Effect of bolus volume and consistency on swallow-induced submental and infrahyoid electromyographic activity.

1. The effect of the volume of swallowed bolus and the form of barium delivered (liquid vs paste) on the timing of bolus transit, submental and infrahyoid electromyographic activity and hyoid movement during the oral and pharyngeal phase of swallowing was studied in 9 healthy volunteers. Using videofluoroscopy, we recorded concurrent submental electromyographic (EMG) activity from over the mylohyoid, geniohyoid and anterior digastric muscle complex (SM EMG) and from over the infrahyoid muscles, which consisted mainly of the thyrohyoids (IH EMG). 2. Bolus volume (2 to 20 ml) did not change the timing or the duration of SM EMG and IH EMG activity, transit of the bolus tail through the mouth and pharynx, or the onset and duration of hyoid movement, for either liquid or paste. 3. Although not volume dependent, the magnitude of SM EMG (2 ml, 79 +/- 9% vs 44 +/- 6%, mean +/- SEM) and IH EMG (2 ml, 73 +/- 15% vs 42 +/- 8%) was greater for barium paste than for liquid barium. 4. Large bolus volumes increased the duration of barium flow through the upper esophageal sphincter (UES), for both liquid (0.30 s, 0.40 s, 0.46 s, 0.50 s for 2, 5, 10, 20 ml) and paste (0.32 s, 0.43 s, 0.53 s, 0.61 s for 2, 5, 10, 20 ml).(ABSTRACT TRUNCATED AT 250 WORDS)