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Dr. Richard Levitan noticed something strange when he treated patients with covid-19 at Bellevue Hospital in New York.
Many of them, despite having below-normal pneumonia and blood oxygenation, had no trouble breathing, which is unusual in patients with these conditions.
In an article published in The New York Times, he reports several cases of patients hospitalized for other reasons, such as accidents or stabbing victims, in which it was only discovered that they had covid-19 after performing CT scans or x-rays to verify damage to the internal organs.
“And this is what really surprised us: These patients did not report any respiratory problems, even though the chest x-rays showed advanced pneumonia and the oxygen was below normal. How could this be possible?”
The doctor discovered that covid-19 has a dangerous peculiarity.
“We are beginning to recognize that covid-19 pneumonia initially causes oxygen deprivation that we call ‘silent hypoxia’ – ‘silent’ because of its treacherous nature, which is difficult to detect,” says Levitan.
The doctor explains that, in the hospital emergency, critically ill patients are intubated for various reasons. “However, in my 30 years of experience, the majority of patients who need emergency intubation are in shock with an altered mental state and have difficulty breathing. Many are unconscious or use all the muscles they have to breathe.” , but, in the case of covid-19 pneumonia, “it is different.”
Most of the patients he treated, Levitan says, had very low oxygen saturation, “virtually incompatible with life,” but “they were talking on their cell phones.”
“Despite their rapid breathing, they did not appear to be affected, despite dangerous low oxygen levels and advanced pneumonia on radiographs.”
A ‘combination almost never seen’
Dr. Clarisse Melo has had a very similar experience so far when caring for patients with covid-19 in a private hospital in Rio de Janeiro.
“Many have very low (oxygen) saturation, but they talk to the family on their cell phones. They get mad at me when I say they have to go to the ICU. I have to show the evidence to convince the person that they need it. receive oxygen, “says the doctor.
The situation is so recurring that it intrigued her and several colleagues and became a recurring topic in conversations about coronavirus patients.
“This is not common in people with pneumonia, but all the doctors I work with have seen patients with hypoxia and shortness of breath. It was unanimous,” says the doctor.
He also says he sees several people who have already sought care with severe respiratory failure. “We keep asking ourselves, ‘How did the person get to this point? How did he not notice the shortness of breath and go to the hospital in such a critical condition?'”
In search of answers, he identified a study led by anesthesiologist Luciano Gattinoni of the University of Göttingen in Germany, which points to silent hypoxia as a common condition among covid-19 patients tested.
At least 50% of the 150 patients in the study had low oxygenation, but lungs with an almost normal level of compliance, as the organ’s ability to expand is called.
“This remarkable combination is almost never seen in severe acute respiratory syndrome,” says Gattoni.
But it is something that, in the first line of the fight against the pandemic, “everyone is watching, every day,” says pulmonologist Paulo Teixeira, a professor at the Federal University of Health Sciences in Porto Alegre.
“Most infected patients will be fine in two to three weeks, but others will progress to serious conditions, and some have this silent pneumonia. We see terrifying CT scans, with a very compromised lung, the person has very low saturation, but is very well, “says Teixeira.
Why does this happen?
Richard Levitan says in his article that doctors and scientists are just beginning to understand why this is so.
A possible explanation he points out is that the coronavirus attacks lung cells that produce surfactants, substances that help the alveoli remain open between breaths and that are essential for the lung to function normally.
“But the lungs initially remain ‘compliant’, not yet stiff or fluid-filled. This means that the patient can expel carbon dioxide and, without the accumulation of carbon dioxide, patients do not experience shortness of breath,” Levitan writes. .
The doctor says that patients try to compensate for low oxygenation by breathing faster and deeper, not realizing that they are doing so. This causes more lung damage, which can lead to acute respiratory failure and be fatal.
“The rapid progression from silent hypoxia to respiratory failure explains the cases of patients with covid-19 who die suddenly, without even feeling out of breath,” says the doctor.
However, Jaques Sztajnbok, supervising physician in the intensive care unit of the Emílio Ribas Institute of Infectology, says that silent hypoxia is not a particular characteristic of covid-19.
“It is not something new, we see that it happens with patients who have other diseases,” says the doctor.
Sztajnbok also explains that each person has their own tolerance to low oxygenation in the blood, according to their physiological characteristics and physical preparation, for example.
“Some patients arrive with low oxygenation, but have no trouble breathing. But several report some breathing difficulties. One explanation for this difference may be individual tolerance to hypoxia,” says Sztajnbok.
The doctor also notes that some necropsies of people who died from the coronavirus indicate that there was thrombosis in the pulmonary vessels, that is, clots formed that obstructed the flow of blood.
This may be the reason for low blood oxygenation in patients who do not experience difficulty breathing.
“For the lung to work, it is necessary to breathe, but also for the blood to reach the alveoli to exchange gases. The lung may have a good compliance, but if the blood does not go where it should, the exchange does not occur correctly.” Sztajnbok says.
Teixeira points to scientific studies that point in this direction. They indicate, for example, that patients with covid-19 have a high level of a substance known as d-dimer, which is produced by the body to try to break down clots.
“The new coronavirus causes a large amount of thrombosis. We are using anticoagulants with these patients, because the scientific literature published so far indicates that their oxygenation improves as well,” says Teixeira.
An early warning for covid-19 pneumonia
Richard Levitan advocates in the article the use of oximeters to identify pneumonia caused by covid-19 before respiratory problems appear.
This device looks like a clothespin and is placed on one of your fingers to measure blood oxygen saturation and heart rate.
Levitan says they are as simple to use as a thermometer, “extremely reliable” and can give an early warning of covid-19 pneumonia.
The doctor argues that anyone with symptoms compatible with those of covid-19 uses the device for two weeks, during which the disease develops, with medical monitoring.
This can prevent many people from reaching critically ill hospitals and needing to intubate. Levitan says the oximeter can prevent deaths.
The broader use of this device would be “ideal,” says Sztajnbok, but it is “impossible” to do so in practice. One of the obstacles is the price of the device, which costs between R $ 100 and R $ 200 in online stores.
In turn, Teixeira believes that using one can be “very important”. “We have controlled the saturation of patients in their homes in this way,” says the pulmonologist.
If a person cannot buy the device, Teixeira says that they should go to the hospital if they have difficulty breathing, and even without fever, because 30% to 40% of people with covid-19 do not have this symptom.
Sztajnbok emphasizes that the recommendations made so far on what to do when having symptoms compatible with those of covid-19 should be followed.
“Find a hospital if you have trouble breathing, have a persistent increased breathing rate, or feel tired when you do activities that would not normally happen.”
The doctor also says that silent hypoxia should be studied better, and that “it’s not a cause for panic.”
“The risk is to fill emergency rooms with people who think they have pneumonia without having any symptoms. Those who need care will not be able to, and the person who went there unnecessarily may return home infected with the coronavirus.”
