Making diagnosis of asthma

Compatible clinical history plus either/or:

? FEV1 ≥ 15% (and 200 ml) increase following administration of a bronchodilator/trial of corticosteroids

? > 20% diurnal variation on ≥ 3 days in a week for 2 weeks on PEF diary

? FEV1 ≥ 15% decrease after 6 mins of exercise

Radiological examination

Radiological examination is generally unhelpful in establishing the diagnosis but may point to alternative diagnoses. Acute asthma is accompanied by hyperinflation, and 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). An HRCT scan may be useful to detect bronchiectasis.

Measurement of allergic status

An elevated sputum or peripheral blood eosinophil count may be observed and 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.

Assessment of airway inflammation

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

Status Asthmaticus

The most severe form of asthma is called status asthmaticus. In this condition, the lungs are no longer able to provide the body with adequate oxygen or adequately remove carbon dioxide. Without oxygen, many organs begin to malfunction. The buildup of carbon dioxide leads to acidosis, an acidic state of the blood that affects the function of almost every organ. Blood pressure may fall to low levels. The airways are so narrowed that it is difficult to move air in and out of the lungs.

Status asthmaticus requires intubation and ventilator support as well as maximum doses of several medications. Support is also given to correct acidosis

Complications

? The most common complications of asthma include pneumonia, pneumothorax or pneumomediastinum, and respiratory failure requiring intubation in severe exacerbations.

? Risk factors for death from asthma include the following:

o Past history of sudden severe exacerbations, history of prior intubation, or ICU admission

o Two or more hospitalizations or 3 or more emergency department visits in the past year; hospitalization or emergency department visit in the past month

o Use of more than 2 short-acting beta-agonist canisters per month

o Current use of systemic corticosteroids or recent taper

o Comorbidity from cardiovascular disease

o Psychosocial, psychiatric, or illicit drug use problems

o Low socioeconomic status or urban residence

? Complications associated with most medications used for asthma are relatively rare. However, in those patients requiring long-term corticosteroid use, complications may include osteoporosis, immunosuppression, cataracts, myopathy, weight gain, addisonian crisis, thinning of skin, easy bruising, avascular necrosis, diabetes, and psychiatric disorders.

Medical Care

The goals for successful management of asthma include the following:

? Achieve and maintain control of symptoms.

? Prevent asthma exacerbations.

? Maintain pulmonary function as close to normal levels as possible.

? Maintain normal activity levels, including exercise.

? Avoid adverse effects from asthma medications.

? Prevent the development of irreversible airflow limitation.

? Prevent asthma mortality.

Principles of management

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.

Patient education

The variable nature of asthma suggests that encouraging patients to take responsibility for control of their disease should lead to improved clinical outcomes. Patient education should begin at the time of diagnosis and be revisited in subsequent consultations. Patients (or their carers) should be taught about the relationship between symptoms and inflammation, the importance of key symptoms such as nocturnal waking, the different types of medication and the use of PEF to guide management decisions. Written action plans may prove helpful in developing these skills.

Avoidance of aggravating factors

This is particularly important in the management of occupational asthma, when removal from the offending agent is one of the few instances when asthma may be cured or substantially improved. Similarly, the identification of sensitisation to a household pet suggests that asthma control may be improved by removing the animal from the home, although it may take several years before dander levels fall substantially. House dust mite exposure may be minimised by replacing carpets with floorboards and using mite-impermeable bedding. However, to date improvements in asthma control following such measures have been difficult to demonstrate. Many patients are sensitised to several antigens making avoidance strategies almost impossible. Measures to reduce fungal exposure and eliminate cockroaches may be applicable in specific circumstances and medications known to precipitate or aggravate asthma should be avoided. Patients should be advised not to smoke.

A stepwise approach to the management of asthma

Step 1: Occasional use of inhaled short-acting β2-adrenoreceptor agonist bronchodilators

For patients with mild intermittent asthma (symptoms less than once a week for 3 months and fewer than two nocturnal episodes/month), it is usually sufficient to prescribe an inhaled short-acting β2-agonist to be used on an as required basis. However, many patients, and their physicians, under-estimate the severity of asthma and these patients should be carefully supervised. A history of a severe exacerbation should lead to a reclassification of the patient's condition as persistent asthma.

Step 2: Introduction of regular preventer therapy

Regular anti-inflammatory therapy (preferably inhaled corticosteroids-ICS) should be started in addition to inhaled β2-agonists taken on an as required basis in any patient who:

has experienced an exacerbation of asthma in the last 2 years

uses inhaled β2-agonists three times a week or more

reports symptoms three times a week or more

is awakened by asthma one night per week.

A reasonable starting dose is 400 μg beclometasone dipropionate (BDP) or equivalent per day in adults. BDP and budesonide (BUD) are approximately equivalent in clinical practice, although there may be variations with different delivery devices. Fluticasone and mometasone provide equal clinical activity to BDP/BUD at half the dosage.

Step 3: Add-on therapy

If the patient remains poorly controlled despite regular use of ICS, a thorough review of the patient should be made with particular regard to adherence and inhaler technique. A further increase in the dose of ICS may benefit some patients but in general, add-on therapy should be considered beyond an ICS dose of 800 μg/day BDP (or equivalent) in adults.

Long-acting β2-agonists (LABAs), such as salmeterol and formoterol (duration of action of at least 12 hours), represent the first choice of add-on therapy as they have consistently been demonstrated to improve asthma control and reduce the frequency and severity of exacerbations when compared to increasing the dose of ICS alone. Fixed combination inhalers of ICS and LABAs have been developed; these are more convenient, increase compliance and avoid concerns that patients may use LABAs as monotherapy.

Leukotriene receptor antagonists (e.g. montelukast 10 mg daily) are a relatively new class of agent that may be delivered orally and may reduce exacerbations. Theophyllines may be useful in some patients but their unpredictable metabolism, propensity for drug interactions and prominent side-effect profile have limited their use.

Step 4: Poor control on moderate dose of inhaled steroid and add-on therapy: addition of afourth drug

In adults the dose of ICS may be increased to 2000 μg BDP/BUD daily. A nasal corticosteroid preparation should be used in patients with prominent upper airway symptoms. Oral therapy with leukotriene receptor antagonists, theophyllines or a slow-release β2-agonist may be considered. If the trial of add-on therapy is ineffective it should be discontinued. Oral itraconazole should be contemplated in patients with ABPA. New therapies such as monoclonal antibodies directed against IgE may prove helpful and further studies are awaited.

Step 5: Continuous or frequent use of oral steroids

At this stage prednisolone therapy (usually administered as a single daily dose in the morning) should be prescribed in the lowest amount necessary to control symptoms. Patients on long-term corticosteroid tablets (> 3 months) or receiving more than three or four courses per year will be at risk of systemic side-effects. Osteoporosis can be prevented in this group of patients using bisphosphonates. Steroid-sparing therapies such as methotrexate, ciclosporin or oral gold may be considered but should be overseen by a specialist and are accompanied by significant side-effects.

Step-down therapy

Once asthma control is established, the dose of inhaled (or oral) corticosteroid should be titrated to the lowest dose at which effective control of asthma is maintained.

Date: 2016-06-13; view: 6