What is a Pulmonary Sequela?
A pulmonary sequela is a long-term consequence or residual abnormality in the lungs that persists after recovery from an acute respiratory disease or injury. These sequelae represent the chronic manifestations that remain following the initial insult to the pulmonary system.
Clinical Context and Common Examples
Pulmonary sequelae encompass a broad spectrum of persistent abnormalities that can affect lung structure, function, and patient symptoms:
Post-Pulmonary Embolism Sequelae
- Persisting dyspnea and functional limitation occur in 20-75% of patients 6 months to 3 years after acute PE, though the majority of cases are not attributable to residual thrombi or progressive pulmonary hypertension 1
- Muscle deconditioning is largely responsible for frequently reported dyspnea and exercise limitation after acute PE, particularly in patients with excess body weight and cardiopulmonary comorbidity 1
- Chronic thromboembolic pulmonary hypertension (CTEPH) represents the most serious sequela, occurring with a 2-year cumulative incidence of 0.79% following symptomatic PE 1
- CTEPH is characterized by fibrotic transformation of pulmonary arterial thrombi causing fixed mechanical obstruction and progressive microvascular remodeling 1
Post-Infectious Sequelae
- Chronic atelectasis, bronchiectasis, obliterative bronchiolitis, and fibrosis can develop following bacterial or viral pneumonia in children 2
- Functional alterations including bronchial hyperreactivity, chronic cough, and asthma may persist long-term 2
- Following COVID-19, approximately 55.7% of patients demonstrate residual CT abnormalities at 3 months post-discharge, with ground glass opacities being most common (44.1%) 3
- Impaired diffusion capacity is the most frequent functional abnormality post-COVID-19, occurring in 34.8% of patients at follow-up 3
Structural Patterns
The pathological manifestations of pulmonary sequelae include:
- Organizing pneumonia patterns (33.3% in post-COVID cohorts) 4
- Interstitial pneumonitis patterns (56.7% nonspecific, 40% usual interstitial pneumonitis) 4
- Parenchymal bands or fibrous stripes (33.9% frequency) 3
- Permanent destructive enlargement of airspaces (emphysema) in chronic obstructive conditions 1
Clinical Significance
Impact on Morbidity and Quality of Life
- Reduced maximal aerobic capacity (peak oxygen consumption <80% predicted) occurs in 47% of PE survivors at 1 year, associated with significantly worse quality of life scores and reduced 6-minute walk distance 1
- Independent predictors of reduced functional capacity include female sex, higher body mass index, history of lung disease, and elevated pulmonary artery pressures 1
- Importantly, pulmonary function tests and echocardiographic results are often within normal limits despite persistent exercise impairment, highlighting the disconnect between objective testing and functional capacity 1
Mortality Implications
- In CTEPH, mean pulmonary artery pressure >30 mmHg relates to poor survival similar to idiopathic pulmonary arterial hypertension 1
- Post-COVID lung parenchymal abnormalities carry a case fatality rate of 16.7%, with only 32% of survivors recovering completely 4
- Untreated chronic thromboembolic disease is usually fatal within 2-3 years of detection 1
Key Clinical Pitfalls
A critical caveat: The absence of abnormalities on routine pulmonary function testing or echocardiography does not exclude clinically significant pulmonary sequelae, as exercise limitation may persist despite normal resting parameters 1. Cardiopulmonary exercise testing provides more sensitive assessment of functional impairment 1.
Prevention consideration: At present, prevention of long-term PE sequelae is not justification for thrombolytic treatment in the acute phase, as it remains unclear whether early reperfusion impacts long-term functional outcomes 1.