Mechanisms of mucous transport.

The relative importance of mucociliary mechanisms in the sinuses are: ciliary beating greater than secretory pressure greater than sneezing greater than gravity. The relative importance for the Eustachian tubes and the middle ear are: ciliary beating much greater than peristalsis greater than secretory pressure. On the other hand for the small airways differential airflow much greater than ciliary beating and for the large airways: differential airflow greater than coughing or sneezing greater than ciliary beating. Differential airflow past any point in the airways comes from the relatively equal inspiratory and expiratory volumes and durations of flow and the narrowing of the airways on expiration. Mathematical modeling shows the mucous pumping to be directly related to the minute volumes. Also that this mucous pumping can, in the absence of ciliary beating at normal resting tidal breathing, pump 15 to 20 milliliters of mucus per day. Intubation of cystic fibrosis patients with volume controlled ventilators using 1:1 inspiratory/expiratory ratios has permitted the majority of these patients to be extubated.