Bolus volume and viscosity effects on pharyngeal swallowing power-How physiological bolus accommodation affects bolus dynamics.

Background Pharyngeal swallowing power (PSP) is a novel measure of pharyngeal bolus-driving function derived from fluid dynamics principles. This study examined the impact of bolus volume and viscosity on PSP to determine bolus effects on pharyngeal bolus dynamics. The impact of bolus accommodation and physical characteristics of boluses were also explored. Methods Key Results Thirty-four healthy subjects swallowed materials consisting of two bolus volumes (10 and 20 mL) and four bolus viscosities (thin liquid, nectar-thick liquid, honey-thick liquid and pudding). High-resolution impedance manometry was used for data collection. The pharyngeal swallowing mechanism was conceptualized as a hydraulic power system with the UES as a conduit, and PSP was calculated as the product of bolus pressure and flow across the UES. The impact of bolus characteristics on PSP was evaluated using a mixed model approach. Both bolus volume (F-1,F-32.8 = 412.73, P < 0.0001) and viscosity (F-3,F-84.7 = 28.94, P < 0.0001) were significant predictors of PSP. PSP for 20 mL bolus volume was greater than for 10 mL bolus volume. PSP was lowest in the thin liquid bolus condition and highest in the pudding bolus. All pairwise comparisons among bolus viscosities were significant except between thin liquid and nectar-thick liquid bolus viscosities. Test of linear trend across bolus viscosities was significant (F-1,F-97.2 = 77.25, P < 0.0001). Conclusions & Inferences Pharyngeal swallowing power variation across bolus conditions illustrates bolus-related changes in bolus dynamics. Bolus effects on PSP likely result from physiological bolus accommodation combined with physical characteristics of boluses.