What can increase resistance to airflow in the bronchial passages?

Bronchoconstriction is the process by which the muscles surrounding the bronchial passages tighten, leading to a narrowing of the airways. This constriction restricts airflow and increases the resistance that air encounters as it moves into and out of the lungs. It can be caused by various factors, including allergens, irritants, respiratory infections, or conditions such as asthma.

In contrast, bronchodilation refers to the widening of the bronchial passages, which decreases airway resistance and facilitates easier airflow. Chest expansion generally aids in effective breathing by increasing lung volume and reducing resistance. Airway clearance techniques are designed to remove mucus and other obstructions from the airways, further reducing resistance rather than increasing it. Thus, bronchoconstriction is the primary factor that significantly increases resistance to airflow in the bronchial passages.