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Updated: Aug 19 2022

Emphysema

Images
https://upload.medbullets.com/topic/120681/images/517px-emphysema2008.jpg
  • Snapshot
    • A 29-year-old man presents to the emergency department with severe pleuritic chest pain. He tells the resident that he is worried he might have another collapsed lung. His temperature is 98.7°F (37.1°C), blood pressure is 118/78 mmHg, pulse is 119/min, respirations are 31/min, and oxygen saturation is 85% on room air. On examination, he appears cachectic. A chest radiograph is obtained.
  • Introduction
    • Clinical definition
      • chronic obstructive pulmonary disease (COPD) is defined as persistent airflow limitation due to mixture of small airway disease and parenchymal destruction
        • early classifications distinguished emphysema and chronic bronchitis 
        • no longer distinguished but helpful to separate for pathophysiologic understanding and clinical management
      • emphysema is defined by alveolar wall destruction and dilation that presents in 2 forms
        • centrilobular
          • almost always due to smoking
        • panlobular/panacinar
          • rare and caused by alpha-1-antitrypsin deficiency
            • misfolded alpha-1-antitrypsin (AAT), which normally inhibits elastase
            • without AAT, elastase is over active and destroys elastic tissues
            • can accumulate in hepatocytes and cause cirrhosis
  • Epidemiology
    • Demographics
      • males > females
      • 4th most common cause of death globally
    • Risk factors
      • tobacco use (most common)
      • air pollution
      • occupational exposure
      • AAT deficiency
  • ETIOLOGY
    • Pathogenesis
      • damage to airways distal to terminal bronchiole (i.e., acinus)
      • abnormal dilation of airspaces and destruction of alveoli walls due to proteinases (i.e., elastase)
      • decreased alveolar and capillary surface area, which decreases gas exchange
  • Presentation
    • Symptoms
      • dyspnea
      • mild cough
      • fatigue
      • hyperventilation
    • Physical exam
      • "pink puffers"
        • non-cyanotic
        • cachectic
        • pursed-lip breathing
      • accessory muscle use
      • hypoxia
      • barrel chest
      • decreased breath sounds
      • end-expiratory wheezing and/or prolonged expiration
      • signs of cirrhosis if associated with AAT deficiency
  • imaging
    • Chest radiograph
      • not required for routine diagnosis
      • hyperinflation/flattened diaphragm
      • bullae and/or blebs
      • may have decreased lung markings
    • Computed tomography
      • not necessary for management but can determine classification of emphysema (centrilobular or panacinar)
  • studies
    • Pulmonary function tests (PFTs)
      • best initial test
      • decreased FEV1 / FVC (< 0.7) that is incompletely reversible
        • obstructive pattern
        • diagnostic
        • FEV1 = forced expiratory volume
        • FVC = forced vital capacity
      • decreased % FEV1
        • used to categorize severity based on Global initiative for chronic Obstructive Lung Disease (GOLD)
          • mild: > 80%
          • moderate: 50-79%
          • severe: 30-49%
          • very severe: < 30%
      • normal or decreased FVC
      • increased total lung capacity (TLC)
        • more than with chronic bronchitis
      • decreased DLCO (vs. normal in chronic bronchitis)
        • DLCO = diffusing capacity of the lungs for carbon monoxide
    • Arterial blood gas (ABG)
      • indicated for O2 saturation < 92%, altered mental status, or acute exacerbation
      • hypoxemia
        • decreased PO2
        • may cause increased hemoglobin/polycythemia
      • acute or chronic respiratory acidosis
        • increased PCO2 (hypercapnia) due to retention
  • Differential
    • Asthma
      • distinguishing factor
        • obstructive pattern on PFTs are reversible after administration of inhaled bronchodilator
    • Bronchiectasis
      • distinguishing factor
        • computed tomography (CT) is gold standard for diagnosis
          • large internal bronchial diameter, thickened bronchial wall, and altered airway geometry
          • "tram-track" and "signet-ring" signs
    • Interstitial lung disease (ILD)
      • distinguishing factor
        • restrictive lung pattern on PFTs
  • Treatment
    • First-line
      • conservative
        • smoking cessation
          • greatest impact on mortality
        • home O2
          • indicated if resting PaO2 < 55 mmHg or SaO2 <89%
        • flu and pneumococcal vaccines
      • pharmacological
        • step-wise depending on GOLD classification of disease severity
          • mild
            • short-acting inhaled bronchodilators
            • short-acting inhaled beta-agonist (e.g., albuterol) as needed
            • short-acting inhaled anticholinergic (e.g., ipratropium) as needed
            • most patients will present in more advanced stages
          • moderate
            • long-acting inhaled bronchodilator
            • long-acting beta-agonist (e.g., salmeterol or formoterol)
            • long-acting anticholinergic (e.g., tiotropium)
            • can be used in combination
          • severe
            • inhaled corticosteroid (e.g., budesonide or fluticasone) + long-acting bronchodilator
          • very severe
            • triple therapy
              • inhaled corticosteroid + long-acting anticholinergic + long-acting beta-agonist
            • may require roflumilast
              • phosphodiesterase (PDE)-4 inhibitor
            • theophylline
              • PDE inhibitor and adenosine receptor blocker
              • indicated for severe and refractory disease
              • low therapeutic index
          • AAT deficiency
            • IV pooled AAT
    • Second-line
      • lung resection or transplantation
        • may be beneficial in severe cases refractory to medical management
  • Complications
    • Acute exacerbation
    • Pneumothorax
      • caused by rupture of bullae
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