Quantitative Study of the Effects of Dehydration on the Viscoelastic Parameters in the Vocal Fold Mucosa

The goal of this study was to quantify the viscoelastic parameters of the vocal fold mucosa at varying dehydration levels.

Healthy canine larynges were obtained postmortem, and the samples were separated from the subglottal wall. The samples were dehydrated in a vacuum dryer. According to the total dehydration time per sample, dehydration levels were divided into four degrees: 0%, 40%, 60%, and 80%. The stepper was set to stretch the sample to a level of 35% strain at the same rate (0.5 mm/s). Data collection was repeated five times under each dehydration condition. The compression resilience, RC% = S'/S*100%, and the hysteresis area were measured according to the stress-strain curves. The varying properties of the samples under different dehydration levels were investigated by fitting the curves.

The area of the hysteresis loops observed in the stress-strain curves increased exponentially with dehydration levels, whereas the RC% decreased linearly. For all curves, low-strain stages can be explained by Hooke's law (σ = E₀*ε). With increasing levels of dehydration, E₀ was shown to increase, whereas the linear range was shortened. High-strain stages resembled exponential rather than the linear curves. And the nonlinear stage of the curve became increasingly apparent in the stress-strain curves of increased dehydration levels.

The quantitative results in this study not only provide a numerical reference for future experimental measurements, but also can be used to verify the biphasic model in future studies.