Stress Effects on Pharyngeal Air Pressure and Upper Esophageal Sphincter Pressure During Phonation: The Influence of Vocal Tract Semi-Occlusion

Abstract

The objective of this study was to determine whether vocal tract semi-occlusion (SOVT) influenced stress effects on pharyngeal air pressure and upper esophageal sphincter (UES) pressure during phonation. Relationships between dysphonia and stress are well recognized but poorly understood. Stress effects act globally on the body, and may be observed beyond intrinsic laryngeal muscles to include pharyngeal muscles and the UES, which contribute to voice modulation. Phonation with SOVT may provide resistance to stress effects on the vocal tract. We hypothesized that stress effects on pharyngeal air pressure and UES pressure would be measurable with a high-resolution, 360° pressure catheter, and that stress effects would be impacted differently by occlusal and non-occlusal phonatory tasks. Ten healthy adults performed sustained vowel tasks (comfortable /a/, and loud /a/), and SOVT tasks (bilabial fricative and straw phonation). Each task was performed during a baseline condition, and during stress induced through a cold pressor task. Pharyngeal air pressure and UES pressure were measured via high-resolution manometry. Changes in pressure between baseline and stress were compared among phonatory tasks. Stress-induced changes to UES pressure differed by phonatory task (P < 0.01). Stress increased UES pressures during vowels, but had no effect during bilabial fricative, and decreased UES pressures during straw phonation. Change in UES pressure with stress was greater for comfortable /a/ and loud /a/ than straw phonation (P=0.048 and P=0.019, respectively), and was not significantly different between comfortable /a/ or loud /a/ and bilabial fricative. Stress-induced changes in pharyngeal air pressure were not significantly different among tasks. These findings help identify possible mechanisms underlying the relationship between stress and voice, and point to the utility of SOVT tasks for training vocal tract resistance to stress. This methodology provides a foundation for measuring changes to extra-laryngeal components of the vocal tract during phonation.