Asthma is a common disease affecting 8 million people in the UK, characterised by chronic inflammation of the airways. The hyper-responsive airways typical of asthma cause symptoms such as shortness of breath, cough and wheeze in response to stimuli.1
On average, 3 people die from an acute asthma attack every day in the UK.2 This article focuses on chronic asthma; for more information on the management of an asthma attack, see the Geeky Medics guide to acute asthma management.
Asthma is characterised by chronic inflammation of the airways. There are several mechanisms which lead to airway inflammation, including:3
Inflammatory cell infiltration of airways
Smooth muscle hypertrophy
Thickening and disruption of the airway membrane
Acute exacerbations of chronic asthma are most frequently caused by respiratory viruses. Other causes include bacterial infections, allergens, pollutants and occupational exposure.3
Several risk factors which are likely to increase the development or persistence of asthma have been identified.1
Non-modifiable risk factors include:
Personal or family history of atopy
Male sex (asthma development) or female sex (persistence to adulthood)
Prematurity and low birth weight
Modifiable risk factors include:
Exposure to tobacco smoke, inhaled particulates and occupational dusts
Infections in infancy
A respiratory history should elicit the typical symptoms of asthma: wheeze, cough and breathlessness. Symptoms are characteristically episodic and diurnal (worse at night and early morning).
Other important areas to cover in the history include:
Triggers (pets, carpets, temperature)
Occupation (exposure to dusts, chemicals)
Frequency of exacerbations and previous hospital/intensive care admissions
Personal or family history of atopy
Best expected and recent peak expiratory flow rate (PEFR)
Adherence with treatment
Smoking (including passive smoking) history
A thorough systems review is important to rule out alternative causes for the presentation.
A combination of history, examination and investigations can lead to a likely diagnosis of asthma. There is no single test that can be used to make a definitive diagnosis.
Alongside basic observations, PEFR is important for monitoring response to treatment and can demonstrate diurnal variation when there is >20% variability in twice daily readings.1 Predicted PEFR can be calculated from age, sex and height.
Basic blood tests include WCC and CRP to look for infection. More specialist tests include eosinophil count and total IgE, IgE to aspergillus, as well as other allergens or fungus.1
If the patient has a productive cough, a sputum sample should be sent for microscopy, sensitivity and culture (MCS).
A chest X-ray is usually normal, but may rarely show signs of hyperinflation or bronchial wall thickening. A chest X-ray is also important to rule out infection, collapse or pneumothorax.
Spirometry with bronchodilator reversibility testing is important to support a diagnosis of suspected asthma.
Spirometry in asthma
Spirometry findings suggestive of asthma include:
FEV1/FVC ratio <70% indicates airflow obstruction
Improvement of FEV1 by 12% AND 200ml with bronchodilators
Improvement of FEV1 by 400ml with bronchodilators
Fractional exhaled nitric oxide (FeNO) testing measures the level of exhaled nitric oxide. FeNO ≥40ppb in adults and ≥35ppb in children confirms eosinophilic inflammation, but is only suggestive of asthma. Importantly, 1 in 5 people with a positive FeNO test do not have asthma and conversely 1 in 5 people with a negative result have asthma.1
Direct bronchial challenge test (using histamine or methacholine) is carried out in specialist centres when there is diagnostic uncertainty.
Skin prick testing can suggest atopy.
Diagnosis of asthma starts with an initial detailed respiratory history and examination. If there is a high probability of asthma based on this assessment, treatment should be initiated and monitored with spirometry and symptom scores.1
If there is an intermediate probability of asthma, spirometry with bronchodilator reversibility should be carried out. Other subsequent tests might include peak flow charts and skin prick testing (1).
If there is a low probability of asthma, other causes should be investigated.1
Asthma should be managed with a multidisciplinary approach, including the patient, asthma nurse, GP, respiratory physician and respiratory physiotherapists where appropriate.
A personalised asthma action plan should be completed. This can be completed with a GP or asthma nurse and covers daily treatment, treatment escalation in an exacerbation and when to seek help in an asthma attack.4 Patients should be encouraged to keep PEFR diaries.
Asthma reviews should be carried out at least annually with a nurse or doctor. A review should include symptoms and asthma control, smoking status, inhaler technique and adherence, PEFR and vaccination status.5
Vaccinations should be kept up to date, and should include childhood, pneumococcal and influenza vaccines.
Lifestyle measures should be considered in management of asthma. Smoking cessation and weight loss should be encouraged, with help offered when appropriate. Asthma triggers should be avoided when possible.
The aim of treatment is to control the disease. This is defined as:1
No daytime symptoms or night time waking due to asthma
No asthma attacks or need for rescue medications
No limitations on activity
Normal lung function
Minimal side effects
Inhalers are the mainstay of medical management in asthma however, other types of treatment including oral leukotriene receptor antagonists (LTRA), theophylline or biologic agents can be used with specialist input.
Treatment should be escalated in a step-wise approach, using the lowest possible dose of inhaled steroid needed for optimum control. Treatment should be escalated when symptoms are not adequately controlled.5,6
All those with symptomatic asthma should be given a short-acting beta-2 agonist (SABA) for reliever therapy as required
Add low dose inhaled corticosteroid (ICS)
Add long-acting beta-2 agonist (LABA)
ICS dose increased or LTRA
Respiratory complications of asthma include:1
Collapse and pneumothorax
Other important complications are an impaired quality of life in uncontrolled asthma, side effects of steroid treatment and death.1
Children with early-onset asthma and male children are more likely to grow out of their asthma before adulthood.1
Asthma is a common disease, causing chronically inflamed and hyper-responsive airways.
Risk factors can be non-modifiable (atopy, male) or modifiable (environmental exposure, social deprivation).
A history should explore typical symptoms of asthma: wheeze, cough and breathlessness. It should also include triggers, exacerbations, treatment adherence and a systems review.
Clinical examination may be normal or may show signs of hypoxia and polyphonic expiratory wheeze.