Effects of surface dehydration on mucosal wave amplitude and frequency in excised canine larynges

Objective. Evaluate the effect of vocal fold surface dehydration on mucosal wave amplitude and frequency. Study Design. Controlled test-retest. Setting. Larynges were mounted on an excised larynx phonation system and attached to a pseudolung in a triple-walled sound-attenuated room that eliminated background noise and maintained a stabilized room temperature and humidity level. Subjects and Methods. High-speed video was recorded for 8 excised canine larynges during exposure to dehumidified air at 20 cm H ₂O. Control trials consisted of high-speed videos recorded for 2 excised canine larynges during exposure to humidified air at the same pressure. Results. In the majority of larynges, increased levels of dehydration were correlated with decreased amplitude and frequency. The slope of the linear regression fitted to the change in amplitude (P = .003) and the percent change (P < .001) between the initial and final trials were significantly decreased in dehydrated larynges. These measurements with respect to the change in frequency were also significantly decreased in dehydrated larynges (P < .001; P = .027). Conclusion. Vocal fold surface dehydration caused a decrease in mucosal wave amplitude and frequency. This study provides objective, quantitative support for the mechanism of voice deterioration observed after extreme surface dehydration.