S8) Asthma Flashcards
What is asthma?
Asthma is a chronic inflammatory disorder of the airways, wherein widespread but variable airflow obstruction and increased airway responsiveness to a variety of stimuli occurs
Identify 5 defining characteristics of asthma
- Chronic inflammatory process
- Susceptibility
- Variable airflow obstruction
- Airway hyper-responsiveness
- Reversibility
Airways obstruction is a feature of both Asthma and Chronic Obstructive Pulmonary Disease (COPD).
How can one distinguish between the two conditions?
- Asthma: airway obstruction is often reversible (> 15% improve spontaneously, with bronchodilators/steroids)
- COPD: airway obstruction is not fully reversible (< 15% improve with treatment)
Identify the most influential cells in asthma
Asthma is a chronic inflammatory process driven by TH2 cells
What do TH2 cells do?
- Release cytokines, which attract and activate inflammatory cells (incl. mast cells and eosinophils)
- Activate B cells, which produce IgE
In a sensitised atopic asthmatic, exposure to antigen results in a 2 phase response.
Briefly, identify and describe these 2 phases
- Immediate response (< 20 mins)
- Late phase response (3 – 12 hours later)
What type of immune response is the immediate response to asthma?
The immediate response is an example of type 1 hypersensitivity
In 5 steps, describe the immediate response to asthma
⇒ Allergen interacts with specific IgE antibodies
⇒ Mast cell degranulation occurs
⇒ Mediators are released (histamine, prostaglandin D2, leukotriene)
⇒ Bronchial smooth muscle contracts
⇒ Bronchoconstriction occurs
What type of immune response is the late phase response to asthma?
The late phase response is an example of type IV hypersensitivity
The late phase response to asthma involves inflammatory cells.
What do they do?
Inflammatory cells release mediators and cytokines which cause airway inflammation
Identify 4 inflammatory cells involved in the late phase response to asthma
- Eosinophils
- Mast cells
- Lymphocytes
- Neutrophils
What do eosinophils do in the late phase response to asthma?
Eosinophils release Leukotriene C4 and other mediators, some of which are toxic to epithelial cells, and causes shedding of epithelial cells
Identify 5 events which causes the airway narrowing observed in asthma as a result of inflammation
- Mucosal oedema due to vascular leak
- Bronchial wall thickening due to inflammatory cell infiltration
- Mucous over-production
- Smooth muscle contraction
- Epithelium shedding
Identify 6 major precipitating factors for asthma
- Allergens e.g. pollen, animals hair/dander
- Cold air (airway hyper-responsiveness)
- Exercise
- Irritants e.g. car exhaust fumes, smoke, strong smells
- Emotional distress
- Viral infections
Identify 6 signs and symptoms of asthma
- Expiratory wheeze
- Cough
- Diurnal variability (worse at night & morning)
- Breathlessness
- Chest tightness
- Exercise induced wheeze
What do the spirometry tracings in an asthmatic patient usually show?
Obstructive condition – FEV1/FVC is reduced
