4.3 COPD + Restrictive Lung Diseases

Question 1

COPD is characterised by airflow limitation associated with chronic inflammatory response to particles or gases. It is usually used as an umbrella term for which two respiratory disorders?

Answer 1

1. Chronic bronchitis = excess mucous + 3 month cough for 2 years
2. Emphysema = permanent enlargement of airspaces, destruction of alveoli walls, loss of elastic recoil (bubbles)

Question 2

What are the symptoms of COPD?

Answer 2

Dyspnoea (shortness of breath on exertion or at rest for later stages)

Chronic cough with/without sputum production

Wheeze

Ankle oedema

Question 3

The expiratory airflow obstruction that characterises COPD has two causes. What are they?

Answer 3

1. Reduced functional airway diameter (asthma + chronic bronchitis)
2. Reduced elasticity of parenchyma (emphysema)

Question 4

Asthma causes airway dysfunction via potent inflammatory mediators and remodelling of the airway wall. What are the characteristics histologic findings of asthma that are collectively called airway remodelling?

Answer 4

Thickening of airway wall (accumulation of mucous in lumen)

Increase in size of submucosal glands + number of airway goblet cells

Sub-basement membrane fibrosis (deposition of collagen)

Increased vascularity (angiogenesis via eosinophil + macrophage recruitment)

Hypertrophy and/or hyperplasis of bronchial wall muscle with increased extracellular matrix (smooth muscle proliferation)

Question 4

Asthma causes airway dysfunction via potent inflammatory mediators and remodelling of the airway wall. What are the characteristics histologic findings of asthma that are collectively called airway remodelling?

Answer 4

Thickening of airway wall (accumulation of mucous in lumen)

Increase in size of submucosal glands + number of airway goblet cells

Sub-basement membrane fibrosis (deposition of collagen)

Increased vascularity (angiogenesis via eosinophil + macrophage recruitment)

Hypertrophy and/or hyperplasis of bronchial wall muscle with increased extracellular matrix (smooth muscle proliferation)

Question 5

What is atopic asthma?

Answer 5

Class example of IgE mediated asthma

Type 1 hypersensitivity response requiring priming

Hyperacute + most common asthma type

Question 6

What is chronic bronchitis?

Answer 6

Infection resulting in excessive mucous + productive cough lasting over 3 months per year for at least 2 consecutive years

Question 7

Chronic bronchitis is characterised by an obstructive outflow. How does this occur>

Answer 7

Bronchial airways suffer critical loss of functional airway diameter via:

1. Mucous (increase in submucousal glands + goblet cells)
2. Oedema (inflammation = swelling)
3. Decrease in elasticity (destruction + fibrosis)

Question 8

What are the potential complications of chronic bronchitis?

Answer 8

Mucocillary escalator compromised (loss of cilia, increase mucous production, squamous cell metaplasia)

Squamous cell carcinoma

Pulmonary hypertension

Question 9

What are the characteristics of emphysema?

Answer 9

Distal to terminal bronchiole

Abnormal enlargement of air spaces (uneven size of alveoli)

Destruction of bronchiolar / alveolar walls

Question 10

Emphysema is a product of smoking or air pollutants + a genetic predisposition. What other factors contribute to the development of emphysema + alveolar wall destruction?

Answer 10

1. Oxidative stress (increased apoptosis + senescence)
2. Inflammatory cells (release of inflammatory mediators)
3. Protease-antiprotease imbalance

Question 11

What is the importance of congenital alpha-1 antitrypsin (a1AT) deficiency in emphysema?

Answer 11

Genetic deficiency to the antiprotease a1AT = enhanced tendency to develop emphysema (compounded by smoking)

a1AT works by inactivating several enzymes, primarily elastase in lungs

Inflammation = inncreased neutrophil released proteases = increased elastin/collagen destruction without a1AT

Question 12

What are the results of emphysema on respiration?

Answer 12

1. Critical loss of air exchange surface area = reduced air exchange
2. Critical loss of elastic recoil = obstructive airflow

Question 13

What is the most common type of emphysema?

Answer 13

Centricacinar

Question 14

Chronic bronchitis and emphysema share a common cause in smoking. What are the key differences in their disease progression?

Answer 14

Chronic bronchitis:
1. Bronchiolar + bronchial injury
2. Continued insult + infection
3. Proximal

Emphysema:
1. Destruction of alveolar walls
2. Continued insult + NO infection
3. Distal