Recent advances in sensing oropharyngeal swallowing function in Japan

Efficacy of hard gummy candy chewing in improving masticatory function in Japanese children aged 6-12 years: a clinical trial

OBJECTIVES

Japanese children have been shown to exhibit decreased masticatory function; however, limited evidence is available regarding the efficacy of certain food items in improving this issue. Therefore, this study examined the effects of chewing hard gummy candy on the masticatory function of Japanese children aged 6-12 years.

METHODS

The study included 26 participants (10 boys and 16 girls; mean age ± standard error = 9.3 ± 0.3 years) who were asked to chew hard gummy candy twice daily for 4 weeks at home. The lip-closing force, occlusal force, and masticatory performance of the participants were recorded before commencement (T1), 4 weeks after commencement (T2), and 4 weeks after completion (T3) of the training. Statistical analyses were performed using the Wilcoxon rank-sum test or the Wilcoxon signed-rank test with Bonferroni correction.

RESULTS

No correlation was observed between masticatory function and sex at T1. The lip-closing and right occlusal forces increased significantly after 4 weeks of exercise, and the effects persisted for another 4 weeks after completion. The masticatory performance also improved after training, although these effects did not persist and deteriorated substantially 4 weeks after completion of the training.

CONCLUSIONS

Habitual mastication training using hard gummy candy markedly enhances masticatory function (e.g., lip-closing force, occlusal force, and masticatory performance) in Japanese children.

Development and validation of a device for monitoring laryngeal motion during swallowing

Objectives: Hyolaryngeal movement during swallowing is essential to airway protection and bolus clearance. Although palpation is widely used to evaluate hyolaryngeal motion, insufficient accuracy has been reported. The Bando Stretchable Strain Sensor for Swallowing (B4S™) was developed to capture hyolaryngeal elevation and display it as waveforms. This study compared laryngeal movement time detected by the B4S™ with laryngeal movement time measured by videofluoroscopy (VF). Methods: Participants were 20 patients without swallowing difficulty (10 men, 10 women; age 30.6 ± 7.1 years). The B4S™ was attached to the anterior neck and two saliva swallows were measured on VF images to determine the relative and absolute reliability of laryngeal elevation time measured on VF and that measured by the B4S™. Results: The intra-class correlation coefficient of the VF and B4S™ times was very high [ICC (1.1) = 0.980]. A Bland-Altman plot showed a strong positive correlation with a 95% confidence interval of 0.00-3.01 for the mean VF time and mean B4S™ time, with a fixed error detected in the positive direction but with no proportional error detected. Thus, the VF and B4S™ time measurements showed high consistency. Conclusion: The strong relative and absolute reliability suggest that the B4S™ can accurately detect the duration of superior-inferior laryngeal motion during swallowing. Further study is needed to develop a method for measuring the distance of laryngeal elevation. It is also necessary to investigate the usefulness of this device for evaluation and treatment in clinical settings.

A Fiber-Optic Non-Invasive Swallowing Assessment Device Based on a Wearable Pressure Sensor

We developed a wearable swallowing assessment device using a hetero-core fiber-optic pressure sensor for the detection of laryngeal movement during swallowing. The proposed pressure sensor (comfortably attached to the skin of the neck) demonstrated a high sensitivity of 0.592 dB/kPa and a linearity of R² = 0.995 within a 14 kPa pressure band, which is a suitable pressure for the detection of laryngeal movement. In addition, since the fabricated hetero-core fiber-optic pressure sensor maintains appreciable sensitivity over the surface of the sensor, the proposed wearable swallowing assessment device can accurately track the subtle pressure changes induced by laryngeal movements during the swallowing process. Sixteen male subjects and one female subject were evaluated in a variety of age groups ranging from 30 to 60 years old. For all subjects, characteristic swallowing waveforms (with two valleys based on laryngeal movements consisting of upward, forward, backward, and downward displacements) were acquired using the proposed wearable swallowing assessment device. Since the denoted time of the first valley in the acquired waveform determines the "aging effect", significant differences in swallowing functions among the different age groups were ultimately determined based on the time of the first valley. Additionally, by analyzing each age group using the proposed device, due to p-values being consistently less than 0.05, swallowing times were found to exhibit statistically significant differences within the same groups.

In situ quantitative assessment of food oral processing parameters: A review of feasible techniques and devices

Oral processing is a combination of various actions, the detailed description of which has always been the subject of relevant research. By means of imaging technology and sensory evaluation, more knowledge of oral processing have been accumulated. Presently, the advances in sensory technology have added quantitative parameters to the qualitative description of oral processing, which also enriched the specifics of each action. Previous studies have shown that oral processing includes lip closure, dental occlusion, masticatory muscles activity, tongue movement, and swallowing, whose processing contains rich information such as the movement of organ and the intensity of organ contacts. "Quantification" was taken in this review as the basic feature of in situ detection information, the relevant parameters and feasible methods for the quantitative description of each activity was recorded in detail. In addition, basic problems and feasible optimization schemes of the existing in situ detection device are also proposed in the hope of promoting the development of in situ detection device thus providing available information for the description of oral processing.

Effects of Tongue-Strengthening Exercise on Tongue Strength and Effortful Swallowing Pressure in Young Healthy Adults: A Pilot Study

PURPOSE

The purpose of this study was to investigate the effects of tongue-strengthening exercise (TSE) on tongue strength and effortful swallowing pressure in young healthy adults.

METHOD

Thirteen young healthy volunteers (six men, seven women; M _age = 20.5 ± 0.5 years) performed 8 weeks of isometric TSE 3 days per week. A tongue pressure measurement device was used to measure maximum isometric tongue pressure (MITP) and conduct the TSE, and a tactile sensor system attached to the hard palate was used to measure effortful swallowing pressure. MITP and effortful swallowing pressure were measured at baseline, after 4 and 8 weeks of training, and at 4 and 8 weeks after the last training session to examine the detraining effects.

RESULTS

The results indicated that both MITP and effortful swallowing pressure increased significantly from baseline to 8 weeks after training. Although the improved MITP significantly decreased at 4 and 8 weeks after training cessation, no detraining effect was observed for effortful swallowing pressure.

CONCLUSIONS

TSE is an effective method for increasing tongue pressure in wide tongue-palate contact areas during effortful swallow. The effortful swallowing pressure gained with TSE appears to be maintained for at least eight nontraining weeks.

Intraoral Swallow Pressure Profiles: General Features and Aids to Categorization

Purpose

The primary goal of this study was to establish a normative data set representing intraoral time series swallow pressure profiles for healthy adults using a novel wearable intraoral pressure sensing system, OroPress, developed to help with dysphagia (swallow disorder) clinical screening.

Methods

Swallow intraoral pressure-time profiles for 35 healthy adults (17 male, 18 female) swallowing water ($$3 \times 5\, {\text{cm}^3}$$ 3 × 5 cm 3 ; $$3 \times 10\, {\text{cm}^3}$$ 3 × 10 cm 3 ) and custard ($$3 \times 5\, {\text{cm}^3}$$ 3 × 5 cm 3 ) boluses ($$N=9 \times 35 = 315$$ N = 9 × 35 = 315 ) were recorded using OroPress.

Results

General swallow profile traits are identified to characterise an effective, efficient swallow. A profile-specific swallow envelope function is devised which in combination with profile metrics, provides a simple means of categorizing swallows as effective or impaired.

Conclusion

The swallow profile data trace with superimposed and colour coded peaks, envelope function and related swallow metrics provides a simple human readable graphic to aid the real-time instrumented identification of subjects warranting more in-depth clinical assessment. It may also prove useful in the selection of training set profiles for machine learning and other analysis tools which could improve the discriminatory capabilities of intraoral pressure measurement in dysphagia diagnostics.

Conformable AlN Piezoelectric Sensors as a Non-invasive Approach for Swallowing Disorder Assessment

Deglutition disorders (dysphagia) are common symptoms of a large number of diseases and can lead to severe deterioration of the patient's quality of life. The clinical evaluation of this problem involves an invasive screening, whose results are subjective and do not provide a precise and quantitative assessment. To overcome these issues, alternative possibilities based on wearable technologies have been proposed. We explore the use of ultrathin, compliant, and flexible piezoelectric patches that are able to convert the laryngeal movement into a well-defined electrical signal, with extremely low anatomical obstruction and high strain resolution. The sensor is based on an aluminum nitride thin film, grown on a soft Kapton substrate, integrated with an electrical charge amplifier and low-power, wireless connection to a smartphone. An ad-hoc designed laryngeal motion simulator (LMS), which is able to mimic the motions of the laryngeal prominence, was used to evaluate its performances. The physiological deglutition waveforms were then extrapolated on a healthy volunteer and compared with the sEMG (surface electromyography) of the submental muscles. Finally, different tests were conducted to assess the ability of the sensor to provide clinically relevant information. The reliability of these features permits an unbiased evaluation of the swallowing ability, paving the way to the creation of a system that is able to provide a point-of-care automatic, unobtrusive, and real-time extrapolation of the patient's swallowing quality even during normal behavior.

Biosignal Sensors and Deep Learning-Based Speech Recognition: A Review

Voice is one of the essential mechanisms for communicating and expressing one's intentions as a human being. There are several causes of voice inability, including disease, accident, vocal abuse, medical surgery, ageing, and environmental pollution, and the risk of voice loss continues to increase. Novel approaches should have been developed for speech recognition and production because that would seriously undermine the quality of life and sometimes leads to isolation from society. In this review, we survey mouth interface technologies which are mouth-mounted devices for speech recognition, production, and volitional control, and the corresponding research to develop artificial mouth technologies based on various sensors, including electromyography (EMG), electroencephalography (EEG), electropalatography (EPG), electromagnetic articulography (EMA), permanent magnet articulography (PMA), gyros, images and 3-axial magnetic sensors, especially with deep learning techniques. We especially research various deep learning technologies related to voice recognition, including visual speech recognition, silent speech interface, and analyze its flow, and systematize them into a taxonomy. Finally, we discuss methods to solve the communication problems of people with disabilities in speaking and future research with respect to deep learning components.

Development of Band-shaped Device and Detection Algorithm of Laryngeal Elevation

This study concerns a measurement device and an algorithm of the laryngeal elevation for the Mendelsohn maneuver. The measurement device is band-shaped and measures the change of the circumferential length of the neck by stretchable strain sensors. The device is lightweight of 35 g. The algorithm detects the onset and offset points in time of the laryngeal elevation by the first-order difference and the dynamic time warping distance. Twelve elderly people participated in an experiment to validate the effectiveness of the device. A clustering method separated the measurement data into two groups based on their waveforms. We defined template data from the measurement data. The algorithm detected the onset and offset time by using the template data. Although the offset time of a group had an error of about 4 s, the onset and offset time points of the other group were errors within 1 s.

Correlation of Temporal Parameters of Laryngeal Excursion by Using Force-Sensing Resistor Sensors with Hyoid Motion in Videofluoroscopic Swallowing Study

Small flexible force-sensing resistor (FSR) sensors can detect laryngeal excursion during swallowing, but the detected laryngeal excursion has not been correlated with videofluoroscopic swallowing study (VFSS) results. Here, we tested the correlation of temporal parameters between the laryngeal excursion recording by FSR sensor and the hyoid motion recording by VFSS under simultaneously swallowing test recordings. Swallowing measurements were recorded in a radiological suite by simultaneously using VFSS and FSR sensors to detect hyoid motion and laryngeal excursion, respectively. Volunteers sat with their head vertical to the Frankfort plane. Two FSR sensors, each for detecting thyroid cartilage excursion and thumb pressing, were placed. VFSS images and FSR sensor signals during single 5-mL barium liquid (30% wt/volume %) bolus swallowing were collected and analyzed for four swallows per participant. In total, 15 men (28.0 ± 4.1 years old); 14 women (28.4 ± 4.2 years old) were recruited. Temporal parameters between VFSS and noninvasive system demonstrated a strong correlation by Pearson's correlation analysis: in men (R = 0.953-0.999) and in women (R = 0.813-0.982), except for VT1-V1 compared with FT1-F1, which demonstrated a moderate correlation in women (R = 0.648; all p < 0.001). Only VT1-V1 and FT1-F1 in women displayed a significant difference (p = 0.001). Therefore, this is the first study to simultaneous record VFSS and noninvasive signals by FSR sensor. The correlation of temporal parameters between these two tests was strong. This finding is valuable for future applications of this noninvasive swallowing study tool.

Changes in maximum lip-closing force after extraction and nonextraction orthodontic treatments

Objective

The aims of the present study were to evaluate the changes in the maximum lip-closing force (MLF) after orthodontic treatment with or without premolar extractions and verify the correlation of these changes with dentoskeletal changes.

Methods

In total, 17 women who underwent nonextraction orthodontic treatment and 15 women who underwent orthodontic treatment with extraction of all four first premolars were included in this retrospective study. For all patients, lateral cephalograms and dental models were measured before (T0) and after (T1) treatment. In addition, MLF was measured at both time points using the Lip De Cum LDC-110R® device. Statistical analyses were performed to evaluate changes in clinical variables and MLF and their correlations.

Results

Both groups showed similar skeletal patterns, although the extraction group showed greater proclination of the maxillary and mandibular incisors and lip protrusion compared to the nonextraction group at T0. MLF at T0 was comparable between the two groups. The reduction in the arch width and depth and incisor retroclination from T0 to T1 were more pronounced in the extraction group than in the nonextraction group. MLF in the extraction group significantly increased during the treatment period, and this increase was significantly greater than that in the nonextraction group. The increase in MLF was found to be correlated with the increase in the interincisal angle and decrease in the intermolar width, arch depth, and incisor-mandibular plane angle.

Conclusions

This study suggests that MLF increases to a greater extent during extraction orthodontic treatment than during nonextraction orthodontic treatment.

Flexible submental sensor patch with remote monitoring controls for management of oropharyngeal swallowing disorders

Successful rehabilitation of oropharyngeal swallowing disorders (i.e., dysphagia) requires frequent performance of head/neck exercises that primarily rely on expensive biofeedback devices, often only available in large medical centers. This directly affects treatment compliance and outcomes, and highlights the need to develop a portable and inexpensive remote monitoring system for the telerehabilitation of dysphagia. Here, we present the development and preliminarily validation of a skin-mountable sensor patch that can fit on the curvature of the submental (under the chin) area noninvasively and provide simultaneous remote monitoring of muscle activity and laryngeal movement during swallowing tasks and maneuvers. This sensor patch incorporates an optimal design that allows for the accurate recording of submental muscle activity during swallowing and is characterized by ease of use, accessibility, reusability, and cost-effectiveness. Preliminary studies on a patient with Parkinson's disease and dysphagia, and on a healthy control participant demonstrate the feasibility and effectiveness of this system.

Compression Test of Soft Food Gels Using a Soft Machine with an Artificial Tongue

Care food is increasingly required in the advanced-aged society. Mechanical properties of such foods must be modified such that the foods are easily broken by the tongue without chewing. When foods are compressed between the tongue and the hard palate, the tongue deforms considerably, and only soft foods are broken. To simulate tongue compression of soft foods, artificial tongues with stiffness similar to that of the human tongue were created using clear soft materials. Model soft gels were prepared using gellan gums. A piece of gel on an artificial tongue was compressed using a texture analyzer. The deformation profile during the compression test was obtained using a video capture system. The soft machine equipped a soft artificial tongue sometimes fractured food gels unlike hard machine, which always fracture gels. The fracture properties measured using the soft machine were better than those obtained from a conventional test between hard plates to mimic natural oral processing in humans. The fracture force on foods measured using this soft machine may prove useful for the evaluation of food texture that can be mashed using the tongue.

A new flexible piezoelectric pressure sensor array for the noninvasive detection of laryngeal movement during swallowing

We tried to develop a new device to detect laryngeal movement noninvasively. We made small piezo pressure sensors (length, 1.5 mm, width, 7.0 mm), and five of these were lined up with 3.0-mm intervals and embedded in the middle of a palm-sized urethane resin sheet. This sheet was lightly attached to the ventral surface of the neck near the laryngeal prominence. The first and second peaks obtained from each sensor should correspond to the period when the larynx moves to the upper and lower positions during swallowing. The mean maximum rising velocities for men and women were about 0.08 and 0.11 m/s, respectively. Similarly, the mean maximum lowering velocities for men and women were about 0.09 and 0.11 m/s, respectively. The swallowing latencies for men and women were about 0.49 and 0.53 s, respectively. In conclusion, we succeeded in developing a new device, which will be useful in evaluating the swallowing function.

Effect of bolus volume and flow time on temporospatial coordination in oropharyngeal pressure production in healthy subjects

The effects of bolus volume and flow time on the sequential coordination of tongue pressure (TP) and pharyngeal pressure (PP), which are important in the biomechanics of swallowing, are unclear. In this study, we measured TP and PP simultaneously in 10 healthy adults at multiple points during dry swallowing and the swallowing of 5 ml and 15 ml of liquids with different viscosities, and investigated changes in the timing of the onset, peak, and offset of these pressures. TP was measured using a sensor sheet system with five measuring points on the hard palate, and PP was measured using a manometry catheter with four measuring points. The order and correlations of sequential events, such as onset, peak, and offset times of pressure production, at each pressure measuring point were analyzed on the synchronized waveforms. We found that the differences between the TP and PP onset times decreased when the bolus volume was larger. The change in bolus volume had very little effect on peak time or offset time. The flow time of the bolus affected the appearance of onset and peak time for both TP and PP. A time difference between TP and PP emerged as the flow time increased, with TP starting to appear before PP. This may be the first detailed analysis of pressure-flow dynamics that treats the mouth and pharynx as a single functional unit. We believe that our analysis is an important step toward extending future research to include a wider range of age groups and dysphagia patients.

Relationship between tongue strength, lip strength, and nutrition-related sarcopenia in older rehabilitation inpatients: a cross-sectional study

Objective

The objective of this study was to clarify the relationship between tongue strength, lip strength, and nutrition-related sarcopenia (NRS).

Patients and methods

A total of 201 older inpatients aged ≥65 years (70 men, median age: 84 years, interquartile range: 79–89 years) consecutively admitted for rehabilitation were included in this cross-sectional study. The main factors evaluated were the presence of NRS diagnosed by malnutrition using the Mini-Nutrition Assessment – Short Form, sarcopenia based on the criteria of the Asian Working Group for Sarcopenia, tongue strength, and lip strength. Other factors such as age, sex, comorbidity, physical function, cognitive function, and oral intake level were also assessed.

Results

In all, 78 (38.8%) patients were allocated to the NRS group, and 123 (61.2%) patients were allocated to the non-NRS group. The median tongue strength and lip strength (interquartile range) were significantly lower in the NRS group (tongue: 22.9 kPa [17.7–27.7 kPa] and lip: 7.2 N [5.6–9.8 N]) compared with the non-NRS group (tongue: 29.7 kPa [24.8–35.1 kPa] and lip: 9.9 N [8.4–12.3 N], P<0.001 for both). Multivariable logistic regression analysis showed that NRS was independently associated with tongue strength (odds ratio [OR] =0.93, 95% confidence interval [CI] 0.87–0.98, P=0.012) and lip strength (OR =0.76, 95% CI 0.66–0.88, P<0.001), even after adjusting for age, sex, comorbidity, physical function, cognitive function, and oral intake level.

Conclusion

The likelihood of occurrence of NRS decreased when tongue strength or lip strength increased. Tongue strength and lip strength may be important factors for preventing and improving NRS, regardless of the presence of low oral intake level in older rehabilitation inpatients.

Development of a portable non-invasive swallowing and respiration assessment device

Dysphagia is a condition that happens when a person cannot smoothly swallow food from the mouth to the stomach. It causes malnourishment in patients, or can even cause death due to aspiration pneumonia. Recently, more and more researchers have focused their attention on the importance of swallowing and respiration coordination, and the use of non-invasive assessment systems has become a hot research trend. In this study, we aimed to integrate the timing and pattern monitoring of respiration and swallowing by using a portable and non-invasive approach which can be applied at the bedside in hospitals or institutions, or in a home environment. In this approach, we use a force sensing resistor (FSR) to detect the motions of the thyroid cartilage in the pharyngeal phase. We also use the surface electromyography (sEMG) to detect the contraction of the submental muscle in the oral phase, and a nasal cannula to detect nasal airflow for respiration monitoring during the swallowing process. All signals are received and processed for swallowing event recognition. A total of 19 volunteers participated in the testing and over 57 measurements were made. The results show that the proposed approach can effectively distinguish the swallowing function in people of different ages and genders.

Sequential coordination between lingual and pharyngeal pressures produced during dry swallowing

The aim of this study was to investigate oropharyngeal pressure flow dynamics during dry swallowing in ten healthy subjects. Tongue pressure (TP) was measured using a sensor sheet system with five measuring points on the hard palate, and pharyngeal pressure (PP) was measured using a manometric catheter with four measuring points. The order and correlations of sequential events, such as onset, peak, and offset times of pressure production, at each pressure measuring point were analyzed on the synchronized waveforms. Onset of TP was earlier than that of PP. The peak of TP did not show significant differences with the onset of PP, and it was earlier than that of PP. There was no significant difference between the offset of TP and PP. The onset of PP was temporally time-locked to the peak of TP, and there was an especially strong correlation between the onset of PP and TP at the posterior-median part on the hard palate. The offset of PP was temporally time-locked to that of TP. These results could be interpreted as providing an explanation for the generation of oropharyngeal pressure flow to ensure efficient bolus transport and safe swallowing.

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.

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.