Effects of neuromuscular electrical stimulation intensity and bolus size on hyoid movement

Carmichael, Christine M.

UNIVERSITY OF FLORIDA, 2008, 82p; 3360648


Dysphagia, a movement disorder in which swallowing is difficult, uncomfortable or painful, is caused by problems with movement, sensation, or physical difficulties, and can disrupt nutritional status and quality of life. The study of healthy anatomy and physiology required for normal swallowing has contributed to a greater understanding of disordered swallowing and its rehabilitation. Traditional swallow therapies include diet alterations, positional changes, oral strengthening exercises and swallowing maneuvers. An emerging and controversial area for treatment of dysphagia that targets muscles for swallow is the clinical application of surface neuromuscular electrical stimulation (NMES), marketed as VitalStim Therapy, which is expanding despite only six empirical studies on NMES swallow outcomes. NMES uses electrical impulse to activate muscles through direct stimulation of the muscle belly to achieve maximal hyolaryngeal excursion in an effort to reduce or eliminate aspiration or penetration events for a safer swallow. It was the goal of this investigation to examine NMES for swallow with 5ml and 20ml thin liquid bolus sizes in order to assess its effects on hyoid movement and to determine swallowing safety of NMES therapy as measured by penetration and aspiration in a healthy population.

Results revealed significant differences in maximum displacement and maximum angle of the hyoid bone at three tested intensity levels (maximum tolerance threshold = 100%, 75% of maximum tolerance, and 50% of maximum tolerance). Significant differences were also found between the lowest (50%) and mid (75%) intensity levels and between the lowest and highest (100%) intensity levels across NMES swallows. However, the mid-intensity level (75%) was not significantly different from the highest level. Penetration-Aspiration Scale scores revealed 17 penetration events during NMES swallows with 64% occurring during the highest intensity level. These results suggest that NMES may pose risk for penetration as presently utilized at maximum intensity levels. Further, NMES intensities lower than the recommended high threshold may provide a similar effect on hyolaryngeal excursion while increasing swallowing safety and decreasing discomfort. No influence of bolus size during NMES swallow on hyoid movement was found in the present study.


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