Lung Recovery After COVID-19: How Reversible is the Damage?

Most Common Abnormalities

The ability of lungs damaged by COVID-19 to recover has been examined in numerous studies. Mo et al. in a small sample of 110 COVID-19 patients discharged from the hospital, first found that the most common lung function abnormality in these individuals is impaired diffusing capacity (DL_CO), followed by restrictive ventilatory disorder, both of which are associated with the severity of the disease. Liu et al. (Ann ATS 2020) retrospectively analyzed data from 51 COVID-19 patients and demonstrated that lung damage caused by COVID-19 could be reversible. Significant improvement was observed as early as 4 weeks post-discharge. Zhao et al. (EclinicalMedicine 2020) however, also revealed that 71% of the 55 patients monitored had abnormal CT scans 3 months after discharge.

Dependence on Course Severity

van den Borst et al. (CID 2020) also published their study on lung recovery after COVID-19. They included 124 patients (59 ± 14 years; 60% men), of which 27 had a mild, 51 a moderate, 26 a severe, and 20 a critical course. Three months after recovering from the acute phase of COVID-19, 93% of patients who had mild disease had normal X-rays. Among those who were hospitalized due to COVID-19, residual pulmonary parenchymal abnormalities were present in 91% of patients 3 months post-discharge and correlated with decreased DL_CO.

Lung Imaging and Function of Convalescents After 3 Months

Currently, lung recovery after COVID-19 seems similar to that of patients who have experienced acute respiratory distress syndrome (ARDS) and other (viral) pneumonias. It can be summarized that approximately 3 months later, the state of patients on average is as follows:

• About 50% of the affected lung parenchyma fully recovers.
• CT abnormalities are still widely present (>90% of examined cases).
• Residual fibrosis is primarily seen in patients who were hospitalized in the ICU.
• DL_CO is lower and this condition is related to residual abnormalities.
• Cases of fulminant pulmonary fibrosis do not seem to be representative of the overall population that has recovered from COVID-19.

Symptoms do not correlate with lung function or residual CT abnormalities after COVID-19. Predictors of persistent residual abnormalities are still being studied.

Eva Srbová
proLékaře.cz editorial team