'Magic' sinus paths could mean new instructions for nasal sprays

Paranasal sinuses are essentially hollow cavities in the skull surrounding your nasal cavity. While the role of the sinuses is debated, it is believed they function to decrease the weight of the anterior skull, increase voice resonance and buffer against facial trauma. Their location and structure provide the ideal environment for bacterial growth, infection or viral deposition, often leading to diseases like chronic rhinosinusitis (CRS). The typical treatments for these conditions consist of topical medications (nasal sprays) and oral antibiotics.

Researchers Saikat Basu, Zainab Farzal and Julia S. Kimbell of the University of North Carolina's School of Medicine will present their research on the anatomy-based flow physics in nasal cavities which generate "magical" streamlines for sinus drug delivery at the 70th annual meeting of the American Physical Society's Division of Fluid Dynamics, being held Nov. 19-21, 2017, at the Colorado Convention Center in Denver, Colorado.

"We found that current package instructions for such sprays are not optimal for maximal drug transport to the sinuses, which is a function of various factors like head orientation of the patient, breathing rates and the spray bottle orientation during drug spray," Basu said.

For the medication to have the greatest effects, the active ingredients must deposit inside or in close proximity of the affected sinus cavities. To ensure accurate anatomical representation in the numerical simulations of the sprayed drug transport process, they used computed tomography (CT) scans from CRS patients and imaging software to develop anatomically realistic digital 3-D models.

Understanding the physics of sinus airflow pathways enables the identification of optimal release points for the nasal sprays. Advances in anatomical modeling make it possible to determine the effect of specific drug routes.

"Ambient respiratory flow physics exert a considerable influence on the transport of sprayed particles in our nasal cavities," Basu said. "With the advances in computational capacities, it is now possible to develop digital 3-D models of complex physiological systems and track transport processes therein through computational fluid mechanics."

The preliminary results of this study are relevant to both the consumer and the manufacturer of nasal sprays. The researchers found that when the spray nozzle was inserted deeper into the nose (10mm) that it performed better and that while the current instructions for the spray bottle recommend holding it at 22.5 degrees, drug transport was better at an angle of 35-45 degrees. Drug providers will be able to recommend more effective instructions and application techniques to ensure that the spray reaches its target. Findings might also suggest improvements in the design of the spray console that would amplify the medication deposits inside the sinus cavities.