Effect of bolus volume and flow time on temporospatial coordination in oropharyngeal pressure production in healthy subjects

The effects of bolus volume and flow time on the sequential coordination of tongue pressure (TP) and pharyngeal pressure (PP), which are important in the biomechanics of swallowing, are unclear. In this study, we measured TP and PP simultaneously in 10 healthy adults at multiple points during dry swallowing and the swallowing of 5 ml and 15 ml of liquids with different viscosities, and investigated changes in the timing of the onset, peak, and offset of these pressures. TP was measured using a sensor sheet system with five measuring points on the hard palate, and PP was measured using a manometry catheter with four measuring points. The order and correlations of sequential events, such as onset, peak, and offset times of pressure production, at each pressure measuring point were analyzed on the synchronized waveforms. We found that the differences between the TP and PP onset times decreased when the bolus volume was larger. The change in bolus volume had very little effect on peak time or offset time. The flow time of the bolus affected the appearance of onset and peak time for both TP and PP. A time difference between TP and PP emerged as the flow time increased, with TP starting to appear before PP. This may be the first detailed analysis of pressure-flow dynamics that treats the mouth and pharynx as a single functional unit. We believe that our analysis is an important step toward extending future research to include a wider range of age groups and dysphagia patients. Bolus volume affected onset time, and bolus viscosity affected onset time and peak time. Offset time was clarified to be unaffected by either bolus volume or viscosity. [Display omitted] •We simultaneously recorded tongue pressures (TP) and pharyngeal pressures (PP) during the swallowing.•The boluses consisted of six different types: 5 ml and 15 ml of liquid, thin liquid (1.0% w/v), and thick liquid (2.5% w/v).•The differences between the TP and PP onset times decreased when the bolus volume was larger.•The viscosity of the bolus affected the appearance of onset and peak time for both TP and PP.•A time difference between TP and PP emerged as the viscosity increased, with TP starting to appear before PP.