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COPD for USMLE Step 2

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Chronic obstructive pulmonary disease for the USMLE Step 2 Exam
Pathophysiology
  • Chronic Inflammation:
    • COPD is driven by chronic inflammation of the airways and lung parenchyma due to long-term exposure to irritants such as cigarette smoke.
    • Neutrophils, macrophages, and CD8+ T cells predominate in the inflammatory response, causing airway narrowing and alveolar destruction.
  • Airflow Limitation:
    • Small Airway Disease: Inflammation and fibrosis narrow the bronchioles, increasing airway resistance.
Small airway disease COPD
    • Emphysema: Destruction of alveolar walls leads to loss of elastic recoil, causing air trapping and hyperinflation.
  • Protease-Antiprotease Imbalance:
    • In smokers and alpha-1 antitrypsin deficiency, increased protease activity leads to destruction of alveoli and small airways.
  • Oxidative Stress:
    • Smoke and inflammatory cells release oxidants, further damaging lung tissue and worsening inflammation.
Clinical Features
  • Chronic Cough and Sputum Production:
    • Early signs of COPD, often worse in the morning with productive sputum.
  • Dyspnea:
    • Progressive shortness of breath is the most characteristic symptom, typically worsening with exertion.
  • Wheezing and Chest Tightness:
    • These symptoms may occur, especially during exacerbations.
Diagnosis
  • Spirometry:
    • Key diagnostic test showing:
    • FEV1/FVC Ratio <0.70: Confirms persistent airflow obstruction.
    • Reduced FEV1: Reflects the severity of obstruction.
  • Chest X-ray:
    • Common findings include hyperinflation, flattened diaphragms, and increased retrosternal air space.
  • Arterial Blood Gas (ABG):
    • In advanced cases or exacerbations, ABG may show hypoxemia or hypercapnia.
Management
  • Smoking Cessation:
    • The most effective intervention to slow COPD progression and improve survival.
  • Bronchodilators:
    • Short-acting beta-agonists (SABAs): Provide symptom relief during exacerbations.
    • Long-acting beta-agonists (LABAs) and long-acting muscarinic antagonists (LAMAs): Maintenance therapy to reduce symptoms and exacerbations.
    • Combination LABA/LAMA: Superior in improving lung function and reducing exacerbations compared to monotherapy.
  • Inhaled Corticosteroids (ICS):
    • Used in combination with bronchodilators (LABA/ICS) for patients with severe COPD or frequent exacerbations.
  • Oxygen Therapy:
    • Long-term oxygen therapy improves survival in patients with severe resting hypoxemia (PaO2 ≤55 mmHg or SaO2 ≤88%).
  • Pulmonary Rehabilitation:
    • A program of exercise and education that improves quality of life, especially in patients with moderate-to-severe COPD.
Exacerbations
  • Definition:
    • Acute worsening of respiratory symptoms beyond normal day-to-day variations, often triggered by infections.
  • Management of Exacerbations:
    • Bronchodilators: SABAs with or without short-acting anticholinergics (e.g., ipratropium).
    • Systemic Corticosteroids: Short courses of prednisone (e.g., 40 mg for 5 days) improve lung function and reduce recovery time.
    • Antibiotics: Used if there is increased sputum purulence, fever, or evidence of infection.
Complications
  • Pulmonary Hypertension and Cor Pulmonale:
    • Chronic hypoxia leads to pulmonary hypertension and eventually right heart failure (cor pulmonale).
  • Acute Respiratory Failure:
    • Exacerbations can result in acute respiratory failure, requiring mechanical ventilation or non-invasive positive pressure ventilation (NIPPV).
Key Points
  • COPD is characterized by chronic inflammation, airflow limitation, and parenchymal destruction, primarily due to smoking.
  • Spirometry (FEV1/FVC <0.70) is essential for diagnosis and staging, with chest X-rays supporting findings in advanced disease.
  • Smoking cessation is the most critical intervention to halt disease progression.
  • Pharmacologic treatment includes bronchodilators (SABAs, LABAs, LAMAs) and inhaled corticosteroids for maintenance and exacerbation prevention.
  • Exacerbations are managed with bronchodilators, corticosteroids, and antibiotics when appropriate.
  • Complications include pulmonary hypertension, cor pulmonale, and respiratory failure.

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