VF evaluation of the speed of bolus flow on the tongue base

Abstract

【Objective】It might be useful to evaluate the effectiveness of changes in bolus viscosity using videofluoroscopic swallowing examination (VF) for patients with dysphagia，because an increase in viscosity can change the speed of bolus flow and thus control the occurrence of aspiration．Compensatory postural maneuvers have been applied to reduce aspiration or improve pharyngeal clearance．Therefore，the purpose of this retrospective study was to evaluate the influence of the bolus viscosity and the position of the patient's head on the speed of bolus flow by means of VF images．

【Material and Methods】VF images of 133 patients with dysphagia were reviewed to examine the phenomenon of bolus trickling from the oral cavity into the vallecule．21 patients including those with cerebral palsy，after stroke， and after treatment for oral cancer were selected as subjects．The speed of bolus trickle on the base of tongue (anterior wall of mid-pharynx) and the angle of the anterior-posterior inclination of the tongue base were measured in each subject's VF images．The viscosities of materials given to the patients were measured with a rotational viscometer．The materials included barium liquid，thickened barium liquid，and puree or paste foods．

【Results and Discussion】The average speed of bolus flow was 155 ± 78 mm/sec in lower-viscosity （under 1000 mPa・s）liquid materials，and 42 ± 31 mm/s in thickened higher-viscosity (over 1000 mPa・s) materials．In the higher-viscosity material，the speed of bolus flow was infｌuenced by the angle of the tongue base inclination．However，the effect of the change of tongue base inclination on the speed of bolus flow was not significant in liquid materials．These results were broadly consistent with the results of a previously reported in-vitro model simulation study．By improving the model simulation system，it may become possible to predict the speed of bolus flow in a patient's pharynx．