The role of mucus in cough research.

Cough is a defense mechanism for promoting airway hygiene when mucociliary clearance is ineffective due to increased mucus secretion, inflammation, infection, or ciliary dysfunction. Secretions can contribute to airflow limitation and chronic hypersecretion can worsen airway inflammation with retained inflammatory cells and mediators. The focus of the Second Annual Cough Conference has been on cough as a troublesome symptom; but to understand the importance and effectiveness of cough clearance, it is critical to understand airway secretions. The biophysical properties of mucus and phlegm determine how readily these secretions can be cleared by coughing.