Rheological properties of microliter quantities of normal mucus

Microliter quantities of normal canine tracheobronchial mucus were obtained by direct sampling from the tracheas of anesthetized dogs. The rheological properties of the mucus samples were determined using a newly developed magnetic rheometer. The data show a very rapid decrease in dynamic viscosity with increasing frequency, and a much less rapid increase in elasticity. Mean values of elasticity and viscosity at 1 rad-s-1 for seven dogs were ca. 300 dyn-cm-2 and ca. 75 P, respectively. The steady-state viscosity values were ca. 3 X 10(4) P, i.e., two orders of magnitude higher than the highest dynamic values measured. The significance of the rheological behavior in terms of the clearance of secretions from the lung is discussed.