Obstructive Airway Diseases

Question 1

What three entities is COPD an umbrella term for?

Answer 1

• Chronic bronchitis
• Emphysema
• Small airway disease - asthma

Question 2

What two major groups do obstructive airway diseases fall into?

Answer 2

• Localised
• Diffuse

Question 2

Describe the epidemiology of COPD.

Answer 2

• Principal cause is cigarette smoking
• Majority of COPD patients have emphysema (air space destruction) and chronic bronchitis (airway inflammation)

Question 3

What is chronic bronchitis characterised by?

Answer 3

• Productive cough for at least 3 months for 2 consecutive years
• In absence of any other identifiable cause

Question 4

Apart from smoking, what are some other causes of chronic bronchitis?

Answer 4

• Air pollutants
• Respiratory tract infections
• Toxic industrial inhalants

Question 5

What are the clinical features of chronic bronchitis?

Answer 5

• Usually affects middle-aged men who smoke heavily
• EARLY SYMPTOMS - Prolonged, persistent, productive cough
• LATER STAGE - Dyspnea on exertion

Question 6

Describe the pathogenesis of chronic bronchitis. PART 1

Answer 6

• Irritation by inhaled air pollutants
• Causes inflammation
• Infiltration by T lymphocytes, macrophages, neutrophils

Question 7

Describe the pathogenesis of chronic bronchitis. PART 2

Answer 7

• Hyperplasia/hypertrophhy of submucosal glands in large airways - develop in response to inhaled irritants and proteases from neutrophils

Question 8

Describe the pathogenesis of chronic bronchitis. PART 3

Answer 8

• Increase in goblet cells in airways - excess mucus production - inflammation and fibrosis of bronchial walls - leads to airway obstruction

Question 9

What are the microscopic appearances of chronic bronchitis?

Answer 9

• Hyperplasia/hypertrophy of submucosal mucus-secreting glands
• Chronic inflammation of airways - infiltration by lymphocytes
• Increase in number of goblet cells
• Squamous metaplasia
• Narrowing of bronchioles - excess mucus production, inflammation, oedema and fibrosis

Question 10

What are the main complications ffrom chronic bronchitis?

Answer 10

• Progress to COPD
• If prolonged, lead to cor pulmonale with cardiac failure
• Squamous metaplasia, dysplasia of respiratory epithelium - environment for cancerous transformation

Question 11

Describe emphysema.

Answer 11

• Abnormal irreversible dilation of airspaces distal to terminal bronchioles
• Caused by destruction of airspace walls

Question 12

What factors can lead to emphysema?

Answer 12

• Smoking and genetic predispositions
• Release of inflammatory mediators
• Alpha-1 antitrypsin deficiency leading to protease-antiprotease imbalance
• Oxidative stress

Question 13

Describe the gross appearance of tissues affected by emphysema.

Answer 13

• Usually severely involves upper two thirds of lungs
• Voluminous lungs from advanced emphysema
• Bullae in irregular/distal acinar emphysema

Question 14

Describe centriacinar emphysema.

Answer 14

• Most common type clinically
• Seen in smokers
• Usually more severe in upper lobes due to alpha1-antitrypsin deficiency
• Involvement of central part of acinus with sparing of alveoli

Question 15

Describe panacinar emphysema.

Answer 15

• Involvement of entire acinus
• Seen with alpha1-antitrypsin deficiency
• More severe in lower lobes at base of lung (region more perfused - more distribution of neutrophils)

Question 16

Describe distal acinar/paraseptal emphysema.

Answer 16

• Distal part of acinus affected - sparing of proximal part of acinus
• Seen in smokers
• Involvement of lung adjacent to pleura
• Associated with development of spontaenous pneumothorax

Question 17

Describe irregular emphysema.

Answer 17

• Associated with fibrosis/scarring
• Most common type histologically

Question 18

What would be seen under a microscope in emphysema?

Answer 18

• Abnormally large alveoli separated by thin septa
• Destruction of alveolar walls
• Loss of attachments of alveoli to outer wall of small airways
• Inflammatory changes
• Bullae in advanced emphysema

Question 19

Describe bronchial asthma

Answer 19

• Characterised by reversible bronchoconstriction in response to various stimuli

Question 20

Apart from bronchoconstriction, what can also occur in bronchial asthma?

Answer 20

• Inflammation of bronchial walls
• Mucus hypersecretion

Question 21

How can bronchial asthma be classified?

Answer 21

• TYPE OF ANTIGEN - atopic (allergic) and non-atopic (without evidence of allergen sensitisation)
• TRIGGER (seasonal, occupational, exercise/drug/smoking induced)

Question 22

Describe atopic asthma.

Answer 22

• Most common - begins in childhood
• Family history of asthma/allergies common
• IgE mediated hypersensitivity
• Triggered environmentally - e.g dust, pollen, food
• Skin test - exposure to allergen causes immediate wheal-and-flare reaction

Question 23

Describe non-atopic asthma.

Answer 23

• Skin tests usually negative
• Family history less common
• No causative exogenous factors identified - no allergen sensitisation
• TRIGGERS - Respiratory infections due to viruses, inhaled pollutants

Question 24

What occurs in sensitisation and inflammation during bronchial asthma?

Answer 24

• Genetically predisposed individuals - sensitised against multiple allergens
• Allergen taken by APCs - triggers hypersensitivity response.
• Promotes IgE production by B cells

Question 25

What is the gross appearance in bronchial asthma?

Answer 25

• Airway occlusion by mucus
• Small areas of atelectasis and some distension of lungs (due to overinflation)