Laryngeal Vibration Increases Spontaneous Swallowing Rates in Chronic Oropharyngeal Dysphagia: A Proof-of-Principle Pilot Study

Abstract

Previously, vibratory stimulation increased spontaneous swallowing rates in healthy volunteers indicating that sensory stimulation excited the neural control of swallowing. Here, we studied patients with severe chronic dysphagia following brain injury or radiation for head and neck cancer to determine if sensory stimulation could excite an impaired swallowing system. We examined (1) if laryngeal vibratory stimulation increased spontaneous swallowing rates over sham (no stimulation); (2) the optimal rate of vibration, device contact pressure, and vibratory mode for increasing swallowing rates; and (3) if vibration altered participants' urge to swallow, neck comfort, and swallow initiation latency. Vibration was applied to the skin overlying the thyroid lamina bilaterally in thirteen participants to compare vibratory rates 30, 70, 110, 150, or 70 + 110 Hz, different devices to neck pressures (2, 4, or 6 kilopascals), and pulsed versus continuous vibration. Swallows were confirmed from recordings of laryngeal accelerometry and respiratory apneas and viewing neck movement. Participants' swallowing rates, urge to swallow, discomfort levels, and swallow initiation latencies were measured. Vibration at 70 Hz and at 110 Hz significantly increased swallowing rates over sham. All vibratory frequencies except 70 + 100 Hz increased participants' urge to swallow, while no pressures or modes were optimal for increasing urge to swallow. No conditions increased discomfort. Vibration did not reduce measures of swallow initiation latency using accelerometry. In conclusion, as non-invasive neck vibration overlying the larynx increased swallowing rates and the urge to swallow without discomfort in patients with chronic dysphagia, the potential for vibratory stimulation facilitating swallowing during dysphagia rehabilitation should be investigated.

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