|dc.description.abstract||Aim: To determine if a universal pressure profile exists between healthy volunteers swallowing liquids of varying viscosity, and to investigate the effects of increased viscosity on these pressure patterns within and between individuals.
Methods: A custom made appliance with 7 miniature pressure transducers located along the mid-line and lateral palate was used to measure absolute pressures during 10ml water and honey-thick liquid swallows. Data were obtained from 10 healthy volunteers (5 males, 5 females; 22-42 years) with full permanent dentition. Following accommodation, subjects performed liquid swallows on command. Each subject performed swallows on 2 subsequent days yielding data from 12 swallows per individual for each liquid. Using the Scope® and Zoom® function of the LabChart® 7.0.2 software by ADInstruments, each individual’s pressure profiles were aligned at the initial major pressure peak of the midpalatal channel to create an average swallowing profile for each liquid type. The average swallowing profiles from each individual were similarly overlaid to create generic average pressure profiles for each liquid.
Results: An underlying pattern common to all subjects was found within the highly variable individual pressure patterns. This was divided in to 4 stages: preparatory, primary propulsive, intermediate and terminal. To facilitate descriptive analysis, these stages were further sub-classified according to pressure patterns generated at the individual level. These were; tipper and dipper patterns in the preparatory stage, roller and slapper in the primary propulsive and monophasic or biphasic during the intermediate stage. Increased viscosity caused significant changes to these pressure patterns in certain individuals with little change in others. Stages most affected by increased viscosity were the preparatory and intermediate phases, whereas the primary propulsive stage was minimally affected. This highly individual response to increased viscosity was also observed with swallowing duration. Inter-individual variation of absolute pressures was too great to derive any significant change at the group level; however, negative pressure gradients were found to be associated with gathering of the bolus prior to the primary and secondary positive pressure clearing waves. Significant changes in absolute pressure values were found at the individual level and these were highly variable with respect to region, symmetry and amplitude.
Conclusion: Despite highly variable individual absolute pressures, there was sufficient similarity in timing and polarity to describe a universal pressure profile. The closely related pressures generated anteriorly and laterally were consistent with a gathering of the bolus into a midline groove prior to a propulsive clearing wave along the midline. Despite this common swallowing pattern, widely disparate responses to increased viscosity occurred at the individual level. Average values were inappropriate for predicting an individual’s response to altered viscosity and as such, clinical interventions would be best aimed at the individual, rather than population level. The presence of an intermediate phase and secondary propulsive waves may indicate a less efficient clearance of the oral cavity and subsequently a greater risk of dysphagia. Further investigation on pressure profiles in geriatric, paediatric and dysphagic populations is required.||