Clinical features
The basic abnormality in asthma is an underlying inflammatory process, affecting the small airways or bronchioles, combined with increased responsiveness to various stimuli. This means that, in response to a specific stimulus (see “Causes of Asthma), the tissue lining the airways, which may or may not already be inflamed, swells up more, due to a sudden inflammatory response, and excessive mucus is produced, which plugs up the bronchioles. Damage to the top lining of the mucus bronchioles also may occur, with shedding of cells. Also, the smooth muscles around the bronchioles tighten up.
The combination of these factors causes diffuse airway narrowing and reduced ability of the air to travel in and out of the lungs (especially out), and this leads to the typical symptoms of an asthma attack, known as an “acute exacerbation”.
Variability is a very common factor in asthma, and the symptoms may only occur with patients in certain circumstances, (i.e. wheeziness associated with viral infections, such as the common cold). There also may be considerable variation in the frequency and duration of attacks.
Asthma causes breathing problems, which are experienced as symptoms of:
- cough,
- wheeze,
- feelings of tightness across and in the chest, and,
- breathlessness.
These problems usually occur in episodes or attacks - sometimes known as exacerbations, and they can be mild, moderate or severe.
Note:
For the majority of people asthma is a mild to moderate condition, well controlled by medication, but for a minority of people they will be severely affected and may have problems with self-care tasks and getting about.
