Lecture 7.1: Asthma

Question 1

What is Asthma?

Answer 1

A chronic disorder characterised by:
* Airway wall inflammation
* Reversible airflow obstruction
* Increase in airway responsiveness
* Airway wall re-modelling

Question 2

What is Extrinsic Asthma?

Answer 2

• Most common
• Early-onset
• Cause is Environmental Allergens
• Often FH atopy
• Type 1 (IgE) hypersensitivity

Question 3

What is Intrinsic Asthma?

Answer 3

• Adult onset
• Often associated with chronic
  bronchitis/cold/exercise-induced
• No FH atopy
• Skin test -ve

Question 4

What is Atopy?

Answer 4

It is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment

Question 5

How many people in the UK have Asthma?

Answer 5

5.4 million people in the UK receive treatment for asthma

Question 6

What are some Risk Factors for Asthma?

Answer 6

• Genetics
• Sensitisation to airborne allergens
• Air pollution
• Tobacco smoke (parental or in utero)
• Fungal spores
• ‘Hygiene’ hypothesis (too clean too
  early)

Question 7

Pathogenesis of Asthma (3)

Answer 7

• Airflow obstruction
• Airway inflammation
• Airway hyper-responsiveness to factors
  causing bronchoconstriction

Question 8

Structural Changes in Asthmatic Lungs/Airways (6)

Answer 8

1) Increased airway smooth muscle thickness
2) Damaged epithelium
3) Thickened basement membrane
4) Increased mucus
5) More WBCs in lamina propria
6) More glands

Question 9

Why does airway wall re-modelling occur in Asthma?

Answer 9

Structural changes due to chronic inflammation

Question 10

What cells and mediators are involved in chronic inflammation? (5)

Answer 10

• Cytokines & Leukotrienes
• CD4+ (Helper T-Cells)
• Eosinophils
• Mast Cells
• Growth Factors

Question 11

Allergic Asthma: Molecular
Pathophysiology from Allergen to Mast Cell

Answer 11

• Allergen
• Dendritic Cell
• CD4+ Cell (T-Helper Cell)
• (IL-4,5,13—>) Plasma Cell
• (IgE—>) Mast Cell
• Produces histamines, leukotrienes,
  prostaglandin D2

Question 12

Allergic Asthma: Molecular
Pathophysiology from Allergen to Eosinophil

Answer 12

• Allergen
• Dendritic Cell
• CD4+ Cell (T-Helper Cell)
• (IL-5—>) Eosinophil
• Produces cytokines and leukotrienes

Question 13

Allergic Asthma Pathophysiology: Acute

Answer 13

• Bronchospasm
• Oedema
• Increased mucus secretion
• Airway obstruction
• Increased WOB (work of breathing)
• Hypoventilation
• Respiratory failure

Question 14

Allergic Asthma Pathophysiology: Chronic

Answer 14

• Hyperresponsiveness
• Inflammation
• SM hypertrophy
• Airway obstruction
• Increased WOB (work of breathing)
• Hypoventilation
• Respiratory failure

Question 15

Phases in Extrinsic Asthma: Early (15 minutes)

Answer 15

• Allergen crosslinks two IgEs on mast.
  cell which degranulate releasing
  histamine etc

Question 16

Phases in Extrinsic Asthma: Late (4 hours)

Answer 16

• Inflammatory mediators from mast cells
  activate macrophages
• This leads to chemotaxis of PMNs into
  the mucosa lining the bronchia.
• These PMNs release histamine,
  prostaglandins, PAF & other cytokines

Question 17

Phases in Extrinsic Asthma: Prolonged Hyperreactivity (days)

Answer 17

• Exaggerated response of airway after
  further exposure to the allergen
• Inflammatory cells in the bronchial
  walls continue giving loss of epithelial
  cells

Question 18

What are some triggers of smooth muscle contraction in airway hyper-responsiveness? (4)

Answer 18

• Muscarinic agonists
• Histamine
• Cold Air
• Arachadonic acid metabolites (eg
  prostaglandins)
• Drugs
• Emotions
• Atmospheric Pollution
• Genetic Factors

Question 19

Diagnosis of Asthma

Answer 19

• Spirometry establishes diagnosis and
  aids in management
  More than one of the following recurrent symptoms:
  1. Wheeze
  2. Breathlessness
  3. Chest tightness
  4. Cough
  5. Variable airflow obstruction

Question 20

What is a Wheeze?

Answer 20

• High-pitched, musical sound in
  expiration
• Originates in narrowed small airways
• Variable intensity and tone (polyphonic)
  in asthma

Question 21

What is Tracheal Tug?

Answer 21

It is an abnormal downward movement of the trachea accompanied by in-drawing toward the thoracic cavity during inspiration

Question 22

Common Presenting Complaints when being diagnosed with Asthma

Answer 22

• Cough
• Chest tightness
• Wheeze
• SOB
• Disturbance to everyday life
• Precipitating factors (cold air, exercise)

Question 23

Common Past Medical History when being diagnosed with Asthma

Answer 23

• Hay fever
• Eczema
• Pre-natal smoke exposure

Question 24

Family History when being diagnosed with Asthma

Answer 24

• Asthma
• Other atopy
• Smoking

Question 25

Occupational History when being diagnosed with Asthma

Answer 25

• Farms
• Wood
• Coal burning fires
• Mining
• Asbestos Exposure

Question 26

Barrel Chest Deformity

Question 27

Primary Prevention of Asthma

Answer 27

• Stop smoking
• Wood/laminate flooring (questionable)
• Cleaning ( questionable)
• Fresh air
• Breast feeding
• Reduce exposure to allergens
• Weight loss
• Diet (questionable)

Question 28

What Drugs can be used to Treat Asthma?

Answer 28

Airway Relaxants (‘relievers’):
* Beta2 agonists (short & long acting)
* Muscarinic antagonists (ipratropium
bromide)
* Theophylline/aminophylline

Anti-inflammatory agents (‘preventers’):
* Corticosteroids
* Leukotriene receptor antagonist

Question 29

Mild Acute Asthma (Adults): Pulse? Resp Rate? PEFR? Wheezing?

Answer 29

• Pulse < 110
• Respiratory rate < 25
• Speech normal
• Minimal wheeze
• PEFR > 75% predicted

Question 30

Moderate Acute Asthma (Adults): Pulse? Resp Rate? PEFR? Wheezing?

Answer 30

• Pulse < 110
• Respiratory rate < 25
• Speech normal
• Wheeze + +
• PEFR > 75-50% predicted

Question 31

Severe Acute Asthma (Adults): Saturation? Pulse? Resp Rate? PEFR? Wheezing?

Answer 31

• Pulse ≥ 110/min
• Respiratory rate ≥ 25/min
• Cannot complete sentences in one
  breath
• PEFR 33-50% best or predicted
• Wheeze + + +