A Guide to Asthma - Medicine BM5 RCR1
- Created by: ex-Lechiayim
- Created on: 24-05-14 12:25
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- Asthma
- Epidemiology
- 5.4 million people in the UK receive treatment
- Affects approximately 1 in 10 children suffer
- Costs the NHS about £1billion p/a
- The UK has one of the highest prevelances and mortality rates
- Defined as a disease of the conducting airways associated with widespread airway narrowing
- Clinical Presentation
- Breathlessness
- Wheeze
- Cough
- Chest tightness
- Rhinitis
- Exacerbating factors
- Cold weather
- Exercise
- Pollution
- Working environment
- Common allergens (house dust mite, grass pollen, cats & dogs)
- Diurnal variation
- Risk factors
- Smoking
- FH of asthma
- Eczema
- Premature birth
- Low birth rate
- Maternal smoking
- Asthma can be classed as allergic and non-allergic
- Allergic asthma tends to have childhood onsent, test positive to IgE allergy tests and respond well to treatment
- Non-allergic asthma tends to have adult onset, react negatively to allergy tests and responds less well to treatment (higher doses of steroid required)
- Investigations
- PEFR
- Influenced by gender, age, height and co-morbidities
- 15% variability between days
- Will be reduced
- Spirometry
- FEV1 - voume of air forcefully expired from full inflation in the first second. mesaured in litres.
- FEV1/FVC ratio should be over 75%.
- FVC - total volume of air that can be forcefully expired from total lung capacity. If the majority of FVC exhalation takes over three seconds --> obstructive lung disease.
- PEFR
- Immunology
- Allergen is inhaled
- Mast cell degranulation
- Release of mediators
- Preformed e.g. histamine
- Newly formed e.g. leukotrienes & prostaglandins
- Release of mediators
- Activation of dendritic cells
- Antigen fragment is presented along with MHCII on cell-surface membrane
- Interacts with TH2 cell receptor
- interaction between CD80/CD86 & CD28 triggers co-simulatory signal that activates TH2 cell
- Activated TH2 cell secretes cytokines
- IL5 - Activates eosinophilic inflammatory process
- IL13 & IL4 activate B cells, which secrete antibodies and promote IgE class switch
- IgE released
- IgE activates FC epsilon R1 receptor on mast cells
- Mast cell degranulation
- Release of mediators
- Preformed e.g. histamine
- Newly formed e.g. leukotrienes & prostaglandins
- Release of mediators
- Mast cell degranulation
- IgE activates FC epsilon R1 receptor on mast cells
- IgE released
- Activated TH2 cell secretes cytokines
- interaction between CD80/CD86 & CD28 triggers co-simulatory signal that activates TH2 cell
- Interacts with TH2 cell receptor
- Antigen fragment is presented along with MHCII on cell-surface membrane
- Mast cell degranulation
- Allergen is inhaled
- Treatment
- 1.Short acting B2 agonist e.g. Salbutamol
- 2. Add an inhaled corticosteroid e.g. Beclometasone/ Fluticasone (200-800mcg)
- 3. Add a long-acting B2 agonist e.g. Salmeterol
- 4. Increase steroid dose (up to 20000mcg daily), or add a leukotriene receptor antagonist (e.g.montelukast), methylxanthine (e.g.theophylline) or anti-IgE drug (e.g. omalizumab)
- 5. Move to an oral steroid e.g. Prednisolone
- Airway smooth muscle contraction
- Bronchodilation: Circulating adrenalineacts on B2 adrenoceptors
- Bronchoconstriction: ACh acts on M3 receptors
- Parasympathetic
- Epidemiology
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