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A comparison of the effects of oral sensory and vibrotactile stimulation on urge and frequency of swallowing: preliminary findings

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Swallowing is a complex behavior involving highly coordinated neuronal activity and sensory input. Food or secretions in the hypopharynx usually provide the input for sensory neural activation of the glossopharyngeal nerve (GPN) and the superior laryngeal nerve (SLN) to elicit swallowing. It was hypothesized that air-puff stimulation to the faucial pillar region could engage the sensory neural inputs of the GPN and external vibratory stimulation could engage sensory neural inputs of the SLN which would elicit swallowing. Input from both forms of stimulation may improve swallow function in people with dysphagia (swallowing disorders) by augmenting input to the swallow control regions and eliciting an urge to swallow.

The purpose of this study was to investigate the effects of various frequencies of laryngeal vibrotactile stimulation and oral air-puff stimulation on frequency and urge to swallow. The vibrotactile stimulation was provided by a motor, affixed to a flexible band and placed on the neck over the laryngeal cartilages. Vibrotactile stimulation was elicited at frequencies of 30, 45, and 60 Hz. The air-puff stimulation was provided by creating a dental prosthesis with a tube affixed and routed to the peritonsillar region of the oral cavity. The tube was then attached to an outer air source, with air-puff stimulation occurring at frequencies of 1, 2, and 4 Hz. A set of five, 60-second trials of a particular stimulation and frequency were presented in a run with variable inter-stimulus intervals between each trial. One non-stimulation run was also included for a baseline comparison of swallow frequency. The runs were randomly presented with 3-minute intervals between each. Swallow frequency was the objective dependent variable of the study. Swallow frequency was assessed both during and after stimulation using a pressure transducer that senses pressure changes during laryngeal elevation for swallowing. Urge to swallow was the subjective dependent variable and was assessed with a visual analog scale for subjects to rate urge to swallow during and directly after stimulation.

We were able to gather preliminary trends from the results of four healthy volunteers. When comparing the effects of the two different types of stimulation on urge to swallow, the urge to swallow directly after air-puff stimulation was higher than for vibrotactile stimulation. Also, the average frequency of swallows was higher after air-puff stimulation when compared to vibrotactile stimulation. Results from this study may have clinical utility in patients with dysphagia as sensory stimulation of the laryngeal and peritonsillar region has potential to increase both frequency and urge to swallow. The study will continue in a larger cohort of healthy volunteers in order to gain a better representation of sensory stimulation and swallowing.

Last updated November 16, 2007