Obstructive Lung Diseases

Question 1

Definition of obstructive lung diseases

Answer 1

• limitation of/increased resistance to airflow
• due to partial/complete obstruction
• normal total lung capacity
• reduced expiratory flow rate
• increase in total lung volume - barrel chest

Question 2

Examples of obstructive lung disease

Answer 2

1. Bronchiectasis
2. Asthma
3. COPD
   - Emphysema
   - Chronic bronchitis
   - Bronchiolitis

Question 3

Features of bronchiectasis

Answer 3

• permanent abnormal dilation of bronchi
• airways dilated + may contain purulent secretions - chronic inflammation of wall with loss of normal epithelium - inf spreads from bronchi to surrounding lung
• recurrent infection, hemoptysis

Question 4

Bronchiectasis is predisposed by (2)

Answer 4

1. Interference with drainage of secretions eg obstruction, abnormality in mucus viscosity (cystic fibrosis), immotile cilia syndrome
2. Recurrent & persistent infection

• obstruction + infection - persistent inflammation & damage to bronchial walls

Question 5

Complications of bronchiectasis (3)

Answer 5

1. Chronic suppuration +/- lung abscess
2. Hematogenous spread of infection
3. Secondary amyloidosis

Question 6

Features of asthma

Answer 6

• characterised by
  1. Hyperresponsiveness of airway
  2. Recurrent reversible airway obstruction - bronchospasm, mucous plugging
  3. Chronic airway inflammation

Question 7

Types of asthma (2)

Answer 7

1. Extrinsic/Allergic
   - IgE mediated type I hypersensitivity
   - environmental allergens, occupational
2. Intrinsic
   - triggered by non-immune stimuli eg cold, exertion
   - prior airway inflammation - lower threshold of vagal receptors to irritants

Question 8

Triggers of asthma (3)

Answer 8

1. Childhood - often stimulated by viral infection, may abate with age
2. Occupational
3. Drugs

Question 9

Pathogenesis of allergic asthma (2)

Answer 9

1. Type 1 hypersensitivity reaction
   (A) Previous sensitization - IgE mediated response
   - activation of mast cells + direct stimulation of nerve receptors
   - release histamine - recruit eosinophils, bronchoconstriction, increased mucus secretion, increased vasc perm
   (B) Recruited eosinophils & T helper cells release more mediators - amplify & sustain inflammatory response
2. Airway remodelling - structural changes due to repeated bouts of allergen exposure/immune reaction

Question 10

Structural changes in asthma airway remodelling (5)

Answer 10

1. Hypertrophy of bronchus smooth muscle
2. Hypersecretion of mucus (more goblet cells)
3. Mucosal edema
4. Infiltration of bronchial mucosa by eosinophils, mast cells, lymphoid cells, macrophages
5. Collagen deposition beneath bronchial epithelium

Question 11

Morphology of asthma

Answer 11

• mucosal & submucosal edema
• leukocytic infiltrate
• epithelial cell necrosis
• bronchial wall fibrosis

Question 12

Features of COPD

Answer 12

• chronic obstructive pulmonary disease
• characterised by airflow limitation that is not fully reversible
• airflow limitation is usually progressive & associated with abnormal inflammatory response

Question 13

Pathologies contributing to COPD

Answer 13

1. Emphysema
2. Chronic bronchitis
3. Bronchiolitis

Question 14

Risk factors for COPD

Answer 14

• smoking
• recurrent childhood infections
• occupational exposure

Question 15

Definition of emphysema

Answer 15

• permanent dilation of air spaces distal to the terminal bronchiole
• with destruction of tissue
• in the absences of scarring/fibrosis
• results in loss of elastic recoil in lungs + reduction in gas exchange capacity

Question 16

Pathogenesis of emphysema

Answer 16

1. Normal connective tissue modelling is governed by a protease-antiprotease balance
   - neutrophil proteases released at site of inflam - parenchymal destruction
   - proteases are inactivated by extracellular protease inhibitors in the lungs eg alpha-1-antitrypsin
2. Decreased alpha-1-antitrypsin - impaired inhibition of proteases
   - deficiency can be congenital or acquired (inactivated by ROS from inflam, smoking)
   - smoking - persistent irritation - more inflam cells - more mediators, enzymes
3. Increased protease levels + decreased protease inhibitor levels - destruction of elastic tissue, alveolar walls - premature collapse of bronchioles during expiration - air trapping

Question 17

Clinical presentations of emphysema

Answer 17

• pink puffers
• barrel chested due to air trapping
• dyspneic with obviously prolonged expiration
• breaths through pursed lips to help maintain positive airway pressure

Question 18

Effects & complications of emphysema (4)

Answer 18

1. Respiratory failure
2. Cor pulmonale
3. Pneumothorax
4. Peptic ulcer (2 to hypercapnia)

Question 19

Definition of chronic bronchitis

Answer 19

• persistent cough
• productive of sputum
• on most days for 3 months of a year for ≥2 successive years

Question 20

Clinical presentations of chronic bronchitis

Answer 20

• blue bloaters
• mild cyanosis
• dyspnea
• persistent productive cough

Question 21

Effects & complications of chronic bronchitis

Answer 21

• airway obstruction related to luminal narrowing & mucous plugging - alveolar hypoventilation
  1. Respiratory failure
  2. Cor pulmonale
  3. Respiratory infections (accumulation of mucus)
  4. Malignancy (metaplasia, dysplasia)

Question 22

Features of bronchiolitis

Answer 22

• inflammation of airways <2mm in diameter
• macrophages & lymphoid cells infiltrate airway wall
• may progress to scarring & narrowing of airways - functional airway obstruction

Question 23

Features of pink puffers

Answer 23

• pink complexion, breathing effort - not yet hypoxic

- compensate by hyperventilation

Question 24

Features of blue bloaters

Answer 24

• V/Q mismatch, unable to shift enough air - poor ventilation (hypoxemia + hypercapnia)
• heart works harder to perfuse lung - RHF, tachycardia, edema
• over a long period - brainstem resets - hypoxemia is the driver of breathing reflex - control O2 delivery & monitor closely