The Influence of Localized Vocal Fold Swelling on Vocal Fold Phonation Threshold Pressure and Collision Pressure

Localized vocal fold (VF) swelling is a common precursor for phonotraumatic vocal hyperfunction (e.g., VF nodules) that arises due to accumulation of fluid. VF nodules increase collision forces during phonation, which can lead to a cascading cycle of damage. However, the initial formation of VF nodules, usually characterized by localized swelling, is not well understood. This study investigates the influence of localized swelling and determines its influence on vocal fold phonation threshold pressure (PTP) and collision pressure. Localized swelling was modeled by creating a spherical void at the midline of a four-layer synthetic VF below the superficial lamina propria. Initially, the void was filled with 0.01 mL of water to denote localized swelling. A hydrogel solution was subsequently injected to simulate increasing stiffness. The VF was placed in a hemilaryngeal flow facility to measure the collision pressure. The results show that initial stages of swelling due to fluid accumulation reduce collision pressure due to higher compliance, which cushions the vocal fold surface. However, as the stiffness of the hydrogel increases, the collision pressure significantly increases.