Asthma is an ailment that affects 8 million people in the UK, characterized by chronic airway inflammation. People with asthma have hyper-responsive airways, which lead to symptoms such as shortness of breath, cough, and wheeze due to stimuli. On average, 3 people die from an acute asthma attack every day in the UK.
Asthma is identified by chronic airway inflammation. This inflammation can be due to multiple mechanisms, such as inflammatory cell infiltration of airways, smooth muscle hypertrophy, and thickening and disruption of the airway membrane. Acute exacerbations are usually caused by respiratory viruses, but other contributing factors include bacterial infections, allergens, pollutants, and occupational exposure.
There are many risk factors associated with the development and persistence of asthma. Non-modifiable risk factors include personal or family history of atopy, male sex for development and female sex for persistence, prematurity, and low birth weight. Modifiable risk factors include exposure to tobacco smoke, inhaled particulates, occupational dust, obesity, social deprivation, and infections in infancy.
A respiratory history should be taken to assess the typical asthma symptoms of wheeze, cough, and breathlessness. These symptoms usually occur in episodes and worsen at night and early morning. Other important topics to cover in the history include triggers, occupation, frequency of exacerbations, atopy, peak expiratory flow rate, adherence to treatment, and smoking history.
It is important to perform a systems review to exclude alternative causes of the symptoms.
Between exacerbations, a respiratory examination may be normal.
Typical clinical findings in asthma may include:
The main symptoms of asthma can be seen in many diseases. Important and common differentials to consider include:
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 more than 20% variability in twice-daily readings. 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, and other allergens or fungus.
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 findings suggestive of asthma include:
Fractional exhaled nitric oxide (FeNO) testing measures the level of exhaled nitric oxide. FeNO greater than 40ppb in adults and greater than 35ppb in children confirms eosinophilic inflammation, but is only suggestive of asthma. Importantly, one in five people with a positive FeNO test do not have asthma and conversely one in five people with a negative result have asthma.
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 a high probability of asthma is detected, treatment should be initiated and monitored with spirometry and symptom scores.
If an intermediate probability of asthma is found, spirometry with bronchodilator reversibility should be performed. Peak flow charts and skin prick testing may also be considered.
If a low probability of asthma is present, other causes must be investigated.
Management of asthma should involve a multidisciplinary approach, including the patient, asthma nurse, GP, respiratory physician and respiratory physiotherapists, if necessary.
A personalised asthma action plan should be made, and patients should be encouraged to keep PEFR diaries.
Asthma reviews should be completed annually by a nurse or doctor, and should include symptoms and asthma control, smoking status, inhaler technique and adherence, PEFR and vaccination status.
Vaccinations should be kept up to date, and lifestyle measures should be considered. Smoking cessation and weight loss should be encouraged, and asthma triggers should be avoided whenever possible.
The aim of treatment is to control the disease, and should involve a step-wise approach with the lowest possible dose of inhaled steroid needed for optimum control. Treatment should be escalated when symptoms are not adequately controlled.
In general, the step-wise approach for managing asthma includes:
Respiratory complications of asthma may include pneumonia, collapse and pneumothorax, respiratory failure, and status asthmaticus. Other important complications are an impaired quality of life in uncontrolled asthma, side effects of steroid treatment, and death.
Children with early-onset asthma and male children are more likely to grow out of their asthma before adulthood.
Asthma is a common condition that results in chronically inflamed and hyper-responsive airways. Risk factors can be non-modifiable (such as atopy and male gender) or modifiable (such as environmental exposure and social deprivation).
When attempting to diagnose asthma, it is important to explore typical symptoms such as wheeze, cough and breathlessness. Additionally, it is important to ask about any triggers, exacerbations, treatment adherence and to carry out a systems review.
Clinical examination may be normal or may show signs of hypoxia and polyphonic expiratory wheeze. It is important to consider alternative diagnoses, including bronchiectasis, COPD, infection, reflux and heart failure.
There is no single test for asthma, although spirometry with reversibility testing, PEFR, FeNO and blood tests can help make a diagnosis when asthma is suspected. Spirometry may be normal in asthma, however a FEV1/FVC ratio of less than 70% indicates airflow obstruction. Improvement in FEV1 of 12% and 200ml with bronchodilators suggests reversible airway obstruction.
The management of asthma is multidisciplinary and aims to control the disease by reducing symptoms. All asthma patients should have a personalised asthma action plan and an annual assessment. Inhalers are the mainstay of treatment and should be used according to a step-wise approach. Possible complications of asthma include reduced quality of life, pneumonia, pneumothorax, respiratory failure and death.
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