Pathology of obstructive lung disease

Question 1

Tests to test respiratory drive and how these are affected in obstructive disease

Answer 1

FEV1/FVC should be 0.8
FEV1 should be 3.5 litres
FVC should be 5 litres 
OR
PEFR= Peak expiratory flow rate 
maximum speed of expiration 
Normally= 400-600 litres

In disease:
PEFR decreases
FEV1 decreases
FEV1/FVC is less than 0.7
FVC can decrease

Question 2

Asthma: the process

Answer 2

1- Mast cell degranulation caused by IGE, drugs, chemicals..
2- Release of chemotactic factors- lead to the release of histamine, lysosomal enzymes, micro thrombi, complement prostaglandins
OR
release of spasmogens e.g. histamine- smooth muscle of bronchioles contract
3- Causes bronchial hypersensitivity
4- leads to inflammation, oedema, epithelial damage, mucus, plasma exudation

Question 3

Chronic bronchitis: the process

What happens when it is complicated?

Answer 3

Cough which produces sputum most days for 3 months consecutively for 2+ years

When complicated= production of mucopurulent i.e. mucus + pus

• in large airways: hyperplasia of mucous glands + goblet cells. Inflammation and fibrosis.
• in small airways: inflammation and fibrosis- more significant. appearance of goblet cells

Question 4

Emphysema: definition + different types

Answer 4

Increase in alveolar spaces at distal end of terminal bronchiole due to dilation or destruction of walls.

• centriacinar: closer to terminal bronchiole
• Periacinar- bulla appear= spaces between alveoli which are greater than 1 cm
• Panacinar- further from TB

Question 5

Emphysema: what usually occurs in the control of elastin fibres and how this is altered

Answer 5

usually:
- controlle by balance between elastase and anti-elastase.
- neutrophils and macrophages stimulate the growth of elastase
- elastase and repair mechanisms contribute to the alveolar repair framework

In smokers:

• anti-elastase inhibited
• increased production of elastase
• leads to tissue destruction

In individuals with alpha-1 antitrypsin deficiency:
-no anti-elastase

Question 6

Hypoxemia

Answer 6

Reduced O2 in tissues
symptoms:
-V/Q mismatch- usually about 0.8
reduced due to alveoli hypoventilation
-shunt: movement of blood from right to left hand site of heart without passing through ventilated area.
-diffusion impairment
-alveolar hypoventilation: reduced air in and out of the lungs. Increase PACO2 so increase PaCO2, reduced PA02,Pa02

Causes:

• Obstructed airways
• reduced respiratory drive
• loss of alveolar SA

Linked to:
Pneumonia
V/Q mismatch during bronchitis/bronchopneumonia
Shunt- bronchopneumonia- no ventilation in abnormal alveoli