Emphysema

Emphysema

Causes
1. Smoking cigarettes
2. Alpha 1 antitrypsin deficiency
Types
1. Centriacinar (centrilobular)
  1. Pathogenesis
    1. (1) It primarily involves the apical segments of the upper lobes.
    2. (2) Distal terminal bronchioles and the RBs are the sites of elastic tissue destruction.
    3. Air trapped behind the collapsed distal terminal bronchioles distends the RBs. >> Trapped air increases RV and TLC.
2. Panacinar
  1. Associated with AAT deficiency
  2. Pathogenesis
    1. Primarly affects lower lobes
    2. Distal terminal bronchioles and all parts of the respiratory units are the sites of elastic tissue destruction
    3. Air trapped behind the collapsed terminal bronchioles distends the entire respiratory unit.
  3. Lab findings : absent alpha 1 globulin peak in SPE
3. Paraseptal
  1. (1) Localized disease in a subpleural location { Primarily targets the alveolar ducts and alveoli}
  2. (2) Does not produce obstructive airway disease
  3. (3) Increased incidence of spontaneous pneumothorax << Rupture of subpleural blebs
4. Irregular
  1. Localized disease associated with scar tissue
  2. (2) Does not produce obstructive airway disease
Pathogenesis
1. Increased COMPLIANCE .. & decreased ELASTICITY
  1. Imbalance between elastase and antielastases
  2. Imbalance between oxidants
  3. Elastase and oxidants derive from neutrophils and macrophages
  4. Net effect of the preceding is destruction of elastic tissue
2. Cigarette smoke is chemotactic to neutrophils and macrophages.
3. FRs in cigarette smoke inactivate AAT and antioxidants. >> Produces a functional AAT deficiency
4. Destruction of elastic tissue causes loss of radial traction. {Small airways collapse, particularly on expiration.}
  1. Sites of elastic tissue destruction
    1. Distal terminal bronchiole at its junction with the respiratory bronchiole (RB)
    2. All or part of the respiratory unit
  2. Site of obstruction and air trapping in emphysema
    1. (1) During expiration the distal terminal bronchioles collapse, which prevents egress of air from the respiratory unit.
    2. (2) Trapped air distends parts of the respiratory unit that have lost their elastic tissue support.
Clinical Findings
1. Progressive Dyspnea and hyperventilation
  1. Dyspnea is severe and occurs early in the disease.
  2. (2) Hypoxemia occurs late in the disease (takes time for destruction of respiratory units)
  3. . (3) Sometimes patients are called “pink puffers.”
2. Chest Radiograph
  1. Hyperlucent lung fields
  2. Increased anteroposterior diameter
  3. Vertically oriented heart
  4. Depressed Diaphragm << hyperinflated lungs
3. Pulmonary function tests and arterial blood gases
  1. Increased TLC due to increase in RV
  2. Decreased FEV1
  3. Decreased FVC & FEV1/FVC ratio
  4. Decreased Pao2 develops late in disease { destruction of capillary bed matches destruction of respiratory unit }
  5. Normal to decreased arterial PCO2 (respiratory alkalosis ; pink puffer)
Treatment
1. Cessation of Smoking
2. Pulmonary rehabilitation program
3. Oxygen
4. Bronchodilators
5. Anticholinergics

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	Created by Farah Mansour about 8 years ago