Kenichi Tamine

Newly developed sensor sheet for measuring tongue pressure during swallowing

PURPOSE The aim of this study was to develop a sensor sheet for measuring tongue pressure during swallowing and to clarify its usefulness by comparing it with a conventional pressure sensor installed in the palatal plate. METHODS A tactile sensor system was used for the construction of the measuring system. Based on our preceding study, a T-shaped sensor sheet with 0.1mm thickness, five measuring points (three points on the median line, two points on the posterior-lateral part) and three sizes based on the morphological analysis of 60 maxillary casts was designed for application on the hard palate. To elucidate the sensing characteristics of the sensor sheet, the output level of the sensor sheet was compared with that of a conventional pressure sensor under the same load. The maximal magnitude of tongue pressure (MP) during the swallowing of 15 ml water was recorded by a sensor sheet attached to the palatal mucosa and was compared with that recorded by pressure sensors installed in the palatal plate. RESULTS The output level of the sensor sheet was smaller than that of the pressure sensor. There was a high correlation between the output levels of the two sensors (R=0.952, P<0.001). Although MP at each sensing point of the sensor sheet was also smaller than that recorded by the pressure sensors, MP collected by the regression equation obtained in our experiment was quite similar to that for the pressure sensors. CONCLUSIONS This system could be useful for evaluating tongue activity during oropharyngeal swallowing.

Age-related Changes in Tongue Pressure during Swallowing

Although swallowing movement is known to change with aging, age-related differences in the tongue pressure for propelling a bolus from the oral cavity into the pharynx have yet to be investigated in a physiological condition. We hypothesized that tongue pressure during swallowing changed with aging and, using a 0.1-mm-thick sensor sheet with 5 measuring points, measured it while a 15-mL quantity of water was swallowed by young and elderly dentate individuals. Both groups showed a similar order of tongue pressure production at each point. However, the elderly group showed longer duration at each point, lower maximal magnitude in the anterio-median part of the hard palate, and higher magnitude in the circumferential parts of the hard palate than the young group. These results provide the first quantitative evidence of the age-related changes in tongue movement during natural swallowing, which could be attributed to muscle weakening and morphological changes in the oropharynx.

Reduced Tongue Pressure Against the Hard Palate on the Paralyzed Side During Swallowing Predicts Dysphagia in Patients With Acute Stroke

Background and Purpose— Dysphagia is important for prognosis in patients with stroke because this condition can cause aspiration pneumonia or nutritional deficits. The present study investigated the relationship between tongue motor deficits and dysphagia in patients with acute stroke. Methods— Maximal tongue pressure on the hard palate when swallowing 5 mL of water was measured using a T-shaped sensor sheet with 5 measuring points in 33 dysphagic and 31 nondysphagic patients with acute stroke. Maximum tongue pressures at each measuring point were compared between dysphagic and nondysphagic groups and between paralyzed and nonparalyzed sides. Results— Tongue pressure at each measuring point was significantly smaller in dysphagic patients than in nondysphagic patients with the largest significant difference on the paralyzed side. The magnitude of tongue pressure to predict dysphagia was calculated as 4.6 kPa on the paralyzed side, offering 71.4% sensitivity and 72.3% specificity. Conclusions— Reduced tongue pressure on the paralyzed side may predict dysphagia in patients with acute stroke.

Relationship between Tongue Pressure and Dysphagia in Stroke Patients

Background: Although poststroke dysphagia is an important issue for determining prognosis, the pathophysiology of oral-phase dysphagia has yet to be clarified due to a lack of adequate devices and protocols. The present study investigated the relationships between swallowing pressure production by the tongue and dysphagia in stroke patients using a newly developed method of tongue pressure measurement with a sensor sheet system. Methods: Subjects were 64 stroke patients, including 30 patients with dysphagia. A T-shaped sensor sheet with 5 measuring points was attached to the hard palate to record tongue pressure while swallowing 5 ml of water. The average maximal magnitude and incidence of abnormalities such as asynchronous and/or polyphasic patterns in tongue pressure waves in 5 locations were compared between patients with and without dysphagia. Results: The average maximal tongue pressure was significantly smaller in patients with dysphagia than in those without dysphagia. Asynchronous and polyphasic patterns showed a sensitivity of 63 and 87%, and a specificity of 91 and 71%, respectively, for identifying patients with dysphagia. Conclusion: Tongue pressure production during swallowing appears closely related to poststroke dysphagia. Tongue pressure measurement appears useful for evaluating the pathophysiology of oral-phase dysphagia in stroke patients.

Tongue pressure modulation for initial gel consistency in a different oral strategy.

Background In the recent hyper-aged societies of developed countries, the market for soft diets for patients with dysphagia has been growing and numerous jelly-type foods have become available. However, interrelationships between the biomechanics of oral strategies and jelly texture remain unclear. The present study investigated the influence of the initial consistency of jelly on tongue motor kinetics in different oral strategies by measuring tongue pressure against the hard palate. Methods Jellies created as a mixture of deacylated gellan gum and psyllium seed gum with different initial consistencies (hard, medium or soft) were prepared as test foods. Tongue pressure production while ingesting 5 ml of jelly using different oral strategies (Squeezing or Mastication) was recorded in eight healthy volunteers using an ultra-thin sensor sheet system. Maximal magnitude, duration and total integrated values (tongue work) of tongue pressure for size reduction and swallowing in each strategy were compared among initial consistencies of jelly, and between Squeezing and Mastication. Results In Squeezing, the tongue performed more work for size reduction with increasing initial consistency of jelly by modulating both the magnitude and duration of tongue pressure over a wide area of hard palate, but tongue work for swallowing increased at the posterior-median and circumferential parts by modulating only the magnitude of tongue pressure. Conversely, in Mastication, the tongue performed more work for size reduction with increasing initial consistency of jelly by modulating both magnitude and duration of tongue pressure mainly at the posterior part of the hard palate, but tongue work as well as other tongue pressure parameters for swallowing showed no differences by type of jelly. Conclusions These results reveal fine modulations in tongue-palate contact according to the initial consistency of jelly and oral strategies.

Development of a System to Monitor Laryngeal Movement during Swallowing Using a Bend Sensor

Background Swallowing dysfunction (also known as dysphagia), which results in a deterioration of nutritional intake, slows rehabilitation and causes aspiration pneumonia, is very common following neurological impairments. Although videofluorographic (VF) examination is widely used for detecting aspiration, an objective and non-invasive method for assessing swallowing function has yet to be established because of a lack of adequate devices and protocols. In this paper, a bend sensor whose resistance is altered by bending was introduced to monitor swallowing-related laryngeal movement. Methods Six healthy male volunteers were recruited in the present study. Specific time points on the signal waveform produced by the bend sensor were defined to describe laryngeal movement by differential analysis. Additionally, the physiological significance of the obtained waveform was confirmed by analyzing the sequential correlations between the signal waveform from the bend sensor and hyoid bone kinetics simultaneously recorded by VF. Results Seven time points were successfully defined on the signal waveform to reference laryngeal movement. Each time point was well correlated with certain VF events, with evidence of no significant time lags, and there were positive correlations between waveform time points and matched VF events. Furthermore, obvious similarities were noticed between the duration of each phase on the signal waveform and the duration of the matched hyoid bone activity. Conclusions The present monitoring system using a bend sensor might be useful for observing the temporal aspects of laryngeal movement during swallowing, and it was well coordinated with hyoid bone movement.

Coordination in oro-pharyngeal biomechanics during human swallowing.

In swallowing, the tongue contacts against the hard palate to generate pressure for propelling a bolus from the oral cavity into the pharynx. Meanwhile, the hyoid and larynx move upward and forward to facilitate the bolus from the pharynx into the esophagus. It has been well known that sequential coordination between those actions is critical for safety accomplishment of swallowing. However, the absence of noninvasive assessment for it limits the detection to the physiological symptom of dysphagia. We applied a sensor sheet on the hard palate to measure tongue contact pressure and a bend sensor on the frontal neck to monitor the laryngeal movement, which was synchronized with hyoid motion for assessing the coordination between both actions in 14 healthy male subjects when swallowing 5ml of water. The sequential order of tongue pressure and hyoid movement was successfully displayed. Tongue pressure was produced after slight movement of the hyoid and closely to the hyoid elevation, then reached a maximum when the hyoid stabilized in the most anterior-superior position, and ceased concurrently with the onset of hyoid descent. Additionally, the synchronized data from both sensors showed positive correlations between identified time points on the laryngeal signal waveform and onset, peak and offset of tongue pressure. Our sensing system successfully showed the coordination between tongue pressure production and hyoid motion, and could be a simple and noninvasive method for clinicians to evaluate the oral and pharyngeal stages of swallowing.

Differences in biomechanical features of tongue pressure production between articulation and swallow

Summary  The purpose of this study was to compare the tongue pressure against the hard palate during the articulation of a monosyllable with that during swallowing. The participants were 20 healthy adults without swallowing or articulation disorder (10 men and 10 women, mean age ± standard deviation: 22·5 ± 0·9 years). Tongue pressure during articulation of [ki] (articulatory pressure) and during dry swallowing (swallowing pressure) was recorded by a 0·1-mm-thick sensor sheet with five measuring points attached to the hard palate. Biomechanical parameters such as maximal magnitude, duration, integrated value and slope gradient were compared between articulatory pressure and swallowing pressure at each measuring point. Although swallowing pressure was produced at each measuring point, articulatory pressure was found only in the posterior circumferential parts of the hard palate and was smaller in magnitude (14·9-16·7% of swallowing pressure) and integrated value, which meant the amount of work by tongue pressing (7·0-7·9%), shorter in duration (26·6-31·8%) and shallower in slope gradient, which meant the speed of tongue pressing (26·9-27·4%). Maximal magnitude was closely correlated with duration (R(2)  = 0·386) and slope gradient (R(2)  = 0·843) for articulatory pressure. These results first show the biomechanical differences between articulation and swallowing in terms of tongue contact with the hard palate. The findings suggest that tongue pressure measurement might be a useful investigation for patients with tongue motor disorder.

Tongue pressure during swallowing is decreased in patients with Duchenne muscular dystrophy

Although dysphagia is a life-threatening problem in patients with Duchenne muscular dystrophy (DMD), the pathophysiology of oral stage dysphagia is yet to be understood. The present study investigated the tongue motor deficit during swallowing in patients with DMD and its relationship with disease-specific palatal morphology. Tongue pressure during swallowing water was recorded in 11 male patients with DMD and 11 age- and sex-matched healthy subjects using an intra-oral sensor with five measuring points, and the state of tongue pressure production was compared between the groups. Palatal morphology was assessed by a non-contact three-dimensional scanner on maxillary plaster models. In patients with DMD, the normal sequential order of tongue-palate contact was lost and the maximal magnitude and integrated value of tongue pressure on the mid-anterior part of palate were smaller than those in healthy subjects. The width of the palate in patients was greater than that in healthy subjects and the depth of the palate in patients had a negative correlation with tongue pressure magnitude on the median palate. Our results suggested that the deteriorated tongue motor kinetics prevented tongue movement during swallowing that was appropriate for the depth of the palate and affects the state of tongue pressure production during swallowing.

Effect of Carbon Dioxide in Carbonated Drinks on Linguapalatal Swallowing Pressure

This study aimed to investigate the influence of carbonated drinks with gas volumes (GV) of 0, 1.5, and 2.7 on linguapalatal swallowing pressure, intraoral carbonation perception, and maximum velocity of a bolus through the pharynx in healthy volunteers (N = 20, all female, age range; 20-21 years). The volunteers swallowed a 12-mL drink in the natural state. Linguapalatal swallowing pressure was measured using a special sensor sheet, and maximum velocity of the bolus through the pharynx was measured using ultrasonic diagnostic imaging equipment. Peak magnitude, integrated value, and duration of linguapalatal swallowing pressure and maximum velocity of a liquid bolus through the pharynx increased with an increase in carbon dioxide content in the carbonated drink. The total integrated values of carbonated drinks with GV of 1.5 and 2.7 were larger than that of the drink without carbon dioxide. These results suggest that the carbon dioxide dissolved in carbonated drinks influences the activity of taste receptors in the mouth and results in neuromotor responses.