The effects of mucolytic agents and stirring on sputum viscoelasticity

Changes in the behavior of sputum viscoelasticity due to differences in macroscopic appearance of sputum brought about by stirring and those due to the addition of an expectorant to purulent sputum in vitro, were studied in a coaxial cylinder rheometer. First, initial results from stirring the sputum indicated the following: Samples of untreated sputum showed no obvious differences among the three macroscopic groups, mucoid, mucopurulent and purulent, on the basis of dynamic viscoelasticity. However, when they were stirred sufficiently, dynamic viscosity and storage modulus increased in mucoid sputum and decreased in purulent sputum. Second, the addition of expectorants revealed the following results: (i) When distilled water was used as a control substance added to sputum, the addition of 0.5% semialkaline proteinase to sputum decreased the dynamic viscosity and storage modulus of the sputum to a large extent. (ii) The addition of 0.2% Bromhexine exerted a small influence upon the dynamic viscosity and slightly increased the storage modulus. (iiii) The addition of 20% N-acetyl-L-cysteine increased the dynamic viscosity slightly, but decreased the storage modulus to a large extent. In brief, each expectorant exerted a unique influence on the viscoelasticity of sputum. These results were discussed with regard to their clinical significance.