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Asthma is defined as episodes of a reversible increase in airway resistance in response to irritant stimuli.
Increased airway resistance is caused by bronchial smooth muscle contraction, mucosal inflammation, and increased mucus production.
Asthma is characterised by episodes of breathlessness, wheeze, and cough. It affects 5-8% of the population and is the most common chronic disease in children.
There is no one symptom, sign or test that is diagnostic of asthma, however, there are several useful investigations outlined below that help to diagnose asthma.
Investigations are used to demonstrate variable airway obstruction and airway inflammation to support a clinical assessment.
If investigations are inconclusive, an asthma diagnosis may be ‘suspected’. In this case, treatment should be initiated and monitored carefully by regular reviews. A good response to treatment supports an asthma diagnosis.
In adults with suspected asthma:
Perform spirometry and exhaled nitric oxide (FeNO)
Carry out a bronchodilator reversibility (BDR) test if spirometry is positive
If the diagnosis is still uncertain, monitor peak expiratory flow (PEF) variability for 2-4 weeks
If the diagnosis is still uncertain, consider a direct bronchial challenge test
Non-pharmacological management includes advice on smoking cessation and weight loss in overweight/obese patients. Advise patients to avoid asthma triggers where possible.
There is clear guidance on the stepwise pharmacological management of asthma. Management is based on bronchodilator ‘relievers’ and anti-inflammatory ‘preventers’.
β2-agonists (‘relievers’) and inhaled corticosteroids (‘preventers’) form the basis of chronic asthma management. They should be offered as first-line treatments to all adults and children over the age of five.
Short-acting β2-agonist (SABA)
β2-agonism causes bronchial smooth muscle relaxation which dilates bronchi to improve airflow in obstructed airways. Salbutamol is the most used SABA.
Tremor is the most common adverse effect. Others include tachycardia, palpitations, and cardiac dysrhythmia.
Low dose inhaled corticosteroid (ICS)
Corticosteroids reduce leukocyte proliferation and downregulate pro-inflammatory cytokine, leukotriene, and chemokine production. This reduces mucosal inflammation, dilates airways, and reduces mucous secretion. An example of an ICS is beclomethasone.
Oral candidiasis is the main adverse effect. They can also cause a hoarse voice. Regular high dose steroid use can cause adrenal suppression, especially in children.
If symptoms remain uncontrolled, add-on therapies can be considered. Before initiating an add-on therapy, recheck adherence, inhaler technique, and elimination of trigger factors.
Additional therapies aside from SABA and ICS include:
Leukotriene receptor antagonist (LTRA): oral therapy taken at night to downregulate inflammatory leukotrienes
Long-acting β2-agonist (LABA): must always be given in combination with ICS
Medium dose inhaled corticosteroids
Trial of additional drugs: theophylline or a long-acting muscarinic antagonist (LAMA)
High dose inhaled corticosteroids
It is important to provide information for patients on asthma and their management:
For all inhalers: proper inhaler technique is especially important, and poor technique is the most common reason for uncontrolled asthma.
For SABA: ensure the patient knows how and when to take the inhaler (e.g. for acute symptoms, pre-emptively before exercise). They should understand that this treats symptoms, not the disease.
For ICS: a spacer should be used with ICS therapy to improve deposition and reduce the risk of oral candidiasis. Also, advise the patient to rinse their mouth and gargle after use. Reassure the patient that little steroid is absorbed into the blood so systemic effects are minimal.
Interactions: NSAIDs may provoke asthma (by inhibiting the COX pathway they promote arachidonic acid conversion to leukotrienes). Beta-blockers are contraindicated in asthma as they reduce the effectiveness of β2-agonists.
Complications of asthma include:
Asthma exacerbations: can lead to respiratory failure and death
Respiratory complications: airway remodelling and persistent airway obstruction
Complications related to corticosteroids: oral candidiasis, adrenal suppression and growth suppression