The rheological properties of sputum

Mucoid sputum has been examined by three different rheological techniques, continuous shear, creep and oscillation. Continuous shear experiments using a Ferranti–Shirley cone and plate viscometer, are limited in their application by the viscoelastic nature of the material. In creep sputum can be represented by a simple four element mechanical model in which the moduli of rigidity and viscosities are appreciable (50–100 dyn cm⁻² and 0.7–2.4 × 10⁴ Poise respectively). Oscillation experiments over the frequency range 8 × 10⁻²–10 Hz, support the view that the structure of sputum is due to the entanglement of mucoprotein chains.