A recent study published in the journal Respiratory research found impaired lung function and dyspnea in survivors of severe COVID-19 pneumonia one year after infection. Meanwhile, many patients with COVID-19 have developed fibrotic-like sequelae as a result of the mild or severe pneumonia associated with the infection.
Study: Lung function and radiological findings 1 year after COVID-19: a prospective follow-up. Image Credit: People Image Studio / Shutterstock
First reported in Wuhan, China in late 2019, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak has spread globally to cause coronavirus disease 2019 (COVID- 19), which claimed the lives of over 6.5 million people worldwide. The disease primarily infects the respiratory system and precipitates long-term sequelae often referred to as post-COVID syndrome or long COVID.
Symptoms of long COVID range from persistent headaches and myalgias to permanent disabilities, affecting quality of life for survivors. Almost a third of infected patients develop acute respiratory distress syndrome (ARDS), while fibrotic lung lesions develop in many.
Evidence suggests that patients on mechanical ventilation during the acute phase of COVID-19 experience more alterations in their pneumocytes, lung endothelial and alveolar cells, as well as interstitial and lung fibrotic changes compared to those on conventional oxygen. A quarter of patients who developed pneumonia had subpleural cystic/reticular lesions, and a third of patients had fibrotic changes after one year and six months after discharge, respectively.
This observational, prospective, multicenter cohort study evaluated patients with bilateral pneumonia as a pulmonary sequela of SARS-CoV-2 infection – for lung function alterations and fibrous lesions persisting one year after discharge from hospital.
The study was conducted in Spain and recruited all adult patients discharged from respiratory wards with a life expectancy of more than one year. Functional changes, evolution of dyspnea and exercise capacity were assessed after discharge, at two months (V1), six months (V2) and twelve months (V3).
The average age of participants was 60.5 years and the majority were male. Notably, men showed a greater preponderance of more serious illnesses. In addition, length of hospital stay, laboratory parameters (C-reactive protein, lymphocyte count, lactate dehydrogenase, D-dimer, and ferritin levels), and RALE scores varied between study groups (screw, V1, V2 and V3). While there were no significant differences between study groups regarding patient demographics, such as body mass index (BMI), age, smoking, and comorbidities.
Gravity and time interaction diagram based on post-hoc analysis of linear mixed model. The boxes indicate the adjusted mean. Error bars indicate 95% confidence interval with Bonferroni’s correction. V1 (2 months), V2 (6 months) and V3 (12 months). Group 1: mild; group 2: moderate; group 3: severe. A Interaction diagram: changes over time and severity in % of predicted DLCO. We found differences between witty and moderate [p = 0.001] or serious [p < 0.001] patients only at 2 months (V1). B Interaction plot: Changes over time and severity of percent FVC from predicted. No differences between the groups were found at any time. VS Interaction diagram: changes over time and severity of dyspnea. No differences between the groups were found at any time. Forced vital capacity FVC, DLCO diffusing capacity of the lungs for carbon monoxide.
Pulmonary function tests revealed that 53.8% of patients had impaired circulation after two months, which gradually improved after six months and one year. The mean lung diffusing capacity for carbon monoxide abnormalities (DLCO) was 78.5 in V1, 81.6 in V2, and 84 in V3. Significant alterations in diffusion were found at 60 days – with respect to time and severity – between mild, moderate and severe patients.
Throughout the cohort, a restricted abnormality was observed in 14.3% of patients at two months, 9.3% at six months and 6.7% at 12 months. The average forced vital capacity (FVC) was 99 at V1, 100.8 at V2 and 104.2 at V3. Meanwhile, no significant difference was found in FVC versus time and severity.
Next, the cohort was analyzed for dyspnea. The mMRC scale represented dyspnoea ≥ 2 in 21.5% of patients at V1, 11.3% at V2 and 9.8% at V3. A significant association was found between dyspnea and follow-up time. However, significant time-dependent differences between severity groups were absent.
Additionally, static lung volumes remained comparable between groups, while the six-minute walk test (6MWT) showed differences in distance walked – with gravity as a confounding factor. An altered DLCO (< 80% at 12 months) is associated with age, female gender, ferritin levels and BMI.
Computed tomography (CT) was advised two months after discharge in patients with abnormal chest x-rays, abnormal pulmonary function test results, and persistent dyspnoea. HRCT was performed after two months on 325 patients. Of these, 38.4% revealed complete resolution, while the rest exhibited ground-glass opacities (GGO). Notably, GGO was the most common (in 73.5%) and showed differences based on age groups.
CT scans were repeated in patients with abnormal prior CT scan findings one year after hospital discharge. In total, 156 out of 200 patients had a V3 CT scan, 78.8% of which presented persistent radiological changes. Of the 200 patients, 45.5% had GGO; the reticular pattern was found in 34% of patients; parenchymal bands were found in 33.4% and traction bronchiectasis was observed in 30.8%.
Of 156 patients, 102 revealed fibrotic-type sequelae – illustrated by a CT scan performed at 12 months. Significant changes between age groups were more frequently detected in severe cases.
Lactate dehydrogenase (LDH) and lung involvement, as seen on admission radiology, were associated with the V3 fibrotic pattern.
Many patients with pneumonia associated with SARS-CoV-2 infection developed fibrous sequelae and presented with dyspnea and impaired lung function one year after discharge from hospital. Therefore, further follow-up of patients who suffered from severe pneumonia associated with COVID-19 is warranted to study the progression of fibrotic lesions over time.