2017 Volume 58 Issue 2 Pages 135-142
The repetitive saliva swallowing test (RSST) is widely used as a simple and non-invasive screening test for dysphagia. However, sufficient research has not been carried out concerning how saliva secretion may influence swallowing frequency. The purpose of this study is to clarify the influence of saliva secretion on swallowing frequency.
Lemon water has been reported to be a good accelerator of saliva secretion. In this study, healthy subjects were instructed to swallow saliva up to ten times each after drinking three different concentrations of 15 ml lemon water (0%, 10% and 30%). Intra-aural swallowing sounds were recorded and analyzed to measure the timing of each swallowing and calculate the interval between two adjacent acts of swallowing.
This study revealed that the swallowing intervals were not affected significantly in the first several acts of swallowing but became longer after several swallowing acts with no stimulation (0% lemon water). However, the acceleration of saliva secretion significantly reduced the elongation of swallowing intervals, with the effect depending on the concentration of lemon water.
The effect of saliva secretion should be taken into consideration when swallowing function is evaluated by swallowing frequency. Repetitive saliva swallowing of lemon water could be a useful test for evaluating the function of saliva secretion as well as swallowing function, together with the conventional RSST.
