Hiroshige Taniguchi

Correspondence between food consistency and suprahyoid muscle activity, tongue pressure, and bolus transit times during the oropharyngeal phase of swallowing

This study aimed to evaluate the effects of food texture and viscosity on the swallowing function by measuring tongue pressure and performing a videofluorographic (VF) examination. Eleven normal adults were recruited for this study. Test foods with different consistencies and liquid contents, i.e., a half-solid nutrient made of 0.8 and 1.5% agar powder, syrup, and a liquid containing 40 wt/vol% barium sulfate, were swallowed, and the anterior (AT) and posterior tongue pressures (PT) and electromyographic (EMG) activity of the suprahyoid muscles were recorded, together with VF images. The timing of each event obtained from EMG, tongue pressure, and VF recordings was measured and then compared. We found that the AT and PT activity patterns were similar and showed a single peak. The peak, area, and time duration of all of the variables for AT and PT and EMG burst increased with increasing hardness of the bolus. The onset of the EMG burst always preceded those of the AT and PT activities, while there were no significant differences in peak and offset times among EMG burst, AT, and PT. Total swallowing time and oral ejection time were significantly longer during the swallowing of 1.5% agar than any other boluses, while pharyngeal transit time and clearance time were significantly longer during the swallowing of syrup, which was as hard as the liquid, but showed a higher viscosity than the liquid. The results suggested that the major effects of food hardness were to delay oral ejection time, which strongly delays total swallowing time. In addition, pharyngeal bolus transit is not dependent on the hardness of food but on its viscosity.

Effects of food texture and head posture on oropharyngeal swallowing.

This study aimed to describe the electromyographic (EMG) activity patterns of the genioglossus (GG) and suprahyoid (SHy) muscles during swallowing. The effects of changes in food texture/consistency and head posture on transport of the swallowed bolus were also investigated. Participants were 10 normal adults. Test foods consisted of a liquid, a syrup, or 4 ml of paste made from 0.5% or 1.0% agar. Each food was swallowed with the head in one of three positions, and EMGs and videofluorographic (VF) images were recorded. Mean values of onset, peak, and offset times, peak amplitude, area, and duration of the EMG burst were measured. The total swallowing time, oral ejection time, pharyngeal transit time, clearance time, fauces transit time, and upper esophageal sphincter (UES) transit time were measured. The GG muscle burst patterns showed two peaks (GG1 and GG2) during each swallowing. The offset time and duration of the GG1 burst and the onset, peak, and offset times and duration of both the GG2 and SHy bursts were significantly affected by food texture. There were no significant differences in bolus transit time among the different experimental conditions. Regression analyses demonstrated significant linear relationships between the tongue tip touching the palate and the peak of the GG1 burst, between passage of the bolus tail at the fauces and offset of the GG1 burst, between passage of the bolus tail at the UES and peak of the GG2 burst, and between passage of the bolus tail at the UES and offset of the SHy burst. These results demonstrate that the duration, but not the amplitude, of tongue and suprahyoid muscle activity were increased with increasing hardness of food during swallowing and that the bolus transit time can be fixed within a certain range of physical food properties.

Role of tongue pressure production in oropharyngeal swallow biomechanics

The tongue is important for orofacial movements, including swallowing. Although numerous studies have focused on tongue pressure against the palate, its physiological role has not been fully evaluated. The tongue pressure generation may have the temporal coordination with the swallowing relational organs. The aim of this study was to clarify the physiological mechanisms of tongue pressure and to investigate the temporal relationship among tongue pressure, supra‐hyoid muscle activity, and videofluorographic (VF) images during swallowing. Fifteen healthy young subjects participated. Tongue pressure measured using a sensor sheet with five channels, electromyographic EMG, and VF was recorded synchronously during 4‐ml barium swallowing. Swallowing behavior in VF images with and without the sensor sheet was compared. Furthermore, the temporal relationship between events measured from tongue pressure, EMG, and VF was evaluated. Swallowing behavior on VF images was not affected by placement of the sensor sheet. Tongue pressure at the posterio‐lateral point of the hard palate tended to have biphasic peaks. Tongue pressure production with a monophasic pattern appeared during the same period as the second peak in the biphasic pattern. The onset of tongue pressure was later than the start of hyoid movement and onset of EMG, and offset was observed between the hyoid at the up‐forward position and reposition. Onset of tongue pressure at the anterior area was correlated with the start of slight hyoid elevation. Offset of tongue pressure at the posterio‐lateral points was strongly time locked with the hyoid at the up‐forward position. The present results suggested the temporal coordination of tongue pressure generation with the swallowing‐related organs. That is, the tongue pressure was produced for bolus propulsion, and was closely related to hyoid movement temporally during swallowing. These results may contribute to clarify the clinical state with the disorder of tongue kinetics.

Effects of Food Consistency on Tongue Pressure during Swallowing

Tongue pressure against the anterior and posterior portions of the hard palate as well as the electromyographic activity of suprahyoid muscle during swallowing test foods with three different consistencies (thinned, medium, and thickened paste) and liquid were recorded. Significant differences and wide variations were noted in the peak amplitude and area of posterior tongue pressure, which was larger for thickened paste compared to liquid, thinned, and medium pastes. Regarding the anterior tongue pressure, the duration was significantly longer during swallowing thickened paste compared to liquid and thinned paste, while there were no differences in the peak amplitude and area. The results suggest that a basic pattern of tongue pressure is maintained during swallowing but is modulated by sensory feedback in a different manner between the anterior and posterior portions of the tongue to complete propulsion of the bolus in the oral cavity.

Individual-dependent effects of pharyngeal electrical stimulation on swallowing in healthy humans.

The present study tested whether electrical stimulation increases the number of voluntary repetitive swallows in humans. In addition, the potential of initiating both voluntary and involuntary swallows was compared using electrical stimulation. Fourteen normal male adults were instructed to perform repetitive voluntary swallowing as quickly as possible over 30 s, and the number of swallows was counted with and without repetitive electrical stimulation (80% of maximal tolerated intensity; 0.1 ms in pulse duration; 30 Hz) of the nasal cavity, nasopharynx, oropharynx, or laryngopharynx. Although the number of swallows was significantly increased during electrical stimulation of the laryngopharynx, oropharynx, and nasopharynx, there was a wide variation in the number among subjects. The number of reflexively evoked swallows (i.e., involuntary swallows) by pharyngeal stimulation also varied greatly, and there was a significant linear correlation in the number of swallows between voluntary and involuntary swallows. The present study demonstrated the facilitatory effects of pharyngeal electrical stimulation on voluntary swallowing in humans. Furthermore, the potentials of initiation of voluntary swallows are identical to those of involuntary swallows, which suggests that the swallowing central pattern generator is a common component of both neuronal networks and therefore is responsible for inter-individual variations.

How do tablet properties influence swallowing behaviours

Behavioural performance of tablet swallowing was evaluated with different tablet conditions in terms of size, number and surface coating.