Low-frequency pulsed ultrasound in the nasal cavity and paranasal sinuses: a feasibility and distribution study.

Bacterial biofilms have been implicated in refractory rhinosinusitis. Biofilms have been shown to respond to treatment with low-frequency ultrasound (LFU) therapy in vitro, and exposure to LFU has shown efficacy in wound repair and topical drug delivery in other fields. This preliminary study was designed to evaluate the safety and feasibility of LFU for use in the nasal cavity and paranasal sinuses. This was an experimental observational study. Six cadaver heads were used to deliver a mixture of Renografin and methylene blue solvent to the paranasal sinuses via LFU both before and after resident endoscopic sinus dissection. Sinus computed tomography (CT) scans of the cadaver heads were performed before and after mixture delivery, and blinded assessments were made for distribution to individual sinuses. Mucosa was harvested from 2 subsites to evaluate LFU-treated cadaver tissue. Predissection, LFU delivered solution to 12 of 12 inferior and middle turbinates, 6 of 12 of the superior turbinates and ethmoid sinuses, and 1 of 12 maxillary sinuses as shown by contrast radiography. Postdissection, all heads showed delivery to the maxillary and sphenoid sinuses, with 8 of 12 sinus cavities showing delivery to the ethmoid region, and 4 of 11 to the frontal recess. Using hematoxylin and eosin (H&E) staining of tissue frozen sections, harvested tissue demonstrated no architectural damage to the mucosal layer from LFU exposure. LFU appears to be capable of reliably delivering topical solution to the turbinates and ethmoid region preoperatively and to all sinuses, except the frontal, postoperatively. The nasal epithelium does not appear to be disrupted histologically from LFU at this time and distance. This data provides a foundation for a prospective human protocol studying the efficacy of this modality in the treatment of patients with chronic rhinosinusitis and biofilm formation.