Asthma

Introduction

Asthma is a chronic inflammatory disorder of the airways with bronchial hyperresponsiveness producing symptoms related to limited airflow that can be reversed.

  • Respiratory symptoms (e.g. wheeze, shortness of breath, cough, chest tightness) vary over time and vary in intensity, together with variable expiratory airflow.
  • However, airflow limitation may later become persistent due to structural remodelling.

The diagnosis of allergic asthma is more likely when the person also has allergy and a family history of asthma, allergic rhinitis or eczema.

  • Lung function is most reliably assessed by spirometry testing, with assessment of forced expiratory volume in 1 second (FEV1) and the ratio of FEV1 to forced vital capacity (FEV1/FVC).



Management

Crude Asthma Mortality Rate

The long-term goals of asthma management are

  • Good long-term symptom control (few/no asthma symptoms, no sleep disturbance due to asthma, and unimpaired physical activity), and
  • Minimizing long-term risk of asthma related mortality, exacerbations, persistent airflow limitation and side effects of treatment.
  • The patient's own goals should also be identified.
Choosing Asthma Controller

Good asthma control is defined as having, in the previous 4 weeks:

  • Daytime symptoms <2 days a week
  • Need for reliever <2 days a week (excluding doses for preventing exercise-induced bronchoconstriction
  • No limitation of activity
  • No symptoms during the night or on waking.

Identify and manage trigger factors, e.g. cigarette smoke, exercise, allergen or irritant exposure, change in weather, certain drugs or food, viral respiratory infections, obesity or comorbidities.

  • Cessation of smoking, environmental tobacco exposure and vaping
  • Physical activity (including the use of SABA or ICS-SABA before exercise)
  • Avoidance of occupational or domestic exposures to allergens or irritants
  • Breathing exercises
  • Weight reduction
  • Dealing with emotional stress

Assess inhaler techniques and adherence.

  • Remind patients to rinse and spit out after using inhaled corticosteroids (ICS).

Vaccination against influenza, respiratory syncytial virus (RSV) and COVID-19

  • Pneumococcal vaccine protects against invasive pneumococcal infection, but asthma alone is not a specific indication for pneumococcal vaccination.



Pharmacological Therapies

In real life, asthma patients often perceive their asthma to be much better controlled than it actually is.

  • Among patients who self-rate their asthma as "well-controlled", many still experience persistent symptoms and rely on their reliever inhaler more than twice a week.
  • This high reliance is dangerous; a higher average use of SABAs over a year is directly associated with an increased risk of severe exacerbations.
  • Despite this risk, many patients are still not being prescribed an anti-inflammatory reliever to reduce their likelihood of a severe flare-up in the subsequent days.
Consequently, since 2019, the GINA has no longer recommended treating adults and adolescents with a SABA alone for safety reasons.
  • All patients in these age groups should receive an inhaled corticosteroid (ICS)-containing medication instead.
  • Although a SABA provides quick temporary relief from symptoms, SABA-only treatment fails to address underlying airway inflammation and is fundamentally associated with an increased risk of severe exacerbations and a long-term decline in lung function.
NOTE: Fenoterol (SABA) is not recommended because of its higher risk of adverse effects (including hypokalaemia and cardiovascular effects), and its association with increased asthma mortality.

Use of anti-inflammatory reliever (AIR), containing a low dose of ICS plus a rapid-acting bronchodilator, reduces the need for oral corticosteroid (OCS), which have cumulative long-term adverse effects.

  • Early initiation of low-dose ICS in patients with asthma leads to a greater improvement in lung function than if symptoms have been present for more than 2-4 years.
  • At a population level, most benefit from ICS is obtained at low dose, but individual ICS responsiveness varies, and some patient whose asthma is uncontrolled on low-dose ICS-LABA despite good adherence and correct inhaler technique may benefit from increasing the maintenance dose to medium doses or short-term high dose.
Asthma Treatment Steps

Selecting Initial Asthma Therapy

Once good asthma control has been achieved and maintained for 2-3 months, consider stepping down gradually to find the patient's lowest treatment that controls both symptoms and exacerbations, while reducing the potential for side-effects.

  • Provide the patient with a written asthma action plan, monitor closely and schedule a follow-up visit.

Leukotriene receptor antagonists, which include montelukast, zafirlukast and zileuton, are less effective than ICS, particularly for exacerbations.

  • Before prescribing montelukast, healthcare professionals should consider its benefits and risks, and patients or parents/caregivers should be counselled about the risk of neuropsychiatric events.

Add-on long-acting muscarinic antagonists (LAMA) can be prescribed as a Step 5 addition if asthma is not well-controlled with medium- or high-dose ICS-LABA despite good adherence and correct inhaler technique.

  • Meta-analyses that included triple therapy with combination or separate inhalers reported an overall 16-17% reduction in risk of severe exacerbations requiring oral corticosteroids.

For patients with severe refractory asthma, adding biologic therapy substantially reduces the need for long-term oral corticosteroids.

  • Anti-IgE (e.g. omalizumab) for severe allergic asthma
  • Anti-interleukin-5/5Rα (e.g. mepolizumab, benralizumab, depemokimab, reslizumab) for severe eosinophilic asthma.
  • Anti-interleukin-4Rα (e.g. dupilumab) for severe eosinophilic/Type 2 asthma
  • Anti-thymic stromal-lymphopoietin (e.g. tezepelumab) for severe asthma
Biologics in Severe Asthma

The assessment of severe asthma includes identification of the inflammatory phenotype, based on blood or sputum eosinophils or FeNO, to assess the patient’s eligibility for various add-on treatments including biologic therapy.

  • A higher baseline blood eosinophil count and/or FeNO predicts a good asthma response to some biologic therapies.



Vitamin D Supplementation

Several cross-sectional studies have shown that low serum levels of Vitamin D are linked to impaired lung function, higher exacerbation frequency and reduced corticosteroid response.

  • Vitamin D supplementation may reduce the rate of asthma exacerbation requiring treatment with systemic corticosteroids or may improve symptom control in asthma patients with baseline 25(OH)D of less than approximately 25-30 nmol/L.
  • There is no good-quality evidence that Vitamin D supplementation leads to improvement in asthma control or reduction in exacerbations, particularly in preschool children and people with severe asthma.



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