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May 5, 2023

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The Long COVID Series Part 5: Pulmonary Impacts

COVID-19 Resources

While COVID-19 affects multiple organ systems, many studies have notably identified adverse and persistent pulmonary issues, particularly in patients with severe acute cases. Much of this pulmonary injury is detectable long after recovery from COVID-19.

Pulmonary Pathophysiology and Long COVID

There is risk of COVID-19-causing irreversible pulmonary damage during the acute phase of COVID-19. Continued viral growth and/or protracted underlying immune/inflammatory stimulation also result in ongoing damage and death in some individuals. This damage can range from microvascular-level destruction to large pulmonary emboli.

Pulmonary Symptoms and Diagnostics

The most common pulmonary-related Long COVID symptoms include fatigue (84%), dyspnea (83%) and cough (71%). Significant pulmonary symptoms, including cough and dyspnea, have been reported to persist for six months or more in up to 30% of COVID-19 survivors.

Existing data suggest that post-acute pulmonary infections affected lung structure, lung function and reduced oxygen diffusion (DLCO). Many individuals studied recovered within one to two years, but some had mild to moderate effects. A recent study indicated that some COVID-19 patients requiring admission demonstrated symptoms 30 days post-recovery compared to non-admitted COVID-19 patients. Another study revealed that DLCO was normal in less than half of patients 30 days post-COVID-19 recovery.

Pulmonary Function Testing (PFT)

Evaluation of post-COVID-19 patients commonly detects significant abnormalities in PFTs. These PFT abnormalities were greatest during the first year post-recovery but also persisted for months in some cases. A study noted no significant difference in PFTs based on the severity of the acute COVID-19 infection. However, DLCO was significantly abnormal in many cases. The severity of acute illness correlated with DLCO abnormalities, which also correlated with the severity of dyspnea reported. These findings were consistent with other studies and may help diagnose and monitor patients with Long COVID pulmonary problems.

Radiographic Findings

Lung parenchymal abnormalities are commonly seen on imaging months following COVID-19 infections. Interestingly, the clinical manifestations of patients with Long COVID and persistent radiographic findings do not always correlate. A similar phenomenon exists with CT and MRI findings of myocardial scarring and dysfunction following COVID-19.

Pulmonary Inflammation and Long COVID

Because of the role of inflammation, several researchers have looked at the utility of inflammatory markers in the triage, diagnosis and management of acute and Long COVID pulmonary problems. Both the initial and ongoing inflammatory states imposed during COVID-19 are important factors in disease severity and the nature of any Long COVID symptoms. However, more research is needed here.

Small Airway Disease and COVID-19

The development of small airway disease is an important process in pulmonary pathology. Persistent inflammation from irritants can result in the activation of inflammatory cascades and eventual pulmonary structural changes. These changes are mainly a consequence of cellular death and tissue remodeling with the replacement of functional tissue with scar tissue. This tissue destruction culminates in the structural collapse of the pulmonary architecture at the small airway and eventually macro levels.

The Preoperative Setting and Long COVID

Another issue worth noting is the impact of Long COVID on the patient needing surgery. Scant information is available as of yet on this topic. However, some clinical recommendations have been made based on existing studies and clinical experience within large pulmonary and anesthesia practices. Namely, patients with persistent symptoms (past seven weeks) should have a pulmonary consultation and detailed evaluation, including adequate management of thromboembolic issues and coagulopathy determination. 

Long COVID Pulmonary Impacts

Persistent pulmonary symptoms are a critical part of the Long COVID constellation of symptoms. Thirty percent or more of post-COVID-19 survivors demonstrate some residual pulmonary dysfunction at 30 days to several years following recovery. Although all COVID-19 survivors can have complications, it is more common and significant in patients suffering severe COVID-19 events.

For a list of references, please click here. To access more resources from the Emerging Infectious Disease Taskforce, please see our other COVID-19 resources.