Objective: The objective of this study is to introduce a novel method for semi-occluded vocal tract (SOVT) therapy called "controlled supraglottic pressure phonation," determine the mechanism by which supraglottic pressure contributes to lowering impedance during SOVT therapy, and provide the optimal supraglottic pressure range for SOVT exercises.
Methods: Twenty-five human subjects were assigned to one of five supraglottic pressure levels, 0, 2, 4, 6, and 8 cmH2O, which were controlled through a continuous positive airway pressure device. Subjects were asked to phonate during both a short- and long-duration task, in which vocal properties were measured before and after. At the end of each task, the subjects reported the levels of discomfort and phonation difficulty on a 0-10 scale to assess the subjective improvement of vocal economy.
Results: Significant differences were observed between pre- and post-task measurements for phonation threshold pressure for both the short-duration and long-duration tasks. Phonation threshold flow and frequency measurements were found to have no statistically significant differences. The subjective measures showed elevated discomfort in the higher pressure inputs for both tasks relative to no air.
Conclusion: Higher supraglottic pressure levels will improve ease of phonation, but the treatment discomfort needs to be considered as well, yielding an optimal supraglottic pressure range of 4-6 cmH2O. "Controlled supraglottic pressure phonation" serves as an alternative to straw phonation that may produce additional benefits.
Keywords: CPAP; Impedance; Phonation threshold pressure; Semi-occluded vocal tract; Supraglottic pressure; Voice.
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