What is a common trigger for bronchospasm?

Bronchospasm is characterized by the contraction of the smooth muscle in the bronchial walls, leading to narrowing of the airways, increased resistance to airflow, and difficulty breathing. This contraction can be triggered by various stimuli, such as allergens, irritants, exercise, and certain medical conditions like asthma.

When bronchial smooth muscles contract, they lead directly to a tightening of the airway lumen, causing the symptoms associated with bronchospasm, such as wheezing and shortness of breath. Understanding this mechanism is important for recognizing and addressing bronchospasm effectively in patients, particularly in a clinical or emergency situation.

The other options do not directly cause bronchial smooth muscle contraction; instead, they either relate to the body's gas exchange processes or environmental conditions that may contribute to but do not directly initiate bronchospasm.