Effects of bolus volume on oropharyngeal swallowing: an electrophysiologic study in man

Different variables of oropharyngeal swallowing change in response to bolus volume and consistency as determined by manometric/videofluoroscopic studies. But the subject is debatable especially from the physiologic point of view. No electrophysiologic studies are available on human subjects.

The effects of bolus volume and viscosity on different variables of oropharyngeal swallowing were investigated using electrophysiologic methods. Mechanical upward and downward laryngeal movements and submental electromyographic (SM-EMG) activity of the laryngeal elevator muscles were recorded during dry and 3-, 10-, and 20-ml water swallowing in 14 normal subjects. Cricopharyngeus (CP) muscle was investigated during 3- and 10-ml water swallowing in 10 normal subjects. Semisolid and liquid swallowing were compared in eight normal subjects.

The total duration of SM-EMG, time necessary for larynx elevation, CP-EMG pause related with upper esophageal sphincter opening and swallowing variability (jitter) all increased significantly with increasing bolus volume. Laryngeal superior relocation time and CP-EMG pause were shorter for semisolid swallowing compared with swallowing the same amount of liquid.

The duration of SM-EMG activity, laryngeal upward-downward movements, and CP-EMG pause are affected by sensory inputs such as volume and viscosity of the bolus swallowed. The results indicate that sensory input modifies the central swallowing pattern although basic events remain the same in normal human subjects.