Pathology of obstructive lung disease

Question 1

How can obstructive lung disease be demonstrated?

Answer 1

Via spirometry: % of predicted (based off of age, sex, height)
In obstructive lung disease FEV1 < 70% FVC

Peak expiratory flow rate
- normal = 400-600L
- 50% - 80% = moderate fall
- <50% = marked fall

Question 2

Explain type 1 hypertension in airways

Answer 2

Smooth muscle constricts and inflammation of mucosa = narrowing of lumen and leading to airflow limitation.

Question 3

What is type 1 hypertension mediated by?

Answer 3

Degradation of mast cells caused by:
- IgE
- Chemicals
- Cold air
- Stress

Question 4

Describe bronchial asthma

Answer 4

Reversible airway obstruction either spontaneously or as a result of medical intervention.
Bronchial smooth muscle contraction and inflammation can be modified by drugs.

Question 5

What is the clinical definition of chronic bronchitis?

Answer 5

Cough productive of sputum most days in at least 3 consecutive months for 2 or more consecutive years

Question 6

What are the signs of complications with chronic bronchitis?

Answer 6

• Mucopurulent sputum (green/yellow)
• FEV1 falls

Question 7

What happens in the large airways with chronic bronchitis?

Answer 7

Mucous gland hyperplasia
Goblet cell hyperplasia
Inflammation and fibrosis is minor

Question 8

What happens in the small airways with chronic bronchitis?

Answer 8

Goblet cells and mucous secreting cells appear (as defence mechanism but end up causing the disease).
Inflammation in long standing disease

Question 9

What is emphysema?

Answer 9

Increases beyond normal size of airspaces distal to the terminal bronchiole arising from either dilation or from destruction of their walls and without obvious fibrosis.

• No fibrosis
• Destruction and loss of alveolar tissue

Question 10

What is the acinus?

Answer 10

Bit of the lung supplied by the terminal bronchiole (all of the alveoli it supplies).

Question 11

What are the different forms of emphysema?

Answer 11

Centriacinar
Panacinar
Scar “irregular”

Question 12

Describe centriacinar

Answer 12

Most clinically important
Common in those who smoke
Begins with bronchial dilation and then alveolar tissue is lost.
Greatest effect on upper lobes of the lungs

Question 13

Describe panacinar

Answer 13

Affects lower lobes of the lungs
Caused by smoking
Whole wipe out of lung acinus

Question 14

Describe scar (“irregular”)

Answer 14

Bullous emphysema
- Bulla = emphysema space > 1cm
- May rupture and lead to spontaneous pneumothorax

Question 15

Why do lungs hyperinflate in obstructive lung disease?

Answer 15

Easier to breath with half inflated lungs as airways are kept half open.

Question 16

What causes emphysema?

Answer 16

SMOKING
- protease-antiprotease imbalance
Aging
Alpha-1-antitrypsin deficiency

Question 17

What happens in a normal lung?

Answer 17

Neutrophils and macrophages keep lungs clean/healthy
Anti-elastase (anti-proteases) make elastase making elastin framework in alveolar tissue.

Question 18

What happens with alpha-1-antitrypsin deficinecy?

Answer 18

Increased production of neutrophils and macrophages
Increased production of anti-elastase (anti-proteases)

Tissue destruction = emphysema

Question 19

What happens to a smokers lungs in emphysema?

Answer 19

Smoking increases numbers neutrophils and macrophages increased elastase (proteases)
Decreases anti-elastase (anti-proteases)

Leads to tissue destruction = emphysema

Question 20

What is the mechanism of obstruction in COPD?

Answer 20

Large airways
- little contribution by glands and mucous
Small airways
- Smooth muscle tone
- Inflammation
- Fibrosis
- Partial collapse of airway wall on expiration

In emphysema LOSS OF ALVELOI ATTATCHAMENTS is most important.

Question 21

What is the importance of alveoli attachments?

Answer 21

There is no cartilage in small airways to keep them open.
Instead they stay open by alveoli attachments (elastic) stretching
If these are wiped out then terminal bronchioles collapse earlier during expiration.

Question 22

Why does hypoxaemia occur? (4)

Answer 22

• Airway obstruction
• Reduced respiratory drive (don’t breath enough and CNS becomes inured to elevated CO2 and H+ levels in the CSF).
• Loss of alveolar surface area
• Shunt (only during severe acute infective exacerbations)

Question 23

What is cor pulmonale?

Answer 23

Hypertrophy of the right ventricle resulting from disease affecting the function and/or the structure of the lung.

The right side of the heart becomes dilated and patient can suffer right heart failure.

Question 24

Describe pulmonary hypertension and how it occurs?

Answer 24

1) Loss of alveoli
2) Loss of blood vessels for blood to go through
3) Bone marrow produces more RBCs
4) Increased blood viscosity due to more RBCs
5) Harder to pump blood through the remaining vessels