Asthma Flashcards
What is asthma? Characterised by? (x3)
Chronic inflammatory airway disease characterised by variable reversible airway obstruction, airway hyperresponsiveness and bronchial inflammation.
What is the aetiology of asthma? (x2)
• GENETICS: family history and almost all patients show atopy (genetic susceptibility to allergic disease with Th2 cell production of IgE on exposure to allergens). There is genetic heterogeneity – multiple chromosomal loci • ENVIRONMENTAL FACTORS: house dust mite, pollen, pets, cigarette smoke, viral respiratory tract infection, Aspergillus, occupation allergens
What are precipitating factors in asthma exacerbations? (x5)
Cold, viral infection, drugs such as beta-blockers and NSAIDs, exercise, emotions.
!!! What is the pathophysiology of asthma? (x3)
- EARLY PHASE (up to 1hr): exposure to inhaled allergens in a pre-sensitised individual results in cross-linking of IgE antibodies on mast cells and release of histamine, prostaglandin D2, leukotrienes and TNF-alpha. These induce smooth muscle contraction (bronchoconstriction), mucous hypersecretion, oedema, and airway obstruction
- LATE PHASE (6-12 hrs): recruitment of eosinophils, basophils, neutrophils and Th2 cells resulting in perpetuation of inflammation, leading to bronchial hyperresponsiveness and collagen deposition in basement membrane.
- Structural cells (bronchial epithelial cells, fibroblasts, smooth muscle, endothelial cells) also release cytokines, profibrogenic and proliferative growth factors which contribute to inflammation, smooth muscle proliferation and airway remodelling.
What are the main interleukins involved in the pathogenesis of asthma? (x3)
IL-5 (eosinophil activation), IL-13 (IgE production, epithelial damage, mucus production and smooth muscle proliferation), and IL-4 (IgE production, epithelial damage, fibrosis)
What is the epidemiology of asthma: Prevalence? Age? Trend? Gender?
10% of children, 5% of adults. Prevalence increasing. Equal gender split.
What are the symptoms of asthma? (x6)
• Wheeze • Breathlessness • Cough • Worse in the morning and night • Chest tightness • Night symptoms
What are the signs of asthma? (x6)
- Tachypnoea
- Use of accessory muscles (tracheal tug, intercostal recession, abdominal muscle usage)
- Prolonged expiratory phase
- Polyphonic wheeze
- Hyperinflated chest
- Nasal polyposis (multiple polyps) are common
What characterises a severe asthma attack? (x5)
PEFR less than 50% of predicted, pulse over 110/min, resp rate over 25/min, inability to complete sentences. Pulsus paradoxus
What characterises life-threatening asthma attack? (x7)
PEFR less than 33% of predicted, silent chest, cyanosis, bradycardia, hypotension, confusion, coma.
What is near-fatal asthma? (x2)
Raised PaCO2 (note that life-threatening asthma has normal PaCO2), and/or requiring mechanical ventilation with raised inflation pressures.
NB: CO2 raises because patient has lost respiratory effort from severity of their asthma. As such, they can no longer breath off their CO2.
How is asthma assessed clinically?
Asthma control test which assesses IMPAIRMENT (symptoms, night awakenings, interference with normal activities, medication use) and RISK of exacerbations.
What are the investigations for acute asthma exacerbations? (x4)
- Peak flow meter readings compared to normal or predicted value is used to assess severity
- CXR to exclude other diagnoses such as pneumothorax and pneumonia. May see hyperinflation
- FBC show increased WCC if infective exacerbation. May also show eosinophilia
- Pulse oximetry as another measure of severity
What are the investigations for chronic asthma? (x5)
- PEFR monitoring: usually diurnal variation with a morning ‘dip’
- FEV₁/FVC <80% of predicted and pulmonary function tests show obstructive defect
- Blood: eosinophilia, IgE level may be raised, Aspergillus antibody titres (indicate Aspergillus aetiology)
- Bronchial challenge test: through exposure to antigens or exercise to diagnose asthma
- Skin prick tests: may help identify allergens responsible for exacerbations
How are acute exacerbations of asthma managed? (x7)
- Resuscitate
- Monitor oxygen saturation, ABG and PEFR
- Nebulised B2-agonist bronchodilator salbutamol (IV if inhaled unreliable); add ipratropium (anticholinergic bronchodilator) if severe
- High flow oxygen Aim to titrate for 94%. If mixed COPD/asthma picture, aim for 88%
- Steroid therapy: IV hydrocortisone followed by oral prednisolone for 5-7 days as this combats inflammation
- IV magnesium sulphate, IV aminophylline infusion or IV salbutamol if no improvement – all are bronchodilators
- Treat aetiology e.g., antibiotics if chest infection
What is the pharmacodynamics of ICS/LABA? Why is this combination used in severe asthma?
ICS (budesonide)/LABA (Formoterol): used in severe asthma because of its synergistic interaction which makes the combination much more efficacious than using them on their own.
