COVID-19 may cause long-term damage to the small airways in the lungs, says a new study published today.

Researchers found a link between COVID-19 and long-term lung disease, according to a new journal article, published in Radiology.

The study discovered that small airway disease occurs regardless of the severity of the initial infection. The long-term effects of this are not yet known.

“There is some disease happening in the small airways independent of the severity of COVID-19,” says study senior author Alejandro P. Comellas.

According to early estimates, more than half of adult survivors of SARS-CoV-2 infection develop post-acute sequelae of COVID-19 (PASC), often known as “long COVID.” Nearly 30% of patients with long COVID, including those who only had a moderate infection, show respiratory symptoms such as cough and dyspnea.

The study was inspired by clinicians at the University of Iowa who noticed that a high proportion of patients with initial SARS-CoV-2 infection who were hospitalized or treated in the ambulatory setting later developed symptoms of chronic lung disease such as shortness of breath and other respiratory symptoms.

In these patients, Dr. Comellas and colleagues established a strategy that included both inspiratory and expiratory CT. The conventional imaging approach for examining lung tissue is inspiratory CT, which is performed after patients inhale, but post-exhalation expiratory scans are required to examine air trapping, a condition in which people are unable to clear their lungs as they breathe out. Many obstructive airway illnesses, such as asthma and chronic obstructive lung disease, are associated with air trapping.

CT scan results from patients with COVID-19 and persistent symptoms were compared to those from a healthy control group for the study. They enrolled 100 patients with COVID-19 who had been symptomatic for more than 30 days after diagnosis, as well as 106 healthy people. The 100 COVID-19 survivors had a median age of 48 years, with 67 being ambulatory (without requiring hospitalization), 17 being hospitalized, and 16 requiring intensive care unit (ICU) care during the acute infection.

In the COVID-19 group, the researchers discovered air trapping on expiratory chest CT scans. The average proportion of total lung damaged by air trapping in the ambulatory group ranged from slightly more than 25% to almost 35% in the hospitalized group, compared to only 7.2% in healthy controls. Eight of the nine subjects who received imaging more than 200 days following diagnosis had air trapped in their lungs.

Regardless of the original illness severity, these images demonstrate a significant incidence of long-lasting air trapping.

Quantitative examination of expiratory chest CT scans using supervised machine learning, a sophisticated sort of artificial intelligence, revealed evidence of small airway disease. While the cause of small airways disease is unknown, evidence shows it is linked to inflammation or remodeling of the small airways, which prevents air from being expelled from the lungs.

“For the first time, we’re describing small airways disease in this population of COVID-19 patients with persistent symptoms,” Dr. Comellas adds. “Something is going on in the distal airways related to either inflammation or fibrosis that is giving us a signal of air trapping.”

The average delay between diagnosis and chest CT imaging was 75 days. The recurrence of respiratory problems in this timeframe, according to the researchers, raises concerns about irreversible airway remodeling and fibrosis following SARS-CoV-2 infection.

Dr. Comellas and his colleagues plan to follow up with the patients in the study registry to observe how many of them improve and recover, and how many of them continue to have aberrant findings.

“If a portion of patients continues to have small airways disease, then we need to think about the mechanisms behind it,” he adds. “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.”

Source: RADIOLOGICAL SOCIETY OF NORTH AMERICA

Image Credit: Getty

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