Severe COVID-19 Patients Face Heightened Risk of Lung Scarring, South Korean Study Finds

A multicenter study from South Korea highlights a critical and severe complication of COVID-19: a heightened risk of pulmonary fibrosis (lung scarring) in patients with severe pneumonia requiring mechanical ventilation. The findings, published in the Journal of Korean Medical Science, underscore the urgent need for better prevention and management strategies for this potentially debilitating long-term effect.

High Prevalence of Lung Damage in Critical Cases

The retrospective, observational cohort study found that a significant proportion of patients who survived a severe bout of COVID-19 developed fibrotic-like changes in their lungs. Specifically, chest computed tomography (CT) scans revealed such changes in 75% of patients with severe COVID-19 pneumonia who required mechanical ventilation (MV).

Pulmonary fibrosis is a serious condition where lung tissue becomes scarred and damaged, permanently impairing the lungs’ ability to function effectively. It is recognized as a presentation of Long COVID, referring to the sustained, long-term effects of SARS-CoV-2 infection that extend far beyond the initial illness. Prior analyses have shown that over 50% of recovered COVID-19 patients exhibit residual pulmonary abnormalities on CT scans three months post-infection.

Study Focus: The High-Risk Ventilated Group

While previous studies have examined pulmonary fibrosis risk across varying degrees of COVID-19 severity, there was limited research on the most vulnerable group: those requiring mechanical ventilation.

The South Korean researchers included 125 patients requiring MV for COVID-19 pneumonia between February 2020 and October 2021 from nine hospitals. Patients were categorized into fibrosis and non-fibrosis groups based on their CT scans.

Key observations regarding the types of fibrotic changes included:

43.2% of all patients showed two or more fibrotic-like changes.
The most frequently observed changes were traction bronchiectasis/bronchiolectasis (60.8%) and architectural distortion/parenchymal bands (44.8%).

Unexpected Insights on Steroid Therapy

The study analyzed the clinical factors associated with the development of pulmonary fibrosis. Interestingly, the factors previously cited as potential risks—such as age, male sex, smoking history, or C-reactive protein—were not significantly associated with fibrosis development in this highly severe cohort.

Instead, a univariable logistic regression analysis identified several factors associated with a reduced risk of pulmonary fibrosis:

Higher Heart Rate: (Odds Ratio [OR], 0.966)
Lower Sequential Organ Failure Assessment (SOFA) score: (OR, 0.868)
Higher Daily Steroid Dose: (OR, 0.964)

The finding on steroid use is particularly significant. While nearly all patients received systemic steroids, the higher daily dosage, rather than the total amount, appeared to offer a protective effect against fibrotic progression.

Mortality and Complications

Mortality was high, with 17.6% of patients dying during hospitalization, and 71.2% experiencing one or more ventilator-associated complications.

When defining pulmonary fibrosis as having two or more fibrotic-like changes, in-hospital mortality was paradoxically higher in the non-fibrosis group (23.9%) than in the fibrosis group (9.3%). The authors note this finding suggests that the very early fibrotic changes may not be the primary driver of acute in-hospital mortality. However, the long-term impact of the scarring remains a critical concern for survivors.

The study authors concluded that their findings strongly suggest that a higher daily dose of steroids may be critical in mitigating fibrotic progression. They call for further research to determine the optimal timing, dosage, and duration of corticosteroid therapy specifically for severe COVID-19 patients to prevent long-term pulmonary sequelae and improve overall clinical outcomes.