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Deciphering the reason for silent breathing in COVID-19 – healing practice

Why COVID-19 lacks oxygen by inhaling it

Some people suffer from COVID-19 with so-called silent breathing (silent hypoxemia), which is life-threatening and has asymptomatic oxygen deficiency. It is very surprising that despite the lack of oxygen, the human body’s alarm systems fail. A new study has revealed what causes silent breathing in COVID-19.

In the study, researchers from the University of Boston and the University of Vermont studied the causes of silent respiratory distress at COVID-19. The results of the study were published in the English journal Nature Communications.

What causes you to breathe silently?

To date, the causes of silent hypoxemia in COVID-19 are unclear. Recent results show that at least part of the problem is poor lung function. With this breakdown, more blood is pumped to the broken areas of the lungs instead. In addition, existing blood clots and lack of blood flow disrupt oxygen exchange, the researchers reported.

Lack of oxygen without typical symptoms?

There are people with COVID-19 who do not show coughing or shortness of breath and show no evidence of severe lung damage, but still have a dangerous lack of oxygen. The oxygen saturation in the blood sometimes reaches such low values ​​that the affected person must actually disappear.

Can COVID-19 disable a critical alarm system?

“We didn’t even know that something like this was physiologically possible,” says author Bela Suki of the University of Boston in a press release. Typically, carotid artery sensors alert the brain as soon as the actual balance of carbon dioxide and oxygen in the blood is incorrect. This alarm system appears to be partially deactivated in the event of a disease with COVID-19. The reasons for this were not clear.

In addition to its other effects, viral infection is thought to also affect the respiratory center of the brain. The intellect explains that this area of ​​the brain causes a feeling of shortness of breath when there is a lack of oxygen.

SARS-CoV-2 can enter the brain

Other research has shown that SARS-CoV-2 can enter the brain and olfactory system, where the coronavirus can also be detected in parts of the brain stem. The respiratory tract is also located in this area.

Why does breathing occur in silence at first?

The researchers were also interested in why silent breathing occurred especially in the early stages of COVID-19. At this stage of the disease, the lungs appear to have only a slight attack. “These patients have hypoxemia, although CT images of the lungs show only minimal areas with poor ventilation,” explained Professor Suki. The research team used patient data and computer simulations to investigate what is happening in the lungs in this case.

Wrong lung control?

Experts assumed that controlling blood flow to the lungs could be a mistake. Usually, a feedback mechanism ensures that the waiting blood flows mainly to the place where the air exchange is working properly. When areas of the lungs are poorly ventilated due to inflammation or injury, the blood vessels in this area narrow. The researchers explained that through this so-called hypoxic constriction, the blood is mainly channeled to an area that is not yet intact and the blood is properly supplied with oxygen.

Is there no hypoxic forest constriction in COVID-19?

It seems that such a deviation does not work properly for some people with COVID-19. In affected people, the blood vessels in the affected lung areas do not contract. This prevents blood flow from deviating. “Failure to do so can lead to a significant disproportion between pulmonary respiration and oxygen exchange,” says Professor Suki.

Lung damage was simulated in a lung model

The research team used a biophysical lung model to determine whether this malfunction explains the lack of oxygen in the affected person. In the model, experts reduced air supply by 17% of lung tissue. These effects are comparable to the lung damage caused by COVID-19 in the early stages, the researchers explained. The group then simulated various scenarios for blood flow and oxygen exchange during the investigation.

What causes oxygen depletion?

It has been shown that if the veins in the affected lung areas are opened or even widened instead of narrowing, the blood can lead to a significant reduction in oxygen uptake. However, experts explain that the observed effect is not sufficient to explain the abnormally low oxygen saturation of some people with COVID-19.

However, there is another factor that can cause hypoxemia. It happened that with COVID-19 disease gas exchange is also impaired in healthy lung areas.

Reasons for the lack of gas exchange

Possible reasons are blood clots and small veins in the lungs. “If such thrombotic emboli occurs in the early stages of COVID-19, it can increase pulmonary malnutrition and hypoxemia,” the research team explained.

Imbalance between ventilation and perfusion

In addition, there is an imbalance between the sufficient supply of oxygen in the alveoli that are still dissolved and its ability to absorb this gas by the blood. In such a case, experts talk about the discrepancy between ventilation and perfusion. Possible reasons for this may be, for example, inflammation of the walls of the tubes, but also insufficient blood flow and blood pressure in the lung capillaries.

Coronavirus directly attacks lung cells

According to the research team, this suggests that coronavirus infection not only directly attacks lung cells, but also disrupts the regulation of lung function in several ways. The researchers summarized why this is why oxygen deficiency occurs in people whose lungs appear to be intact.

“People react very differently to this virus,” Professor Suki explained. Therefore, it is especially important to find all the causes of the dangerous oxygen deficiency that occurs. According to experts, this may help identify the appropriate treatment for COVID-19 patients. (as)

Author and source information

This text is in accordance with the requirements of medical literature, medical guidelines and current research and has been verified by medical professionals.


  • Jacob Herrmann, Vitor Mori, Jason HT Bates, Béla Suki: Modeling lung perfusion abnormalities to explain early COVID-19 hypoxemia, in Nature Communications (veröffentlicht 28.09.2020), in Nature Communications.
  • University of Boston: Three reasons why COVID-19 can cause silent hypoxia (see 08.10.2020), Boston University

Important Note:
This article is for general guidance only and should not be used for self-diagnosis or self-treatment. It cannot replace a doctor’s visit.

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