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Asthma – DR DEACPIMP Definition Chronic immune response Airway obstruction – bronchoconstriction Airway hyperresponsiveness Reversible with β-2 agonists Risk Factors Other atopic disorders (eczema, allergic rhinitis, atopic dermatitis) Family history Hygiene hypothesis Smoking/parental smoking Differential diagnoses COPD Bronchitis Bronchiectasis α-1 anti-trypsin deficiency Epidemiology 1/10 children 1/20 adults Hygiene hypothesis – less common if rural, high pathogen exposure, natural birth, fewer antibiotics Aetiology Genetic Environmental triggers o Exercise o Emotion o Cold air o Infection o Allergens Clinical features Dyspnoea Expiratory wheeze Diurnal variation – worse when wake up/wake up with cough Triggered by environmental stimuli Reversible with salbutamol (short-acting beta 2 agonists) Reduced PEV (peak expiratory volume) – peak flow Pathophysiology Chronic: increased IgE and CD4 Th2 cells in circulation Allergen/stimulus is presented on antigen-presenting cells Activated CD4 cells and antibodies (IgE) activate mast cells Mast cell degranulation causes release of mediators such as cytokines and histamine that cause eosinophil recruitment and inflammation, and also smooth muscle contraction/bronchoconstriction Chronic inflammation leads to hypertrophy of smooth muscle Fibrosis/remodelling Hyperplasia of goblet cells (secrete mucus) Damaged epithelia (allows future allergens easy access) Investigations Peak flow – PERF or PEV is below 80% of expected (CHECK) Peak flow diary Spirometry shows obstructive pattern (FEV1 <80% predicted, FEV1% <70%) Reversibility: 4 puffs (400mg) of salbutamol, wait 15min, FEV should improve by 15% or 400ml. PEFR improves by 20% CXR to rule out other causes Management Short acting beta-2 agonist (Ventolin/salbutamol) for exacerbations. 1 puff per 30 seconds. If need more than twice a week, is poorly controlled o Act on beta-2 receptors, and cause smooth muscle relaxation o Inhibit release of mediators from mast cells Long acting beta-2 agonist – salmeterol, taken twice daily as adjunct therapy. Side effects: tremor, tachycardia Theophylline – given if beta agonists don’t work, also cause smooth muscle relaxation Inhaled steroids – Glucocorticoids such as beclomethasone – act as anti-inflammatory drugs, prevent Th2 recruitment of eosinophils and IgE release Oral steroids – prednisolone – not routinely used, but can be if other options don’t work Monoclonal antibodies – anti IgE: omalizumab, in allergic asthma and allergic rhinitis Prognosis Many asthmatics have poor control, and poor inhaler technique Asthma attack can be fatal Brittle asthma: generally well controlled, but have flare ups and asthma attacks anyway