Accommodation to changes in bolus viscosity in normal deglutition: a videofluoroscopic study

Area of Science:

• Swallowing physiology
• Deglutition biomechanics

Background:

• Understanding how different bolus characteristics affect the complex biomechanics of swallowing is crucial for diagnosing and managing dysphagia.
• Videofluoroscopic swallow studies (VFSS) are a standard tool for assessing swallowing function.

Purpose of the Study:

• To compare swallowing variables during the ingestion of paste and liquid boluses using videofluoroscopy.
• To identify changes in swallow gesture displacement, timing, and bolus movement timing based on bolus viscosity.

Main Methods:

• Sixty healthy adult volunteers underwent videofluoroscopic swallow studies.
• Measurements were taken during swallows of standardized paste (3-cm3) and liquid (3-mL) boluses.
• Swallowing variables, including gesture displacement, timing, and bolus transit, were analyzed and compared.

Main Results:

• Pharyngeal transit time remained consistent across both paste and liquid boluses.
• Oropharyngeal transit was faster for liquid boluses, associated with earlier aryepiglottic fold elevation.
• Hyoid bone elevation (timing, rate, extent) was consistent regardless of bolus viscosity.
• Hyoid elevation duration was longer for liquid boluses, correlating with prolonged pharyngoesophageal sphincter opening.
• The pharyngoesophageal sphincter exhibited a wider opening with paste boluses compared to liquid ones.

Conclusions:

• Swallowing adaptations occur in response to bolus viscosity, influencing specific kinematic parameters.
• While overall pharyngeal transit is unaffected, oropharyngeal transit and sphincter dynamics vary with bolus type.
• The hyoid bone's movement is largely independent of bolus viscosity, but its duration of elevation is influenced by liquid boluses.