Healthy Swallowing Research Articles

Efficacy for aspiration prevention through thickening of liquid foods evaluated using a swallowing model apparatus

Abstract An apparatus simulating the swallowing process of liquid foods was constructed using a flow channel. In the channel, a circular cylindrical obstruction was fixed to serve as an epiglottis in the mesopharynx. The apparatus was designed with an adjustable gate for flow control to represent the processes of healthy swallowing and dysphagia. The parameters considered were the holding time and flow resistance controlled by the gate, which were assumed to indicate the swallowing reflex and power, respectively. When a Newtonian liquid with relatively low viscosity was used, the flow experiment performed using the apparatus under conditions of shorter holding time and larger flow resistance successfully reproduced a phenomenon similar to aspiration in a patient with dysphagia. In addition to a Newtonian liquid with high viscosity, non-Newtonian liquids thickened to various concentrations using commercially available thickeners were used. In flow experiments with these test liquids, the efficacy for aspiration prevention was inferred based not only on the viscosity of the liquid but also its elasticity, depending on its viscosity.

A Preliminary Study of Vallecular Bolus Aggregation in Healthy Swallowing of Solid Food Boluses.

The pharyngeal swallow typically begins within 400 ms following the arrival of a liquid bolus in the pharynx. By contrast, processed food particles aggregate in the valleculae prior to swallow initiation. With solid foods, swallow reaction time (SRT), the interval between bolus passing the ramus of mandible and hyoid burst onset (HYB) can be subdivided into components of vallecular aggregation time (VAT) and the subsequent end of aggregation to hyoid burst interval (EOA-to-HYB). However, expected durations of these timing measures remain unclear. We aimed to study bolus aggregation in healthy swallowing for International Dysphagia Diet Standardisation Initiative Food Levels 5 (minced and moist [MM5]), 6 (soft and bite-sized [SB6]), and 7 (regular [RG7]). Understanding typical patterns and durations of vallecular aggregation with solids in healthy swallowing will inform the identification of impaired swallow timing in patient populations. Twenty healthy adults (10 males, Mage = 28 years, range: 23-55 years) swallowed two boluses each of MM5, SB6, and RG7 foods in videofluoroscopy. Blinded duplicate ratings determined bolus location at swallow onset, SRT, VAT, and EOA-to-HYB. Texture-based differences were measured using Friedman's tests. Bolus location was at/above the valleculae at swallow onset for 85% of boluses, with no differences by texture. SRT, VAT, and EOA-to-HYB did not vary by texture, with overall median values (interquartile range) of 99 ms (-66 to 743 ms) for SRT, 347 ms (66 to 891 ms) for VAT, and -132 ms (-231 to -83 ms) for EOA-to-HYB. These data corroborate prior evidence that it is not unusual for food particles to aggregate in the valleculae prior to swallow initiation in healthy swallowing. However, durations of vallecular aggregation are typically < 1 s in healthy adults.

Using Sequence Analyses to Quantitatively Measure Oropharyngeal Swallowing Temporality in Point-of-Care Ultrasound Examinations: A Pilot Study.

(1) Background: Swallowing is a complex process that comprises well-timed control of oropharyngeal and laryngeal structures to achieve airway protection and swallowing efficiency. To understand its temporality, previous research adopted adherence measures and revealed obligatory pairs in healthy swallows and the effect of aging and bolus type on the variability of event timing and order. This study aimed to (i) propose a systemic conceptualization of swallowing physiology, (ii) apply sequence analyses, a set of information-theoretic and bioinformatic methods, to quantify and characterize swallowing temporality, and (iii) investigate the effect of aging and dysphagia on the quantified variables using sequence analyses measures. (2) Method: Forty-three participants (17 young adults, 15 older adults, and 11 dysphagic adults) underwent B-mode ultrasound swallowing examinations at the mid-sagittal plane of the submental region. The onset, maximum, and offset states of hyoid bone displacement, geniohyoid muscle contraction, and tongue base retraction were identified and sorted to form sequences which were analyzed using an inventory of sequence analytic techniques; namely, overlap coefficients, Shannon entropy, and longest common subsequence algorithms. (3) Results: The concurrency of movement sequence was found to be significantly impacted by aging and dysphagia. Swallowing sequence variability was also found to be reduced with age and the presence of dysphagia (H(2) = 52.253, p < 0.001, η2 = 0.260). Four obligatory sequences were identified, and high adherence was also indicated in two previously reported pairs. These results provided preliminary support for the validity of sequence analyses for quantifying swallowing sequence temporality. (4) Conclusions: A systemic conceptualization of human deglutition permits a multi-level quantitative analysis of swallowing physiology. Sequence analyses are a set of promising quantitative measurement techniques for point-of-care ultrasound (POCUS) swallowing examinations and outcome measures for swallowing rehabilitation and evaluation of associated physiological conditions, such as sarcopenia. Findings in the current study revealed physiological differences among healthy young, healthy older, and dysphagic adults. They also helped lay the groundwork for future AI-assisted dysphagia assessment and outcome measures using POCUSs. Arguably, the proposed conceptualization and analyses are also modality-independent measures that can potentially be generalized for other instrumental swallowing assessment modalities.

Quantification of swallowing movements by ultrasound imaging in normal and disordered subjects

Ultrasound imaging may be useful for tracking oral-pharyngeal structures of the vocal tract critical for effective swallowing, but use of this technology has been hampered by a lack of validation against standard clinical measures derived from x-ray video fluoroscopy (Modified Barium Swallow Studies or MBSS). Here, we compare quantitative tracking of hyoid bone and tongue motion from ultrasound imaging and simultaneously measured MBSS from a range of participants with disordered and healthy swallowing behavior. The proximal edge of the hyoid bone in MBSS and ultrasound recordings is tracked using CASM (Computational Analysis of Swallowing Mechanics) software, while tongue motion is tracked using TonguePART software, originally developed for analysis of speech. Hyoid trajectories and velocities measured from synchronized ultrasound and MBSS recordings are compared and standard deviations of differences between the two measurements are evaluated. Tongue motion during swallowing is characterized by analysis of root, dorsum, and blade displacement, velocity, and timingas well as tongue base retraction in the pharynx. Preliminary findings show quantitatively similar patterns in ultrasound and MBSS, suggesting that ultrasound has potential utility as an accessible tool for bedside diagnosis and biofeedback. Characteristic patterns separating normal from healthy swallowing, as well as potential therapeutic targets for biofeedback treatment of dysphagia, will be discussed.

Non-Invasive Sensor-Based Estimation of Anterior-Posterior Upper Esophageal Sphincter Opening Maximal Distension.

Dysphagia management relies on the evaluation of the temporospatial kinematic events of swallowing performed in videofluoroscopy (VF) by trained clinicians. The upper esophageal sphincter (UES) opening distension represents one of the important kinematic events that contribute to healthy swallowing. Insufficient distension of UES opening can lead to an accumulation of pharyngeal residue and subsequent aspiration which in turn can lead to adverse outcomes such as pneumonia. VF is usually used for the temporal and spatial evaluation of the UES opening; however, VF is not available in all clinical settings and may be inappropriate or undesirable for some patients. High resolution cervical auscultation (HRCA) is a noninvasive technology that uses neck-attached sensors and machine learning to characterize swallowing physiology by analyzing the swallow-induced vibrations/sounds in the anterior neck region. We investigated the ability of HRCA to noninvasively estimate the maximal distension of anterior-posterior (A-P) UES opening as accurately as the measurements performed by human judges from VF images. Trained judges performed the kinematic measurement of UES opening duration and A-P UES opening maximal distension on 434 swallows collected from 133 patients. We used a hybrid convolutional recurrent neural network supported by attention mechanisms which takes HRCA raw signals as input and estimates the value of the A-P UES opening maximal distension as output. The proposed network estimated the A-P UES opening maximal distension with an absolute percentage error of 30% or less for more than 64.14% of the swallows in the dataset. This study provides substantial evidence for the feasibility of using HRCA to estimate one of the key spatial kinematic measurements used for dysphagia characterization and management. Clinical and Translational Impact Statement: The findings in this study have a direct impact on dysphagia diagnosis and management through providing a non-invasive and cheap way to estimate one of the most important swallowing kinematics, the UES opening distension, that contributes to safe swallowing. This study, along with other studies that utilize HRCA for swallowing kinematic analysis, paves the way for developing a widely available and easy-to-use tool for dysphagia diagnosis and management.

A preliminary deep learning study on automatic segmentation of contrast-enhanced bolus in videofluorography of swallowing

Although videofluorography (VFG) is an effective tool for evaluating swallowing functions, its accurate evaluation requires considerable time and effort. This study aimed to create a deep learning model for automated bolus segmentation on VFG images of patients with healthy swallowing and dysphagia using the artificial intelligence deep learning segmentation method, and to assess the performance of the method. VFG images of 72 swallowing of 12 patients were continuously converted into 15 static images per second. In total, 3910 images were arbitrarily assigned to the training, validation, test 1, and test 2 datasets. In the training and validation datasets, images of colored bolus areas were prepared, along with original images. Using a U-Net neural network, a trained model was created after 500 epochs of training. The test datasets were applied to the trained model, and the performances of automatic segmentation (Jaccard index, Sørensen–Dice coefficient, and sensitivity) were calculated. All performance values for the segmentation of the test 1 and 2 datasets were high, exceeding 0.9. Using an artificial intelligence deep learning segmentation method, we automatically segmented the bolus areas on VFG images; our method exhibited high performance. This model also allowed assessment of aspiration and laryngeal invasion.

Swallowing assessment in patients with dysphagia: Validity and reliability of a pocket-sized ultrasound system.

BackgroundThe use of ultrasound as an adjunct to clinical swallowing evaluation provides quantitative physiological and morphological data. As a low‐risk procedure, ultrasound imaging can be performed outside of a medical setting. This is particularly important for patients living in rural areas with restricted access to a hospital. Technical advances have produced pocket‐sized ultrasound technology that is more affordable, and therefore within the fiscal reach of most allied health services.AimsTo explore the validity and reliability of pocket‐sized ultrasound technology in dysphagia assessment.Methods & ProceduresData were acquired from 43 patients with dysphagia using the Clarius ultrasound device. Ultrasound and videofluoroscopic measures of hyoid and laryngeal displacement during liquid and puree swallowing were collected concurrently to quantify correlation and agreement between identical measures derived from the two instruments. Reliability of ultrasound was assessed for measures of hyoid and laryngeal displacement, tongue thickness, and size of the submental muscles in eight patients. Reliability was evaluated for the entire process of data acquisition including scanning and online measurement using an iPad in a clinical setting and for offline measurement on a computer screen to explore environmental influences on reliability.Outcomes & ResultsResults revealed poor correlation between the measures of interest across instruments. Reliability of the entire process of data acquisition in a clinical setting was insufficient while reliability was more promising for offline measurements.Conclusions & ImplicationsThe clinical use of pocket‐sized ultrasound devices, such as the Clarius system, for swallowing evaluation is not indicated at this time. Enhanced validity and reliability of the entire process of data acquisition are needed prior to clinical translation of such technology.WHAT THIS PAPER ADDSWhat is already known on the subject The use of ultrasound allows for radiation‐free, non‐invasive swallowing assessment. Some data suggest that ultrasound is valid and reliable in the evaluation of swallowing using standard‐sized equipment. Insufficient validity and reliability have been reported for pocket‐sized ultrasound technology in the assessment of healthy swallowing. What this paper adds to existing knowledge This research is the first to provide validity and reliability data of the pocket‐sized Clarius technology in the evaluation of swallowing in patients with dysphagia. Insufficient validity and reliability of online data acquisition in a clinical environment were found. Reliability for offline measurement was more promising. What are the potential or actual clinical implications of this work? The clinical use of pocket‐sized ultrasound devices, such as the Clarius system, for swallowing assessment is not indicated at this time.

Potential for Behavioural Pressure Modulation at the Upper Oesophageal Sphincter in Healthy Swallowing.

Supratentorial structures are known to be involved in the neural control of swallowing, thus the potential for volitional manipulation of pharyngeal swallowing is of rehabilitative interest. The extent of volitional control of the upper oesophageal sphincter (UOS) during swallowing remains unclear. Prior research has shown that the UOS opening duration can be volitionally prolonged during execution of the Mendelsohn manoeuvre, which does not change the UOS opening time in isolation but the swallowing response in its entirety. This study explored the capacity of healthy adults to increase the period of pressure drop in the region of the UOS (UOS-Pdrop) during swallowing, through volitional UOS pressure modulation in the absence of altered pharyngeal pressure. The period of UOS-Pdrop was used as a proxy of UOS opening duration that is associated with a pressure decrease at the region of the UOS. Six healthy adults were seen 45min daily for 2 weeks and for one follow-up session. During training, high-resolution manometry contour plots were provided for visual biofeedback. Participants were asked to maximally prolong the blue period on the monitor (period of UOS-Pdrop) without altering swallowing biomechanics. Performance was assessed prior to training start and following training. There was evidence within the first session for task-specific volitional prolongation of the period of UOS-Pdrop during swallowing with biofeedback; however, performance was not enhanced with further training. This may suggest that the amount to which the period of UOS-Pdrop may be prolonged is restricted in healthy individuals. The findings of this study indicate a potential of healthy adults to volitionally prolong UOS opening duration as measured by the period of pressure drop at the region of the UOS. Further research is indicated to evaluate purposeful pressure modulation intra-swallow in patient populations with UOS dysfunction to clarify if the specificity of behavioural treatment may be increased.

Effect of Volitional Effort on Submental Surface Electromyographic Activity During Healthy Swallowing.

The effortful swallowing technique aims to compensate for or rehabilitate impaired swallowing by using maximal volitional effort to behaviorally modify aspects of swallowing physiology. Given that swallowing is a submaximal task, swallowing at submaximal levels has recently been suggested as a more task-specific therapeutic technique. The aim of this study was to investigate differences in muscle activity during minimum, regular, and maximum effort swallowing of different boluses and across different ages, with the goal of characterizing the task specificity of minimum effort and maximum effort swallowing. Forty-three healthy adults (22 female) representing four age groups (20-39, 40-59, 60-79, and 80 + years) participated in the study. They were verbally cued to swallow saliva and 5 mL water boluses using participant-determined minimum, regular, and maximum levels of effort, in randomized order. sEMG peak amplitude and duration of each swallow were measured. Linear mixed effects analyses demonstrated that compared to regular effort swallowing, maximum effort swallowing resulted in increased sEMG amplitude (p < .001) and prolonged duration (p < .001), while minimum effort swallowing resulted in decreased amplitude (p < .001) but no significant difference in duration (p = .06). These effects occurred regardless of age or bolus type. Differences in sEMG activity were smaller between regular and minimum effort swallowing than regular and maximum effort swallowing. Both increasing and decreasing volitional efforts during swallowing translate to significant modulation of muscle activity. However, regular swallowing is more similar to minimal effort swallowing. Results reinforce the concept of swallowing as a submaximal task, and provide insight into the development of sEMG biofeedback techniques for rehabilitation.

Which Physiological Swallowing Parameters Change with Healthy Aging?

Research suggests there are age-related changes in swallowing that do not constitute impairment (“presbyphagia”). The goal of this study was to explore the influence of age on quantitative measures of healthy swallowing by controlling for the effects of sex and sip volume in order to determine the specific characteristics of presbyphagia. Videofluoroscopy recordings of thin liquid swallows from 76 healthy adults (38 male), aged 21–82 were analysed. Blinded duplicate ratings of swallowing safety, efficiency, kinematics, and timing were made using the ASPEKT method. Hierarchical regression models were used to determine the effects of age, sex, and sip-volume on swallowing. There were no age-related changes in sip volume, number of swallows per bolus, frequency or severity of penetration-aspiration, duration of the hyoid-burst (HYB)-to-upper-esophageal-sphincter (UES) opening interval, time-to-laryngeal-vestibule-closure (LVC), peak hyoid position, hyoid speed, or pharyngeal residue. Significant changes seen with increasing age included: longer swallow reaction time, UES opening duration and LVC duration; larger pharyngeal area at rest and maximum constriction; and wider UES diameter. Male participants had larger sip volume and pharyngeal area at rest. Larger sip volumes were associated with multiple swallows per bolus and shorter hyoid-burst-to-UES opening intervals. These results help to define presbyphagic changes in swallowing that can be expected in healthy older adults up to 80 years of age, and distinguish them from changes that represent impairment. Certain parameters showed changes that were opposite in direction to changes that are usually considered to reflect impairment: longer UES opening, longer LVC duration and wider UES opening. These changes may reflect possible compensations for slower bolus transit. Further research is needed to determine the points along the age continuum where observed age-related changes in swallowing begin to emerge.

Variations in Hyoid Kinematics Across Liquid Consistencies in Healthy Swallowing.

PurposeJudgments regarding hyoid movement are frequently included in evaluations of swallowing. However, the literature lacks reference values for measures of hyoid kinematics in healthy swallowing. This study explores hyoid movement across the continuum from thin to extremely thick liquids.MethodParticipants were 39 healthy adults under the age of 60 years (19 men) who underwent videofluoroscopy involving three sips each of 20% w/v thin barium and six sips each of slightly, mildly, moderately, and extremely thick barium. Half of the thickened stimuli were prepared using xanthan gum; and half, with a starch-based thickener. Sip volume was derived from pre- and post-sip cup weights. Hyoid position was tracked frame-by-frame relative to the anterior–inferior corner of C4. Measures of peak hyoid position (along the XY axis) were normalized to a C2–C4 scalar, and measures of time-to-peak position, speed, and time-to-peak speed were derived. As a first step, Spearman's correlations confirmed the influence of sip volume on these hyoid measures. Linear mixed-effects models then explored the effects of stimulus, sip volume, and task repetition on the dependent variables.ResultsThe data set comprised 975 swallows with available hyoid tracking data. Sip volume was correlated with peak hyoid XY position (rs = .15, p < .01), time-to-peak position (rs = −.15, p < .05), and speed (rs = .13, p < .01). No significant differences in hyoid kinematics were found across stimuli.ConclusionMeasures of hyoid movement in healthy swallowing remain stable across the range from thin to extremely thick liquids with no systematic alterations in hyoid position or kinematics.

How Closely do Machine Ratings of Duration of UES Opening During Videofluoroscopy Approximate Clinician Ratings Using Temporal Kinematic Analyses and the MBSImP?

Clinicians evaluate swallow kinematic events by analyzing videofluoroscopy (VF) images for dysphagia management. The duration of upper esophageal sphincter opening (DUESO) is one important temporal swallow event, because reduced DUESO can result in pharyngeal residue and penetration/aspiration. VF is frequently used for evaluating swallowing but exposes patients to radiation and is not always feasible/readily available. High resolution cervical auscultation (HRCA) is a non-invasive, sensor-based dysphagia screening method that uses signal processing and machine learning to characterize swallowing. We investigated HRCA's ability to annotate DUESO and predict Modified Barium Swallow Impairment Profile (MBSImP) scores (component #14). We hypothesized that HRCA and machine learning techniques would detect DUESO with similar accuracy as human judges. Trained judges completed temporal kinematic measurements of DUESO on 719 swallows (116 patients) and 50 swallows (15 age-matched healthy adults). An MBSImP certified clinician completed MBSImP ratings on 100 swallows. A multi-layer convolutional recurrent neural network (CRNN) using HRCA signal features for input was used to detect DUESO. Generalized estimating equations models were used to determine statistically significant HRCA signal features for predicting DUESO MBSImP scores. A support vector machine (SVM) classifier and a leave-one-out procedure was used to predict DUESO MBSImP scores. The CRNN detected UES opening within a 3-frame tolerance for 82.6% of patient and 86% of healthy swallows and UES closure for 72.3% of patient and 64% of healthy swallows. The SVM classifier predicted DUESO MBSImP scores with 85.7% accuracy. This study provides evidence of HRCA's feasibility in detecting DUESO without VF images.

A Systematic Review of the Influence of Bolus Characteristics on Respiratory Measures in Healthy Swallowing.

There have been a number of studies on the effect of bolus volume, consistency, texture, temperature and taste on the oropharyngeal swallowing physiology. However, its influence on the respiratory function associated with swallow is not well understood. This study aimed at systematically analysing and documenting the prevailing research literature on respiratory functions before, during, and after healthy swallows of boluses with varied characteristics. The PRISMA guidelines were followed for retrieval of relevant research. From among the 48,329 reports screened for inclusion criteria, 25 articles were included for data extraction. Each of these reports was evaluated for its design, methodology and reporting quality and also the level of evidence provided by them. The results revealed that the scientific evidence in this regard was restricted to level II. Majority of the studies included considered bolus volume as the variable than bolus consistency, taste or temperature. Expiratory phase was preferred surrounding the apnea irrespective of volume, consistency or taste but changed with temperature variations across age groups. The reports are equivocal on the duration of respiratory apnea, and length of respiratory cycles before and after the apnea. The temporal coordination of pharyngeal swallow events was found to be independent of bolus volume. This review concluded that bolus characteristics have differential effects on the respiratory functions during swallow beyond a 'central sensory threshold' level. Objective standardization of bolus characteristics may be the immediate requirement for generalization of future research findings in this direction.

Physiological Flow of Liquids in Healthy Swallowing

Physiological Flow of Liquids in Healthy Swallowing

Modulation of Tongue Pressure According to Liquid Flow Properties in Healthy Swallowing.

PurposeDuring swallowing, the tongue generates the primary propulsive forces that transport material through the oral cavity toward the pharynx. Previous literature suggests that higher tongue pressure amplitudes are generated for extremely thick liquids compared with thin liquids. The purpose of this study was to collect detailed information about the modulation of tongue pressure amplitude and timing across the range from thin to moderately thick liquids.MethodTongue pressure patterns were measured in 38 healthy adults (aged under 60 years) during swallowing with 4 levels of progressively thicker liquid consistency (International Dysphagia Diet Standardisation Initiative, Levels 0 = thin, 1 = slightly thick, 2 = mildly thick, and 3 = moderately thick). Stimuli with matching gravity flow (measured using the International Dysphagia Diet Standardisation Initiative Flow Test; Cichero et al., 2017; Hanson, 2016) were prepared both with/without barium (20% weight per volume concentration) and thickened with starch and xanthan gum thickeners.ResultsAfter controlling for variations in sip volume, thicker liquids were found to elicit significantly higher amplitudes of peak tongue pressure and a pattern of higher (i.e., steeper) pressure rise and decay slopes (change in pressure per unit time). Explorations across stimuli with similar flow but prepared with different thickeners and with/without barium revealed very few differences in tongue pressure, with the exception of significantly higher pressure amplitudes and rise slopes for nonbarium, starch-thickened slightly and mildly thick liquids.ConclusionsThere was no evidence that the addition of barium led to systematic differences in tongue pressure parameters across liquids with closely matched gravity flow. Additionally, no significant differences in tongue pressure parameters were found across thickening agents.Supplemental Material https://doi.org/10.23641/asha.7616537

A Survey of Clinician Decision Making When Identifying Swallowing Impairments and Determining Treatment.

Speech-language pathologists (SLPs) are the primary providers of dysphagia management; however, this role has been criticized with assertions that SLPs are inadequately trained in swallowing physiology (Campbell-Taylor, 2008). To date, diagnostic acuity and treatment planning for swallowing impairments by practicing SLPs have not been examined. We conducted a survey to examine how clinician demographics and swallowing complexity influence decision making for swallowing impairments in videofluoroscopic images. Our goal was to determine whether SLPs' judgments of swallowing timing impairments align with impairment thresholds available in the research literature and whether or not there is agreement among SLPs regarding therapeutic recommendations. The survey included 3 videofluoroscopic swallows ranging in complexity (easy, moderate, and complex). Three hundred three practicing SLPs in dysphagia management participated in the survey in a web-based format (Qualtrics, 2005) with frame-by-frame viewing capabilities. SLPs' judgments of impairment were compared against impairment thresholds for swallowing timing measures based on 95% confidence intervals from healthy swallows reported in the literature. The primary impairment in swallowing physiology was identified 67% of the time for the easy swallow, 6% for the moderate swallow, and 6% for the complex swallow. On average, practicing clinicians mislabeled 8 or more swallowing events as impaired that were within the normal physiologic range compared with healthy normative data available in the literature. Agreement was higher among clinicians who report using frame-by-frame analysis 80% of the time. A range of 19-21 different treatments was recommended for each video, regardless of complexity. Poor to modest agreement in swallowing impairment identification, frequent false positives, and wide variability in treatment planning recommendations suggest that additional research and training in healthy and disordered swallowing are needed to increase accurate dysphagia diagnosis and treatment among clinicians.

Modulation of Upper Esophageal Sphincter (UES) Relaxation and Opening During Volume Swallowing.

UES opening occurs following cricopharyngeus deactivation and submental muscle contraction causing hyolaryngeal elevation and UES distraction. During impedance manometry, the inverse of impedance (admittance) can be used to measure bolus presence and infer UES opening. We hypothesized that the temporal relationship between UES relaxation, opening and hyolaryngeal elevation would change with increasing bolus volume. Simultaneous intramuscular cricopharyngeal (CP) electromyography (EMG), surface submental EMG (SM-EMG), and high-resolution impedance manometry were recorded in eight (aged 27±7years, 5M) healthy volunteers, while swallowing 0.9% saline boluses of 2, 5, 10, and 20ml. Data were exported and analyzed via Matlab. Statistical analysis comprised repeated measures one-way ANOVA and Pearson correlation. A P value of <0.05 was considered significant. Duration of CP deactivation increased at 20ml volume (P<0.001). UES relaxation and opening increased with increasing bolus volume (P<0.001); however, overall duration of SM activation did not change. As UES opening occurs progressively earlier with increasing volumes, peak SM-EMG activity occurs relatively later (P<0.001) and shifts from occurring before to following peak UES distention. During healthy swallowing, there is sensory modulation of cricopharyngeal and submental muscle activity. Intrabolus pressures, transmitted from the tongue base and pharynx, play a progressively more important role in sphincter opening with increasing volume. The findings may explain why some healthy elderly and patients with oropharyngeal dysphagia have difficulty swallowing larger while tolerating smaller bolus volumes.

A Randomized Trial Comparing Two Tongue-Pressure Resistance Training Protocols for Post-Stroke Dysphagia.

The objective of this study was to compare the outcomes of two tongue resistance training protocols. One protocol ("tongue-pressure profile training") emphasized the pressure-timing patterns that are typically seen in healthy swallows by focusing on gradual pressure release and saliva swallowing tasks. The second protocol ("tongue-pressure strength and accuracy training") emphasized strength and accuracy in tongue-palate pressure generation and did not include swallowing tasks. A prospective, randomized, parallel allocation trial was conducted. Of 26 participants who were screened for eligibility, 14 received up to 24 sessions of treatment. Outcome measures of posterior tongue strength, oral bolus control, penetration-aspiration and vallecular residue were made based on videofluoroscopy analysis by blinded raters. Complete data were available for 11 participants. Significant improvements were seen in tongue strength and post-swallow vallecular residue with thin liquids, regardless of treatment condition. Stage transition duration (a measure of the duration of the bolus presence in the pharynx prior to swallow initiation, which had been chosen to capture impairments in oral bolus control) showed no significant differences. Similarly, significant improvements were not seen in median scores on the penetration-aspiration scale. This trial suggests that tongue strength can be improved with resistance training for individuals with tongue weakness following stroke. We conclude that improved penetration-aspiration does not necessarily accompany improvements in tongue strength; however, tongue-pressure resistance training does appear to be effective for reducing thin liquid vallecular residue.

The Effect of Bolus Consistency on Hyoid Velocity in Healthy Swallowing.

The aim of this study was to determine whether measures of hyoid velocity increase when swallowing liquids of thicker consistency at a constant volume. A gender-balanced sample of 20 healthy young participants (mean age 31.5) each swallowed 3 boluses of 5 ml volume in 3 consistencies (ultrathin, thin, and nectar-thick barium). Using frame-by-frame tracking of hyoid position, we identified the onset and peak of the hyoid movement and derived measures of velocity (i.e., distance in anatomically normalized units, i.e., % of the C2-4 vertebral distance, divided by duration in ms) for the X, Y, and XY movement directions. Peak hyoid velocity was also identified for each movement direction. Where significant differences were identified, the component measures of hyoid movement distance and duration were further explored to determine the strategies used to alter velocity. The results showed increased velocities and higher peak velocities with the nectar-thick stimuli compared to thin and ultrathin stimuli. This was achieved by a primary strategy of larger hyoid movement distances per unit of time when swallowing nectar-thick liquids. These results point to one mechanism by which thickened liquids may contribute to improved airway protection by facilitating more timely laryngeal vestibule closure.

Upper esophageal sphincter mechanical states analysis: a novel methodology to describe UES relaxation and opening.

The swallowing muscles that influence upper esophageal sphincter (UES) opening are centrally controlled and modulated by sensory information. Activation of neural inputs to these muscles, the intrinsic cricopharyngeus muscle and extrinsic suprahyoid muscles, results in their contraction or relaxation, which changes the diameter of the lumen, alters the intraluminal pressure and ultimately inhibits or promotes flow of content. This relationship that exists between the changes in diameter and concurrent changes in intraluminal pressure has been used previously to calculate the “mechanical states” of the muscle; that is when the muscles are passively or actively, relaxing or contracting. Diseases that alter the neural pathways to these muscles can result in weakening the muscle contractility and/or decreasing the muscle compliance, all of which can cause dysphagia. Detecting these changes in the mechanical state of the muscle is difficult and as the current interpretation of UES motility is based largely upon pressure measurement (manometry), subtle changes in the muscle function during swallow can be missed. We hypothesized that quantification of mechanical states of the UES and the pressure-diameter properties that define them, would allow objective characterization of the mechanisms that govern the timing and extent of UES opening during swallowing. To achieve this we initially analyzed swallows captured by simultaneous videofluoroscopy and UES pressure with impedance recording. From these data we demonstrated that intraluminal impedance measurements could be used to determine changes in the internal diameter of the lumen when compared to videofluoroscopy. Then using a database of pressure-impedance studies, recorded from young and aged healthy controls and patients with motor neuron disease, we calculated the UES mechanical states in relation to a standardized swallowed bolus volume, normal aging and dysphagia pathology. Our results indicated that eight different mechanical states were almost always seen during healthy swallowing and some of these calculated changes in muscle function were consistent with the known neurally dependent phasic discharge patterns of cricopharyngeus muscle activity during swallowing. Clearly defined changes in the mechanical states were observed in motor neuron disease when compared to age matched healthy controls. Our data indicate that mechanical state predictions were simple to apply and revealed patterns consistent with the known neural inputs activating the different muscles during swallowing.