Experts: "silent hypoxia" kills coronavirus patients
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Experts: "silent hypoxia" kills coronavirus patients

22 April , 16:54Science
American doctors urge to measure the oxygen content in the blood with a pulse oximeter.

The New York Times publishes material written by an emergency physician, intubation and airway rehabilitation specialist Richard Levitan. The text is entitled “Infection that silently kills patients with coronavirus. What I learned from 10 days of treatment for COVID pneumonia at Bellevue Hospital. ” This is what the doctor writes, working at the peak of the disease in a New York hospital.

Irina Ziganshina

One of the main reasons why a pandemic has such an unprecedented mortality is the pneumonia that the virus causes in the early stages of the disease. Usually in the emergency department there are patients with various conditions, ranging from serious ones: heart attacks, strokes and traumatic injuries, and ending with life-threatening ones, such as minor lacerations, intoxication, orthopedic injuries and migraines. Now almost all ambulance patients have pneumonia caused by COVID-19.

“During the first hour of my first shift, I inserted breathing tubes into two patients,” the author writes. - A patient with a stab wound to the shoulder, whom we had X-rayed because we were afraid that he had lung collapse, actually had COVID pneumonia. In patients who we did computed tomography because of a fall injury, we accidentally discovered COVID pneumonia. In elderly patients who lost consciousness for unknown reasons, as well as in a number of patients with diabetes, this disease was also detected. But what really surprised us was that none of them reported breathing problems, although radiographs of their chest showed diffuse pneumonia and the oxygen level was below normal. How could this happen? ”

As practice shows, COVID pneumonia initially causes a form of oxygen deficiency, which, due to its insidious, elusive nature, can be called “silent hypoxia.” Pneumonia is usually an infectious lung disease in which the alveoli are filled with fluid. In this case, the patient usually feels chest discomfort, breathing pain and other breathing problems. But in the case of COVID pneumonia, patients do not feel shortness of breath, even when their oxygen level drops. By the time they begin to feel something, they already have, as a rule, dangerously low oxygen levels and moderate or severe pneumonia (this can be seen on radiographs). Normal oxygen saturation for most people is from 94% to 100%. In patients with COVID pneumonia, this rate can be as low as 50%.

Most patients, the author continues, felt sick for a week or so: they had a fever, cough, indigestion and fatigue. But they began to choke only on the day when they came to the hospital. Their pneumonia clearly continued for several days, but by the time they felt they should see a doctor, they were often already in critical condition.

Ambulance patients are intubated for a variety of reasons. However, all who need this procedure, as a rule, are in a state of shock, have an altered mental status or wheeze, trying to breathe. Those who are intubated due to acute hypoxia are often unconscious or painfully straining all their muscles to take a breath. Cases with COVID-19 look completely different. Patients with COVID pneumonia can have surprisingly low, almost incompatible life oxygen levels in the blood - and still have a quiet conversation on the phone. Why is this happening?

Coronavirus infects the lung cells that produce surfactant - a mixture of surfactants that line the alveoli from the inside and help them not stick together between breaths. When COVID pneumonia causes inflammation, it leads to destruction of the alveoli and a decrease in oxygen levels. At the same time, the lungs continue to maintain elasticity for some time, so that the patient can still emit carbon dioxide - but without the accumulation of carbon dioxide, shortness of breath is not felt. To compensate for the lack of oxygen in the blood, a person begins to breathe faster and deeper, but does not realize this. This silent hypoxia and physiological reaction to it cause even more inflammation and destruction of more alveoli, and pneumonia is aggravated until the oxygen level drops.

That is, a person injures his own lungs, breathing harder and harder. After that, 20% of patients with COVID pneumonia undergo a transition to the second, more dangerous phase of lung damage: the fluid accumulates, the lungs lose their elasticity, the level of carbon dioxide rises, and acute respiratory failure develops. By the time a person begins to feel breathing problems and gets to the hospital, he already has dangerously low oxygen levels, and sometimes artificial ventilation is necessary.

Due to the fact that many are in the hospital already with severe pneumonia, there is a shortage of mechanical ventilation devices. But even being on mechanical ventilation, many die. Silent hypoxia, rapidly progressing to respiratory failure, explains the sudden death of patients with COVID-19 who do not feel short of breath until the last moment.

There is a method by which patients with COVID pneumonia could be detected earlier, and therefore more effectively treated. And this is not a coronavirus test, but a device called a pulse oximeter that can detect latent hypoxia.

Using a pulse oximeter is no more difficult than using a thermometer. The device is turned on with one button, placed on the fingertip, and after a few seconds two numbers are displayed: oxygen saturation and pulse rate. Pulse oximeters are very good at detecting problems with oxygenation and an increased heart rate.

Doctors use it to catch COVID-19 at an early stage, when the oxygen level decreases, and take action in time. Probably, the detection of hypoxia, early treatment and careful monitoring helped to cure the British Prime Minister Boris Johnson.

Pulse oximetry screening for COVID pneumonia — whether people are testing themselves at home or with a doctor — can provide an early warning system for breathing problems associated with coronavirus. Although for those who conduct screening on their own, in any case, it is necessary to consult a doctor to make sure that they correctly interpret the results. Sometimes borderline and slightly reduced oxygen saturation is a sign of chronic lung problems and is not related to COVID-19.

Anyone who has a positive coronavirus test should be given pulse oximetric monitoring for two weeks, during which time COVID pneumonia usually develops. Everyone who has cough, fatigue, and fever should also take a pulse oximeter testimony, even if they did not pass the virus test or their smear test was negative: tests do not always give the correct result.

Oximeters are not 100% accurate, and this is not a panacea. Deaths will be anyway. But now, when doctors are torn from the influx of patients, early detection and treatment of the initial phase of COVID pneumonia by screening for latent hypoxia is necessary.

Not so long ago, Novye Izvestia already wrote about a pulse oximeter, including the fact that over the course of a few days of the epidemic, this device went up several times in online stores. But you probably already have enough people who don’t need him anymore and are ready to share or sell it.

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