Case 7.1 – Asthma Exacerbation

Asthma is characterised by chronic airway inflammation and increased airway hyper-responsiveness leading to symptoms of wheeze, cough, chest tightness and dyspnoea. Asthma is not a uniform disease but a dynamic clinical syndrome with a variety of features.

Typical Symptoms:

• Recurrent episodes of wheezing, chest tightness, breathlessness and cough
• Common precipitants include exercise, particularly in cold weather, exposure to airborne allergens or pollutants, and viral upper respiratory tract infections

Disease Patterns:

• Mild intermittent asthma: Patients are usually asymptomatic between exacerbations which occur during viral respiratory tract infections or after exposure to allergens
• Persistent asthma: The pattern is one of chronic wheeze and breathlessness

Key Clinical Features:

• Asthma characteristically displays a diurnal pattern, with symptoms being worse in the early morning
• Particularly when asthma is poorly controlled, symptoms such as cough and wheeze disturb sleep and have led to the use of the term 'nocturnal asthma'
• Cough may be the dominant symptom in some patients

Physical Examination Should Include:

• Respiratory examination including assessment of wheeze
• Respiratory rate
• Pulse rate
• Pulse oximetry
• Blood pressure (pulsus paradoxus)
• Peak flow
• Examine the chest for the use of accessory muscles of respiration
• Hyper inflated chest
• Reduced breath sounds
• Prolonged expiratory phase of respiration

The diagnosis is made on the basis of a compatible history combined with demonstration of variable airflow obstruction.

Investigations include:

Pulmonary Function Tests:

• The measurement of forced expiratory volume over 1 sec (FEV₁) and vital capacity (VC) by spirometry allows the demonstration of airflow obstruction
• Following the administration of a bronchodilator, confirms the diagnosis when a 15% (and 200 ml) improvement in FEV₁ is noted
• Spirometry is also particularly helpful in monitoring the severity of airflow obstruction in patients with impaired lung function

Chest X-ray:

• Radiological examination is generally unhelpful in establishing the diagnosis but may point to alternative diagnoses
• Acute asthma is accompanied by hyperinflation
• Lobar collapse may be seen if mucus has occluded a large bronchus
• Flitting infiltrates, on occasion accompanied by lobar collapse, suggest asthma complicated by allergic bronchopulmonary aspergillosis (ABPA)
• High resolution CT scan may be useful to detect bronchiectasis

Allergy Testing:

• An elevated sputum or peripheral blood eosinophil count may be observed
• The serum total IgE is typically elevated in atopic asthma
• Skin prick tests are simple and provide a rapid assessment of atopy
• Similar information may be provided by the measurement of allergen-specific IgE

Induced Sputum:

• Induced sputum and exhaled breath allow the non-invasive assessment of airway inflammation
• May prove useful in the diagnosis of asthma and assist in the monitoring of disease activity

1. Airflow limitation that reverses spontaneously or with treatment
2. Airway hyper reactivity characterized by an exaggerated broncho-restriction response to a wide range of non-specific stimuli e.g. exercise, cold air
3. Airway inflammation characterized by eosinophils, lymphocytes, mast cells, neutrophils; associated oedema, smooth muscle hypertrophy and hyperplasia, thickening of basement membrane, mucous plugging and epithelial damage

Two-Phase Bronchoconstrictor Response:

The inhalation of an allergen in a sensitised atopic asthmatic patient results in a two-phase bronchoconstrictor response.

Early Phase:

• The inhaled allergen rapidly interacts with mucosal mast cells via an IgE-dependent mechanism
• Results in the release of mediators such as histamine and the cysteinyl leukotrienes
• Causes resulting bronchoconstriction

Late Phase:

• In persistent asthma a chronic and complex inflammatory response ensues
• Characterised by an influx of numerous inflammatory cells
• The transformation and participation of airway structural cells
• The secretion of an array of cytokines, chemokines and growth factors

Note: The response shows an initial rapid drop in peak flow (early reaction) followed by recovery, then a second drop 4-8 hours later (late reaction) before gradual recovery over 24 hours.

The reversibility test requires forced expiratory manoeuvres before and 20 minutes after inhalation of a β₂-adrenoceptor agonist.

Clinical Utility:

• Demonstrates airflow obstruction before bronchodilator administration
• Shows improvement in lung function 20 minutes after bronchodilator drug is administered
• A 15% improvement in FEV₁ (and 200 ml) confirms the diagnosis of asthma
• Helps differentiate asthma from other causes of airflow obstruction (like COPD)

In the majority of patients with asthma, the disease can be effectively managed in primary care by partnerships between doctors, nurses and, most importantly, patients themselves. The goals of asthma therapy have been endorsed by several sets of guidelines. Management may be directed towards achieving these goals by following a stepwise approach.

Step Up Approach (Treatment Steps):

1. Step 1: Occasional use of inhaled short-acting β₂-adrenoceptor agonists
2. Step 2: Low-dose inhaled corticosteroids (or other anti-inflammatory agents)
3. Step 3: Low- to moderate-dose inhaled corticosteroids plus long-acting inhaled β₂-adrenoceptor agonist or leukotriene receptor antagonist
4. Step 4: High-dose inhaled corticosteroids and regular bronchodilators
5. Step 5: Addition of regular oral corticosteroid therapy

Step Down Approach:

• Consider step-down if good symptom control for 3 or more months
• Only think of withdrawing anti-inflammatory treatment if patient well for at least 6 months
• Start high and step down for better control
• Occasional temporary step-ups will be needed to control exacerbations

The variable nature of asthma suggests that encouraging patients to take responsibility for control of their disease should lead to improved clinical outcomes.

Key Components of Patient Education:

• Patient education should begin at the time of diagnosis and be revisited in subsequent consultations
• Patients and their carers need to be taught about the relationship between symptoms and inflammation
• The importance of key symptoms such as nocturnal waking
• The different types of medication
• The use of PEF (Peak Expiratory Flow) to guide management decisions

Written Action Plans:

• Written action plans may prove helpful in developing these skills
• They provide clear guidance on what to do when symptoms worsen
• Help patients recognize early warning signs
• Empower patients to take appropriate action before severe exacerbations occur