The asthma pathophysiology is complex and not completely understood. Asthma is described as inflammatory response disease.
The main cause of breathlessness is due to airway wall constriction and airway wall inflammation.
There are three main asthma pathophysiology responses that characterize the disease.
- Airway inflammation
- Hyper-responsiveness and
- Obstruction of the airway due to the constriction of bronchiole
Hyper-responsiveness and airway obstruction are the causes known to have asthmatic episode but recently inflammation of the airways has been recognized as the third cause.
But, some of them consider inflammation plays an important role in asthma pathophysiology and much of the research carried out concentrates on this point.
To understand asthma pathophysiology, airway anatomy is required. Complex interactions among inflammatory cells, tissues and mediators in the airways cause inflammation.
The release of inflammatory mediators from mast cells, eosinophils, macrophages and other cells in the airways are activated by the stimuli. The other inflammatory cells are signaled by the mediators to migrate to the airways where they are activated.
This causes secretion of mucus, prolonged contraction of smooth muscle, injury of the epithelium, as well as swelling and changes in the involuntary control of the airway. Therefore inflamed airways become more narrow and obstructed.
When a trigger is introduced, excessive narrowing of airway and hyper-responsiveness of the airways is caused due to inflammation. The triggers can be various infections, cold or flu. Other triggers are allergen such as dust mites, pollen, tobacco smoke and cold air.
If you inhale pollen, it travels through the bronchioles before reaching lungs. If you are sensitive to pollen, the cells that line the bronchi will have receptors on their surface which are activated when they come into contact with pollen grains. [Symptoms of Pollen Allergy]
Many cases of asthma are allergy related and these allergic reactions can cause asthma. Children are sensitized to the allergies if they are introduced to indoor or occupational allergens or respiratory viral infections at an early age.
If child grow and become an adult, this sensitization remains with them in an exaggerated level. Every time if the children come in contact with the allergens to which they are sensitive, an allergic reaction occurs which characterize asthma pathophysiology.
According to the asthma pathophysiology, some of them are not allergic to any common airborne allergens and their asthma is triggered by food allergies, exercise and cold air.
In case of food allergies, a small amount of the allergen will cause the immune system to overreact. In addition to the asthmatic event, nose, eyes and skin may also be affected producing the symptoms of an allergic reaction.
Asthma pathophysiology, in case of exercise induced asthma are caused by inhaling cold air, which affects the muscles within the bronchioles and causes it to constrict and spasm more than normal.
There are number of medications which reverse the constriction quickly and allow normal breathing to resume.