Low-Frequency, Pulsatile Delivery of Water Vapor to the Maxillary Sinus: Feasibility, Limitations, and Design Implications

Efficient aerosol delivery to the maxillary sinuses remains challenging because narrow ostia limit sinus entry. This in vitro study evaluated whether low-frequency, large-amplitude pulsatile flow can deliver humidifier-generated water aerosols to the maxillary sinuses, compared retention with e-vapor under identical conditions, and identified setup modifications required for water aerosol transport. Experiments used three transparent anatomically realistic sinonasal models: two single-passage models with narrow-long (NL) and wide-short (WS) ostial geometries, and one dual-passage dual-maxillary-sinus (RL) model. Water aerosols and e-vapor were delivered using a modified servo-actuated syringe generator under fixed conditions: 50 mL stroke volume, 0.33 Hz frequency, 1 L/min vacuum-induced flow, and 1.5 min delivery. Water aerosols were larger than e-vapor aerosols (D50 = 5.553 µm vs. 3.394 µm) and required setup modification because of greater wall interactions, condensation, coalescence, and transport losses. Pulsatile delivery achieved plume entry into all tested maxillary sinuses. E-vapor showed greater retained mass than water aerosols in NL (1.060 ± 0.152 vs. 0.540 ± 0.089 mg) and WS (0.800 ± 0.071 vs. 0.520 ± 0.110 mg). Water-sensitive Sar-Gel visualization confirmed bilateral water aerosol retention in RL. These findings support pulsatile delivery as a feasible strategy for water aerosol transport to the maxillary sinuses but with a lower efficiency than e-vapor aerosols.