find out if COVID-19 interferes with the normal ratio of air-to-blood flow that the lungs need to function normally. This type of mismatched air-to-blood flow ratio is something that happens in many respiratory illnesses, such as with asthma patients, Suki says, and it can be a possible contributor to the severe, silent hypoxia that has been observed in COVID-19 patients. Their models suggest 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.
Conclusion
The combinations could vary from patient to patient, clinicians can make more informed choices about treating patients using measures like ventilation and supplemental oxygen.
By having a better understanding of these underlying mechanisms, and how the combinations could vary from patient to patient, clinicians can make more informed choices about treating patients using measures like ventilation and supplemental oxygen.
Reference
https://www.sciencedaily.com/releases/2020/11/201119153946.htm