Investigation of Sinonasal Airflow and Transport

Abstract

This work comprises an investigation of airflow and transport in the human upper airways, which not only perform essential air conditioning physiological functions (heat and water exchange and primary filtration) but also house the olfactory receptors. The conflicting requirements posed by efficient air transit on the one hand and sampling for olfaction on the other renders the geometry of the upper airways complex. Knowledge of the geometry and flow conditions are primary requirements for understanding the physiological mechanics of the airways. This work describes the application of imaging and experimental measurement techniques to determine the variations in nasal airway geometry and the characteristics of nasal inspiratory flow. Whilst the results are relevant to a host of applications, the particular case of sinonasal ventilation well illustrates the interrelation between form, flow and function as well as motivating the development of improved techniques for clinical management. Specifically 3T MR imaging has been investigated as a means to define the anatomy in congested and decongested states. Results show very large changes in nasal airway calibre and moreover allow the variation in mucosal engorgement throughout the nasal cavity to be mapped. Highly time resolved hot wire measurements of inspiratory flow profiles revealed for the first time the rapid temporal development of inspiratory flow during normal inspiration and dramatically so during sniffing. Variations in flow profile were recorded across a cohort of subjects for conditions of normal inspiration, sniffing and smelling. Sinonasal gas exchange is of particular interest given the common occurrence of sinus pathologies. Here short half-life Krypton imaging has been used to investigate gas exchange between the maxillary sinus and the nasal cavity. It has been shown that the technique can provide quantitative assessment of volume flow rate in a model, demonstrating the rapid venting associated with an accessory ostium.