The disturbing symptom of Covid-19 that occurs before breathing difficulties. Patients feel fine, even though their condition is serious.

Mari Seim, a general practitioner in Oslo, was called home by a man over 60 who had had flu symptoms for a week. Ready to deal with a coronavirus case, the doctor went to examine the potential patient, but found him in a condition that stumped her. The man’s daughter asked for help when she noticed that her father was breathing fast.

“I found him sitting in a chair and smiling. He didn’t feel bad at all,” he said.

However, the man’s respiratory rate was almost three times faster than normal. Her lips and fingers were slightly cyanotic. He realized the severity of his condition only when he measured his oxygen height, which was 66%, compared to over 90% as usual.

The patient had what doctors know is a specific feature of SARS-CoV-2 infection, which they often cannot recognize in the early stages of the disease: hypoxia that develops silently. Unlike other respiratory diseases, COVID-19 gradually leaves the body without oxygen so that infected people do not realize how sick they are because they do not have respiratory problems.

Difficulty breathing goes hand in hand with loss of elasticity of the lung tissues. Most respiratory diseases lead to their hardening due to inflammation, injury, or accumulated fluid. Carbon dioxide can no longer be removed effectively, so patients feel an acute need to breathe. Difficulty breathing occurs when carbon dioxide accumulates and the brain signals the need for oxygen.

However, in patients with COVID-19 in the early stages, these alarm signals do not go off, pulmonologists explain. The lungs remain flexible enough for patients to breathe well. As oxygen saturation decreases, the respiratory rate accelerates more and more to compensate, causing the expulsion of a large volume of carbon dioxide. The consequence: an insidious hypoxia facility in which low oxygen saturation is combined with the maintenance of low levels of carbon dioxide, hence the lack of an alarm signal.

“In almost every case we face, lung problems are both oxygen consumption and carbon dioxide removal,” says Richard Levitan, an emergency room physician who voluntarily treated pneumonia-infected patients in a New York hospital. “This disease is different,” he said.

Silent hypoxia also occurs in climbers and pilots, the expert said. And in your case, the respiratory rate increases in conditions of low oxygen levels. This allows oxygen to be transported more efficiently in the body, in the tissues that need it most.

Something similar occurs at the beginning of COVID-19 disease: the faster respiratory rate maintains a good function of the heart for a time, so that blood circulates well in the extremities. If infected people cannot maintain a low CO2 level, oxygen saturation could be even lower, further complicating an already severe form of the disease.

The specialists cannot explain very well how the disease ends up causing slow hypoxia, but they have some hypotheses. One is that the virus attaches to lung cells and alveoli in the lungs, ensuring the transfer of oxygen to the blood. As the virus infects more cells, the immune response is activated and a fight occurs that causes damage, including impaired oxygen transfer. At the same time, the transfer of CO2 is not affected as much, since it is carried out more easily.