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| The no-symptoms nCovid-19 phenomenon is explained (image is from setkab.go.id) |
The global pandemic of nCovid-19 disease has been created a confusion situation among researchers and medical staff around the world. As it is the next generation of corona virus that can be seen from its previous predecessor, SARS and MERS, nCovid-19 is still difficult to be understood thoroughly. One of these confusing aspects is the physiophatological features of COVID-19, in which the patients suffer "silent hypoxemia". What is this condition? and how it happens? is it the cause to the fatality rate?
Silent Hypoxemia
Normal biological mechanisms in the body, in particular that is related to the oxygen flowrate within the body, may have been experienced by lots of people. Have a look with an example, when someone is actually loss its breath due to physical factors, such as nasal congestion as lots of people experience when the surrounding temperatures suddenly become lower. This condition leads to what we call as oxygen deficiency within the blood, or "hypoxemia" or sometimes it is called "hypoxia".
Oxygen is required for the body particularly by the organs such as brain, liver, or the cell itself to perform the metabolism procedure. However, during this dangerous stage, a patient may have realized the condition, and apparently the body itself realizes this condition by providing noticeable symptoms such as skin-color changing, cough, fast heart rate, shortness of breath. These symptoms are famous with the disease associated to asthma.
Interestingly, in COVID-19 patient, these symptoms remain silent. It means, people actually partially realize that their body suffer this phenomenon, and the biological reasons behind this condition are still uncovered (unknown). Certain reports have suggested that COVID-19 patients actually experienced severe pneumonia indicated by the reduction of oxygen levels within their arterial blood. Unfortunately, the other symptoms like shortness of breath as it is explained earlier, have not been reported, as well as the fast heart rate due to the needs of oxygen.
As a result, this undetected dyspnea creates a sudden imbalance situation to the body, which leads to a critical state that eventually causes death. Although the body, biologically can respond, undetected oxygen level drops by the body due to the block of signal to the brain cannot be supervised. So, it looks like the virus blocking the alarm?
The infection occurred in carotid
Previously, it has been briefly explained about the biological mechanism of realizing the decrease of oxygen levels within the blood. The one which is responsible of this condition is the sensing cells in the carotid body. When the body experiences sudden drops of oxygen level, these cells immediately alarm the body via sensory fibers, implying to the stimulation of neurons in the brainstem in inducing certain responses including the increased of heart rate. As a result, the body suffers to asthma.
Unlike normal patient that suffers asthma during those symptoms, the COVID-19 patients that experience unaware of these stimulation, or the stimulation is being blocked by the virus due to the inhibition in the carotid area provide different phenomenon. According to the study published by in Journal Function, the team scientists have hypothetically suggested that the infection that results this unaware condition or "silent hypoxemia" may have occurred in carotid tissue of the patients. Thus, given that the confirmation of the infection could have been observed in this tissue, then therapeutic treatments such as carotid activators as respiratory stimulants could have been prescribed.
Well, this sounds promising, but how can they propose this kind of suggestion? the reason lies on the biological characteristics of carotid body. As in the previous paragraph has been explained, the early stage of infection that causes the drop of oxygen level is caused by the inhibiting stimulation to the neurons. The sensing cells in carotid tissue are organized very well in a form of cells clusters called glomeruli, in which each of these clusters is composed by nerve systems (known as 4-8 neuron). It implies that, these cells apparently are enriched by abundant synaptic vesicles as well as neurotransmitters. Apparently, these two are the natural sensors within the body, that are released rapidly by the time the body recognizes something dangerous. Thus, this is the plausible explanation behind the unawareness of body in generating the symptoms.
This hypothesis is very promising, which could become the main interest in overcoming the SARS-Cov-2 pandemic, and this proposal also provides possible therapeutic treatments.