‘Long COVID’ linked to persistent airways disease
Imaging the lungs after a patient exhales reveals hidden physical changes in the small airways of patients affected by long COVID. These newly observed air-trapping abnormalities may explain some of the persistent breathing problems associated with long COVID and may help guide targeted treatment of these symptoms.
The specialized lung scans, known as expiratory CT scans, may also provide a tool to help diagnose a condition that is notoriously hard to pin down.
The findings come from a new University of Iowa study published March 15 in the journal Radiology. The study also found that small airways disease occurred independently of initial infection severity.
“For the first time, we’re discovering small airways disease in this population of COVID-19 patients with persistent symptoms,” says Alejandro Comellas, MD, professor of internal medicine in the Division of Pulmonary and Critical Care Medicine with University of Iowa Health Care. “Something is going on in the distal airways related to either inflammation or fibrosis that is giving us a signal of air trapping. We need to investigate further to see whether it is transient or more permanent.”
While small airways disease is not fully understood, evidence suggests it may be related to either inflammation or remodeling of the small airways that prevents small pockets of air from being exhaled from the lungs. Air trapping is a characteristic of many known obstructive airway diseases, such as asthma and chronic obstructive pulmonary disease (COPD).
Long COVID, common and concerning
There is growing recognition that long COVID is a relatively common and long-lasting consequence of COVID-19 infection. Recent studies suggest that it may affect between 10 and 30% of adults who have had COVID-19, including people who were not very sick with the original infection. The condition is not easily defined or diagnosed because it can cause a wide variety of symptoms, including shortness of breath, fatigue, and brain fog. Nevertheless, long COVID can cause significant disability and, because it is so new, there are no proven treatments.
In the early stages of the pandemic, Comellas and his colleagues were quick to recognize the potential problem that long COVID could cause for patients and established the Post-COVID-19 clinic at UI Hospitals & Clinics. The clinic was one of the first in the country and is the only such clinic in Iowa.
Lung scans reveal long-lasting effect of COVID-19
For the new study, the team compared expiratory lung CT findings from 100 clinic patients who had COVID-19 and had persistent symptoms to scans from 106 healthy people who made up a control group.
Of the 100 patients with long COVID, 67 never required hospitalization for their COVID disease (the “ambulatory” group), 17 were hospitalized because of COVID-19, and 16 required care in the intensive care unit (ICU) during acute infection.
The researchers were able to detect air trapping on expiratory chest CT images in the COVID-19 group. The average percentage of total lung affected by air trapping ranged from slightly more than 25% in the ambulatory group to almost 35% in the hospitalized group, compared with only 7.2% in healthy controls.
Information from a small group of nine patients who underwent imaging more than six months after their COVID-19 diagnosis suggests that the abnormal air trapping is long lasting in many patients regardless of the initial severity of infection; eight of the nine patients still showed air trapping more than 200 days after initial diagnosis.
Overall, the findings show that disease of the small airways in the lungs is a potential long-lasting effect of COVID-19.
Using a form of artificial intelligence known as supervised machine learning, the team was also able to quantify the amount of small airway disease. This approach may allow researchers to measure patients’ improvement over time and track the effects of potential therapies in the future.
Comellas and colleagues intend to follow the patients in the study registry and see how many improve and recover and how many remain with abnormal findings.
“If a portion of patients continues to have small airways disease, then we need to think about the mechanisms behind it,” he says. “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.”
In addition to Comellas, the UI team included Jocalyn Cho, Raul Villacreses, Prashant Nagpal, Junfeng Guo, Alejandro Pezzulo, Andrew Thurman, Nabeel Hamzeh, Robert Blount, Spyridon Fortis, Eric Hoffman, and Joseph Zabner.