Asthma
Asthma is a respiratory condition in which air flow becomes obstructed due to bronchoconstriction, increased mucus secretion and inflammation. Most asthma attacks are (frequently allergic) reactions to substances in the air or sometimes in food. The smooth muscle of bronchi and bronchioles spasm, causing increased Raw resulting in extremely difficult breathing. Also the FRC and the RV are increased.
Asthma is caused by narrowing of the fine airways (bronchioles) due to (involuntary) contraction of muscles in their walls, perhaps because of sensitivity to something in the air. This makes it difficult to breathe air into the lungs, and (paradoxically) difficult to get medicines into the airways to reduce the constriction.