COPD: Emphysema & Bronchitis Reference

Pulmonary: Emphysema

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FreeMedSite USMLE STEP 1 REVIEW
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1. Pathological Definition
“Permanent enlargement of airspaces distal to the terminal bronchioles, with destruction of alveolar walls, without obvious fibrosis.”

Key Consequence

↓ Elastic Recoil → Airflow limitation & Hyperinflation

2. Pathophysiology
  • → ↑ Compliance (Enlarged airspaces + decreased recoil)
  • → ↓ DLCO (Destruction of alveolar walls = impaired exchange)
  • → Reduced blood volume in pulmonary capillaries (contributes to hypoxemia)
  • → Protease-Antiprotease Imbalance: ↑ Elastase (Neutrophils/Macrophages) overcomes ↓ Antiprotease (α1-antitrypsin)
3. Morphological Types
Type Cause/Location Key Features
Centrilobular Smoking / Upper Lobes Respiratory bronchioles; distal alveoli spared initially.
Panlobular A1AT Def. / Lower Lobes Respiratory bronchioles + alveoli; diffuse acinus involvement.
Paraseptal Distal acinus / Pleura Risk: Spontaneous Pneumothorax
Irregular Scarring / Variable Usually asymptomatic.
4. Clinical Presentation
  • • Barrel Chest (↑ AP Diameter)
  • • Pursed-lip breathing (↑ pressure prevents collapse)
  • • Dyspnea (often out of proportion to cough)
  • • "Pink Puffer" phenotype (Weight loss/cachexia)
  • • Mild cough (usually non-productive)
  • • Hypoxemia (mild early, worsens late)
5. Comps & Mgmt

Complications

  • Respiratory Failure (Late)
  • Pulm HTN → Cor Pulmonale
  • Pneumothorax

Management

  • Smoking Cessation (Most Important)
  • Bronchodilators (β2, Anticholinergics)
  • Oxygen (if hypoxemic)
Feature Emphysema (Pink Puffer) Chronic Bronchitis (Blue Bloater)
Primary Symptom Dyspnea Productive Cough
DLCO Decreased (↓) Normal
Recoil / Compliance ↓ Recoil, ↑ Compliance Normal
Chest X-Ray Lucency, Flat Diaphragm ↑ Lung Markings
Spirometry (FEV1/FVC) < 0.7 < 0.7
High-Yield Flashcard Review

Q1: Compliance

What is the compliance profile of Emphysema?

Ans: Increased compliance (due to loss of elastic fibers).

Q2: Histology

What cells release the elastase that destroys the acinus?

Ans: Neutrophils and Macrophages.

Q3: α1-antitrypsin

Where is α1-antitrypsin normally produced?

Ans: The Liver (Deficiency often presents with Cirrhosis).

Q4: Mechanisms

How do pursed lips prevent airway collapse?

Ans: By increasing back-pressure (PEEP-like effect) in the airways.

Q5: Distribution

Why is Centrilobular emphysema in the upper lobes?

Ans: Smoke is less dense than air and rises to the apex.

Q6: Panacinar Severity

Which type has more severe gas exchange impairment?

Ans: Panacinar (Panlobular) - involves both bronchioles and alveoli.

Q7: Complications

Which type is most linked to spontaneous pneumothorax?

Ans: Paraseptal emphysema (due to subpleural blebs).

Q8: Hypoxemia

What happens to capillary blood volume in emphysema?

Ans: It is reduced, contributing to hypoxemia.