Kinematic and temporal factors associated with penetration-aspiration in swallowing liquids

Relationship between pharyngeal response time and lateralized brain lesion in stroke

Objectives: To analyze the relationship between pharyngeal response time (PRT) and lateralization of brain lesions. Methods: A Cross-sectional study. 73 videofluoroscopic swallow studies (VFSS)were conducted on patients after stroke The study subjects were divided into : group 1 (G1) consisting of 39 individuals with left cortical lesion and group 2 (G2) consisting of 34 individuals with right cortical lesions. The VFSS of G1 and G2 subjects were analyzed using puree (A) and liquid (B) consistencies, and  were also subdivided into young adults and older persons. . The mean PRT was divided into times shorter and longer than 250 ms. Results: No statistically significant difference was observed between G1 and G2 for the A and B consistencies, being obtained : G1 (A mean: 56.6 ms; B mean: 99.5 ms; A mean: 3627 ms; B mean: 1712 ms) and G2 (A mean: 79.6 ms; B mean: 110.7 ms; A mean: 2040 ms, B mean: 1529 ms), for PRT shorter (A:p = .673; B: p = 1.000) and longer (A: p = .435; B: p = .847) than 250 ms, respectively. No statistically significant difference was found regarding the variable age in the comparison between young and old adults for mean PRT according to the A and B consistencies in G1 (A: p = .260; B: p = .732) and G2 (A: p = .586; B: p = .104). Conclusion: No relationship between PRT and lateralization of brain lesion was observed with respect to subject age and to the swallowing of different food consistencies.

The Penetration-Aspiration Scale: Adaptation to Open Partial Laryngectomy and Reliability Analysis

A standard for assessing swallowing function after open partial horizontal laryngectomy (OPHL) is still not established. The variability in the measures used to investigate swallowing functional outcomes after OPHL limits the communication among clinicians and the possibility to compare and combine results from different studies. The study aims to adapt the PAS to the altered anatomy after OPHLs using fiberoptic endoscopic evaluation of swallowing (FEES) and to test its reliability. To adapt the PAS, two landmarks were identified: the entry of the laryngeal vestibule and the neoglottis. Ninety patients who underwent an OPHL were recruited (27 type I, 31 type II and 32 type III). FEES was performed and video-recorded. Two speech and language therapists (SLTs) independently rated each FEES using the PAS adapted for OPHL (OPHL-PAS). FEES recordings were rated for a second time by both SLTs at least 15 days from the first video analysis. Inter- and intra-rater agreement was assessed using unweighted Cohen's kappa. Overall, inter-rater agreement of the OPHL-PAS was k = 0.863, while intra-rater agreement was k = 0.854. Concerning different OPHL types, inter- and intra-rater agreement were k = 0.924 and k = 0.914 for type I, k = 0.865 and k = 0.790 for type II, and k = 0.808 and k = 0.858 for type III, respectively. The OPHL-PAS is a reliable scale to assess the invasion of lower airway during swallowing in patients with OPHL using FEES. The study represents the first attempt to define standard tools to assess swallowing functional outcome in this population.

Do Ratings of Swallowing Function Differ by Videofluoroscopic Rate? An Exploratory Analysis in Patients After Acute Stroke

OBJECTIVE

To determine differences between continuous videofluoroscopic swallow studies (VFSS) with a pulse rate and frame rate of 30 and the same swallows reduced to 15 frames per second (fps) on measures of swallowing function in patients after acute ischemic stroke.

DESIGN

Blinded comparison.

SETTING

Acute hospital.

PARTICIPANTS

Patients after ischemic stroke (N=20).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Single and sequential sips of thin liquids, single sips of nectar liquids, pudding, and cookie boluses were rated on measures of timing of swallowing events, Modified Barium Swallowing Impairment Profile component scores, and Penetration-Aspiration Scale scores. The ratings for videos at 15 fps and 30 fps were compared by Wilcoxon signed rank tests.

RESULTS

Pharyngeal transit time was longer and bolus entry into the hypopharynx was later for 30 fps than for 15 fps. Components of Oral Residue and Pharyngoesophageal Segment Opening ratings were more severe for 15 fps than 30 fps, whereas Bolus Transport and Initiation of Pharyngeal Swallow were rated as more severe for 30 fps than for 15 fps. There was no difference between 30 fps and 15 fps on the remaining measures, including Penetration-Aspiration Scale scores.

CONCLUSION

Continuous VFSS recorded at 30 fps and their down-sampled 15 fps duplicates yielded contrasting results on certain durational and functional measures of swallowing, though not on others. VFSS should be administered continuously or at 30 pulses per second for valid assessment of swallowing while using other methods to reduce radiation exposure.

The association between temporal measures of swallowing with penetration and aspiration in patients with dysphagia: A meta-analysis

INTRODUCTION

Temporal features of swallowing physiology vary with age in healthy normals and have the potential to impact swallow safety and efficiency in patients with dysphagia. We conducted a meta-analysis to assess the relation between temporal features of swallowing with penetration, aspiration and residue in adult patients with dysphagia regardless of etiology.

METHODS

Operational definitions of relevant terms were defined a priori. A search of 5 databases was conducted to November 2016 without restriction to language. Two independent raters reviewed abstracts and full articles, with discrepancies resolved by consensus. All accepted articles advanced to data extraction and critical appraisal according to Cochrane standards. Analysis of pooled data compared measures between groups.

RESULTS

Of the 11 articles accepted, the temporal measures used in three or more studies were grouped into morphofunctional categories: bolus transit time; pharyngeal response time; laryngeal closure time; and upper esophageal opening time. Across all selected articles, definitions varied for abnormal swallow and only 4 articles reported rater blinding and reliability for measures related to timing. Pooled data identified two main findings: a. longer pharyngeal response time was associated with penetration and/or aspiration (MD = 0.40 95% CI 0.59 - 0.22), and longer upper esophageal opening duration was associated with only aspiration (PAS ≥ 6) (MD = 0.09 95% CI 0.16 - 0,02). No studies were found that related temporal measures and residue.

CONCLUSION

Our pooled findings identified an association of two temporal measures with penetration and/or aspiration but none with residue. The current evidence remains limited due to the heterogeneity across studies in how swallow measures were operationalized. Future work with a standardized and reproducible approach is direly needed.

The Prediction of Risk of Penetration-Aspiration Via Hyoid Bone Displacement Features

Videofluoroscopic swallow studies are widely used in clinical and research settings to assess swallow function and to determine physiological impairments, diet recommendations, and treatment goals for people with dysphagia. Videofluoroscopy can be used to analyze biomechanical events of swallowing, including hyoid bone displacement, to differentiate between normal and disordered swallow functions. Previous research has found significant associations between hyoid bone displacement and penetration/aspiration during swallowing, but the predictive value of hyoid bone displacement during swallowing has not been explored. The primary objective of this study was to build a model based on aspects of hyoid bone displacement during swallowing to predict the extent of airway penetration or aspiration during swallowing. Aspects of hyoid bone displacement from 1433 swallows from patients referred for videofluoroscopy were analyzed to determine which aspects predicted risk of penetration and aspiration according to the Penetration-Aspiration Scale. A generalized estimating equation incorporating components of hyoid bone displacement and variables shown to impact penetration and aspiration (such as age, bolus volume, and viscosity) was used to evaluate penetration and aspiration risk. Results indicated that anterior-horizontal hyoid bone displacement was the only aspect of hyoid bone displacement predictive of penetration and aspiration risk. Further research should focus on improving the model performance by identifying additional physiological swallowing events that predict penetration and aspiration risk. The model built for this study, and future modified models, will be beneficial for clinicians to use in the assessment and treatment of people with dysphagia, and for potentially tracking improvement in hyolaryngeal excursion resulting from dysphagia treatment, thus mitigating adverse outcomes that can occur secondary to dysphagia.

Cough response to aspiration in thin and thick fluids during FEES in hospitalized inpatients

BACKGROUND

The modifications of fluid viscosity and/or volume are common strategies in dysphagia management, with increased viscosity or reduced volume intended to reduce aspiration. Little attention has been given to whether cough response to aspiration varies across different viscosities and volumes.

AIMS

This prospective observational study investigated aspiration prevalence and cough response to aspiration in thin and thick fluids of two different volumes in patients referred for flexible endoscopic evaluation of swallowing (FEES) in an acute hospital setting.

METHODS & PROCEDURES

Consecutive inpatients (N = 180) referred for FEES were recruited: stroke 51 (28%); other neurological condition (traumatic brain injury, progressive neurological) 33 (18%); cardiovascular critical care 51 (28%); respiratory illness/condition 23 (13%); spinal injury 9 (5%); and other 13 (7%). A standardized protocol was completed on 268 FEES (180 first FEES, 88 repeat FEES). Penetration-aspiration scale (PAS) scores were obtained for thin and mildly thick fluids at two volumes: 5 ml teaspoon and 50 ml continuous drinking.

OUTCOMES & RESULTS

The incidence of aspiration (PAS > 5) was 32% for thin fluids and 18% for thick fluids. There was a significant association between cough response to aspiration and viscosity (p < .001) and volume (p < .001). There was a higher prevalence of silent aspiration in thick fluids than thin fluids. Some patients demonstrated variable cough responsiveness to aspiration across different viscosities and volumes. With 5 ml volumes, 20 patients coughed when they aspirated thin fluids but silently aspirated thick fluids. In comparison, discrepancies in the 50 ml volume were fewer, with three patients coughing when they aspirated thin fluids but silently aspirating thick fluids.

CONCLUSIONS & IMPLICATIONS

Cough response to aspiration differs across bolus volumes and viscosities. The finding of inconsistent cough response to aspiration in some patients strongly encourages the use of instrumental assessment to guide decisions regarding diet modifications.

Changes in Hyolaryngeal Movement During Swallowing in the Lateral Decubitus Posture

Objective

To investigate the differences in hyolaryngeal kinematics at rest and during swallowing in the upright sitting (UP) and the lateral decubitus (LD) postures in healthy adults, and delineating any potential advantages of swallowing while in the LD posture.

Methods

Swallowing was videofluoroscopically evaluated in 20 healthy volunteers in UP and LD postures, based on the movements of hyoid bone, vocal folds, and the bolus head. Parameters included the Penetration-Aspiration Scale (PAS), horizontal and vertical displacement, horizontal and vertical initial position, horizontal and vertical peak position, time to peak position of the hyoid bone and vocal folds, and pharyngeal transit time (PTT).

Results

Nine participants were rated PAS 2 in the UP and 1 was rated PAS 2 in the LD (p=0.003) at least 1 out of 3 swallows each posture. The hyoid and vocal folds showed more anterior and superior peak and initial positions in the LD. In addition, swallowing resulted in greater vertical and smaller horizontal displacement of the hyoid in LD posture compared with UP. Time to peak position of the hyoid was shorter in LD. The maximal vertical and horizontal displacement of the vocal folds, and PTT were comparable between postures.

Conclusion

The results showed that the peak and initial positions of the hyoid and larynx and the pattern of hyoid movement varied significantly depending on the body postures. This study suggests that the LD posture was one of the safe feeding postures without any increased risk compared with UP posture.

A Preliminary Videofluoroscopic Investigation of Swallowing Physiology and Function in Individuals with Oculopharyngeal Muscular Dystrophy (OPMD)

Dysphagia is one of the primary symptoms experienced by individuals with Oculopharyngeal Muscular Dystrophy (OPMD). However, we lack understanding of the discrete changes in swallowing physiology that are seen in OPMD, and the resulting relationship to impairments of swallowing safety and efficiency. This study sought to describe the pathophysiology of dysphagia in a small sample of patients with OPMD using a videofluoroscopy examination (VFSS) involving 3 × 5 mL boluses of thin liquid barium (22% w/v). The aim of this study is to extend what is known about the pathophysiology of dysphagia in OPMD, by quantifying changes in swallow timing, kinematics, safety, and efficiency, measured from VFSS. This study is a secondary analysis of baseline VFSS collected from 11 adults (4 male), aged 48-62 (mean 57) enrolled in an industry-sponsored phase 2 therapeutic drug trial. Blinded raters scored the VFSS recordings for safety [Penetration-Aspiration Scale (PAS)], efficiency [Normalized Residue Ratio Scale (NRRS)], timing [Pharyngeal Transit Time (PTT), Swallow Reaction Time (SRT), Laryngeal Vestibule Closure Reaction Time (LVCrt), Upper Esophageal Sphincter Opening Duration (UESD)], and kinematics (hyoid movement, pharyngeal constriction, UES opening width). Impairment thresholds from existing literature were defined to characterize swallowing physiology and function. Further, Fisher's Exact tests and Pearson's correlations were used to conduct a preliminary exploration of associations between swallowing physiology (e.g., kinematics, timing) and function (i.e., safety, efficiency). Compared to published norms, we identified significant differences in the degree of maximum pharyngeal constriction, hyoid movement distance and speed, as well as degree and timeliness of airway closure. Unsafe swallowing (PAS ≥ 3) was seen in only 3/11 patients. By contrast, clinically significant residue (i.e., NRRS scores ≥ 0.09 vallecular; ≥ 0.2 pyriform) was seen in 7/11 patients. Fisher's Exact tests revealed associations between prolonged SRT, PTT, and unsafe swallowing. Weak associations were also identified between post-swallow residue and poor pharyngeal constriction during the swallow. Detailed analysis of swallowing physiology in this series of adults with OPMD aligns with impaired muscular function (e.g., reduced pharyngeal constriction, incomplete laryngeal vestibule closure) associated with the disease, and primary functional challenges with swallow efficiency. Further work is needed to explore a greater range of food and liquid textures, and to identify additional physiological mechanisms underlying swallowing impairment in OPMD.

Cricopharyngeal function or dysfunction: what's the deal?

PURPOSE OF REVIEW

The purpose of the review is to examine current research focused on upper oesophageal sphincter (UES) and cricopharyngeus muscle function, and how better understanding UES physiology will translate to improved management.

RECENT FINDINGS

Although much is known about UES function, new information describing the dynamics of the UES and cricopharyngeus is being identified through manometry, combined fluoromanometry, and anatomic study. Response of the UES to injury, reflux, and surgical interventions is reported. Direct surgical treatment of cricopharyngeus noncompliance with or without diverticuli continues to show benefit and long-term results support a sustained improvement in three-quarters of patients.

SUMMARY

UES and cricopharyngeus function is complex and dynamic. It is affected by internal signals such as posture and constitution of refluxate, aging, and interventions particularly radiation and surgery. Clear understanding of the triggers and responses of the UES will enable clinicians to choose the correct therapy for their dysphagic patients.

Semi-automatic tracking, smoothing and segmentation of hyoid bone motion from videofluoroscopic swallowing study

Motion analysis of the hyoid bone via videofluoroscopic study has been used in clinical research, but the classical manual tracking method is generally labor intensive and time consuming. Although some automatic tracking methods have been developed, masked points could not be tracked and smoothing and segmentation, which are necessary for functional motion analysis prior to registration, were not provided by the previous software. We developed software to track the hyoid bone motion semi-automatically. It works even in the situation where the hyoid bone is masked by the mandible and has been validated in dysphagia patients with stroke. In addition, we added the function of semi-automatic smoothing and segmentation. A total of 30 patients’ data were used to develop the software, and data collected from 17 patients were used for validation, of which the trajectories of 8 patients were partly masked. Pearson correlation coefficients between the manual and automatic tracking are high and statistically significant (0.942 to 0.991, P-value<0.0001). Relative errors between automatic tracking and manual tracking in terms of the x-axis, y-axis and 2D range of hyoid bone excursion range from 3.3% to 9.2%. We also developed an automatic method to segment each hyoid bone trajectory into four phases (elevation phase, anterior movement phase, descending phase and returning phase). The semi-automatic hyoid bone tracking from VFSS data by our software is valid compared to the conventional manual tracking method. In addition, the ability of automatic indication to switch the automatic mode to manual mode in extreme cases and calibration without attaching the radiopaque object is convenient and useful for users. Semi-automatic smoothing and segmentation provide further information for functional motion analysis which is beneficial to further statistical analysis such as functional classification and prognostication for dysphagia. Therefore, this software could provide the researchers in the field of dysphagia with a convenient, useful, and all-in-one platform for analyzing the hyoid bone motion. Further development of our method to track the other swallowing related structures or objects such as epiglottis and bolus and to carry out the 2D curve registration may be needed for a more comprehensive functional data analysis for dysphagia with big data.

Change in Excitability of Cortical Projection After Modified Catheter Balloon Dilatation Therapy in Brainstem Stroke Patients with Dysphagia: A Prospective Controlled Study

Although the modified balloon dilatation therapy has been demonstrated to improve pharyngeal swallowing function post stroke, the underlying neural mechanisms of improvement are unknown. Our aims are (1) to investigate the effect of modified balloon dilatation on the excitability of corticobulbar projections to the submental muscle in dysphagic patients with brainstem stroke and (2) the relation between changes in excitability and pharyngeal kinematic modifications. Thirty patients with upper esophageal sphincter (UES) dysfunction due to unilateral brainstem stroke were recruited into two groups. The patients in dilatation group received modified balloon dilatation and conventional therapies, and those in control were only treated by conventional therapies (twice per day). The amplitudes of bilateral submental motor evoked potentials (MEPs) induced by transcranial magnetic stimulations over bilateral motor cortex, diameters of UES opening (UOD) and maximal displacement of hyoid (HD) were all assessed at baseline and the endpoint of treatments. Repeated ANOVA analysis revealed significant main effect of group, time and MEP laterality on MEP amplitudes (p = 0.02). There were no differences in the pretreatment measures between groups (all p > 0.05). After treatment, the amplitudes of affected submental MEP evoked by ipsilateral cortical pulse as well as UOD and HD were significantly different in dilatation group compared to control (amplitude: p = 0.02, UOD: p < 0.001, HD: p = 0.03). The differences of pre- and post-treatment amplitudes of the affected MEP evoked by ipsilateral stimulation showed a positive correlation with the improvement of HD (dilatation: R ² = 0.51, p = 0.03; control: R ² = 0.39, p = 0.01), rather than UOD in both groups (all p > 0.05). In conclusion, modified balloon dilatation therapy can increase the excitability of affected projection in patients with unilateral brainstem stroke.

Sagittal Plane Kinematics of the Jaw and Hyolingual Apparatus During Swallowing in Macaca mulatta

Studies of mechanisms of feeding behavior are important in a society where aging- and disease-related feeding disorders are increasingly prevalent. It is important to evaluate the clinical relevance of animal models of the disease and the control. Our present study quantifies macaque hyolingual and jaw kinematics around swallowing cycles to determine the extent to which macaque swallowing resembles that of humans. One female and one male adult Macaca mulatta were trained to feed in a primate chair. Videofluoroscopy was used to record kinematics in a sagittal view during natural feeding on solid food, and the kinematics of the hyoid bone, thyroid cartilage, mandibular jaw, and anterior-, middle-, and posterior-tongue. Jaw gape cycles were defined by consecutive maximum gapes, and the kinematics of the swallow cycles were compared with those of the two consecutive non-swallow cycles preceding and succeeding the swallow cycles. Although there are size differences between macaques and humans, and macaques have shorter durations of jaw gape cycles and hyoid and thyroid upward movements, there are several important similarities between our macaque data and human data reported in the literature: (1) The durations of jaw gape cycles during swallow cycles are longer than those of non-swallow cycles as a result of an increased duration of the jaw-opening phase; (2) Hyoid and thyroid upward movement is linked with a posterior tongue movement and is faster during swallow than non-swallow cycles; (3) Tongue elevation propagates from anterior to posterior during swallow and non-swallow cycles. These findings suggest that macaques can be a useful experimental model for human swallowing studies.

Swallowing Mechanics Associated With Artificial Airways, Bolus Properties, and Penetration-Aspiration Status in Trauma Patients

PURPOSE

Artificial airway procedures such as intubation and tracheotomy are common in the treatment of traumatic injuries, and bolus modifications may be implemented to help manage swallowing disorders. This study assessed artificial airway status, bolus properties (volume and viscosity), and the occurrence of laryngeal penetration and/or aspiration in relation to mechanical features of swallowing.

METHOD

Coordinates of anatomical landmarks were extracted at minimum and maximum hyolaryngeal excursion from 228 videofluoroscopic swallowing studies representing 69 traumatically injured U.S. military service members with dysphagia. Morphometric canonical variate and regression analyses examined associations between swallowing mechanics and bolus properties based on artificial airway and penetration-aspiration status.

RESULTS

Significant differences in swallowing mechanics were detected between extubated versus tracheotomized (D = 1.32, p < .0001), extubated versus decannulated (D = 1.74, p < .0001), and decannulated versus tracheotomized (D = 1.24, p < .0001) groups per post hoc discriminant function analysis. Tracheotomy-in-situ and decannulated subgroups exhibited increased head/neck extension and posterior relocation of the larynx. Swallowing mechanics associated with (a) penetration-aspiration status and (b) bolus properties were moderately related for extubated and decannulated subgroups, but not the tracheotomized subgroup, per morphometric regression analysis.

CONCLUSION

Specific differences in swallowing mechanics associated with artificial airway status and certain bolus properties may guide therapeutic intervention in trauma-based dysphagia.

Reflections on Clinical and Statistical Use of the Penetration-Aspiration Scale

The 8-point Penetration-Aspiration Scale (PAS) was introduced to the field of dysphagia in 1996 and has become the standard method used by both clinicians and researchers to describe and measure the severity of airway invasion during swallowing. In this article, we review the properties of the scale and explore what has been learned over 20 years of use regarding the construct validity, ordinality, intervality, score distribution, and sensitivity of the PAS to change. We propose that a categorical revision of the PAS into four levels of increasing physiological severity would be appropriate. The article concludes with a discussion of common errors made in the statistical analysis of the PAS, proposing that frequency distributions and ordinal logistic regression approaches are most appropriate given the properties of the scale. A hypothetical dataset is included to illustrate both the problems and strengths of different statistical approaches.

Hyoid bone displacement as parameter for swallowing impairment in patients treated for advanced head and neck cancer

Reduced hyoid displacement is thought to contribute to aspiration and pharyngeal residues in head and neck cancer (HNC) patients with dysphagia. To further study hyoid elevation and anterior excursion in HNC patients, this study reports on temporal/kinematic measures of hyoid displacement, with the additional goal to investigate correlations with clinical swallowing impairment. A single-blind analysis of data collected as part of a larger prospective study was performed at three time points before and after chemoradiotherapy. Twenty-five patients had undergone clinical swallowing assessments at baseline, 10-weeks, and 1-year post-treatment. Analysis of videofluoroscopic studies was done on different swallowing consistencies of varying amounts. The studies were independently reviewed frame-by-frame by two clinicians to assess temporal (onset and duration) and kinematic (anterior/superior movement) measures of hyoid displacement (ImageJ), laryngeal penetration/aspiration, and presence of vallecula/pyriform sinus residues. Patient-reported oral intake and swallowing function were also evaluated. Mean maximum hyoid displacement ranged from 9.4 mm (23 % of C2-4 distance) to 12.6 mm (27 %) anteriorly, and from 18.9 mm (41 %) to 24.9 mm (54 %) superiorly, depending on bolus volume and consistency. Patients with reduced superior hyoid displacement perceived significantly more swallowing impairment. No correlation between delayed or reduced hyoid excursion and aspiration or residue scores could be demonstrated. Hyoid displacement is subject to variability from a number of sources. Based on the results, this parameter seems not very valuable for clinical use in HNC patients with dysphagia.

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 Sequence of Swallowing Events During the Chin-Down Posture

PURPOSE

This study investigated the effect of the chin-down posture on the sequence of swallowing events in healthy adults.

METHOD

Sixteen healthy participants performed 45 5-ml thin liquid swallows during videofluoroscopy: 5 neutral head position, 30 chin-down posture, and then 10 neutral head position. Eight swallowing events were measured: the time of hyoid burst, bolus head in the pharynx, bolus tail in the pharynx, laryngeal vestibule closure (LVC), upper esophageal sphincter (UES) opening, bolus head in the UES, bolus tail exiting the pharynx, and laryngeal vestibule opening (LVO).

RESULTS

Our key finding is that LVC was one of the first 3 swallowing events in 69% of neutral swallows and in 78% of chin-down swallows (p = .006). Also, LVO occurred last in 14% of chin-down swallows but never occurred last in the preceding neutral swallows (p ≤ .001). Thus, in chin-down swallows, LVC occurred earlier and LVO occurred later.

CONCLUSIONS

The chin-down posture may be beneficial for individuals with delayed onset of LVC and reduced duration of the LVC. Future studies are needed to examine this effect in individuals with dysphagia.

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.

The Relationship Between Pharyngeal Constriction and Post-swallow Residue

Pharyngeal constriction has been proposed as a parameter that may distinguish functional from impaired swallows. We employed anatomically normalized pixel-based measures of pharyngeal area at maximum constriction, and the ratio of this measure to area at rest, and explored the association between these measures and post-swallow residue using the normalized residue ratio scale (NRRS). Videofluoroscopy data for 5 ml boluses of 22 % (w/v) liquid barium were analyzed from 20 healthy young adults and 40 patients with suspected neurogenic dysphagia. The frames of maximum pharyngeal constriction and post-swallow hyoid rest were extracted. Pixel-based measures of pharyngeal area were made using ImageJ and size-normalized using the squared C2–C4 vertebral distance as a reference scalar. Post-swallow residue and the areas of the vallecular and pyriform sinus spaces were measured on the hyoid rest frame to calculate the NRRSv and NRRSp. The dataset was divided into swallows with residue within or exceeding the upper confidence interval boundary seen in the healthy participants. Mixed model repeated measures ANOVAs were used to compare pharyngeal area (rest, constriction) and the pharyngeal constriction ratio, between individuals with and without residue. Measures of pharyngeal area at maximum constriction were significantly larger (i.e., less constricted, p = 0.000) in individuals with post-swallow residue in either the valleculae or the pyriform sinus. These results support the idea that interventions targeted toward improving pharyngeal constriction have the potential to be effective in reducing post-swallow residue.

Adapting human videofluoroscopic swallow study methods to detect and characterize dysphagia in murine disease models

This study adapted human videofluoroscopic swallowing study (VFSS) methods for use with murine disease models for the purpose of facilitating translational dysphagia research. Successful outcomes are dependent upon three critical components: test chambers that permit self-feeding while standing unrestrained in a confined space, recipes that mask the aversive taste/odor of commercially-available oral contrast agents, and a step-by-step test protocol that permits quantification of swallow physiology. Elimination of one or more of these components will have a detrimental impact on the study results. Moreover, the energy level capability of the fluoroscopy system will determine which swallow parameters can be investigated. Most research centers have high energy fluoroscopes designed for use with people and larger animals, which results in exceptionally poor image quality when testing mice and other small rodents. Despite this limitation, we have identified seven VFSS parameters that are consistently quantifiable in mice when using a high energy fluoroscope in combination with the new murine VFSS protocol. We recently obtained a low energy fluoroscopy system with exceptionally high imaging resolution and magnification capabilities that was designed for use with mice and other small rodents. Preliminary work using this new system, in combination with the new murine VFSS protocol, has identified 13 swallow parameters that are consistently quantifiable in mice, which is nearly double the number obtained using conventional (i.e., high energy) fluoroscopes. Identification of additional swallow parameters is expected as we optimize the capabilities of this new system. Results thus far demonstrate the utility of using a low energy fluoroscopy system to detect and quantify subtle changes in swallow physiology that may otherwise be overlooked when using high energy fluoroscopes to investigate murine disease models.