Mucociliary clearance in maxillary sinuses

Paranasal sinuses are hollow spaces within the bones surrounding the nose. Of these, the largest are the maxillary sinuses, that are situated near the cheek region. The sinuses are lined with a ciliated epithelium, which is the site of mucus production. The cilia constantly sweep this mucus out of the sinus into the nasal cavity, thus maintaining a clean mucus layer within the sinuses, which is essential for a healthy nasal environment. We present here an experimentally informed continuum mathematical model of this mucus clearance process: the flow of a thin fluid film produced by a wall-normal flux and swept out of the domain due to the effective action of cilia, and subject to both gravity and surface tension. Our modelling includes both one-dimensional systems and patient-specific sinus geometry. In each case, we identify physical conditions under which a steady mucus flow is possible, which allows us to highlight the competition between gravitational retention and boundary-driven drainage in the mucus dynamics.