RHEOLOGY OF BRONCHIAL-SECRETIONS AND MUCOCILIARY TRANSPORT

Abstract

Optimal relationships between mucociliary clearance and rheological properties of bronchial secretions expectorated by patients with chronic bronchitis were analyzed by successive measurements of visco-elasticity with a rotational rheometer and of transport velocity of frog palate mucosa. The role of the elastic component is apparently predominent. Sputum characterized by very low strain recovery (SR < 4 units) or conversely by very high elasticity (SR > 20 units) is transported at a low rate in comparison to that of the control frog mucus (relative transport rate < 0.5). Pronounced hyperviscosity of sputum (.eta.0 > 200 poises) appears also as a limiting factor to the mucociliary transport. The best transported secretions (relative transport rate > 0.7) are characterized by a relative elasticity (SR) of 4 to 13 units and a viscosity (.eta.0) of 25-200 poises. Under the action of mucolytic agents such as N-acetylcysteine, sputum initially characterized by low strain recovery (SR < 4 units) is transported at a much slower rate which is related to the increased loss of elasticity. Mucolytic drugs should be administered with great care in patients with chronic bronchitis and they should not be used in patients with very low visco-elastic secretions which reflect the non-functional state of the bronchial mucosa.