How can chloride ions affect water transport and mucus buildup in cystic fibrosis?

Altered cell functio: Simple chemistry-water moves along with salt movement. Fundamental defect in epithelial cell (lining cell of airway) of CF patient is an inability to secrete salt (chloride) to airway lumen and secondarily to secrete water in the presence of excessive salt and water reabsortion. The end result is dessication of respiratory secretion, and this dry thickened mucus is hard to expectorate.