Clinical Assessment of Mucociliary Disorders

There has been growing appreciation of the significant role played by the mucociliary transport system in the body. Mucociliary clearance is a critical host defense mechanism of the airways. Effective mucociliary clearance requires appropriate mucus production and coordinated ciliary activity. Mucociliary transport is responsible for primary innate immunity in the respiratory tract. In order to assess mucociliary transport and diseases resulting from mucociliary transport dysfunction, it is first necessary to understand the cellular anatomy and physiology that drive mucociliary function. The primary function of this epithelium is as a protective barrier. There are two different liquid layers coating the epithelial surface: the viscous outer gel layer and the thin inner periciliary layer. The gel layer of the mucus consists of mucin glycoproteins, secreted by goblet cells and submucosal glands. The mucin traps the bacterial compounds, pathogens, and inhaled debris, and coordinated ciliary activity propels the debris-laden mucus toward the glottis for elimination. This action is called mucociliary clearance. Ciliary disorders are divided into two categories: primary (inherited) and secondary (acquired). Primary ciliary dyskinesia (PCD) is a collection of genetic defects in cilia structure resulting in defective ciliary activity. Secondary ciliary dyskinesia (SCD) or acquired ciliary dyskinesia is a transient defect immunociliary clearance that occurs after viral or bacterial infection, tobacco smoke, pollutant exposure, as well as during allergic inflammation. In this chapter, clinical assessment of mucociliary disorders are discussed.