The mucociliary clearance (MC) system is a vital host defence in the lungs and upper airways. Airway mucus traps inhaled bacteria, viruses, fungi and toxins. Underneath the mucus, airway cilia beat synchronously within a thin, watery periciliary liquid layer, propelling the overlying mucus layer towards the mouth. MC is dependent on ciliary structure and function and the composition and hydration of the airway surface liquid. When functioning normally, the MC system prevents mucus obstruction and clears pathogens and toxins (including cigarette smoke) from the airways. Cough clearance augments MC. MC is absent in primary ciliary dyskinesia (PCD).1 Other lung diseases such as cystic fibrosis (CF),2 chronic obstructive pulmonary disease (COPD),3 asthma4 and bronchiectasis5 have been associated with insufficient MC.

MC rates can be measured in vivo using nuclear imaging after the delivery of radiolabelled particulate into the airways.2 6 MC transport can be assessed in vitro in airway cell cultures or ex vivo in isolated airway sections using fluorescent probes. Ciliary motion and beat frequency can be measured using video microscopy. …