Pathophysiology of Asthma Exacerbation
Core Pathophysiological Mechanisms
- Airway inflammation is the fundamental underlying process in asthma, involving chronic inflammation with activation of mast cells, eosinophils, neutrophils, T lymphocytes, macrophages, and epithelial cells 1
- Bronchoconstriction rapidly narrows airways in response to various stimuli, including allergens and irritants 1
- Airway hyperresponsiveness is a hallmark feature of asthma, characterized by an exaggerated bronchoconstrictor response to stimuli 1
- Airway edema develops as inflammation progresses, further limiting airflow 1
- Airway remodeling leads to structural changes, including sub-basement fibrosis, epithelial cell injury, smooth muscle hypertrophy, and angiogenesis 1
Triggers of Exacerbations
- Respiratory infections, particularly viral infections, are the most common triggers of asthma exacerbations 3
- Allergen exposure can trigger asthma exacerbations in sensitized individuals 1
- Environmental irritants, such as air pollution, smoke, and strong odors, can also trigger exacerbations 1
- Psychological stress can amplify airway inflammatory responses to irritants, allergens, and infections 4
- Medication non-adherence, including underuse or poor adherence to controller medications, can contribute to exacerbations 5
Clinical Manifestations
- Progressive symptoms, including increasing shortness of breath, cough, wheezing, and chest tightness, are characteristic of asthma exacerbations 2
- Decreased lung function, measured by expiratory airflow (FEV₁ or PEF), is a key feature of exacerbations 6
- Increased work of breathing, including use of accessory respiratory muscles and tachypnea, is common in exacerbations 5
- Hypoxemia, characterized by decreasing oxygen saturation, can occur as severity increases 5
Risk Factors for Severe Exacerbations
- Previous severe exacerbation requiring intubation or ICU admission is a significant risk factor for future severe exacerbations 2
- Frequent healthcare utilization, including multiple hospitalizations or ED visits per year, is associated with an increased risk of severe exacerbations 2
- High SABA use, defined as more than two canisters per month, is a risk factor for severe exacerbations 2
- Poor perception of airway obstruction and psychosocial factors, including psychiatric comorbidities, can contribute to severe exacerbations 2, 4
- Comorbid conditions, such as cardiovascular disease and chronic lung disease, can increase the risk of severe exacerbations 2