Pharyngeal Swallow Adaptations to Bolus Volume Measured with High-Resolution Manometry

Objective: To determine the effect of bolus volume on pharyngeal swallowing using high-resolution manometry (HRM). Study Design: Repeated measures with subjects serving as own controls. Methods: Twelve subjects swallowed four bolus volumes in the neutral head position: saliva; 5 mL water; 10 mL water; and 20 mL water. Pressure measurements were taken along the length of the pharynx using a high-resolution manometer, with emphasis placed on the velopharynx, tongue base, and upper esophageal sphincter (UES). Variables were analyzed across bolus volumes using three-way repeated measures analysis of covariance (ANCOVA) investigating the effect of sex, bolus volume, and pharynx length. Pearson's product moment tests were performed to evaluate how pharyngeal pressure and timing events changed across bolus volume. Results: Velopharyngeal duration, maximum tongue base pressure, tongue base pressure rise rate, UES opening duration, and total swallow duration varied significantly across bolus volume. Sex did not have an effect, whereas pharynx length appeared to affect tongue base pressure duration. Maximum velo-pharyngeal pressure and minimum UES pressure had a direct relationship with bolus volume, whereas maximum tongue base pressure had an inverse relationship. Velopharyngeal pressure duration, UES opening duration, and total swallow duration increased as bolus volume increased. Conclusions: Differences in pharyngeal pressures and timing of key pressure events were detected across varying bolus volumes. Knowing the relationships between bolus volume and pharyngeal pressure activity can be valuable when diagnosing and treating dysphagic patients.