EFFECTS OF BOLUS VOLUME ON OROPHARYNGEAL SWALLOWING - AN ELECTROPHYSIOLOGIC STUDY IN MAN

Objective: Different variables of oropharyngeal swallowing change in r esponse to bolus volume and consistency as determined by manometric/vi deofluoroscopic studies. But the subject is debatable especially from the physiologic point of view. No electrophysiologic studies are avail able on human subjects. Methods: The effects of bolus volume and visco sity on different variables of oropharyngeal swallowing were investiga ted using electrophysiologic methods. Mechanical upward and downward l aryngeal movements and submental electromyographic (SM-EMG) activity o f 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 n ormal subjects. Semisolid and liquid swallowing were compared in eight normal subjects. Results: The total duration of SM-EMG, time necessar y for larynx elevation, CP-EMG pause related with upper esophageal sph incter opening and swallowing variability (jitter) all increased signi ficantly with increasing bolus volume. Laryngeal superior relocation t ime and CP-EMG pause were shorter for semisolid swallowing compared wi th swallowing the same amount of liquid. Conclusion: The duration of S M-EMG activity, laryngeal upward-downward movements, and CP-EMG pause are affected by sensory inputs such as volume and viscosity of the bol us swallowed. The results indicate that sensory input modifies the cen tral swallowing pattern although basic events remain the same in norma l human subjects.