Technical Approaches to Analyze the In Vivo Ion Composition of Airway Surface Liquid

Airway surface liquid (ASL) is generally described as a two-layer system formed by a “sol” (or periciliary) and a “gel” layer (overlying the cilia). The ASL, whose total thickness is estimated to be between 10 and 40 �m, contributes to mechanical and antimicrobial defense systems in host airways. In cystic fibrosis (CF), lack of functional cystic fibrosis transmembrane conductance regulator (CFTR) protein may modulate the composition of ASL and lead to an impaired mucociliary clearance associated with inhibition of host defense activity.