Changes in phonation threshold pressure with induced conditions of hydration

Abstract

The purpose of this pilot study was to investigate the relationship between phonation threshold pressure and level of hydration in human subjects. Six adult subjects produced consonant-vowel-consonant strings as quietly as possible at low, medium, and high pitches in no-treatment, hydrated, and slightly dehydrated conditions. Average oral pressures for these trials were used to estimate minimal subglottal pressures required for phonation (phonation threshold pressure). Main effects for hydration and for pitch were significant, as was the interaction of hydration times pitch. Overall, the lowest pressures were seen for the hydrated (or “wet”) condition, and reduction in baseline pressures was greatest for high pitches in this condition. The highest pressures were found for the dry condition, and the greatest increase in pressure relative to the baseline was found at low pitches for this condition. Threshold pressures for intermediate (speaking) pitches were not affected by hydration condition. The findings are consistent with previously reported theoretical predictions regarding the relationship between oscillation threshold pressures and tissue viscosity. They are also consistent with previous empirical reports on the effect of direct hydration of vocal fold tissue in nonhuman subjects. The purpose of this pilot study was to investigate the relationship between phonation threshold pressure and level of hydration in human subjects. Six adult subjects produced consonant-vowel-consonant strings as quietly as possible at low, medium, and high pitches in no-treatment, hydrated, and slightly dehydrated conditions. Average oral pressures for these trials were used to estimate minimal subglottal pressures required for phonation (phonation threshold pressure). Main effects for hydration and for pitch were significant, as was the interaction of hydration times pitch. Overall, the lowest pressures were seen for the hydrated (or “wet”) condition, and reduction in baseline pressures was greatest for high pitches in this condition. The highest pressures were found for the dry condition, and the greatest increase in pressure relative to the baseline was found at low pitches for this condition. Threshold pressures for intermediate (speaking) pitches were not affected by hydration condition. The findings are consistent with previously reported theoretical predictions regarding the relationship between oscillation threshold pressures and tissue viscosity. They are also consistent with previous empirical reports on the effect of direct hydration of vocal fold tissue in nonhuman subjects.