[Rheology of bronchial secretions and mucociliary transport (author's transl)].

Optimal relationships between mucociliary clearance and rheological properties of bronchial secretions expectorated by patients with chronic bronchitis have been analysed by successive measurements of visco-elasticity with a rotational rheometer and of transport velocity on frog palate mucosa. It appears that the role of the elastic component is predominent. Sputum characterized by very low strain recovery (SR less than 4 units) or conversely by very high elasticity (SR greater than 20 units) is transported at a low rate in comparison to that of the control frog mucus (relative transport rate less than 0.5). Pronounced hyperviscosity of sputum (no greater than 200 poises) appears also as a limiting factor to the mucociliary transport. The best transported secretions (relative transport rate greater than 0.7) are characterized by a relative elasticity (SR) of 4 to 13 units and a viscosity (no) of 25 to 200 poises. Under the action of mucolytic agents such as N-acetylcysteine, sputum initially characterized by low strain recovery (SR less than 4 units) is transported at a much slower rate which is related to the increased loss of elasticity. These results indicate that mucolytic drugs must be administered with great care in patients with chronic bronchitis. Moreover, they should not be used in patients with very low visco-elastic secretions which reflect the non-functional state of the bronchial mucosa.