Asthma is a common pulmonary condition characterized by chronic inflammation of respiratory tubes, tightening of respiratory smooth muscle, and episodes of bronchoconstriction. The pathophysiology of asthma is complex and involves airway inflammation, intermittent airflow obstruction, and bronchial hyperresponsiveness. The following are the key features of the pathophysiology of asthma:

• Bronchoconstriction: During an asthma episode, inflamed airways react to environmental triggers such as smoke, dust, or pollen. The airways narrow and produce excess mucus, making it difficult to breathe. In essence, asthma is the result of an immune response in the bronchial airways. The airways of asthma patients are "hypersensitive" to certain triggers, also known as stimuli. In response to exposure to these triggers, the bronchi (large airways) contract into spasm (an "asthma attack"). Inflammation soon follows, leading to a further narrowing of the airways and excessive mucus production, which leads to coughing and other breathing difficulties.

• Airway inflammation: Inflammation in asthma may be acute, subacute, or chronic, and the presence of airway edema and mucus secretion also contributes to airflow obstruction and bronchial reactivity. The inside walls of the airways are often swollen and inflamed, leaving less space inside. Preventer or controller medicines work by reducing the inflammation that causes the swelling.

• Bronchial hyperresponsiveness: The presence of airway hyperresponsiveness or bronchial hyperreactivity in asthma is an exaggerated response to numerous exogenous and endogenous stimuli. The mechanisms involved include direct stimulation of airway smooth muscle and indirect stimulation by pharmacologically active substances from mediator-secreting cells such as mast cells or nonmyelinated sensory neurons.

• Tissue remodeling: Ongoing inflammation in the airways can lead to the development of scar tissue and “tissue remodeling”. This results in thickened airway walls and increased smooth muscle.

In summary, asthma is a complex condition that involves inflammation, bronchoconstriction, bronchial hyperresponsiveness, and tissue remodeling. The pathophysiology of asthma is characterized by airway inflammation, intermittent airflow obstruction, and bronchial hyperresponsiveness.