Lecture 7.1: Asthma Flashcards
What is Asthma?
A chronic disorder characterised by:
* Airway wall inflammation
* Reversible airflow obstruction
* Increase in airway responsiveness
* Airway wall re-modelling
What is Extrinsic Asthma?
- Most common
- Early-onset
- Cause is Environmental Allergens
- Often FH atopy
- Type 1 (IgE) hypersensitivity
What is Intrinsic Asthma?
- Adult onset
- Often associated with chronic
bronchitis/cold/exercise-induced - No FH atopy
- Skin test -ve
What is Atopy?
It is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment
How many people in the UK have Asthma?
5.4 million people in the UK receive treatment for asthma
What are some Risk Factors for Asthma?
- Genetics
- Sensitisation to airborne allergens
- Air pollution
- Tobacco smoke (parental or in utero)
- Fungal spores
- ‘Hygiene’ hypothesis (too clean too
early)
Pathogenesis of Asthma (3)
- Airflow obstruction
- Airway inflammation
- Airway hyper-responsiveness to factors
causing bronchoconstriction
Structural Changes in Asthmatic Lungs/Airways (6)
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
Why does airway wall re-modelling occur in Asthma?
Structural changes due to chronic inflammation
What cells and mediators are involved in chronic inflammation? (5)
- Cytokines & Leukotrienes
- CD4+ (Helper T-Cells)
- Eosinophils
- Mast Cells
- Growth Factors
Allergic Asthma: Molecular
Pathophysiology from Allergen to Mast Cell
- Allergen
- Dendritic Cell
- CD4+ Cell (T-Helper Cell)
- (IL-4,5,13—>) Plasma Cell
- (IgE—>) Mast Cell
- Produces histamines, leukotrienes,
prostaglandin D2
Allergic Asthma: Molecular
Pathophysiology from Allergen to Eosinophil
- Allergen
- Dendritic Cell
- CD4+ Cell (T-Helper Cell)
- (IL-5—>) Eosinophil
- Produces cytokines and leukotrienes
Allergic Asthma Pathophysiology: Acute
- Bronchospasm
- Oedema
- Increased mucus secretion
- Airway obstruction
- Increased WOB (work of breathing)
- Hypoventilation
- Respiratory failure
Allergic Asthma Pathophysiology: Chronic
- Hyperresponsiveness
- Inflammation
- SM hypertrophy
- Airway obstruction
- Increased WOB (work of breathing)
- Hypoventilation
- Respiratory failure
Phases in Extrinsic Asthma: Early (15 minutes)
- Allergen crosslinks two IgEs on mast.
cell which degranulate releasing
histamine etc
Phases in Extrinsic Asthma: Late (4 hours)
- 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
Phases in Extrinsic Asthma: Prolonged Hyperreactivity (days)
- Exaggerated response of airway after
further exposure to the allergen - Inflammatory cells in the bronchial
walls continue giving loss of epithelial
cells
What are some triggers of smooth muscle contraction in airway hyper-responsiveness? (4)
- Muscarinic agonists
- Histamine
- Cold Air
- Arachadonic acid metabolites (eg
prostaglandins) - Drugs
- Emotions
- Atmospheric Pollution
- Genetic Factors
Diagnosis of Asthma
- 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
What is a Wheeze?
- High-pitched, musical sound in
expiration - Originates in narrowed small airways
- Variable intensity and tone (polyphonic)
in asthma
What is Tracheal Tug?
It is an abnormal downward movement of the trachea accompanied by in-drawing toward the thoracic cavity during inspiration
Common Presenting Complaints when being diagnosed with Asthma
- Cough
- Chest tightness
- Wheeze
- SOB
- Disturbance to everyday life
- Precipitating factors (cold air, exercise)
Common Past Medical History when being diagnosed with Asthma
- Hay fever
- Eczema
- Pre-natal smoke exposure
Family History when being diagnosed with Asthma
- Asthma
- Other atopy
- Smoking
