Chapter 82

Introduction

After I'd written to you yesterday I had an attack of asthma and an incessantly running nose, which forced me to tramp about, lighting cigarettes at every tobacconist etc. And worse was to come: I went to bed about midnight, feeling all right after spending a long time inhaling smoke, but 3 or 4 hours later came the real attack of the summer.

Marcel Proust, letter to his mother, 1901

Asthma is defined by the presence of both of the following:1

• excessive variation in lung function (‘variable airflow limitation’ i.e. variation in expiratory airflow that is greater than that seen in healthy people)

• respiratory symptoms (e.g. wheeze, shortness of breath, cough, chest tightness) that vary over time and may be present or absent at any point in time

In young children in whom lung function testing is not feasible, including most preschool children, asthma is defined by the presence of variable respiratory symptoms.

Key facts and checkpoints

• Asthma continues to be underdiagnosed and undertreated.3 It is increasing worldwide.

• It has an unacceptable mortality rate of approximately 5 per 100 000 of the population.

• About one child in four or five has asthma (usually in a mild form).

• It tends to develop between the ages of 2 and 7 years, but can develop at any age.

• Most children present with a cough.

• Most children are free from it by puberty.

• At least one in seven adolescents has asthma.

• About one adult in eight has or has had asthma.

• The focus of management should be on prevention; an acute asthmatic attack represents failed treatment.

• Measurement of function is vital as ‘objective measurement is superior to subjective measurement’.

• Spirometry is the key investigation.

• The earlier steroid therapy is introduced, the better the outcome.

• Inhaled corticosteroids are the cornerstone of asthma treatment.

• Avoid concomitant medication that may exacerbate asthma (e.g. beta blockers, aspirin, NSAIDs).

• New aerosols, notably hydrofluoroalkanes, have non-CFC propellants leading to increased lung deposition and thus requiring overall lower dosage.

Pathophysiology1

Chronic asthma is an inflammatory disease with the following pathological characteristics:

• infiltration of the mucosa with inflammatory cells (especially eosinophils) and cellular elements

• airway hyper-responsiveness2

• intermittent airway narrowing (due to bronchoconstriction, congestion or oedema of bronchial mucosa or a combination of these) (see FIG. 82.1)

FIGURE 82.1

Airway changes in asthma: (a) normal airway, (b) airway in asthma

Causes of asthma

No single cause for asthma has been found, but a variety of factors may trigger an attack. These include specific factors such as viruses, allergens and non-specific factors such as temperature or weather changes and exercise. A checklist of trigger factors includes:

1. allergens—pollens, animal dander, dust ...

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