Effects of submental neuromuscular electrical stimulation on pharyngeal pressure generation

Objective: To investigate the immediate and late effects of submental event-related neuromuscular electrical stimulation (NMES) on pharyngeal pressure generation during noneffortful and effortful saliva swallows. Design: Before-after trial. Setting: Swallowing rehabilitation research laboratory. Participants: Sex-matched (N=20) healthy research volunteers. Interventions: Participants received 80Hz NMES of 4-second duration to floor of mouth muscles that was time-locked to 60 volitional saliva swallows. Main Outcome Measures: Manometry measures of peak pressures and duration of pressure events in the oropharynx, hypopharynx, and the upper esophageal sphincter (UES) were derived during execution of noneffortful and effortful saliva swallows. Measures were taken at baseline, during stimulation, and at 5-, 30-, and 60-minutes poststimulation. Results: Baseline pharyngeal and UES pressures did not differ between stimulated and nonstimulated swallows. At 5- and 30-minutes poststimulation, peak pressure decreased at the hypopharyngeal and at the UES sensor during noneffortful swallows. The effect lasted up to an hour only in the hypopharynx. No changes in duration of pressure events were observed. Conclusions: Using this treatment paradigm, decreased peak amplitude in the hypopharynx up to an hour after treatment indicates a potential risk of decreased bolus flow associated with NMES. On the other hand, decreased UES relaxation pressure may facilitate bolus transit into the esophagus.