What causes blood oxygenation to drop in many Covid patients?
The decreased arterial blood oxygen levels in many Covid-19 cases could be caused by infection in carotid bodies by SARS-CoV-2, the virus responsible for the pandemic, says a new study.
Carotid bodies, located on either side of the neck next to the carotid artery, detect the drop in blood oxygen and send signals to the brain to stimulate the respiratory centre.
The new research, detailed in the journal Function, relies on experiments that have revealed a high presence of the enzyme ECA2, the protein the coronavirus uses to infect human cells, in the carotid body.
One of the physiopathological characteristics of Covid-19 that has most baffled the scientific and medical community is what is known as "silent hypoxemia" or "happy hypoxia".
Patients suffering this phenomenon, the causes of which are still unknown, have severe pneumonia with reduced arterial blood oxygen levels -- known as hypoxemia.
Patients with "silent hypoxemia" often suffer a sudden imbalance, reaching a critical state that can be fatal.
In patients with Covid-19, the coronavirus circulates in the blood.
Therefore, in this study researchers from the University of Seville in Spain suggest that infection of the human carotid body by SARS-CoV-2 in the early stages of the disease could alter its ability to detect blood oxygen levels, resulting in an inability to "notice" the drop in oxygen in the arteries.
If this hypothesis, which is currently being tested in new experimental models, is confirmed, this would justify the use of activators of the carotid body independent of the oxygen sensing mechanism as respiratory stimulants in patients with Covid-19.