An elder adult patient with a history of chronic bronchitis is admitted to the ICU with exacerbated respiratory distress. He is producing a significant amount of thick mucus. Despite aggressive treatment, he becomes increasingly hypoxemic, and a chest x-ray reveals a new area of lung collapse (atelectasis). Which mechanism best explains why one or more segments of the patient's lungs have lost volume or collapsed due to failure in routinely clearing the airway mucus?
a) The mucus triggers a reflexive spasm of the bronchial walls, reducing airway diameter and leading to alveolar collapse.
b) The mucus directly compresses the alveoli, mechanically forcing air out and causing collapse.
c) Excessive mucus stimulates a localized inflammatory reaction that results in alveolar damage and subsequent collapse.
d) Air becomes resorbed from the alveoli distal to the mucus plug, leading to atelectasis.