Post COVID-19 Lung Injury: What We Know So Far

Aaron B. Holley, MD


June 28, 2021

With vaccination rates increasing and new infections declining, we all hope the worst of the COVID-19 pandemic is over (fingers crossed really tight). Regardless, the post–COVID-19 syndrome pandemic has already begun. What is post–COVID-19 syndrome (or long-haulers or long-COVID)? Is it standard postviral fatigue? Prolonged deconditioning following debilitating illness? Permanent lung or vascular injury? Common sense and past experience say it's all of these.

In theory, the burden of actual lung injury post-COVID-19 should be the easiest to quantify, so let's discuss what we think we know. I've heard experts break post–COVID-19 lung injury into three broad categories:

  • Pre-existing lung disease that is exacerbated by acute COVID-19 infection

  • Acute COVID-19 infection that causes acute respiratory distress syndrome (ARDS) or other acute lung injury (ALI)

  • Non–critically ill acute COVID-19 with residual lung damage and abnormal repair

These categories are necessarily imprecise, making it challenging to fit some patients neatly into a single definition.

For patients in the first category, management will largely be dictated by the nature of the pre-existing lung disease. For those in category two, we already know a lot about what their recovery from ARDS will look like. There's no longer reason to believe that COVID-19–related ARDS is particularly unique, and all things being equal, lung recovery should mimic that seen with non–COVID-19 ARDS. It's going to take patience and time, and beyond targeted rehabilitation it's not clear that we have anything available to expedite the process.

The third category of patients is the most intriguing. Is there a group of patients who have residual lung injury but didn't have evident ARDS/ALI during their acute COVID-19 infection? Anecdotally we think so, but we know little about prevalence and less about management. A recent study published in Annals of the American Thoracic Society addresses both issues. In an observational report on patients recovering after being hospitalized with COVID-19 infection, the authors found that 3.6% of patients had residual lung injury that improved with 3 weeks of corticosteroid treatment.

The report is timely and helpful but hardly definitive. It's observational, and patients required extensive screening and identification by a multidisciplinary committee of experts in interstitial lung disease. Patients were diagnosed as having organizing pneumonia (OP) as their "lung injury" if certain radiographic criteria were met. There were no biopsies. Last, there was no control group. Still, this report is critically important. It tells us that at 6 weeks post-discharge, about 3.6% of patients who were hospitalized for COVID-19 will have persistent symptoms, radiographic abnormalities, and a plateau in their recovery.

Beyond that, it tells us little. Did these patients really have OP? It's impossible to know. The CT findings used to establish the diagnosis are nonspecific. Response to steroids is consistent with OP, but the treatment course was quite short. If truly OP, one would expect a high relapse rate after steroid withdrawal. Patients weren't followed long enough to monitor recurrence rates. Also, as appropriately discussed in the accompanying editorial, there's no control group so we can't know whether the patients treated with steroids would have recovered without treatment. There was objective improvement in lung function for the two to three patients they followed who did not receive steroids. However, it was of lesser magnitude than in the steroid group.

Post–COVID-19 symptoms will remain a challenge for the foreseeable future. More than 30 million patients have been diagnosed with COVID-19 in the United States and close to half will experience persistent dyspnea. Putting the numbers together, I conclude that the vast majority will not have identifiable lung injury that will benefit from steroids. I wish I could prescribe patience to both physicians and patients.

Aaron B. Holley, MD, is an associate professor of medicine at Uniformed Services University and program director of pulmonary and critical care medicine at Walter Reed National Military Medical Center. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.

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