How Do Tube Diameter and Vocal Tract Configuration Affect Oral Pressure Oscillation Characteristics Caused by Bubbling During Water Resistance Therapy?

Purpose: The present study aimed at observing the effect of tube diameter and vocal tract configuration on frequency, amplitude, and regularity of Poral oscillation caused by bubbling during water resistance therapy (WRT). A secondary objective was to examine the degree of self-perceived sensation of massage-like effect produced by bubbles during WRT. Methods: Forty-two participants were included in this study. Assessment protocol included: (1) self-assessment of massage-like sensation and (2) objective assessment of air pressure-related variables. In the first section, participants were instructed to select and produce a sustained-vowel like phonation into three different tubes (varying inner diameter) submerged 5 cm below the water surface. Also, two different vocal tract configurations were produced by all subjects: (1) horizontal position (regular vocal tract position), (2) vertical position (yawning position with low vertical laryngeal position). Participants were asked to self-assess their massage-like sensation. In the second section, objective measurements of air pressure-related variables were acquired during WRT exercises. Results: Statistical differences were driven by tube inner diameter for oral pressure oscillation frequency, amplitude, jitter and shimmer and self-perceived massage-like sensation. Vocal tract position generated differences for medium-size tube and large-size tube only for self-perceived massage-like sensation. Conclusion: Inner diameter of tube and configuration of vocal tract affect bubble characteristics and massage-like sensation during WRT. Larger tube diameters and vocal tract volumes seem to produce more regular bubbles, lower bubble frequency, and larger bubble amplitude, causing a more evident massage-like sensation. Therefore, control of these variables is apparently relevant to obtain the best effect in patients with voice disorders.