Still out of breath? Here are 3 ways COVID-19 can damage the lungs in the long term: ScienceAlert

“I can’t do what I used to do anymore.”

As pulmonologists and critical care physicians treating patients with lung disease, we have heard from many of our patients recovering from COVID-19 telling us so even months after their initial diagnosis. Although they may have survived the most life-threatening phase of their illness, they have yet to return to their pre-COVID-19 baseline, struggling with activities ranging from strenuous exercise to laundry.

These lingering effects, called long COVIDs, have affected up to one in five American adults diagnosed with COVID-19.

Long COVID includes a wide range of symptoms such as brain fog, fatigue, coughing, and shortness of breath.

These symptoms can result from damage or dysfunction in multiple organ systems, and understanding the causes of long COVID is a special research goal of the Biden-Harris administration.

Not all breathing problems are related to the lungs, but in many cases the lungs are affected.

Examining the basic functions of the lungs and how they may be affected by disease can help clarify what’s on the horizon for some patients after COVID-19 infection.

Normal lung function

The main function of the lungs is to bring oxygen-rich air into the body and expel carbon dioxide. When air enters the lungs, it is brought close to the blood, where oxygen diffuses into the body and carbon dioxide diffuses.

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This process, simple as it may seem, requires an extraordinary coordination of airflow, or ventilation, and blood flow, or perfusion.

There are more than 20 divisions in your airways, starting with the main trachea, or trachea, to the little balloons at the end of the airways, called alveoli, which are in close contact with your blood vessels.

By the time an oxygen molecule reaches the end of the airways, there are approximately 300 million of these tiny alveoli in which it could end up, with a total area of ​​over 1000 square feet (100 square meters) where gas exchange. .

Appropriate ventilation and perfusion rates are essential for basic lung function, and damage anywhere along the airway can lead to difficulty breathing in several ways.

Obstruction – decreased airflow

One form of lung disease is the obstruction of airflow in and out of the body.

Two common causes of deficiencies like these are chronic obstructive pulmonary disease and asthma.

In these diseases, the airways narrow due to either damage from smoking, as is common in COPD, or allergic inflammation, as is common in asthma. In both cases, patients experience difficulty expelling air from their lungs.

Researchers have observed continued airflow obstruction in some patients who have recovered from COVID-19.

This condition is usually treated with inhalers that deliver medication that opens the airways. Such treatments may also be helpful during recovery from COVID-19.

Restriction – reduced lung volume

Another form of lung disease is called restriction or difficulty expanding the lungs. The restriction decreases the volume of the lungs and therefore the amount of air they can take in.

The restriction often results from the formation of scar tissue, also called fibrosis, in the lungs due to injury.

Fibrosis thickens the walls of the alveoli, which makes gas exchange with the blood more difficult.

This type of scarring can occur in chronic lung diseases, such as idiopathic pulmonary fibrosis, or following severe lung damage in a condition called acute respiratory distress syndrome, or ARDS.

ARDS can be caused by injuries originating in the lungs, such as pneumonia, or serious disease in other organs, such as pancreatitis. About 25% of patients who recover from ARDS develop restrictive lung disease.

The researchers also found that patients who have recovered from COVID-19, especially those who had severe disease, may later develop restrictive lung disease.

COVID-19 patients who need a ventilator may also have similar recovery rates to those who need a ventilator for other conditions. The long-term recovery of lung function in these patients is still unknown. Drugs treating fibrotic lung disease after COVID-19 are currently in clinical trials.

Impaired perfusion – decreased blood flow

Finally, even when airflow and lung volume are not affected, the lungs cannot complete their function if blood flow to the alveoli, where gas exchange occurs, is impaired.

Illustration of how gas exchange in the lungs
Illustration of gas exchange in the lungs. (ttsz/iStock/Getty Images Plus

COVID-19 is associated with an increased risk of blood clots. If the blood clots travel to the lungs, they can cause a life-threatening pulmonary embolism which restricts blood flow to the lungs.

In the long term, blood clots can also cause chronic problems with blood flow to the lungs, a condition called chronic thromboembolic pulmonary hypertension or CTEPH.

Only 0.5% to 3% of patients who develop a pulmonary embolism for reasons other than COVID-19 develop this chronic condition.

However, there is evidence that severe COVID-19 infections can directly damage blood vessels in the lungs and impair blood flow during recovery.

And after?

The lungs can function less optimally in all three of these general ways, and COVID-19 can lead to all of them. Researchers and clinicians are still looking for ways to best treat the long-term lung damage seen in long COVID.

For clinicians, closely following patients who have recovered from COVID-19, especially those with persistent symptoms, can lead to faster diagnoses of long-lasting COVID.

Severe cases of COVID-19 are associated with higher rates of long COVID. Other risk factors for the development of long COVID include pre-existing type 2 diabetes, the presence of virus particles in the blood after initial infection, and certain types of abnormal immune function.

For researchers, the long COVID is an opportunity to study the mechanisms underlying the development of different types of lung disease resulting from COVID-19 infection.

Uncovering these mechanisms would allow researchers to develop targeted treatments to speed up recovery and make more patients feel and breathe like before the pandemic again.

In the meantime, everyone can keep up to date with recommended vaccinations and use preventative measures such as good hand hygiene and wearing a mask when appropriate.The conversation

Jeffrey M. Sturek, assistant professor of medicine, University of Virginia and Alexandra Kadl, assistant professor of medicine and pharmacology, University of Virginia.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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