Obstructive & Restrictive Lung Disease

Question 1

What is the aetiological seive for pathology?

Answer 1

Diseases can be congenital or genetic, however they may also be acquired. This may occur through:

- Infection
- Degenerative	
- Inflammation/Immune reactions	
- Vascular
- Iatrogenic (drugs, surgery, radiotherapy)
- Neoplastic
- Environmental 
- Trauma
- Idiopathic
- Metabolic
- Endocrine

Question 2

Give an overview of Normal Lung Anatomy & Histology?

Answer 2

In the lung there are 23 divisions:

• Trachea -> Bronchus (mainstem (2), Lobar (3,2), Segmental (10,8), Subsegmental)
• Bronchus -> Bronchiole -> Terminal Bronchioles ( Alveolar Sacs -> Alveoli

Question 3

What are some of the cell types involved in:Bronchi/Bronchioles?

Answer 3

Bronchi/Bronchioles:

• Respiratory Epithelial Cells
  
  • Tall columnar cells
  • Pseudostratified
  • Ciliated
• Goblet Cells
• Neuroendocrine Cells
• Basal Cells

Question 4

What are some of the cell types involved in: Alveoli?

Answer 4

Alveoli

• Alveolar Macrophages
• Type I Pneumocytes
• Type II Pneumocytes
• Fibroblasts
• Inflammatory Cells
• Endothelial Cells

Question 5

What is the difference between Obstructive & Restrictive Lung Disease?

Answer 5

A group of lung diseases which are chronic, diffuse and non-infectious.
Obstructive Lung Diseases include asthma, COPD (chronic bronchitis, emphysema, small airways disease/chronic bronchiolitis) & Bronchiectasis.
Restrictive Lung Diseases include idiopathic pulmonary fibrosis, Pneumoconiosis (asbestosis), Sarcoidosis & ‘honey-comb’ lung.

Question 6

What are some features of asthma?

Answer 6

Defined as increased responsiveness of airways to various stimuli leading to episodic bronchoconstriction which is at least partly reversible.
Diagnosis is made on clinical and physiological evidence, not histology.
There are several types including:
- atopic or allergic asthma
-> increased serum IgE
-> specific external allergens
- non-allergic asthma
-> normal serum IgE
-> non-specific triggers
- Others
Triggers can include environmental allergens, respiratory tract infections, exercise, cold weather, some drugs, inhaled chemicals.

Question 7

What is the mechanism of asthma?

Answer 7

In asthma, the trigger -> release of mediators (i.e. histamine) from mast cells -> immediate and late responses.
Acute/Immediate Response includes increased vascular permeability (oedema), increased mucus production and bronchospasm. The late phase response (4-8 hour later) includes chemotaxis of eosinophils, mast cells, lymphocytes, macrophages etc. causing ongoing inflammation and epithelial damage.

Question 8

What are some complications of asthma?

Answer 8

Complications of asthma include short term consequences (death, atelectasis, spontaneous pneumothorax and/or pneumomediastinum (rare)) as well as consequences of severe chronic asthma such as airway remodeling (fibrosis and irreversible obstruction) and chronic hypoxia leading to pulmonary hypertension and cor pulmonale.

Question 9

What are some characteristics of asthma attacks?

Answer 9

Attacks are characterised by wheezing, shortness of breath, coughing, anxiety and hyperinflated lungs. Status asthmaticus is acute severe asthma that is not responding to bronchodilators.

Question 10

Define emphysema?

Answer 10

Defined as abnormal, permanent enlargement of air spaces distal to the terminal bronchiole from destruction of the alveolar wall without fibrosis.
There are several types including:
	- Centriacinar (centrilobular) 
	- Panacinar (panlobular) 
	- Distal acinar (Paraseptal) 
	- Irregular

Question 11

What are the mechanisms and complications of emphysema?

Answer 11

Emphysema causes airway obstruction via loss of elastic recoil:
- loss of supporting elastic tissue around small airways leads to collapse
- Dynamic airway collapse during forced expiration
Some associated conditions are small airways disease and chronic bronchitis.
Complications of emphysema include hypoxia caused by airflow obstruction and loss of diffusion capacity (late), pulmonary hypertension, cor pulmonale, and pneumothorax.
Other forms of emphysema are Bullous emphysema, compensatory emphysema & interstitial emphysema.

Question 12

What is the definition of Chronic Bronchitis?

Answer 12

Defined clinically as persistent cough productive of sputum for at least 3 months in 2 consecutive years with no other cause.

Question 13

What is the pathogenesis of Chronic Bronchitis?

Answer 13

The pathogenesis is that chronic irritation occurs by inhaled substances including mainly cigarette smoke but rarely grain dust, silica etc.
This leads to increased mucus production –> larger airways.
Airway inflammation, scarring and narrowing can occur –> smaller airways

Question 14

What is the morphology of Chronic Bronchitis?

Answer 14

Morphology surrounding chronic bronchitis includes:

- excessive mucus due to hypertrophy of mucus secreting glands and increased 	Goblet cells.
- mild increase in lymphocytes, macrophages ad plasma cells --> oedema
- Peribronchial fibrosis in small airways and may have squamous metaplasia

Question 15

What are some complications of Chronic Bronchitis?

Answer 15

Complications of chronic bronchitis are:

- superimposed infective exacerbations
- hypoxia, pulmonary hypertension, cor pulmonale
- squamous metaplasia, squamous dysplasia - premalignant

Question 16

What is meant by small airways disease?

Answer 16

Small Airways Disease
Caused by cigarette smoke leading to chronic inflamation, fibrosis and obstruction of terminal bronchioles
- an important component of COPD

Question 17

What are some features of COPD?

Answer 17

> 90% caused by cigarette smoking
It generally involves emphysema, chronic bronchitis and small airways disease (and some reversible bronchospasm or asthma) in varying propertions.
It is characterised by slow progression with superimposed infective exacerbations. (Bacterial bronchitis & increased bronchospasm)

Question 18

What are some components of cigarette smoke?

Answer 18

Components of cigarette smoke:
- Particulate and gas phases
- 1000s of compounds including carcinogens and ciliotoxins in
- droplets of liquid and tar –nicotine, oxidants, >40 carcinogens
- gaseous component –room air, CO, volatilised hydrocarbons
A high fraction of the particulate matter is deposited and retained in the lower respiratory tract.

Question 19

What are some impacts of smoking on COPD?

Answer 19

Smoking is a risk factor for COPD, Respiratory bronchiolitis-associated interstitial lung disease, asthma exacerbations, lung cancer, acute bronchitis and pneumonia.
Smoking predisposes to pulmonary infections by:
– Inhibition of the muco-ciliary escalator
– Increased mucus
– Inhibition of leukocyte function
– Direct damage to the epithelial layer

Question 20

What are some general features of Bronchiectasis?

Answer 20

Irreversible, abnormal dilation of the bronchi/bronchioles.
It leads to severe destructive inflammation of the airways (severe or recurrent infection/obsturction) and loss of surrounding elastic tissue and muscle which exceeds contraction of fibrous tissue. The ability to clear organisms and fluid is also impaired.

Question 21

What are some common causes of Bronchiectasis?

Answer 21

Bronchiectasis can be caused by:
– Necrotising infections
- Staph aureus, Influenza, Aspergillus
– Obstruction (+ infection)
– Cystic fibrosis
– Cilia disorders
– Non-infectious inflammatory conditions
- Connective tissue diseases
- Graft versus host disease
- Allergic bronchopulmonary aspergillosis

Question 22

What is the general mechanism for Bronchiectasis?

Answer 22

In Bronchiectasis the dilated airways are often full of pus. Clinically it leads to the following pattern:

Severe cough productive of copious amounts of foul smelling sputum
↓
Episodic fever
↓
Shortness of Breath and cyanosis
↓
Cor Pulmonale
↓
Metastatic infection in the brain
↓
Amyloidosis (rare)

Question 23

What is a general overview of Restrictive (Interstitial) Lung Disease?

Answer 23

A group of diverse conditions sharing these features:
- Chronic, diffuse, non-infectious o Restrictive spirometry
- Inflammation and fibrosis of inter-alveolar septa (interstitium)
- Diffuse reticulo-nodular and/or ground-glass patterns on CXR
Prognosis varies from dismal to excellent, depending on the specific diagnosis. A specific cause or diagnosis is often not identified.

Question 24

Give some general features of idiopathic pulmonary fibrosis?

Answer 24

Idiopathic Pulmonary Fibrosis
- Cause unknown
- Histologic pattern is “usual interstitial pneumonitis”
– Interstitial inflammation, fibrosis at varying stages of development
- Inevitable progression to end-stage lung
- Mean survival 3 years