The impact of geometrical parameters on acoustically driven drug delivery to maxillary sinuses

Acoustically driven nebulized drug delivery (acoustic aerosol delivery) is the most efficient noninvasive technique for drug delivery to maxillary sinuses (MS). This method is based on the oscillation of the air plug inside the ostium to transport drug particles from the nasal cavity (NC) to the MS. The larger the wavelength of the air plug oscillation in the ostium, the greater the penetration of drug particles to the MS. However, using this technique, the maximum drug delivery efficiency achieved to date is 5%, which means 95% of the aerosolized drugs do not enter the MS and are wasted. Since the largest amplitude of the air plug oscillation occurs at its resonance frequency, to achieve an improved MS drug delivery efficiency, it is important to determine the resonance frequency of the nose-sinus combination accurately. This paper aims to investigate the impact of geometrical parameters on the resonance frequency of the nose-sinus model. Both experimental and computational acoustic models, along with the theoretical analysis, were conducted to determine the resonance frequency of an idealized nose-sinus model. The computational modeling was carried out using computational fluid dynamics (CFD) and finite element analysis (FEA), whereas in the analytical solution, the mathematical relationships developed for a conventional Helmholtz resonator were employed. A series of experiments were also conducted to measure the resonance frequency of a realistic NC-MS combination. The results demonstrated a good agreement between the experimental and CFD modeling, while the FEA and theoretical analysis showed a significant deviation from the experimental data. Also, it was shown that the resonance frequency of the idealized nose-sinus model increases by up to twofold with increasing the ostium diameter from 3 to 9 mm; however, it has an inverse relationship with the ostium length and sinus volume. It was also reported that the resonance frequency of the nose-sinus model is independent of the NC width and MS shape.