Asthma Flashcards
2 types
Allergic/eosinophilic
Non-Allergic/Non-Eosinophilic
What causes Non-allergic asthma
Exercise, cold air, stress
Obesity, Smoking associated
Subtypes of allergic asthma
Extrinsic (atopic)
Intrinsic
Describe extrinsic atopic asthma
Most frequent
Occurs in atopic individuals and is commonly accompanied by eczema
When does intrinsic asthma start and what usually triggers it
Often starts middle-aged and triggered by respiratory infection
Examples of occupational agents (extrinsic cause) that can can non atopic individuals to develop asthma (middle aged)
Flour dust and additives in flour
Toluene diisocyanate
Intolerance to NSAIDs (like aspirin)
Block the protective effect of endogenous catecholamines
What is atopy
Individuals who rapidly develop IgE against common environmental antigens
Examples of environmental antigens that cause rapid IgE development in atopic individuals
House dust mites
Grass pollen
Fungal spores
True or false:
Airway hyper-responsiveness and prevalence of asthma is linked to elevated IgE serum levels
True
True or False
Asthma involves just one gene
False
Asthma is not one single gene but several genes in combination with environmental factors
Give example of gene associated with asthma
ADAM33 - associated with airway hyper-responsiveness and tissue remodelling
Genes controlling production of cytokines IL-3,4,5,9,13
Examples of environmental factors that increase chance of asthma
Early childhood exposure to allergens and maternal smoking has a major influence on IgE production
Growing up in a ‘clean’ environment may predispose towards an IgE response to allergens
Risk factors of asthma
- Personal history of atopy
- Family history of asthma or atopy
- Obesity
- Inner-city environment
- Premature birth
- Socio-economic deprivation
What is primary abnormality in asthma
Narrowing of airway due to smooth muscle contraction, thickening of airway wall by cellular infiltration and pressure of secretions within the airway lumen
Pathophysiology
Copious mucus secretion Inflammation Contraction of bronchial muscle Allergen recognised by Th2 cells Release of Interleukin (IL)-4, 5, 13
Role of IL-4
Stimulates eosinophils and stimulates B lymphocytes
B lymphocytes produce IgE, which causes mast cells to release histamine
Histamine causes bronchoconstriction
Role of IL-5
Stimulates eosinophils
Role of IL-13
Stimulates mucus secretion
What is asthma
Chronic, inflammatory disease that is characterised by reversible airway obstruction
Signs and symptoms of asthma
Wheezing
Shortness of breath
Coughing
Remember to ask patient for Hx of atopy e.g. hayfever, eczema
Triggering factors of asthma
Dust/pets/vapours
Emotion
Drugs e.g. beta-blockers
Investigations of asthma
Peak expiratory flow rate: note diurnal variation Sputum sample ABG (in emergency) Spirometry (for obstructive defects) Bloods (increased IgE, FBC) CXR - pneumothorax, consolidation
Conservative treatment
Patient education Advice on inhaler technique Avoidance of triggering factors Annual asthma review Influenza vaccine required
**Medical treatment
British Thoracic Society Guidelines
(British Thoracic Society Guidelines)
Step 1: salbutamol/short-acting beta-2 receptor agonist
Step 2: Add Beclometasone (inhaled steroid)
Step 3: Add Salmeterol (long acting beta-2 receptor agonist) + increased total dose of inhaled steroid
Step 4: Add increased dose of inhaled steroid and consider adding additional therapy
Step 5: Instead oral prednisolone (steroid) and high dose inhaled steroid (refer to specialist)
Example of Step 4 medical treatment additional therapy
Theophylline (xanthine derived bronchodilator that inhibits phosphodiesterase)
Montelukast (leukotriene receptor antagonist)
First step of asthma medical treatment
salbutamol/short-acting beta-2 receptor antagonist
Treatment of acute asthma
O SHIT
Oxygen
Salbutamol
Hydrocortisone
Ipratropium
Theophylline
Complications
Death
Disturbed sleep
Persistent cough
Side effects of steroids
Weight gain Thinning of skin Striae formation Cataracts Cushing's syndrome
