Long COVID: Can it cause persistent lung disease?

It has been difficult to estimate the prevalence of long-term symptoms following SARS-COV2 infection, partly because diagnostic criteria remain unclear.

However, last year, the Office for National Statistics published data suggesting that longterm symptoms occur in 7–18% of people who experienced symptomatic COVID-19.

These long-term effects after Covid-19trusted Source are known as long COVID or post-acute sequelae of COVID-19 (PASC).

PASC can range from mild to debilitating, with new symptoms arising or evolving long after the initial infection.

Dr. Brett M. Elicker, M.D., a clinical professor in the Department of Radiology and Biomedical Imaging at the University of California, San Francisco, discusses radiology findings in an editorial that accompanies the recent research.

Dr. Elicker explains that the longterm effects of viral pneumonia depend on the direct injury that the virus causes and the body’s immune reaction to the virus. Damage to the lungs occurs in two patterns:

Constrictive bronchiolitis, or small airway disease: Inflammation within the bronchioles — the small airways — and surrounding areas results in airway narrowing due to scarring or fibrosis.

Diffuse alveolar damage (DAD): Fibrosis to the alveoli — tiny balloonshaped structures at the end of the bronchioles that exchange gas in the lungs — which may improve over time, but often some scarring remains.

Small airway damage

Researchers from the University of Iowa recently conducted a study to understand the long-term effects of COVID-19 on lung function. They published their findings in the journal Radiology.

The study enrolled 100 adults with a confirmed SARS-COV-2 infection who remained symptomatic for more than 30 days following the diagnosis, with a control group of 106 healthy participants.

The most common persistent PASC symptoms were:

- shortness of breath (73%) - fatigue (56%) - cough (34%)

Alongside a chest CT scan, the researchers performed several pulmonary function tests Trusted Source to measure how well the lungs worked. These tests included:

Forced vital capacity (FVC): The total volume of air a person exhales during maximal exhalation.

* Forced expiratory volume in 1 second (FEV1): The volume of air an individual exhales after a maximal inhalation in 1 second.

* FEV1/FVC: The proportion of FVC a person exhales in 1 second.

* Total lung capacity (TLC): The volume of air in the lungs at maximal inflation.

* Residual volume (RV): The volume of air in the lungs after exhaling maximally.

* Diffusing capacity of the lung for carbon monoxide (DLCO): This indicates how efficiently oxygen gets into the blood from the air.