Thermal oral-pharyngeal stimulation and elicitation of swallowing.

The influence of thermal stimulation of the oral and pharyngeal mucosa on the elicitation of swallowing was studied in 14 healthy volunteers. The Repeated Dry Swallowing Test was used to study the ability to elicit swallows. The test consists of 11 manometrically recorded dry swallows performed at maximum speed. The time between swallows 1 and 11 (Swallowing Test Time) is considered a measure of the ease of eliciting the swallowing reflex. The study includes two controlled experiments, each consisting of an active test done immediately after a cold stimulus and a control done after a stimulus at body temperature. In one experiment the stimulus consisted of stimulation of the fauces with a laryngeal mirror and in the other of swallowing water. Each subject served as his or her own control. The order of the tests was randomized and the results read blindly. In the mirror experiment, the swallowing test times obtained after application of a cold laryngeal mirror did not differ significantly from those obtained after stimulation at body temperature. In the water experiment, swallowing test times were shorter after swallowing cold water compared to those after swallowing water at body temperature in 11 of the 14 volunteers (n.s.). The concept that swallowing is significantly facilitated by cold applied to the oral-pharyngeal mucosa was thus not supported by the present study. The importance of these findings is discussed.