Asthma pathophysiology

Although the precise causes of asthma are unknown, exposure to particular inhaled substances, such as tobacco smoke, allergens or air pollution may irritate the airways and trigger an asthma attack.

Asthma is an inflammatory disease, and it is this inflammation which is responsible for the symptoms associated with the disease. Activation of inflammatory cascades leads to hyperresponsiveness of the airways, with consequent airflow limitation and breathing difficulties. Inflammation also plays a key role in airway remodelling – a pathological change observed with persistent inflammation.

Figure 1: The inflammatory cascade in asthma 

The complex chain of molecular events, which brings about inflammation in asthma, involves many different cell types and mediators (Figure 1). The chronic inflammation causes irreversible changes in normal airways, resulting in inelastic and narrow vessel walls and significantly impairing lung function in affected patients (Figure 2).

In asthma, airways throughout the lung are affected by inflammation. These include the large bronchioles down to small airways (<2mm diameter); the latter make up a large proportion of total lung volume and contribute actively to asthma pathophysiology.¹ Read more on Small airways in asthma.

Figure 2: The process of airway remodelling in asthma²

References:

1. Contoli M, Bousquet J, Fabbri LM, et al. The small airways and distal lung compartment in asthma and COPD: a time for reappraisal. Allergy 2010;65:141-151.
2. From the Global Strategy for Asthma Management and Prevention, Global Initiative for Asthma (GINA) 2011. Available from: http://www.ginasthma.org/.