Small airways disease may persist for many with long COVID

Small airways disease was common in patients with persistent symptoms following COVID-19, independent of severity of initial infection, according to a single-center study published in Radiology.

“For the first time, we’re describing small airways disease in this population of COVID-19 patients with persistent symptoms,” Alejandro P. Comellas, MD, professor of internal medicine and faculty in the division of pulmonary, critical care and occupational medicine at Carver College of Medicine at the University of Iowa, Iowa City, said in a related press release. “Something is going on in the distal airways related to either inflammation or fibrosis that is giving us a signal of air trapping.”

The single-center study included 100 participants (median age, 48 years; 66% women) with post-acute sequelae of COVID-19 for at least 30 days enrolled from June to December 2020 and 106 matched healthy participants enrolled from March to August 2018. Those with post-acute sequelae of COVID-19, or long COVID, were categorized based on the highest level of acute care received: ambulatory (67%), hospitalized (17%) or requiring ICU care (16%). Researchers collected symptoms, pulmonary function tests and chest CT images, and performed inspiratory CT after inhalation and evaluated post-exhalation expiratory scans to assess air trapping and compare the two groups.

The mean percent of total lung classified as ground glass opacities was 3.7% in the ambulatory group compared with 13.2% in the hospitalized group and 28.7% in the ICU group (P < .001 for both comparisons).

The mean percentage of total lung affected by air trapping was 25.4% in the ambulatory group, 34.6% in the hospitalized group and 27.3% in the ICU group compared with 7.2% among healthy participants (P < .001). This air trapping persisted among eight of nine participants who underwent imaging more than 200 days after diagnosis.

Quantitative analysis of expiratory chest CT images, performed with supervised machine learning, showed evidence of small airways disease, according to the release.

Median time from diagnosis to chest CT imaging was about 75 days. The researchers noted that persistence of respiratory abnormalities in this period raises concern for permanent airway remodeling and fibrosis following SARS-CoV-2 infection, according to the release.

“There is some disease happening in the small airways independent of the severity of COVID-19,” Comellas said in the release. “We need to investigate further to see whether it is transient or more permanent.”

The researchers plan to follow the patients to evaluate how many improve 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,” Comellas said in the release. “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.”

Brett M. Elicker, MD, clinical professor in the department of radiology and biomedical imaging at the University of California, San Francisco, discussed the findings in an accompanying editorial in Radiology. Elicker said “it is important to note that not all pulmonary fibrosis ... is permanent. ... Regardless of the imaging findings, the most important question is whether the airway obstruction and post-[organizing pneumonia]/[diffuse alveolar damage] fibrosis contribute to persistent symptoms after COVID-19 infection with the contribution of airways disease higher in the outpatients, and the contribution of OP/DAD greater in the patients admitted to ICU. Longer-term studies assessing the clinical and imaging manifestations 1-2 years after the initial infection are needed to fully ascertain the permanent manifestations of post-COVID fibrosis.”

References:

• Elicker BM. Radiology. 2022;doi:10.1148/radiol.220449.
• ‘Long COVID’ linked to lasting airways disease. Published March 15, 2022. Accessed March 22, 2022.