Dynamics of functional changes in the respiratory system after COVID-19-associated lung injury at one year after hospital discharge

Morphological examination reveals microcirculation disorders in combination with small areas of lung damage in the long term after COVID-19. Therefore, the function of the respiratory system should be assessed after COVID-19. Aim of this study was to evaluate the dynamics of respiratory dysfunction in patients with COVID-19-associated lung injury using a complex examination of lung function (spirometry, body plethysmography, and lung diffusion testing) one year after hospital discharge. Methods. 60 patients (38 men/22 women, aged 39 to 80 years) with a diagnosis of “COVID-19-associated interstitial process in the lungs” were examined. Lung function (spirometry, body plethysmography, and lung diffusion capacity testing) was examined in all patients twice, at 1 – 6 months (visit 1) and at 12 – 24 months (visit 2) after hospital discharge. Results. At visit 1, 60% of patients had restrictive pulmonary ventilation disorders. Obstructive ventilation disorders were detected in only 1 patient. Decreased lung diffusion capacity (D CO corr. ) was found in 78% of patients. At visit 2, obstructive disorders were detected in 1 patient, and the frequency of restrictive ventilation disorders was 29%. Decreased DL CO corr. was noted in 57% of cases. The parameters of pulmonary ventilation and pulmonary gas exchange function differed significantly between visits. Significant correlations were found between changes in the functional parameters of the respiratory system and disorders identified at visit 1 after hospital discharge. Conclusion. Thus, there is a decrease in the lung diffusion capacity and the rate of restrictive ventilation disorders even one year after severe COVID-19-associated lung injury. However, our results suggest a marked improvement in respiratory system function over time.