The post-COVID-19 pulmonary sequelae: manifestations, mechanisms and treatment strategies

Recent studies have increasingly demonstrated that coronavirus disease 2019 (COVID-19) patients may develop long-term sequelae of varying severity, collectively referred to as long COVID or post-COVID-19 condition. Pulmonary sequelae are particularly common, which significantly impair patients' quality of life. The mechanisms underlying post-COVID-19 pulmonary sequelae are complex and multifactorial, and their management is still at an exploratory stage. This review explores the manifestations, underlying mechanisms, and potential treatment approaches for post-COVID-19 pulmonary sequelae. Fatigue, dyspnea, myalgia, and sleep disturbances are the most commonly reported symptoms following COVID-19 infection, while anxiety and depression are also prevalent. Respiratory symptoms include dyspnoea, persistent cough, hypoxia, and reduced exercise capacity. Impaired lung diffusion capacity is the most frequently observed pulmonary function abnormality, and residual abnormalities on chest computed tomography (CT) commonly include ground-glass opacities (GGO) and fibrotic-like changes. Air trapping is also an important CT finding and has been reported to associated with impaired lung diffusion function. The potential mechanisms may include pulmonary fibrosis, chronic inflammation, immune dysregulation, coagulation abnormalities and thrombosis, and persistent viral infection. Current treatment strategies encompass vaccination, pulmonary rehabilitation, and pharmacological interventions such as antifibrotic, anti-inflammatory, and anticoagulant therapies. A comprehensive understanding of the recovery trajectory and the mechanisms underlying post-COVID-19 pulmonary sequelae is crucial for improving patient outcomes.