Asthma Comprehensive Notes

Asthma – Comprehensive Notes 1. Definition Asthma is a constriction of the airway due to inflammation and muscular contraction of the bronchioles, leading to airflow obstruction. 2. Pathophysiology and Symptoms Key Processes • Bronchospasm and airway hyper-responsiveness • Excessive mucous production • Chronic inflammation • Airflow obstruction Common Symptoms • Wheeze • Shortness of breath (SOB) • Chest tightness • Cough 3. Causes/Triggers • Allergens: Dust mites, pollen, animal dander, ingested allergens • Viral infections • Stress • Environmental pollutants • Exercise • Cold air • Drugs: Beta-blockers, NSAIDs 4. Allergic Asthma – Mechanism 1. Allergen → activates dendritic cells and T helper cells 2. Cytokine release → stimulates: 3. B cells → IgE antibody production 4. Eosinophils → inflammation and recruitment of more immune cells 5. Mast cells → express IgE receptors, amplifying the immune response 1 Chemical Mediators of Bronchospasm • Histamine • Cysteinyl-leukotrienes • Prostaglandin D2 5. Asthmatic Responses Early Asthmatic Response • Occurs immediately after allergen exposure • Characterized by bronchospasm Late Asthmatic Response • Occurs 6–24 hours after exposure • Characterized by: • Bronchial inflammation • Vasodilation • Oedema • Excess mucus • Further bronchospasm Role of Chemokines and Chemotaxins • Recruit eosinophils and mononuclear cells → amplify inflammation Inflammatory Mediators • Leukotrienes (can cause anaphylaxis in excess) • Cytokines: IL-3, IL-4, IL-5 • Chemokine: IL-8 • Toxic proteins → epithelial cell damage 6. Diagnosis Methacholine Challenge Test • Used when spirometry is inconclusive • Assesses airway hyper-responsiveness Procedure: 1. Patient inhaled with increasing doses of methacholine 2. Spirometry performed before and after 3. Bronchoconstriction observed if lung function drops >20% 4. Bronchodilator administered to reverse effects 2 7. Guidelines for Asthma Management • SIGN/BTS joint guidance 158 – chronic & acute management • NICE guideline 80 – chronic management • NICE quality standard 25 – defines clinical best practice 8. Goals of Chronic Asthma Management • No daytime symptoms • No night-time wakening due to asthma • No need for rescue medication • No asthma attacks • No limitation of activity, including exercise • Normal lung function / PEF >80% • Minimal side effects from medications 9. Stepwise Asthma Management Step 1 – Preventer • Low-dose ICS (e.g., Beclometasone ≤400mcg/day) Step 2 – Initial Add-on • LABA (e.g., Salmeterol, Formoterol) • Only continued if effective Step 3 – Additional Control • Increase ICS to medium dose or add LTRA • Stop LABA if ineffective Step 4 – Specialist Therapies • High-dose ICS • Additional preventers (LTRA, MR theophylline, oral Beta-2 agonists) • Long-term corticosteroids if needed Step 5 – Reliever • SABA as needed (Salbutamol, Terbutaline) 10. Medications Short Acting Beta-2 Agonists (SABA) • Mechanism: Activate β2-adrenergic receptors → smooth muscle relaxation → bronchodilation 3 • Examples: Salbutamol, Terbutaline • Side Effects: Tachycardia, palpitations, tremor, sweating, insomnia Inhaled Corticosteroids (ICS) • Mechanism: Promote anti-inflammatory gene transcription in epithelial cells • First-line: Beclometasone dipropionate Long Acting Beta-2 Agonists (LABA) • Mechanism similar to SABA but longer action • Examples: Salmeterol, Formoterol (BD), Indacaterol, Vilanterol (OD) Leukotriene Receptor Antagonists (LTRA) • Mechanism: Block leukotrienes → reduce bronchoconstriction, inflammation, mucus • Examples: Montelukast, Zafirlukast • Side Effects: Zafirlukast → liver toxicity Theophylline • Mechanism: Smooth muscle relaxation + suppress airway hyper-responsiveness • Cautions: Narrow therapeutic window, drug interactions, smoker metabolism issues • Brands: Uniphyllin Continus, Neulin SA, Slo-phyllin, Aminophylline (Phyllocontin Continus) Oral Corticosteroids • Example: Prednisolone • Use lowest effective dose • Long-term risks: Bone loss, gastrointestinal issues → consider calcium, gastroprotection 11. Monitoring and Assessment • Symptom control • Lung function (PEF diary) • Asthma attacks, steroid use, missed days • Inhaler technique • Bronchodilator use • Personalised asthma action plan Key Assessment Questions - Sleep disruption due to asthma? - Daytime asthma symptoms? - Interference with daily activities? 12. Environmental Considerations • CFCs banned → hydrofluorocarbons still potent greenhouse gases • Environmental-friendly inhalers: Dry powder inhalers (Easyhaler, Accuhaler, Turbohaler) • Reduce carbon footprint by: • Smoking cessation 4 • Exercise • Good inhaler technique • Prescribe devices with lower environmental impact 13. MART (Maintenance and Reliever Therapy) • Same inhaler used for maintenance + reliever • Examples: Budesonide/Formoterol (Symbicort, DuoResp Spiromax), BDP/Formoterol (Fostair pMDI) 5