Emphysema

Question 1

What is emphysema? Give a brief descriptioin.

Answer 1

Emphysema is an obstructive pulmonary disease that is characterised by the abnormal enlargement (as the result of destruction of normal tissue) of the terminal bronchiole.

Question 2

How is emphysema classified? What are the major classifications and give a description of each?

Answer 2

Emphysema is classifed based on its anatomic distribution within the acinus.

The major classifications are:

• Centriacinar:
  
  • Destruction of the central and/or proximal acinus. The distal acinus is spared.
  • Predominantly occurs in the apices/upper lobes.
  • Most common in male smokers
• Panacinar:
  
  • Uniform destruction and enlargement of the acinus.
  • Predominatnly occurs in the basal zones.
  • Strongly associated with alpha-1 antitrypsin def’y
• Paraseptal:
  
  • Mostly distal destruction of the acinus, sparing the proximal
  • Found near the pleura and around fibrosis and/or scarring
  • Often the cause of spontaneous pneumothorax
• Irregular:
  
  • Irregular involvement of the acinus
  • Associated w/ scarring
  • Usually asymptomatic
  • Related to bullous and interstitial emphysema

Question 3

Describe the mechanism of injury in emphysema.

Answer 3

The protease/anti-protease theory.

Emphysema is dependant on either a def’y or inactivation of alpha-1 antitrypsin (A1-AT), also known as alpha-1 antiprotease inhibitor. A1-AT protects tissues from inflammatory enzymes, **especially neutrophil protease. **Emphysema is thought to result from an imbalance between proteases and anti-proteases in the lung.

Two main causes:

1. Hereditary def’y of A1-AT -> low levels or absence of A1-AT.
2. Inactivation of A1-AT by oxidants in tobacco smoke.

NB: Tobacco smoke has a secondary action of activating macrophages and recruiting neutrophils to the exposed airways. This results in an increase in both macrophage and neutrophil elastase.

The imbalance between proteases and anti-proteases leads to a net breakdown in elastic tissue in the lung -> decreased radial traction -> resp’y bronciole collapse during expiration -> obstruction.

Smoking acts synergistically in the presence of A1-AT def’y to bring on emphysema at even younger ages.

Additional mechanisms include:

• Goblet cell metaplasia -> mucus plugging
• Infiltration by inflam’y cells
• Thickened bronchiole walls -> narrowed lumen

Lungs are voluminous, with enlarged airspaces (due destruction of tissue), thin walled and compression of septal capillaries.

Question 4

List some of the treatments for emphysema.

Answer 4

• Bronchodilators
• Steroids
• Bullectomy
• Lung reduction surgery
• Transplant

Question 5

Describe the clinical course of emphysema.

Answer 5

• Dyspnoea
• Cough
• Wt loss
• Barrel chest
• Pursed lip breathing
• Red’d exp’y airflow (FEV₁ dec’d)
• Inc’d RR (pink puffers)
• Increased pulm’y BP -> cor pulmonale
• CCF
• Right HF
• Pneumothorax
• Death

Question 6

Which type of emphysema is most associated with smoking?

Answer 6

Centriacinar

Question 7

What type of emphysema is associated with alpha-1 antitrypsin def’y?

Answer 7

Panacinar emphysema

Question 8

What type of emphysema most commonly results in spontaneous pneumothroax?

Answer 8

Paraseptal (distal) emphysema

Question 9

What is the most common form of emphysema? Why?

Answer 9

Centriacinar. Smoking.

Question 10

What is another name for paraseptal emphysema?

Answer 10

Distal emphysema

Question 11

Can airway resistance in emphysema be normal?

Answer 11

Yes

Question 12

What is the most plausible theory for the pathogenesis of emphysema? Give a brief outline of this theory.

Answer 12

Protease - antiprotease imbalnce.

Increased protease:antiprotease ratio leads to destruction of elastin in the lung -> reduced dec’d radial traction -> collapse of small airways airways during expiration -> obstruction.

Question 13

What type of cell is most important in the pathogenesis of emphysema? Why?

Answer 13

Neutrophils.

Recruitment of neutrophils by exposure to tobacco smoke -> increased release of neutrophil protease -> imbalance of proteases and anti-proteases.

NB: Macrophage numbers don’t increase but they are stimulated to release macrophage proteases and contribute to the disease in this way.

Question 14

What parts of the acinus are affected in centriacinar emphysema?

Answer 14

Central and proximal. Distal segments are spared.

Question 15

What parts of the lungs are most affected by centriacinar emphysema?

Answer 15

Apicies

Question 16

What parts of the lungs are most affected by panacinar emphysema?

Answer 16

Lower zones