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Introduction
  • A condition characterized by dilation of air spaces (with ↓ elasticity and ↑ compliance)
    • due to alveolar wall destruction
      • normally, elastin in the wall functions to keep alveoli open
    • capillaries are destroyed along with the alveoli
  • Causes
    • smoking
      • most common cause
    • α1-antitrypsin (AAT) deficiency
      • AD disorder (codominant)
        • MM phenotype is normal
        • ZZ phenotype results in disease
      • AAT normally inhibits the action of elastase
      • without AAT elastase is unchecked and destroys the elastic tissue of the alveoli  
      • as a result emphysema develops at early age
        • may also develop cirrhosis due to the inability to release an abnormal form of AAT from the liver resulting in hepatotoxicity 
Classification
  • Centriacinar 
    • dilated respiratory bronchiole
    • most common presentation of emphysema due to smoking
      • result of inhaled tobacco toxins arriving first in the respiratory bronchioles before traveling to the alveolus
    • most commonly in the upper lobes
      • result of upper lobes receiving exposure to smoke
  • Panacinar
    • dilated alveoli
    • most common presentation of AAT deficiency
      • also due to a functional AAT deficiency as a result of smoking
        • oxidants and inflammatory reaction of smoke can destroy AAT
        • smoking exacerbates effects of genetic AAT deficiency 
    • most commonly in the lower lobes
      • result of lower lobes recieving ↑ perfusion allowing more immune cells to traffic into the alveoli
  • Paraseptal
    • most commonly involves young, otherwise healthy males
    • does not obstruct the airway
      • associated with bullae
      • found near the pleura
      • increased risk for spontaneous pneumothorax
Presentation
  • Symptoms
    • dyspnea
    • classic pursed-lip breathing
      • results in increased airway pressure and prevents airway collapse during exhalation
  • Physical exam
    • decreased breath sounds on auscultation
    • increased anterior-posterior diameter (barrel chest)
    • hyperresonant to percussion
    • "pink puffer" (end-stage)
Imaging
  • Chest radiograph
    • increased AP diameter with flattened diaphragms 
    • hyperinflated lungs
    • loss of lung markings
    • elongated heart
Evaluation
  • Labs
    • ABG during exacerbation shows hypoxemia and acute respiratory acidosis
    • AAT shows no α-globin peak on electrophoresis
  • Pulmonary function tests
    • decreased FEV1 sec / FVC
    • increased TLC and RV
    • decreased diffusion capacity from destruction of capillaries
Treatment
  • Conservative 
    • smoking cessation
    • ambulatory O2 
  • Pharmacologic
    • bronchodilators 
      • for symptom improvement
    • inhaled steroids
      • reduce exacerbations
    • oral/IV steroids and antibiotics
      • for acute exacerbations
 

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