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NASHVILLE, Tenn. -- Radiographic evidence of pulmonary pathology was common months after acute infection among people with ongoing exertional or respiratory symptoms, early results of a study exploring the physiology of long COVID showed.

Fully 55% of the subset of persistently symptomatic patients with a high-resolution CT showed radiographic evidence of pulmonary pathology at least 3 months post-infection in an 80-patient interim analysis of a study exploring the physiology of long COVID.

These radiographic changes did not correlate with significant changes in pulmonary function test findings or declines in physical function as measured by 6-minute walking test (6MWT), reported Stephen Goertzen, DO, of Brooke Army Medical Center in Houston.

He presented the findings in a session devoted to long COVID research at CHEST 2022, the annual meeting of the American College of Chest Physicians.

"Other than radiographic findings, there were no unified findings that could shed further light on the effects of COVID-19 that would predispose an individual to ongoing symptoms," Goertzen said, noting that some 10-57% of patients in prior studies have reported lasting symptoms after recovering from the acute phase of COVID-19.

In the U.S. Department of Defense's COVID-19 , a prospective observational cohort study designed to look at long COVID, about 30% of people had symptoms after around 100 days, Goertzen noted.

His group's analysis of that study included 80 patients experiencing dyspnea, respiratory symptoms, chest pain, or a combination thereof at least 3 months after recovery from acute COVID-19.

Study participants were grouped according to initial COVID-19 severity. The mild COVID group included people with initial symptoms lasting less than a week, the moderate group included patients with symptoms lasting more than a week, and severe group included anyone who was hospitalized with COVID-19.

The participants underwent electrocardiography (EKG), 6MWT, high-resolution chest CT, transthoracic echocardiography, and multiple forms of pulmonary function testing, including spirometry, total lung capacity (TLC), diffusing capacity, and impulse oscillometry.

No significant change in heart rate was observed in the long COVID group, nor were any significant desaturations reported.

In all, 55% of those with CT scans showed radiographic evidence of pulmonary pathology, including nodular pattern (38%), mosaic attenuation (34%), residual ground glass opacities (28%), septal thickening (14%), emphysema (10%), and other patterns (20%).

However, about 18% of patients who had an EKG showed evidence of non-specific changes. Of patients who had echocardiography, 8% showed evidence of right atrial dilation and 4% showed evidence of left atrial dilation.

Goertzen noted that while the number of patients with EKG data was small, the finding of right heart disease in a significant percent correlates with the reporting of right heart disease identified in many patients treated in ICUs with severe COVID.

Evidence of lung obstruction was noted in just under 9% of the population, and positive bronchodilator response was noted in about 10%, Goertzen said.

He added that a significant percentage of patients exhibited evidence of small airway disease.

"As we are trying to figure out what is going on with these patients post-COVID, certainly there is a lot of data coming out. But this study, in particular, shows that there are at least some sequelae associated with long-COVID that are causing dyspnea," he said.

Another study presented in the Sunday morning session sought to shed light on whether dyspnea symptoms related to long COVID are improving over time by following patients attending a long COVID clinic in Chicago.

At total of 32 of the 591 clinic patients (59% female, average age 56 years) underwent at least two rounds of pulmonary function testing, and these patients were included in the analysis presented by Amy Ludwig, MD, of Northwestern University's McGaw Medical Center in Chicago.

Sixteen patients (50%) had been hospitalized due to COVID-19, and seven (22%) had required ICU care.

The mean time from illness onset to first pulmonary function test was 207 days, and the mean time between the first and second pulmonary function test was 204 days.

Significant improvements in lung function included those in forced vital capacity (FVC), TLC and diffusion capacity of carbon monoxide (DLCO), but not forced expiratory volume at one second (FEV₁) in the year following acute COVID-19 illness.

Total lung capacity improved most rapidly (median 10.9% per year, IQR 0-24), followed by DLCO (median 6.6%). FVC increased by a median of 5.1% per year, and FEV₁ increased by a median of 3.9% per year (IQR -12.5 to 22).

"There was an improvement in lung function metrics in our post-acute sequelae of COVID-19 cohort, which is consistent with other reports," Ludwig said. "With the burden of COVID-19 illness worldwide, it is crucial that we can accurately risk-stratify those at high risk for persistent symptoms as well as understand the trajectory of recovery."

But several people attending the long COVID session expressed concern that the rapidly evolving nature of COVID-19 is complicating the identification and study of ongoing symptoms.

Pulmonologist Vlassi Baktidy, MD, of Northwell Health in Manhasset, New York, who was not part of either study, noted in a question-and-answer session that commonly reported long COVID symptoms during the early months of the pandemic -- when the SARS-CoV-2 Alpha variant was predominant -- differ from those most often seen during later Delta and Omicron predominant periods.

"COVID in 2020 was different from COVID in 2021 and 2022," he said, adding that radiologic changes were commonly identified in early long COVID cases, but are being reported much less frequently in the Omicron era.

He said he is seeing less dyspnea, chest pain, and significant pulmonary issues in his patients with lasting symptoms but more chronic cough, persistent post-nasal drip, and heartburn.

In an interview with 麻豆传媒, Baktidy said long COVID studies must address these SARS-CoV-2 variant changes.

"Treating this as one disease for the purposes of understanding long COVID is like saying cancer is one disease," he said. "We know that is not true with cancer and it is not true with COVID. We need to distinguish between old COVID and new COVID."