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"Long Covid" linked to disease in the lung airways

According to a new study led by the University of Iowa, disease in the small airways of the lungs is a potential long-lasting effect of Covid-19. This condition has often occurred independently of initial infection severity and its long-term consequences are still unknown.

Early reports indicate that over 50 percent of Covid-19 survivors experience post-acute sequelae commonly known as “long Covid.” Nearly 30 percent of patients who had long Covid – including those with initial mild infections – continue to have respiratory symptoms such as cough and dyspnea for a long time after the acute phase of the disease subsides.

A team of researchers and clinicians from the University of Iowa set out to study such long-term effects by enrolling a cohort of 100 adults with confirmed Covid-19 who had remained symptomatic for over 30 days, along with 106 healthy participants in a control group. The Covid survivors, with a median age of 48, included 67 classified as ambulatory, or not requiring hospitalization, 17 who were hospitalized, and 16 who required intensive care during the acute phase of their infection. 

The scientists performed both inspiratory and expiratory CT in these patients. While inspiratory CT (performed after patients inhale) is the standard imaging technique for observing lung tissue, post-exhalation expiratory scans are sometimes needed in order to assess “air trapping,” a condition in which people are not able to empty their lungs completely when they breathe out. Air trapping is found in many obstructive airway diseases, such as asthma or chronic obstructive pulmonary disease (COPD).

After performing these clinical exams, the researchers found that air trapping was highly prevalent among the long Covid group. 

“For the first time, we’re describing small airways disease in this population of Covid-19 patients with persistent symptoms,” said study senior author Dr. Alejandro Comellas, a professor of Internal Medicine at Iowa. “Something is going on in the distal airways related to either inflammation or fibrosis that is giving us a signal of air trapping.”

Dr. Cornellas and his colleagues found that the mean percentage of total lung area affected by air trapping ranged from 25 percent in the ambulatory group to almost 35 percent in the hospitalized group, compared to only 7.2 percent in the control group. This condition persisted in eight of the nine participants who underwent CT scans over 200 days after their initial diagnosis. 

The persistence of respiratory abnormalities raises concerns for permanent airway remodeling and fibrosis after SARS-CoV-2 infection and requires further research in order to understand its causes and devise proper treatments.

“If a portion of patients continues to have small airways disease, then we need to think about the mechanisms behind it,” said Dr. Cornellas. “It could be something related to inflammation that’s reversible, or it may be something related to a scar that is irreversible, and then we need to look at ways to prevent further progression of the disease.”

The study is published in the journal Radiology.

By Andrei Ionescu, Staff Writer

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