Noninvasive Evaluation of the Biomechanical Accommodations to Bolus Volume during Human Swallowing.

Bolus volume is very important in the biomechanics of swallowing. By noninvasively characterizing swallow responses to volume challenges, we can gain more knowledge on swallowing and evaluate swallowing behavior easily. This study aimed to evaluate the impact of bolus volume on the biomechanical characteristics of oropharyngeal swallowing events with a noninvasive sensing system. Fifteen healthy male subjects were recruited and instructed to swallow 5, 10, and 15 ml of water. The sensing system consisted of a tongue pressure sensor sheet, bend sensor, surface electrodes, and a microphone. They were used to monitor tongue pressure, hyoid activity, surface EMG of swallowing-related muscles, and swallowing sound, respectively. In addition to the onset, the peak time and offset of the above four structures, certain characteristics, such as the duration, peak value, and interval of the structure motions, were measured during the different drinking tasks. The coordination between the hyoid movement and tongue pressure was also assessed. Although no sequence of the structural events changed with volume, most of the timings of the structural events were significantly delayed, except for certain hyoid activities. The swallowing volume did not affect the active durations of the monitored structures, the peak values, or intervals of tongue pressure and supra- and infrahyoid muscle activity, but certain hyoid kinetic phases were prolonged when a larger volume was swallowed. Additionally, sequential coordination between hyoid movement and tongue pressure was confirmed among the three volumes. These findings suggest that oropharyngeal structural movements change in response to bolus volume to facilitate safe swallowing. The noninvasive and quantitative measurements taken with the sensing system provide essential information for understanding normal oropharyngeal swallowing.

Effect of fracture properties of gels on tongue pressure during different phases of squeezing and swallowing.

To provide appropriate foods for elderly people with eating difficulties, it is necessary to take account of the ability of compensatory mastication such as tongue squeezing. However, the biomechanics of tongue squeezing is still unclear. The aim of present study is to investigate the effect of the initial mechanical properties of gels on the change in tongue pressure production during squeezing and swallowing. As test sample, nine kinds of gels with three fracture force and three fracture strain were prepared. Tongue pressure during squeezing and swallowing gels was measured by using an ultra-thin tongue pressure sensor with five measuring points attached on the hard palate in seven healthy participants, and analyzed at four phases; Initial squeeze, Middle squeeze, Last squeeze, and Swallowing. The maximal magnitude of tongue pressure was increased for gels with higher fracture force at most measuring points and was decreased for gels with higher fracture strain at some measuring points on the median line during Initial and Middle squeezing. However, no influence by fracture force and strain was found in magnitude during Last squeezing and Swallowing. The duration of tongue pressure increased for gels with higher force at most measuring points during Middle squeezing, although no influence by strain was found during each phase. The results clearly show how the initial fracture properties of gels influence on tongue pressure production during each phase of food oral processing, which clarified one aspect of squeezing with tongue, as the compensatory mastication.

Evaluation of hyoid movement during swallowing using a bend sensor.

BACKGROUND: Movement of the hyoid and laryngeal complex is critical for preventing aspiration, as well as smooth bolus passage through the pharynx. We have developed a non-invasive system for measuring laryngeal movement during swallowing with a bend sensor and have already reported the time coordination between the signal waveform from the sensor and hyoid movement. OBJECTIVE: The aim of this study was to clarify the quantitative association between the output value of the sensor and hyoid movement during swallowing. METHODS: A small bend sensor was fixed on the skin surface along the midline of the neck of 13 healthy men (mean age, 30.8 ± 4.5 years). Laryngeal and hyoid movements during swallowing of 5 mL of water were recorded synchronously by the bend sensor and videofluorography. The relationship between the bend sensor output value (LM value) and hyoid position (x- and y-axis displacements) by videofluorography from the onset to the offset of the signal waveform was analysed for all tasks and for each task using Pearson's correlation coefficients. RESULTS: There was a positive correlation between the LM value and hyoid position for all tasks (x-axis displacement: r = .647, y-axis displacement: r = .233). In particular, there was a moderate to high correlation between the LM value and x-axis displacement for each task (.453 ≤ r ≤ .934). CONCLUSION: The LM value can be a quantitative parameter of anterior hyoid movement during swallowing that might be associated with bolus flow and upper oesophageal sphincter opening.

Coordination of tongue pressure production, hyoid movement, and suprahyoid muscle activity during squeezing of gels.

OBJECTIVE: The aim of this study was to evaluate tongue movement and its biomechanical effects during squeezing, one of the oral strategies for processing soft foods, by tongue pressure sensors, videofluorography, and surface electromyography. DESIGN: Fifteen healthy men (mean age, 31.0 ± 4.1 years) without dysphagia were recruited. A 0.1-mm-thick pressure sensor sheet with five measuring points, videofluorography, and surface electromyography were used for synchronous measurements of tongue pressure, hyoid movement, and suprahyoid muscles activity, respectively, while squeezing 5 mL of gels. Amplitude, duration, area, and their sequential order during initial squeezing were analyzed. Differences in hyoid position at the onset, peak, and offset of hyoid movement were also analyzed. RESULTS: At the beginning of initial squeezing, tongue pressure at the middle area of the hard palate, hyoid movement, and suprahyoid muscle activity appeared simultaneously, followed by tongue pressure at the anterior area and then at the posterior area. When the hyoid was in an elevated position, the amplitude of suprahyoid muscle activity and tongue pressure peaked. At the end of initial squeezing, the hyoid position at the offset of hyoid excursion was superior to that at the onset. All evaluation items of tongue pressure, hyoid movement, and suprahyoid muscle activity were modulated according to the texture of gels. CONCLUSIONS: During initial squeezing, tongue pressure, hyoid movement, and suprahyoid muscle activity were coordinated while being modulated by the food texture. At the end of initial squeezing, the hyoid was maintained in an elevated position, which might be beneficial for subsequent squeezing.

The biomechanical coordination during oropharyngeal swallowing: an evaluation with a non-invasive sensing system.

Swallowing is a very important and complex physiological behaviour. The dynamic of swallowing has created great interest as any procedural abnormality will result in dysphagia and even lower quality of life. However, a non-invasive evaluation of biomechanical coordination during oropharyngeal swallowing, which includes the activities of the tongue, the hyoid and swallowing-related muscles, has not yet been achieved. In the present study, we recruited fifteen subjects, and a non-invasive sensing system composed of a pressure sensor, a bend sensor, surface electrodes and a microphone was created to simultaneously monitor tongue pressure, hyoid motion, and surface EMG of swallowing-related muscles, as well as take sound recordings, when the subjects swallowed 5 ml of water. In addition to obtaining the durations of certain motor events, the considerable time (beginning, peak and ending time) of tongue pressure production, suprahyoid and infrahyoid muscle activity and hyoid motion were successfully measured. Moreover, the significant correlations between swallowing-related muscles, tongue pressure, and the hyoid were confirmed. These findings suggest that the non-invasive sensing system has potential as a good candidate for monitoring and evaluating the oropharyngeal process of swallowing, which may be useful in clinical work involving dysphagia evaluation and rehabilitation.

[The study of tongue pressure during swallowing liquid in healthy adults].

OBJECTIVE: To investigate the tongue pressure (TP) produced by tongue-hard palate contact in the process of normally swallowing liquid in healthy adults. METHODS: Thirteen adult male subjects were recruited to perform a single swallow of 5 ml water when sitting with upright position. The tongue pressure sensor sheet was used to monitor TP as a result of tongue-hard palate approximatation in the anteriomedian, midmedian, posteriomedian and circumferential parts, and the swallowing sound was recorded by microphone. The temporal sequence of TP at each measured part was obtained after setting the swallowing sound as the reference time. Also, the total duration, pre-peak duration, post-peak duration, maximum magnitude and integrated value of TP were recorded and compared among the measured parts. RESULTS: TP was produced from anterior to posterior along the midline of hard palate during normal swallowing of water [Ch1: (-0.40 ± 0.22) s, Ch2: (-0.36 ± 0.21) s, Ch3: (-0.24 ± 0.18) s], with the circumferential TP [Ch4: (-0.38 ± 0.23) s, Ch5: (-0.40 ± 0.23) s] occurring nearly to the anteriomedian one (P > 0.05). Before the swallowing sound (P < 0.05), TP at each part reached a peak synchronously [Ch1: (-0.12 ± 0.24) s, Ch2: (-0.16 ± 0.22) s, Ch3: (-0.13 ± 0.21) s, Ch4: (-0.16 ± 0.23) s, Ch5: (-0.17 ± 0.23) s] in a rapid manner (P > 0.05), then decreased gradually until disappeared simultaneously [Ch1: (0.32 ± 0.23) s, Ch2: (0.27 ± 0.21) s, Ch3: (0.23 ± 0.16) s, Ch4: (0.33 ± 0.31) s, Ch5: (0.33 ± 0.29) s] (P > 0.05) after the swallowing sound (P < 0.05). The TP related parameters (the total duration of TP:Ch1: (0.72 ± 0.20) s, Ch2: (0.63 ± 0.16) s, Ch3: (0.47 ± 0.17) s, Ch4: (0.70 ± 0.35) s, Ch5: (0.73 ± 0.29) s; the pre-peak duration of TP: Ch1: (0.28 ± 0.21) s, Ch2: (0.20 ± 0.16) s, Ch3: (0.12 ± 0.10) s, Ch4: (0.21 ± 0.22) s, Ch5: (0.23 ± 0.21) s; the post-peak duration of TP: Ch1: (0.44 ± 0.23) s, Ch2: (0.43 ± 0.18) s, Ch3: (0.36 ± 0.18) s, Ch4: (0.49 ± 0.25) s, Ch5: (0.50 ± 0.23) s; the maximum magnitude of TP: Ch1: (13.80 ± 7.73) kPa, Ch2: (12.40 ± 6.51) kPa, Ch3: (10.26 ± 7.15) kPa, Ch4: (12.16 ± 5.38) kPa, Ch5: (13.08 ± 5.05) kPa; the integrated value of TP: Ch1: (4.99 ± 3.69) kPa×s, Ch2: (4.25 ± 2.13) kPa×s, Ch3: (2.88 ± 1.87) kPa×s, Ch4: (4.32 ± 3.47) kPa×s, Ch5: (4.63 ± 2.49) kPa×s were significantly smaller in the posteriomedian part among all the five parts measured. No laterality was found in TP produced at the circumferential parts of the hard palate (P > 0.05). CONCLUSIONS: The TP at each part coordinates precisely during swallowing. The effective measurement of TP by tongue pressure sensor sheet will facilitate the evaluation of oral swallowing and the diagnosis of dysphagia simply and non-invasively.

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.

Effect of complete denture wearing on tongue motor biomechanics during swallowing in edentulous older adults.

AIM: Contact of the tongue against the hard palate plays an important role in swallowing. Therefore, age-related decline in tongue function has received much attention. The purpose of the present study was to investigate the effect of complete denture wearing on tongue motor biomechanics during swallowing in healthy edentulous older adults. METHODS: A total of 19 edentulous patients (6 males and 13 females, mean age 76.2 ± 7.2 years) without any history of neuromuscular disease or dysphagia were selected. All patients were wearing complete dentures in both the upper and lower jaws. Tongue pressure against the hard palate during swallowing saliva was recorded using an original T-shaped sensor sheet with five measuring points. Measurements were carried out both with and without the prostheses. For evaluating swallowing ability, the frequency of swallowing saliva in 30 s was recorded (Repetitive Saliva Swallowing Test). RESULTS: With the prostheses, the maximal magnitude and duration of tongue pressure was larger at Ch. 1 (anterior-median part of the hard palate) and Ch. 2 (mid-median part) right and left circumferential parts than without the prostheses. As for the integral of tongue pressure, that with prostheses was larger at all 5 channels than that without prostheses. There was significant improvement in the Repetitive Saliva Swallowing Test value while wearing prostheses. CONCLUSIONS: These results suggested that swallowing function deteriorated as a result of the decline in tongue-palate contact on removing complete dentures in edentulous older adults. CLINICAL RELEVANCE: The present study showed the effect of wearing prostheses on swallowing in edentulous older adults.

Effect of supraglottic and super-supraglottic swallows on tongue pressure production against hard palate.

The objectives of this study were to evaluate the state of tongue pressure production during supraglottic swallow (SS) and super-supraglottic swallow (SSS) performed by healthy adults, and to investigate the effects of these swallowing maneuvers on the oral stage of swallowing. The participants were 19 healthy individuals. Tongue pressure against the hard palate during swallowing was measured using a tongue pressure sensor sheet system with five pressure-sensitive points. The tasks comprised swallowing 5 mL of water by normal wet swallow, SS, and SSS, and the parameters for analysis were the duration, the maximal magnitude, and the integrated value of tongue pressure during swallowing. The duration of tongue pressure was significantly longer at the anterior-median part of the hard palate during both SS and SSS than with normal wet swallow. The maximal magnitude increased significantly only at the posterior part of the hard palate during SS, but at all points during SSS. The integrated value increased significantly only at the posterior-median part of the hard palate during SS, but at all points except the mid-median part of the hard palate during SSS. The maximal magnitude and integrated value were also significantly higher at the anterior-median and posterior circumferential parts during SSS than during SS. These results show that these two swallowing maneuvers, which are known primarily as techniques to protect the airway, also function to strengthen the tongue pressure produced by the contact between the tongue and the hard palate during swallowing and this effect is more pronounced during SSS.

[Effects of tongue pressure sensor sheet on the signal waveform of laryngeal movement produced by bend sensor during deglutition].

OBJECTIVE: To evaluate the effects of the application of tongue pressure sensor sheet on the signal waveform of laryngeal movement produced by the bend sensor during deglutition. METHODS: Twelve adult male subjects were recruited to perform a single swallow of 5 ml water when sitting on the dental chair with upright position. The data recorded by bend sensor was obtained with attaching tongue pressure sensor sheet simultaneously or not. Then the measured parameters by bend sensor with or without concurrent application of tongue pressure sensor sheet were compared. RESULTS: There were no significant differences between the same time point on the signal waveform produced by bend sensor whether concurrently attaching tongue pressure sensor sheet or not (P > 0.05). Additionally, we found no statistical significances between matched phases on the signal waveform recorded by bend sensor with or without application of tongue pressure sensor sheet (P > 0.05). CONCLUSION: The findings in this study suggest us that the usage of tongue pressure sensor sheet exerted no influences on the waveform of the laryngeal movement produced by bend sensor during deglutition, facilitating us to further apply tongue pressure sensor sheet and bend sensor simultaneously to record tongue pressure production and hyoid activity during deglutition.

Tongue pressure generation during tongue-hold swallows in young healthy adults measured with different tongue positions.

Tongue-hold swallow (THS) has the potential to be a resistance exercise not only for the pharyngeal constrictor but for the tongue muscles. To elucidate the physiological mechanisms of THS, this study investigated intraoral pressure generation during THS in relation to different extents of tongue protrusion. Tongue pressure was measured by a 5-point pressure sensor sheet placed onto the hard palate of 18 healthy young subjects who performed three swallow tasks: normal dry swallow, THS with slight tongue protrusion, and THS with greater tongue protrusion. Subjects randomly repeated each task five times. Maximum range of tongue protrusion was also measured in each subject to estimate lingual flexibility. With an increase in the extent of tongue protrusion, pressure generation patterns became irregular and variable. Duration of pressure generation increased with statistical significance in the posterior circumferential parts of the hard palate (p < 0.05). Maximal magnitude and integrated value of the pressure recorded at these locations increased in eight subjects as the extent of tongue protrusion increased, but it decreased in nine. The former group showed greater lingual flexibility, while the latter group exhibited less flexibility. THS may place different amounts of load on the tongue muscles by adjusting the degree of tongue protrusion.

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.

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.