Viscoelastic properties of bronchorrhoea sputum in bronchial asthmatics

Dynamic viscoelastic properties of 13 bronchorrhoea sputum samples from asthmatics with bronchorrhoea, defined as the production of watery sputum of 100 ml or more per day during asthmatic attacks, were examined and then compared with 7 saliva and 12 mucoid sputum samples obtained from patients during remission. Dynamic viscosity (eta') and elasticity (G') of bronchorrhoea sputum increased rapidly with time up to 2 hours after collection and slowly thereafter, whereas eta' and G' of saliva and mucoid sputum remained unchanged up to 6 hours after collection. Then, eta' and G' of saliva, bronchorrhoea and mucoid sputum samples were measured between 2 to 4 hours after expectoration. Bronchorrhoea sputum samples showed significantly larger values at frequencies of both 0.1 and 1.0 rad/sec than did saliva samples and also significantly smaller values than did mucoid sputum samples. Thus, bronchorrhoea sputum differed in dynamic viscoelastic properties from saliva, indicating that it does not result from hypersalivation. Based on data of viscoelastic changes with time, it can be assumed that the viscoelasticity of bronchorrhoea sputum in the airways is considerably less than the optimal range reported previously for mucociliary velocity, suggesting the possibility of impaired mucociliary transport.