Long-term consequences of the functional state of the respiratory system after SARS-CoV-2-associated lung damage

Aim . To study the dynamics of respiratory system function in patients without a history of bronchopulmonary pathology after SARS-CoV-2 infection with virus-associated lung damage. Materials and methods . A retrospective study was conducted on 29 patients (median age 46 [43-51] years) at two stages: visit 1 (1-4 months) and visit 2 (8-13 months) from the onset of COVID-19. Data from spirometry, bodyplethysmography, diffusion capacity test, impulse oscillometry (IOS), and chest computed tomography (CT) obtained during the acute phase of the disease (CTmax), as well as dyspnea assessed by the mMRC scale, were analyzed. Results . The median CTmax was 75%, and 66% of patients received treatment in the intensive care unit. At visit 1, dyspnea was of mild or moderate severity. Medians of vital capacity (VC), total lung capacity (TLC), residual volume (RV), and diffusion capacity of the lungs (DLco) were reduced (<80% predicted). The median forced expiratory volume in the first second (FEV1) and IOS parameters were within normal ranges. However, increased reactance area (AX) and absolute frequency dependence of resistance (R5–R20) were found in 59% and 24% of cases, respectively. At visit 2, mild dyspnea persisted. Lung volumes were within normal limits, with statistically significant differences between visits. The median DLco was reduced at visit 1 but increased to normal at visit 2, with statistically significant differences between visits. The median IOS parameters remained within normal limits, with no statistically significant differences between visits. However, in visit 1 increased AX and (R5–R20) were observed in 59% and 24%, in visit 2 – 45% and 17% of cases, respectively, with no statistically significant differences between visits. Conclusions . Among the long-term functional consequences of SARS-CoV-2 infection with virus-associated lung damage, decreased lung diffusion capacity (reduced DLco) and small airway dysfunction (increased AX and/or R5-R20) were noted in some patients. Impulse oscillometry should be included in the comprehensive functional assessment plan for patients after SARS-CoV-2 infection to diagnose small airway dysfunction.