Pilot Study of a New Technique for Assessing Mucociliary Clearance and Airway Surface Liquid Volume in Cystic Fibrosis

Improper function of the mucociliary clearance system in the Cystic Fibrosis (CF) lung is a major factor contributing to the chronic respiratory manifestations of the disease. Normally this host defense mechanism removes inhaled pathogens and toxins from the inner surfaces of the lung. In CF, mutations in the CF gene result in dysfunction of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) ion channel on the cells that line the airway epithelium, causing improper fluxes of ions such as sodium, chloride, and bicarbonate. The so called "low volume" hypothesis of CF pathogenesis contends that the liquid lining the airways becomes very thin and viscous due to abnormal absorption of sodium from the airways, which draws water out of the airways, partially or totally defeating mucociliary clearance. The rate at which the mucociliary system clears materials from the lungs can be quantified using a nuclear medicine test called a mucociliary clearance scan. This study pilots a new variation of the mucociliary clearance scan that uses both "floating" and "penetrating" radioisotope tags. The difference in clearance between these tags will provide information on how airway surface liquid volume affects mucociliary clearance. This pilot trial will include the imaging of n=5 CF subjects and n=5 healthy subjects.