17.01.1 Introduction to Asthma

The symptoms of bronchial asthma are coughing, wheezing, shortness of breath, and chest tightness. Asthma remains a significant health problem in Australia, with prevalence and death rates that are high by international standards despite declines Asthma affects more than 1 in 10 Australians - equivalent to over 2 million people and in 2008, 447 Australians died from asthma. The reason for the high prevalence of asthma in Australia is not known

There are more paediatric hospital admissions for asthma than for any other cause.

What is bronchial asthma? Bronchial asthma is an inflammatory disease with increased airway thickness, increased number of inflammatory cells, inflammation, bronchial hyper-reactivity and bronchoconstriction. Bronchial hyper-reactivity is cough and wheeze in response to stimuli (such as strong odours, cold air, pollutants and histamine) that would not provoke such a response in normal subjects. Some asthma is allergic. In severe asthma, 50-80% of this has an allergic component. In allergic asthma immunoglobulin E (IgE) plays an important part in the inflammatory cascade, and a logical way to treat allergic asthma is to prevent the effects of IgE.

The increased number of inflammatory cells in bronchial asthma occurs under basal conditions and with the presence of allergen. As there are many mediators involved in inflammatory processes, targeting one mediator is not always successful. For instance, histamine is a mediator of inflammation, but histamine acting at histamine H₁-receptors only has a minor role in bronchial asthma. Consequently, the anti-histamines (histamine H₁-receptor antagonists) are ineffective in the treatment of asthma.

Leukotrienes, cytokines and other mediators have a major role in bronchial asthma. Drugs that target only one of the inflammatory mediators are not fully effective in inflammation. Thus, drugs that target more than one inflammatory mediator have a major role in treating the inflammation of asthma. Asthma is usually a short-term impairment in respiration, whereas Chronic Obstructive Pulmonary Disease (COPD) is long-term impairment in respiration, and can be permanent.