Aerodynamically driven phonation of individual vocal folds under general anesthesia in canines

Abstract

Objectives/hypothesis: We previously developed an instrument called the Aerodynamic Vocal Fold Driver (AVFD) for intraoperative magnified assessment of vocal fold (VF) vibration during microlaryngoscopy under general anesthesia. Excised larynx testing showed that the AVFD could provide useful information about the vibratory characteristics of each VF independently. The present investigation expands those findings by testing new iterations of the AVFD during microlaryngoscopy in the canine model.

Study design: Animal model.

Methods: The AVFD is a handheld instrument that is positioned to contact the phonatory mucosa of either VF during microlaryngoscopy. Airflow delivered through the AVFD shaft to the subglottis drives the VF into phonation-like vibration, which enables magnified observation of mucosal-wave function with stroboscopy or high-speed video. AVFD-driven phonation was tested intraoperatively (n = 26 VFs) using either the original instrument design or smaller and larger versions three-dimensionally printed from a medical grade polymer. A high-fidelity pressure sensor embedded within the AVFD measured VF contact pressure. Characteristics of individual VF phonation were compared with typical two-fold phonation and compared for VFs scarred by electrocautery (n = 4) versus controls (n = 22).

Results: Phonation was successful in all 26 VFs, even when scar prevented conventional bilateral phonation. The 15-mm-wide AVFD fits best within the anteroposterior dimension of the musculo-membranous VF, and VF contact pressure correlated with acoustic output, driving pressures, and visible modes of vibration.

Conclusions: The AVFD can reveal magnified vibratory characteristics of individual VFs during microlaryngoscopy (e.g., without needing patient participation), potentially providing information that is not apparent or available during conventional awake phonation, which might facilitate phonosurgical decision making.

Level of evidence: NA Laryngoscope, 130: 1980-1988, 2020.

Keywords: Canine; dog; lamina propria; larynx; mucosal wave; phonation; vibration; vocal fold; voice.