The Effect of Swallowing Cues in Healthy Individuals: An Exploratory Study.

The goal of this study was to determine whether providing verbal and visual cues about swallowing changes the timing of swallowing events, and whether this information interacts with bolus volume. 20 healthy adults swallowed 5 ml and 15 ml liquid barium mixed with orange juice under videofluoroscopy during 2 conditions: one condition absent swallowing-specific cues and one condition with verbal and visual input about the swallowing process. Outcome measures included the timing of 10 swallowing events and the number of swallows per bolus. As expected, volume had a significant effect on all outcome measures (p < 0.05). Three timing events differed by cueing condition: 1. swallowing reaction time was earlier for control (- 9.45 ms vs. - 2.01 ms, p = 0.033); 2. the time between initial hyoid movement and maximum hyoid elevation was longer for control (152.85 ms vs. 143.79 ms; p = 0.015); and 3. the onset of upper esophageal sphincter opening occurred later after bolus entry into the pharynx for the swallowing cues condition (111.9 ms vs. 103.31 ms; p = 0.017); however, effect sizes were small (< 0.2). There was a significant interaction between cue condition and bolus volume on swallowing frequency, such that the mean number of swallows of 15 ml boluses was slightly higher during the control condition than during the swallowing cues condition. There were no significant interactions on measures of timing, suggesting distinct mechanisms for the effect of bolus volume and cues on swallowing kinematics. Further research is needed to investigate the effects of different cue modalities and focus (internal vs. external) on swallowing physiology.

"Hidden in Plain Sight": A Descriptive Review of Laryngeal Vestibule Closure.

A major emphasis in the evaluation of swallowing is to identify physiological abnormalities in swallowing that contribute to or explain unsafe swallowing (i.e., ingested material enters the trachea; post-swallow residue in the pharynx). Impairments in laryngeal vestibule closure are widely recognized as one of the major causes of unsafe swallowing, as it is the primary mechanism and first line of defense for preventing material from penetrating the airway during swallowing. However, this complex mechanism is often overlooked and understudied in swallowing research and dysphagia management. The purpose of this review is to promote a better understanding of the mechanism of laryngeal vestibule closure. We discuss where gaps in research exist and propose future directions for incorporating laryngeal vestibule closure as a primary outcome measure in swallowing research. Additionally, we propose that an increased knowledge of the mechanism of laryngeal vestibule closure will increase diagnostic accuracy and optimize dysphagia management for patients with dysphagia.

Swallowing Changes in Community-Dwelling Older Adults.

Older adults may evidence changes in swallowing physiology. Our goals were to identify dysphagia risk in community-dwelling older adults with no history of dysphagia, and to compare swallowing physiology and safety between older and younger adults. Thirty-two older adults with no history of dysphagia were prospectively recruited and completed the Dysphagia Handicap Index (DHI), two trials of a 3 oz. swallow screen, and videofluoroscopy (VFSS). Self-ratings of swallowing function were compared to published norms by paired t tests, and multivariate logistic regression models were generated to determine whether these ratings and VFSS analysis of swallowing function were associated with failure of one or both swallow screen trials. Archived VFSS of 33 younger adults were compared to older adults with Wilcoxon rank-sum tests. The DHI scores of older adults were higher than published non-dysphagic adults but lower than dysphagic adults. Older participants with greater Oral Residue scores were more likely to fail both swallow screen trials. Older adults received higher median MBSImP™© scores for select pharyngeal components than younger adults. The two age groups did not differ on Penetration-Aspiration Scale scores, and no aspiration was observed. Measures of swallowing in older individuals may reflect age-related sensory and motor changes in the context of functional swallowing and adequate airway protection.

Kinematic Visual Biofeedback Improves Accuracy of Learning a Swallowing Maneuver and Accuracy of Clinician Cues During Training.

Submental surface electromyography (ssEMG) visual biofeedback is widely used to train swallowing maneuvers. This study compares the effect of ssEMG and videofluoroscopy (VF) visual biofeedback on hyo-laryngeal accuracy when training a swallowing maneuver. Furthermore, it examines the clinician's ability to provide accurate verbal cues during swallowing maneuver training. Thirty healthy adults performed the volitional laryngeal vestibule closure maneuver (vLVC), which involves swallowing and sustaining closure of the laryngeal vestibule for 2 s. The study included two stages: (1) first accurate demonstration of the vLVC maneuver, followed by (2) training-20 vLVC training swallows. Participants were randomized into three groups: (a) ssEMG biofeedback only, (b) VF biofeedback only, and (c) mixed biofeedback (VF for the first accurate demonstration achieving stage and ssEMG for the training stage). Participants' performances were verbally critiqued or reinforced in real time while both the clinician and participant were observing the assigned visual biofeedback. VF and ssEMG were continuously recorded for all participants. Results show that accuracy of both vLVC performance and clinician cues was greater with VF biofeedback than with either ssEMG or mixed biofeedback (p < 0.001). Using ssEMG for providing real-time biofeedback during training could lead to errors while learning and training a swallowing maneuver.

The Effect of Radiation Dose on Swallowing: Evaluation of Aspiration and Kinematics.

Radiation oncologists have focused on the pharyngeal constrictors as the primary muscles of concern for dysphagia. However, our prior investigations have demonstrated that radiation dose to the geniohyoid rather than the constrictor muscles was more closely related to penetration aspiration scores (PAS). We examined the relationship between (1) radiation dose and swallowing temporal kinematics, and (2) between PAS and swallowing kinematics in these patients. Videofluoroscopic swallowing studies of 41 patients following radiation therapy for oropharyngeal cancer were analyzed for thin liquid boluses. Timing measures included duration of laryngeal vestibule closure (DLVC), duration to maximum hyoid elevation (DTMHE), duration to cricopharyngeal opening (DTCPO), and pharyngeal transit time (PTT). PAS was extracted for each swallow and considered normal if ≤ 2. As minimum and mean dose to the geniohyoid increased, DTMHE, DTCPO, and PTT increased. Worse PA scores were most strongly correlated with radiation dose received by geniohyoid (r = 0.445, p < 0.0001). Mean DLVC varied according to PAS group (normal PAS mean = 0.67 s, abnormal PAS mean = 0.13 s; p < 0.001). Similarly, DTCPO was significantly different based upon PAS (normal PAS mean = 0.22 s, abnormal PAS mean = 0.37 s, p = 0.016). As PAS increased, DTPCO and PTT increased (r = 0.208, p = 0.04; r = 0.204, p = 0.043). A negative correlation was noted between PAS and DLVC (r = -0.375, p = 0.001). Higher doses of radiation to the geniohyoid muscles are associated with increased severity of dysphagia as measured through both kinematics and PAS. Consideration of dose to the geniohyoid should be considered when planning radiation.

New directions for understanding neural control in swallowing: the potential and promise of motor learning.

Oropharyngeal swallowing is a complex sensorimotor phenomenon that has had decades of research dedicated to understanding it more thoroughly. However, the underlying neural mechanisms responsible for normal and disordered swallowing remain very vague. We consider this gap in knowledge the result of swallowing research that has been broad (identifying phenomena) but not deep (identifying what controls the phenomena). The goals of this review are to address the complexity of motor control of oropharyngeal swallowing and to review the principles of motor learning based on limb movements as a model system. We compare this literature on limb motor learning to what is known about oropharyngeal function as a first step toward suggesting the use of motor learning principles in swallowing research.

Human hyolaryngeal movements show adaptive motor learning during swallowing.

The hyoid bone and larynx elevate to protect the airway during swallowing. However, it is unknown whether hyolaryngeal movements during swallowing can adjust and adapt to predict the presence of a persistent perturbation in a feed-forward manner (adaptive motor learning). We investigated adaptive motor learning in nine healthy adults. Electrical stimulation was administered to the anterior neck to reduce hyolaryngeal elevation, requiring more strength to swallow during the perturbation period of this study. We assessed peak hyoid bone and laryngeal movements using videofluoroscopy across thirty-five 5-ml water swallows. Evidence of adaptive motor learning of hyolaryngeal movements was found when (1) participants showed systematic gradual increases in elevation against the force of electrical stimulation and (2) hyolaryngeal elevation overshot the baseline (preperturbation) range of motion, showing behavioral aftereffects, when the perturbation was unexpectedly removed. Hyolaryngeal kinematics demonstrates adaptive, error-reducing movements in the presence of changing and unexpected demands. This is significant because individuals with dysphagia often aspirate due to disordered hyolaryngeal movements. Thus, if rapid motor learning is accessible during swallowing in healthy adults, patients may be taught to predict the presence of perturbations and reduce errors in swallowing before they occur.

Tactile, gustatory, and visual biofeedback stimuli modulate neural substrates of deglutition.

It has been well established that swallowing kinematics are modified with different forms of exogenous and endogenous input, however the underlying neural substrates associated with these effects are largely unknown. Our objective was to determine whether the swallowing BOLD response is modulated with heightened sensory modalities (taste, cutaneous electrical stimulation, and visual biofeedback) compared to water ingestion (control) in healthy adults across the age span. Habituation and sensitization were also examined for each sensory condition. Our principal findings are that each sensory swallowing condition activated components of the swallowing cortical network, plus regions associated with the particular sensory modality (i.e. primarily frontal motor planning and integration areas with visual condition). Overall, the insula was most commonly active among the sensory modalities. We also discuss gradual increases and decreases in BOLD signal with repeated exposures for each condition. We conclude that both stimulus- and intention-based inputs have unique cortical swallowing networks relative to their modality. This scientific contribution advances our understanding of the mechanisms of normal swallowing cortical control and has the potential to impact clinical uses of these modalities in treatments for neurogenic dysphagia.

Electrical stimulation and swallowing: how much do we know?

Consequences of dysphagia substantially reduce quality of life, increase the risk of medical complications and mortality, and pose a substantial cost to healthcare systems. As a result, it is of no wonder that the clinical and scientific communities are showing interest in new avenues for dysphagia rehabilitation. Electrical stimulation (e-stim) for the treatment of swallowing impairments is among the most studied swallowing interventions in the published literature, yet many unanswered questions about its efficacy remain. In the meantime, many speech-language pathologists who treat dysphagia are attending educational and training sessions to obtain certifications to use this technique. Here, we review the values and limitations of the published literature on the topic of e-stim for swallowing to assist clinicians in decision making in their clinical practice. The discussion provides a review of swallowing anatomy and physiology, the fundamentals of e-stim, and information essential for the readers' independent critique of these studies--all of which are crucial for evaluating the possible effects of e-stim.

Impact of the Chin-Down Posture on Temporal Measures of Patients With Dysphagia: A Pilot Study.

Purpose The chin-down position is a commonly prescribed posture by health care professionals to alleviate the symptoms of dysphagia. Yet, how the technique influences swallowing physiology lacks clarity. Our goal was to examine the impact of the postural technique on patients with various medical conditions and swallowing impairments. Method Temporal and functional measures were examined with videofluoroscopy in the chin-down and neutral head position on 15 patients. Also, timing differences between head positions were examined to determine the presence of improvement during the chin-down posture. Results The primary finding was chin-down posture swallows prolonged the elapsed time between when the prematurely spilled bolus entered the pharynx relative to swallow onset compared to the neutral head position (p = .006). Also, no improvement in airway protection was found when performing the postural technique. Conclusions The chin-down posture may benefit patients with specific swallowing impairments. However, the general use of the technique for all patients who experience swallowing difficulty might be negligent and could potentially have adverse or no effect on patient outcomes. Future studies examining patients with the same pathophysiology are needed to understand the benefit of the chin-down posture based on swallowing impairment.

Validation of the Normalized Laryngeal Constriction Ratio in Normal and Disordered Swallowing.

PURPOSE: The timing of laryngeal vestibule closure (LVC) is important for airway protection during swallowing. However, it is unknown whether the extent of LVC contributes to airway protection. The goal of this study is to validate the extent of LVC via a measure called laryngeal constriction ratio (LCR). METHODS: A retrospective analysis of videofluoroscopic swallows was conducted on 38 stroke participants and 40 healthy controls. The LCR was calculated by deriving a size-normalized area of airspace from a 1) maximum closed laryngeal vestibule and a 2) maximum open laryngeal airspace (at rest). Airway invasion severity was derived via the Penetration-Aspiration Scale score. RESULTS: Six hundred forty-nine videofluoroscopic swallows were analyzed. A mixed model analysis revealed a statistically significant mean difference between the normalized laryngeal constriction ratios of healthy individuals (mean (m) = 0.003) versus older dysphagic patients (m = .026) (P = 0.001), quantifying less closure in older patients with dysphagia. Additionally, swallows with airway compromise had a statistically worse LCR when compared to swallows without airway compromise (P = 0.001). CONCLUSION: The normalized LCR might be a valid fluoroscopic surrogate measure for LVC and, furthermore, airway compromise during swallowing. By investigating spatial measurements in the laryngeal vestibule during safe and unsafe swallows, the LCR provides a direction for further research to allow for critical examination of the physiology relating to closure degree in order to precisely detect and treat abnormalities during swallowing. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:E190-E198, 2020.

Neurophysiology of swallowing: effects of age and bolus type.

This study examined age-related changes in swallowing from an integrated biomechanical and functional imaging perspective in order to more comprehensively characterize changes in swallowing associated with age. We examined swallowing-related fMRI brain activity and videoflouroscopic biomechanics of three bolus types (saliva, water and barium) in 12 young and 11 older adults. We found that age-related neurophysiological changes in swallowing are evident. The group of older adults recruited more cortical regions than young adults, including the pericentral gyri and inferior frontal gyrus pars opercularis and pars triangularis (primarily right-sided). Saliva swallows elicited significantly higher BOLD responses in regions important for swallowing compared to water and barium. In separate videofluoroscopy sessions, we obtained durational measures of supine swallowing. The older cohort had significantly longer delays before the onset of the pharyngeal swallow response and increased residue of ingested material in the pharynx. These findings suggest that older adults without neurological insult elicit more cortical involvement to complete the same swallowing tasks as younger adults.

Kinematic Visual Biofeedback Improves Accuracy of Swallowing Maneuver Training and Accuracy of Clinician Cues During Training in Stroke Patients with Dysphagia.

BACKGROUND: Dysphagia (swallowing impairment) is a common and often life-threatening problem after stroke. Submental surface electromyography (ssEMG) visual biofeedback is a commonly used clinical tool to train novel swallowing maneuvers, even though its effectiveness has been questioned. OBJECTIVE: To compare the effect of ssEMG and videofluoroscopy (VF) visual biofeedback on swallowing airway protection accuracy when training the volitional laryngeal closure swallowing maneuver (vLVC) in poststroke patients with dysphagia. Researchers also examined whether clinicians accurately judged vLVC performance. The hypothesis was that patient vLVC accuracy and clinician verbal cue accuracy will be greatest with VF (kinematic) visual biofeedback. PATIENTS: Nineteen patients with dysphagia post stroke. SETTING: Outpatient swallowing research laboratory. DESIGN: Randomized clinical trial. METHODS: Patients underwent 2 study phases. Phase 1: first demonstrated ability to perform the vLVC accurately. Phase 2: vLVC training. Participants were randomized into three biofeedback groups including the ssEMG group (ssEMG biofeedback in both phases), the VF group (VF biofeedback in both phases), and the mixed group (VF phase 1, ssEMG phase 2). To promote the best vLVC performance, a clinician provided real-time, verbal cueing using only the visual biofeedback type also seen by the patient, although both VF and ssEMG were recorded for all participants. MAIN OUTCOME MEASURE: Patient performance accuracy and clinician feedback accuracy for performing the vLVC maneuver. RESULTS: Both accuracy of vLVC training performance and clinician feedback accuracy were worse in the ssEMG group compared with the VF and mixed groups (P < .001). CONCLUSIONS: Swallowing airway protection requires precisely timed movements of small, hidden laryngeal and pharyngeal structures. Kinematic biofeedback (VF) may be required, at some point, to ensure that target swallowing movements are being trained during rehabilitation, rather than maladaptive movements. LEVEL OF EVIDENCE: I.

The effect of surface electrical stimulation on vocal fold position.

OBJECTIVES/HYPOTHESIS: Closure of the true and false vocal folds is a normal part of airway protection during swallowing. Individuals with reduced or delayed true vocal fold closure can be at risk for aspiration and may benefit from intervention to ameliorate the problem. Surface electrical stimulation is currently used during therapy for dysphagia, despite limited knowledge of its physiological effects. DESIGN: Prospective single effects study. METHODS: The immediate physiological effect of surface stimulation on true vocal fold angle was examined at rest in 27 healthy adults using 10 different electrode placements on the submental and neck regions. Fiberoptic nasolaryngoscopic recordings during passive inspiration were used to measure change in true vocal fold angle with stimulation. RESULTS: Vocal fold angles changed only to a small extent during two electrode placements (P < or = .05). When two sets of electrodes were placed vertically on the neck, the mean true vocal fold abduction was 2.4 degrees; while horizontal placements of electrodes in the submental region produced a mean adduction of 2.8 degrees (P = .03). CONCLUSIONS: Surface electrical stimulation to the submental and neck regions does not produce immediate true vocal fold adduction adequate for airway protection during swallowing, and one position may produce a slight increase in true vocal fold opening.

Dysphagia in the elderly.

The capacity to swallow or eat is a basic human need and can be a great pleasure. Older adults look forward to sharing mealtimes and participating in social interactions. The loss of capacity to swallow and dine can have far-reaching implications. With age, the ability to swallow undergoes changes that increase the risk for disordered swallowing, with devastating health implications for older adults. With the growth in the aging population, dysphagia is becoming a national health care burden and concern. Upward of 40% of people in institutionalized settings are dysphagic. There is a need to address dysphagia in ambulatory, acute care, and long-term care settings.

Elucidating inconsistencies in dysphagia diagnostics: Redefining normal.

Speech-language pathologists (SLPs) are the primary healthcare providers responsible for the evaluation and treatment of dysphagia. Fundamental to this role is the ability to make accurate clinical judgements to distinguish between normal versus disordered swallowing for subsequent treatment planning. In this review, we highlight recent data collected from practising clinicians in the USA that reveal low levels of agreement across clinicians and poor to moderate levels of accuracy for making binary diagnostic ratings (normal vs. disordered). We then propose and discuss barriers that may represent challenges to practising SLP's understanding of normal swallowing physiology. Proposed barriers include: (1) an educational focus on the disordered system; (2) system 1 processing; (3) complexity of the swallowing system; (4) inability to directly visualise the swallowing process; (5) degree of variability of normal swallowing; and (6) high clinical productivity requirements. This article concludes with suggestions for reducing identified educational and clinical barriers to ultimately improve diagnostic decision-making practices and to benefit patient-related outcomes in dysphagia management.

How Gender Stereotypes May Limit Female Faculty Advancement in Communication Sciences and Disorders.

Purpose: The field of communication sciences and disorders (CSD) faces a critical shortage of the faculty essential to train the future workforce of speech-language pathologists and audiologists. Despite a predominance of women in the field, men receive doctoral degrees, tenure status, academic leadership positions, and American Speech-Language-Hearing Association awards at disproportionately higher rates than women. The purpose of this review is to explore how implicit gender bias may contribute to female faculty advancement, including current and projected faculty workforce shortages, and to propose tangible solutions. Method: The authors present proportions of men and women who receive doctoral degrees, advance to each faculty rank, receive tenure status, hold department chairs in CSD, and receive American Speech-Language-Hearing Association honors and awards. They review ways in which cultural stereotypes give rise to implicit gender bias and discuss myriad ways that implicit gender bias may influence the decisions of students considering an academic career in CSD and their career trajectories. Conclusions: Cultural stereotypes about men and women lead to implicit gender bias that may have real consequences for female faculty advancement in CSD. Such implicit bias can influence career selection and outcomes within the field in multiple ways. To ensure that CSD continues to attract top talent and maintain a robust pipeline of future faculty in doctoral training programs, the field must recognize the existence of implicit gender bias and implement evidence-based strategies to minimize its potentially damaging effects on the future of the profession.

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

Purpose: 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. Method: 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. Results: 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. Conclusions: 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.

Taste Perception and Water Swallow Screen Results in Old-Old Women.

Changes in both swallowing and taste commonly occur in advanced age, though the relationship between the two is unknown. This study examined the association between a water swallow screen test and taste identification and intensity rating. Participants included 47 community-dwelling women aged 85-94 years. Participants completed three trials of a water swallow screen and were observed for signs of aspiration, which, if present, indicated failure. Four pure taste stimuli at low and high concentrations and water were presented, and participants selected one of five taste labels and rated their intensity on the generalized Labeled Magnitude Scale. Ratios of intensity ratings were computed for each taste stimulus to compare the perception of low and high concentrations. The association between water swallow screen failure, correct taste identification, and taste intensity ratio was evaluated with logistic regression modeling, with mediating factors of frailty and number of comorbidities. Failure of three water swallow screen trials was associated with a higher taste intensity ratio for caffeine (bitter) and a lower taste intensity ratio for sucrose (sweet). Correct identification of taste, frailty, and number of comorbidities were not associated with failure of any number of water swallow screen trials. Intensity ratings of certain tastes may be associated with swallowing in old-old women. Heightened vigilance in this population may be necessary to prevent complications related to dietary intake.

Effects of Submental Surface Electrical Stimulation on Swallowing Kinematics in Healthy Adults: An Error-Based Learning Paradigm.

Purpose: Hyoid bone and laryngeal approximation aid airway protection (laryngeal vestibule closure) while moving toward their peak superior and anterior positions during swallowing. Submental surface electrical stimulation (SES) is a therapeutic technique that targets the muscles that move the hyoid bone during swallowing. It is unknown whether submental SES only increases peak hyoid bone swallowing positions but not peak laryngeal swallowing positions, which could require faster or greater laryngeal movement to achieve adequate laryngeal vestibule closure. Method: We examined the effects of submental SES on hyo-laryngeal kinematics in 30 healthy adults who swallowed 50 times using an error-based learning paradigm. Results: Submental SES did not alter any hyo-laryngeal swallowing kinematic. However, submental SES significantly changed the starting position of the hyoid bone just prior to the swallow onset (more anterior; p = .003). On average, submental SES immediately prior to swallow onset can position the hyoid approximately 20% closer to its peak swallowing point. Conclusions: These findings indicate that electrical stimulation of the agonists for hyoid movement might not alter swallowing outcomes tested in this study. However, submental SES could have clinical utility by minimizing swallowing impairments related to reduced hyoid swallowing range of motion in individuals with dysphagia.