Obstructive lung disease Flashcards
How is lung volume measured? What are the normal values for tidal lung volume, inspiratory reserve and expiratory reserve?
Measured via spirometry Health male: Tidal lung volume = ~7ml/kg Inspiratory reserve = 2-3L Expiratory reserve = ~1L
How is forced expiratory volume measured?
Via vitalograph/pneumotachograph
How does FEV1/FVC ratio change in obstructive lung disease?
- FEV1 reduced (due to narrowed airways)
- FVC usually normal/closer to normal than FEV1
- Therefore FEV1/FVC ratio reduces
What are the characteristics of asthma?
Reversible airway obstruction
Smaller airways
Airway hyperresponsiveness
What are the essential features of asthma?
- Bronchoconstriction
- Secretion of mucus
- Airway inflammation
How is asthma diagnosed?
Spirometry –> calculate peak flow and FEV1/FVC ratio
What are the symptoms of asthma?
Troublesome cough PND Wheezing Breathing problems Colds >10 days Relief of symptoms with medication
What are the signs of asthma?
Wheezing during normal breathing Hyperexpansion of thorax Atopic dermatitis, eczema Increased nasal secretions Reduced peak expiration flow Airways reflexes are HYPERresponsive + prolonged
Why is airflow limited in asthma?
- bronchoconstriction
- oedema
- mucus hypersecretion
What happens during an asthma attack?
- smooth muscle around bronchioles constrict –> narrows airways
- inflammation produces oedema (thickens airway wall, increased narrowing)
- Excess mucus secretion narrows the airways
What causes asthma? (talk about immune cells, cytokines etc.)
- inhaled particles = antigens –> get trapped in mucus in airways
- antigen binds to IgE antibodies on APCs and stimulates T-helper cells
- however, there is hyperresponsiveness
- T cells secrete a surplus of ILs (Il3, 4 + 5)
- ILs stimulate B cells –> become plasma cells, make IgE
- IgE molecules specific to the antigen attach to mast cells
- Next exposure to antigen causes degranulation of IgE-primed mast cells
- release histamine and pro-inflammatory cytokines
- -> causes local inflammation, bronchoconstriction and mucus secretion
- repeated exposure and release of cytokines causes eosinophils and polymorphonuclear neutrophils to migrate into lung tissue (delayed asthma response occurs)
- -> eosinophils are now stimulated even further so there is more powerful bronchoconstriction and increased mucus secretion (mediated by vagus nerve)
- epithelial cells can be damaged by eosinophils = cilia are less effective in transporting mucus
Explain the MOA of bronchodilators. Give examples of shorting acting and long acting bronchodilators (beta-agonists).
Anti-muscarinics: reduce bronchoconstriction and hypersecretion
–> example: ipratropium + tiotropium - antagonise M3 receptors
Phosphodiesterase inhibitors: prevent formation and release of pro-inflammatory cytokines
–> example: theophylline + aminophylline
Beta-2-agonists: mimic adrenaline
—> Short-acting (Relievers) = SALBUTAMOL, terbutaline, bitolterol, fenoterol, orciprenaline
–> Long-acting (Preventers) = FORMOTEROL, bambuterol, clenbuterol, salmeterol
Describe anti-inflammatory agents used to control asthma.
- corticosteroids: reduce constriction, reduce expression of inflammatory genes
- -> examples: beclomethasone/fluticasone dipropionate - Leukotriene antagonists: reduce signalling
- Anti-IgE antibodies
- Monoclonal antibodies: reduce IgE receptors and stabilise mast cells
- -> example: Omalizumab - Magnesium: used in emergencies to reduce contractility of smooth muscle
Compare spacers and nebulisers in treating asthma.
Spacers:
- improve penetration of drugs
- reduce side effects from medication
Nebulisers:
- inhaled mist
- used in small children/severe asthma attack
Give examples of COPD.
Chronic bronchitis
Emphysema
