The ultimate goal of this study is to develop a new therapeutic strategy that induce the swallowing reflex through esophageal stimulation for patients with dysphagia. In this study in healthy subjects, we aimed to verify whether the swallowing reflex can be evoked by peripheral esophageal stimulation and whether the response differ depending on the stimulated area and the volume or speed of stimulation.

Ten healthy individuals participated in this study. A catheter was inserted through the nose, and the tip was placed every 5cm from the distal end of the upper esophageal sphincter (UES) to the upper, upper-middle, lower-middle, or lower esophageal region for injection. An intra-esophageal injection of 3mL or 10mL thickened water was administered. The injection rate was controlled at 3mL/s or 10mL/s. Latencies from the start of the injection to the onset of UES relaxation were compared regarding injection locations, amounts, and rates.

Swallowing reflex occurred in 100%, 98%, 95%, and 55% within 30seconds at the upper, upper-middle, lower-middle, or lower esophageal regions, respectively. Latency after the 10-mL injection was shorter than that for the 3-mL injection in all regions at an injection rate of 10mL/s (P<0.01). There was a significant difference between injection amounts only in the upper region at an injection rate of 3mL/s. Although there was no difference between injection rates with the 3-mL injection (P>0.05), a significant difference was observed between injection rates with the 10-mL injection (P<0.01).

Esophageal stimulation by fluid injection can induce the swallowing reflex in healthy adults. Reflex latencies and esophageal movement can be changed by locations, amounts, and rates. The most effective condition for inducing the swallowing reflex involved a larger fluid amount with a faster injection rate in the upper esophagus.