*Introduction -
Bronchitis is an inflammation of the bronchial tree’s mucosal lining, characterized by cough and sputum production. It can present acutely or chronically, affecting millions worldwide and imposing significant morbidity and healthcare costs. This article explores bronchitis in depth: its epidemiology, pathophysiology, clinical manifestations, diagnosis, management strategies, complications, and preventive measures.
Epidemiology
• Global burden: Acute bronchitis is among the top 10 reasons for outpatient visits in many countries; chronic bronchitis affects approximately 2–12% of adults globally.
• Age distribution: Acute bronchitis peaks in children and older adults; chronic bronchitis is most common between ages 45–65.
• Gender differences: Historically more common in men, but as smoking patterns have equalized, prevalence has become similar between sexes.
• Seasonality: Acute bronchitis often rises in winter months, correlating with viral respiratory infections.
Pathophysiology
1. Mucosal inflammation: Viral or irritant exposure damages bronchial epithelium, triggering inflammatory cascades.
2. Mucus hypersecretion: Goblet cell hyperplasia and submucosal gland enlargement increase mucus production.
3. Ciliary dysfunction: Inflammation impairs mucociliary clearance, prolonging pathogen retention.
4. Airway obstruction: Edema and mucus plugs narrow bronchi, causing cough and dyspnea.
5. Chronic remodeling: In chronic bronchitis, persistent injury leads to airway fibrosis and fixed obstruction.
Etiology and Risk Factors
Acute Bronchitis
• Infectious causes
o Viruses (90% of cases): influenza, respiratory syncytial virus (RSV), rhinoviruses, coronaviruses.
o Bacteria (rare): Mycoplasma pneumoniae, Chlamydophila pneumoniae, Bordetella pertussis.
• Non-infectious: Air pollution, occupational exposures (dust, fumes, chemical irritants).
Chronic Bronchitis
Defined clinically by productive cough for ≥3 months in 2 consecutive years.
• Tobacco smoking: Primary risk factor—accounts for >80% of cases.
• Environmental pollutants: Indoor biomass fuels, outdoor air pollution.
• Occupational hazards: Coal dust, silica, textile fibers.
• Genetic predisposition: Rare, e.g., α₁-antitrypsin deficiency.
Classification
1. Acute Bronchitis
o Self-limited, typically 7–21 days.
o Predominantly viral.
2. Chronic Bronchitis
o A phenotype of chronic obstructive pulmonary disease (COPD).
o Progressive, irreversible airway obstruction.
3. Recurrent Bronchitis
o ≥3 episodes of acute bronchitis in a 12-month period.
o Often in individuals with underlying airway hyperreactivity.
Clinical Presentation
Symptoms
• Cough: Cardinal symptom.
o Acute: Initially dry, becoming productive.
o Chronic: Daily productive cough (“smoker’s cough”), especially in mornings.
• Sputum: Purulent or mucoid; volume may vary.
• Wheezing: Due to bronchospasm.
• Dyspnea: Particularly in chronic disease or severe acute episodes.
• Systemic: Mild fever, malaise, myalgias (more common in acute).
Signs
• Auscultation:
o Coarse crackles (rales) at lung bases.
o Wheezes diffusely.
• Vitals:
o Low-grade fever (acute).
o Tachypnea and mild hypoxemia in chronic or severe cases.
Diagnosis
Diagnosis is primarily clinical, supplemented by investigations when indicated.
History & Examination
• Duration and pattern of cough, sputum characteristics.
• Smoking history, occupational exposures, comorbidities.
• Physical exam: lung auscultation, assessment for complications (e.g., pneumonia).
Laboratory Investigations
• Complete blood count: Leukocytosis in bacterial superinfection.
• C-reactive protein (CRP)/Procalcitonin: May aid in distinguishing bacterial from viral etiology.
Microbiological Testing
• Not routinely required for acute bronchitis.
• Consider in pertussis-suspected cases (PCR or culture).
• Sputum gram stain and culture in chronic bronchitis with frequent exacerbations.
Imaging
• Chest radiograph: Exclude pneumonia or alternative diagnoses if high fever, tachycardia, focal findings.
• CT scan: Rarely needed; may detect bronchiectasis in refractory chronic bronchitis.
Pulmonary Function Tests (PFTs)
• Reserved for chronic bronchitis to assess airflow limitation.
• Show reduced FEV₁/FVC ratio (<0.70) and may demonstrate reversibility testing.
Differential Diagnosis
• Pneumonia: Distinct by focal signs on exam, radiographic infiltrates, higher fever.
• Asthma: Intermittent wheezing, reversible obstruction on PFTs, atopy history.
• Bronchiolitis: Primarily in children <2 years with RSV.
• Bronchiectasis: Chronic productive cough with copious purulent sputum, clubbing.
• Gastroesophageal reflux disease (GERD): Chronic cough without sputum predominance.
• Postnasal drip: Characterized by throat clearing, nasal discharge.
Management
Acute Bronchitis
1. Supportive Care
o Hydration, rest.
o Analgesics/antipyretics (acetaminophen, NSAIDs).
o Humidified air.
2. Antitussives and Expectorants
o Dextromethorphan for cough suppression in nonproductive cough.
o Guaifenesin may help thin mucus but evidence is limited.
3. Bronchodilators
o In patients with wheezing or underlying airway hyperreactivity, short-acting β₂-agonists (albuterol) may relieve symptoms.
4. Antibiotics
o Not routinely indicated for viral bronchitis.
o Consider in patients with suspected pertussis (macrolides), or those ≥65 years with comorbidities and signs of bacterial infection.
Chronic Bronchitis
1. Smoking Cessation
o The single most effective intervention to slow disease progression.
2. Pharmacologic Therapy
o Bronchodilators
Short-acting β₂-agonists (SABAs) for symptom relief.
Long-acting β₂-agonists (LABAs) and long-acting muscarinic antagonists (LAMAs) for maintenance.
o Inhaled corticosteroids (ICS)
In combination with LABAs for patients with frequent exacerbations.
o Mucolytics
N-acetylcysteine may reduce exacerbations.
o Vaccinations
Annual influenza vaccine; pneumococcal vaccination per guidelines.
3. Non-Pharmacologic Interventions
o Pulmonary rehabilitation: Exercise training, education, nutrition counseling.
o Oxygen therapy: For chronic hypoxemia (PaO₂ ≤55 mm Hg or SpO₂ ≤88%).
4. Exacerbation Management
o Increased dyspnea, sputum purulence/volume.
o Short course of systemic corticosteroids (e.g., prednisone 40 mg daily ×5 days).
o Antibiotics if bacterial infection suspected.
5. Surgical Options
o Rare; lung volume reduction surgery or transplantation in select severe cases.
Complications
• Acute
o Secondary bacterial pneumonia.
o Respiratory failure in patients with COPD.
• Chronic
o Progressive airflow limitation (COPD).
o Cor pulmonale: right heart failure due to pulmonary hypertension.
o Recurrent exacerbations → hospitalizations, reduced quality of life.
o Bronchiectasis in longstanding disease.
Prognosis
• Acute bronchitis: Excellent—most recover fully within 3 weeks without sequelae.
• Chronic bronchitis: Variable—smoking cessation improves outcomes; ongoing inflammation leads to progressive decline in lung function.
• Exacerbation frequency: Predictor of mortality; >2 exacerbations/year indicates higher risk.
Prevention
1. Smoking avoidance and cessation: Eliminates primary irritant.
2. Air quality control: Minimize exposure to pollutants, occupational hazards.
3. Vaccination: Influenza and pneumococcal vaccines reduce infection risk.
4. Hand hygiene and respiratory etiquette: Curtails viral transmission.
5. Protective equipment: Masks in high-risk environments (polluted areas, occupational exposures).
Patient Education and Self-Management
• Symptom monitoring: Keeping track of cough, sputum changes, breathlessness.
• Action plan: Recognizing exacerbation signs, when to seek medical attention.
• Inhaler technique: Proper use of metered-dose and dry-powder inhalers.
• Lifestyle modifications: Nutrition, exercise, weight management.
Future Directions and Research
• Novel anti-inflammatory agents: Targeting specific cytokines and chemokines.
• Regenerative therapies: Stem cells to repair airway epithelium.
• Biomarkers: For predicting exacerbations and tailoring therapy.
• Vaccines: Against RSV and other respiratory viruses implicated in acute bronchitis.
Conclusion
Bronchitis, whether acute or chronic, remains a prevalent respiratory condition with significant impact on health systems and patient quality of life. While acute bronchitis is typically self-limited and managed with supportive care, chronic bronchitis requires a multifaceted approach—smoking cessation, pharmacotherapy, rehabilitation, and preventive strategies—to mitigate progression and improve outcomes. Ongoing research into targeted therapies and preventive measures promises to further enhance care and reduce the global burden of bronchial inflammation.
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