respiratory,

Asthma

Aug 29, 2020

Key facts

  • A chronic reversible inflammatory disease of the airway
  • Comprise of 3 components: 1) Reversible and variable airflow obstruction 2) Airway hyper-responsiveness to stimuli e.g. cold, air, irritants, pollutants) and 3) Inflammation of the bronchi

Precipitating factors

  • Precipitants: Cold air, exercise, emotion, allergens (house dust mite, pollen, fur), infection, smoking and passive smoking, pollution, NSAIDS, beta -blockers.
  • Diurnal variation in symptoms or peak flow. Marked morning dipping of peak flow (due to high body cortisol level) is common and can tip the balance into a serious attack, despite having normal peak flow at other times.
  • Exercise: Quantify the exercise tolerance.
  • Disturbed sleep: Quantify as nights per week (a sign of severe asthma).
  • Acid reflux: 40–60% of those with asthma have reflux; treating it improves spirometry— but not necessarily symptoms.
  • Other atopic disease: Eczema, hay fever, allergy, or family history?
  • The home (especially the bedroom): Pets? Carpet? Feather pillows or duvet? Floor cushions and other ‘soft furnishings’?
  • Occupational asthma: If symptoms remit at weekends or holidays, work may cause trigger (15% of cases are work-related—more for paint sprayers, food processors, welders, and animal handlers). Ask the patient to measure his peak flow at intervals at work and at home (at the same time of day) to confirm this

Signs and symptoms

  • Cough
  • Dyspnoea
  • Polyphonic wheeze
  • Chest tightness
  • Symptoms precipitated by allergen exposure, cold air, exercise, emotion
  • Diurnal variation in symptom severity
  • PMH and/or FH of atopy
  • Reduced peak expiratory flow rate (PEFR)

Investigations

  • A Peak flow charts: A diurnal variation of >20% on >/=3d a week for 2 weeks
  • Lung function tests: FEV1/FVC <0.7; Reversibility testing with bronchodilators (>/=15% improvement in FEV1)
  • CXR: to exclude chest infection (if signs present)or pneumothorax in acute exacerbation
  • Tests of atopy: Skin prick testing, blood eosinophilia, ↑ IgE
  • Further investigations
    • Methacoline PC20 challenge– the provocative concentration of methacholine required to cause a 20% fall in FEv1 (if lung function test inconclusive)
    • Histamine challenge
    • Fractional exhaled Nitric Oxide (FeNO)– measured exhaled NO concentration; high level thought to be related to eosinophilic lung inflammation PRCS consensus 2019
    • Indirect challenges – e.g. exercise challenge
    • Sputum eosinophil count

Management of asthma

Non-pharmacological management

  • Self-management plan
  • Allergen avoidance
  • Smoking cessation and weight loss
  • Immunisations

    Pharmacological management (for adults >17yo)

  • SABA PRN
  • SABA + Low dose ICS as preventer if:
    • Use an inhaled SABA three times a week or more, and/or
    • Have asthma symptoms three times a week or more, and/or
    • Are woken at night by asthma symptoms once weekly or more
    • In addition, an ICS should be considered for adults and children over the age of 5 years who have had an asthma attack requiring treatment with oral corticosteroids in the past two years.
  • SABA + Low dose ICS+ Leukotrione Receptor antagonist (LRTA)
  • SABA + Low dose ICS + LABA +/- LRTA
  • Low dose MART (Maintenance And Reliever Therapy) contains low dose ICS and short-acting LABA +/- LRTA
  • Moderate dose MART +/- LRTA OR Fixed dose ICS + LABA +SABA
  • High dose ICS as fixed regime or muscurinic receptor antagonists or Theophylline and consider specialist referral


Comprise of 3 components: 1) Reversible and variable airflow obstruction 2) Airway hyper-responsiveness to stimuli e.g. cold, air, irritants, pollutants) and 3) Inflammation of the bronchi
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