Mucus viscoelasticity and mucociliary transport rate.

The aim of this research was to define in quantitative terms the relationship between the viscoelastic properties of mucus and the velocity at which it can be transported by a ciliated mucosa. To this effect, tests were performed on frog palates with normal beating cilia which were washed free of endogenous mucus. Experimental sputum samples encompassing a wide range of viscoelastic properties were applied to the palates, and their transport velocity was measured under a dissecting microscope. The results indicated that the fastest transport, per palate, was achieved by sputa whose Newtonian viscosity and linear elastic modulus fell within the range of 1,000 to 3,000 poises and 10 to 25 dynes/cm2, respectively. The transport velocity decreased when the sputum viscoelasticity was above or below this optimal range. The latter condition is of particular importance since it indicates that marked fluidification may hinder rather than promote mucus clearance.