Effects of submental neuromuscular electrical stimulation on pharyngeal pressure generation

Impact of Varying Transcutaneous Electrical Stimulation Pulse Frequency on Swallow Timing Measures in Healthy Adults

The impaired swallow timing subsequent to dysphagia or aging can potentially endanger swallowing safety and efficiency. Preliminary evidence has suggested that transcutaneous electrical stimulation (TES) may have the potential to affect swallow timing. However, limited knowledge exists regarding which TES parameters can optimize swallow timing. Pulse frequency is one of the primary TES parameters that can affect the quality of muscle contraction. Yet, no clear information exists regarding how changing pulse frequency impacts the timing of swallowing events. This study aimed to investigate the varying effects of submental TES pulse frequency on swallowing events during and post-15-min TES administration. Twenty-six healthy individuals between the ages of 20 and 54 participated in this study and were assigned to high pulse frequency (HPF) (80 Hz) or low pulse frequency (LPF) (30 Hz) groups. Videofluoroscopic swallowing study (VFSS) was used to record swallowing. Three trials of 10 mL pureed mixed with barium sulfate were presented under three different conditions, including pre-TES, during TES, and post-TES, in which measures were taken following 15 min of TES delivery. The swallow timing events that were measured in each condition were time to maximum hyoid elevation, time to maximum laryngeal elevation, laryngeal vestibule closure reaction time (LVCrt), laryngeal vestibule closure duration (LVCd), time to maximum pharyngeal constriction, and pharyngoesophageal segment (PES) opening duration. No significant pulse frequency effect was found on any swallow timing measures during or after 15 min of TES. Both protocols decreased the duration of some swallowing events during TES including time to maximum hyoid elevation [p < 0.017, ηp2 = 0.185], LVCrt [p < 0.032, ηp2 = 0.158], and time to maximum pharyngeal constriction [p < 0.034, ηp2 = 0.155]. None of the significant TES effects were continued when TES ceased after 15 min. Overall, both protocols have comparable immediate effects on shortening the duration of some swallowing events during TES. Future clinical trials should examine whether these physiologic timing changes can lead to safer and more efficient swallows in patients with dysphagia.

Effects of Varying Transcutaneous Electrical Stimulation Pulse Duration on Swallowing Kinematics in Healthy Adults

Prior research in swallowing physiology has suggested that using submental transcutaneous electrical stimulation (TES) with short pulse duration (PD) (300 μs) may enhance the impact on deep extrinsic tongue muscles, thereby pulling the tongue down during swallowing. However, it was unclear whether that same TES protocol could have a differential impact on hyolaryngeal kinematics and timing. This study aimed to compare the effect of submental TES with varying PDs on anterior and superior hyolaryngeal kinematics and timing both at rest and during swallowing in healthy adults. Twenty-four healthy adults between the ages of 22 and 77 participated in this study. Anterior and superior hyolaryngeal excursion magnitude and duration measures were collected using videofluoroscopic swallowing study. Each subject swallowed three 10 ml pudding trials under three conditions: no TES, TES with short PD (300 μs), and TES with long PD (700 μs). TES was delivered using two-channel surface electrodes in the submental area. In both short and long PD conditions, TES amplitude was gradually increased until participants reached their maximum tolerance level. Videofluoroscopic data were analyzed using VideoPad Video Editor and Image J programs. One-way repeated measure ANOVAs were conducted to identify within-subject effect of TES condition. For hyoid movement, TES with short PD selectively placed the hyoid bone on a more anterior position at rest and reduced anterior hyoid excursion during swallowing compared with the no TES condition. Regarding laryngeal movement, both TES protocols resulted in the larynx taking on a more anterior position at rest and reduced anterior laryngeal excursions during swallowing when compared with the no TES condition. Varying PDs had no significant effect on the superior hyoid and laryngeal movements at rest and during swallowing. Both TES protocols induced shorter hyoid elevation duration during swallowing Findings suggest that though both TES protocols demonstrated a comparable impact on reducing anterior laryngeal excursions, the TES protocol with short PD had an enhanced effect on reducing anterior hyoid excursion during swallowing. This reduced range of motion may result from stimulating the deep submental muscles, which primarily place the hyoid and larynx into a more forward position before swallowing onset. Overall, the TES protocol with short PD may have an increased benefit in facilitating swallowing in patients with dysphagia.

Immediate effect of neuromuscular electrical stimulation on swallowing function in individuals after oral and oropharyngeal cancer therapy

Objective

To analyze the immediate effect of sensory and motor neuromuscular electrical stimulation, in oral and pharyngeal stages of swallowing, in individuals after oral and oropharyngeal cancer therapy.

Methods

The study was conducted on 10 individuals (mean age of 58 years) submitted to oral and oropharyngeal cancer therapy. The individuals were submitted to videofluoroscopy, during which they were randomly asked to swallow 5 mL of liquid, honey, and pudding, in three conditions: without stimulation, with sensory neuromuscular electrical stimulation, and with motor neuromuscular electrical stimulation. The degree of swallowing dysfunction was scored (Dysphagia Outcome and Severity Scale), as well as the presence of food stasis (Eisenhuber scale), and measurement of the oral and pharyngeal transit time. The results were statistically analyzed by the Friedman test or analysis of variance for repeated measures.

Results

The Dysphagia Outcome and Severity Scale revealed improvement for one individual with both sensory and motor stimuli, and worsening in two individuals, being one with motor and one with sensory stimulus. In the Eisenhuber scale, the neuromuscular electrical stimulation changed the presence of residues to variable extents. Concerning the oral and pharyngeal transit time, no difference was observed between the different stimulation levels for the consistencies tested (p > 0.05).

Conclusion

Both sensory and motor neuromuscular electrical stimulations presented a varied immediate impact on the oral and pharyngeal stages of swallowing in individuals after oral and oropharyngeal cancer therapy. Thus, the results of the immediate effect suggest that the technique is not indicated, evidencing the need of caution in the use of neuromuscular electrical stimulation for the rehabilitation of dysphagia, after HNC treatment.

Transcutaneous Electrical Stimulation and Dysphagia Rehabilitation: A Narrative Review

Transcutaneous electrical stimulation (TES) was introduced as a modality for dysphagia rehabilitation more than a decade ago. The underlying premise of this modality is improving the structural movements and enhancing neural activation based on stimulation-induced muscle contractions. However, divisive evidence exists regarding the effectiveness of this treatment modality. This manuscript reviews current evidence regarding the effects of transcutaneous electrical stimulation (TES) on clinical and physiological aspects of swallowing function. Furthermore, this narrative review delineates the knowledge gap in this area and recommends future research roadmap. This review gives a comprehensive picture regarding current knowledge of TES to practicing speech and language pathologists and interested researchers. It highlights the need for more robust studies in this area. It also encourages researchers to focus more on the physiologic studies to understand the physiologic underpinning behind this treatment modality.

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.

Immediate effect of laryngeal surface electrical stimulation on swallowing performance

Surface electrical stimulation of the laryngeal region is used to improve swallowing in dysphagic patients. However, little is known about how electrical stimulation affects tongue movements and related functions. We investigated the effect of electrical stimulation on tongue pressure and hyoid movement, as well as suprahyoid and infrahyoid muscle activity, in 18 healthy young participants. Electrical stimulation (0.2-ms duration, 80 Hz, 80% of each participant's maximal tolerance) of the laryngeal region was applied. Each subject swallowed 5 ml of barium sulfate liquid 36 times at 10-s intervals. During the middle 2 min, electrical stimulation was delivered. Tongue pressure, electromyographic activity of the suprahyoid and infrahyoid muscles, and videofluorographic images were simultaneously recorded. Tongue pressure during stimulation was significantly lower than before or after stimulation and was significantly greater after stimulation than at baseline. Suprahyoid activity after stimulation was larger than at baseline, while infrahyoid muscle activity did not change. During stimulation, the position of the hyoid at rest was descended, the highest hyoid position was significantly inferior, and the vertical movement was greater than before or after stimulation. After stimulation, the positions of the hyoid at rest and at the maximum elevation were more superior than before stimulation. The deviation of the highest positions of the hyoid before and after stimulation corresponded to the differences in tongue pressures at those times. These results suggest that surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. NEW & NOTEWORTHY Surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. Tongue muscles may contribute to overshot recovery more than hyoid muscles.

O efeito da eletroestimulação neuromuscular na contração da musculatura supra-hióidea durante a deglutição de indivíduos com disfagia

RESUMO Objetivo: verificar o efeito da Eletroestimulação Neuromuscular na contração da musculatura supra-hióidea durante a deglutição em indivíduos pós-Acidente Vascular Cerebral com disfagia orofaríngea. Métodos: participaram da pesquisa oito indivíduos pós-Acidente Vascular Cerebral com disfagia, de ambos os sexos, encaminhados para terapia fonoaudiológica com objetivo de trabalhar a função da deglutição, em início de processo terapêutico. Anteriormente ao início da primeira sessão, foi realizada a mensuração do tempo e amplitude da atividade elétrica muscular através da Eletromiografia de Superfície de Biofeedback. Os pacientes foram divididos aleatoriamente em dois grupos: Grupo Experimental (n=4): pacientes que receberam a fonoterapia tradicional e aplicação da Eletroestimulação Neuromuscular; Grupo Controle (n=4): pacientes que receberam a fonoterapia tradicional. Após oito sessões, todos os pacientes passaram novamente pela Eletromiografia de Superfície de Biofeedback para verificar a atividade elétrica da musculatura supra-hióidea. Os registros dos exames pré e pós intervenção foram comparados nos dois grupos. Resultados: comparando-se as médias das variáveis de amplitude e tempo da atividade elétrica muscular durante a deglutição de saliva e nas duas deglutições de pastoso, não foram observadas diferenças estatisticamente significantes entre os grupos estudados, na comparação dos valores pré e pós intervenção. Conclusões: o uso da Eletroestimulação Neuromuscular nos parâmetros e na metodologia empregada não mostrou-se eficiente em promover maior contração da musculatura supra-hióidea durante a deglutição em indivíduos pós-Acidente Vascular Cerebral com disfagia orofaríngea. Os dados encontrados podem ser decorrentes da metodologia utilizada nesta pesquisa com relação ao protocolo de aplicação da técnica e à forma de mensuração dos resultados.

Neuromuscular Electrical Stimulation for Treatment-Refractory Chronic Dysphagia in Tube-Fed Patients: A Prospective Case Series

OBJECTIVE

The aim of this study was to evaluate the role of neuromuscular electrical stimulation (NMES) in tube-fed patients with severe and chronic dysphagia refractory to traditional swallowing therapy (TT).

PATIENTS AND METHODS

A total of 11 consecutive dysphagic patients with tube-dependent nutrition and who had not responded to 6 months of TT were enrolled. Each patient received NMES for 30 min and TT for 30 min, twice a day, 5 days per week for 4 weeks. In order to evaluate the swallowing impairment, each patient underwent a fiberoptic endoscopic examination of swallowing immediately before the beginning of the treatment, after 2 weeks and after 4 weeks.

RESULTS

All enrolled patients managed to complete the swallowing treatment protocol for at least 2 weeks. After the 4-week treatment, 6 of 11 enrolled patients passed to a total oral diet with single or multiple consistencies despite specific food limitations or special preparation or compensation. Five patients, all affected by the most severe form of dysphagia, maintained tube-dependent nutrition.

CONCLUSION

NMES as adjunctive treatment to TT may offer a new possibility for the management of tube-fed patients who are refractory to TT.

Effect of transcutaneous electrical stimulation amplitude on timing of swallow pressure peaks between healthy young and older adults

OBJECTIVES

This study compared the effect of transcutaneous electrical stimulation (TES) amplitude on timing of lingual-palatal and pharyngeal peak pressures during swallowing in healthy younger and older adults.

BACKGROUND

Transcutaneous electrical stimulation amplitude is one parameter that may have different impacts on the neuromotor system and swallowing physiology. One aspect of swallowing physiology influenced by age is the timing of swallowing events. However, the effect of varying TES amplitudes on timing of swallowing physiology is poorly understood, especially in older adults.

MATERIALS AND METHODS

Thirty-four adults (20 younger and 14 older) swallowed 10 ml of nectar-thick liquid under three TES conditions: no stimulation, low-amplitude stimulation and high-amplitude stimulation. TES was delivered by surface electrodes on the anterior neck. Timing of pressure peaks for lingual-palatal contacts and pharyngeal pressures were measured under each condition.

RESULTS

A significant age × stimulation amplitude interaction was identified for the base of tongue (BOT) [F(2,62) = 5.087, p < 0.009] and the hypopharynx (HYPO) [F(2,62) = 3.277, p < 0.044]. At the BOT, low-amplitude TES resulted in slower swallows in the younger adults compared with no TES. In older adults, low-amplitude TES resulted in faster swallows compared with high-amplitude TES. At the HYPO, no significant differences were identified in pressure timing across the three TES amplitudes in both age groups. In each case, low-amplitude TES resulted in faster swallows in older adults compared with younger adults.

CONCLUSIONS

Transcutaneous electrical stimulation influences pharyngeal pressure timing differently in young and old people, which questions the appropriateness of using a 'one-size-fits-all' TES amplitude for rehabilitating people with dysphagia.

Adoption into clinical practice of two therapies to manage swallowing disorders: exercise-based swallowing rehabilitation and electrical stimulation

PURPOSE OF REVIEW

To review recent literature depicting a shift in dysphagia rehabilitation in adults. Distinguishing rehabilitation from compensation in dysphagia management, a review of basic exercise principles is followed by description of recent publications depicting exercise-based therapies. Subsequently, transcutaneous electrical stimulation (TES) is reviewed as it may contribute to exercise-based dysphagia rehabilitation in adults.

RECENT FINDINGS

Surveys have documented extensive variability in the clinical application of dysphagia therapy techniques. Despite this variability, two trends are emerging in dysphagia rehabilitation research: documentation of physiologic and functional changes within the swallowing mechanism subsequent to therapy; and prophylactic exercise-based therapies. In addition, extensive efforts have emerged describing the potential application of TES in dysphagia rehabilitation. Though results of these efforts are conflicted, TES may serve a useful role as an adjunct to well developed exercise-based rehabilitation for dysphagia.

SUMMARY

The focus of dysphagia rehabilitation in adults is changing. Current efforts indicate that exercise-based therapies should incorporate multiple principles of exercise physiology and document physiologic change within the impaired swallowing mechanism. TES may function as an adjunctive modality; however, current practices should be evaluated to develop additional parameters of stimulation that are focused toward specific dysphagia impairments.

Immediate effects of transcutaneous electrical stimulation on physiological swallowing effort in older versus young adults

OBJECTIVE

This study compared the immediate impact of different transcutaneous electrical stimulation (TES) amplitudes on physiological swallowing effort in healthy older adults versus young adults.

BACKGROUND

Swallowing physiology changes with age. Reduced physiological swallowing effort in older adults including lower lingua-palatal and pharyngeal pressures may increase risk for swallowing dysfunction (i.e. dysphagia). Transcutaneous electrical stimulation (TES) has been advocated as an adjunctive modality to enhance outcomes in exercise-based therapy for individuals with dysphagia. However, significant variation in how TES is applied during therapy remains and the physiological swallowing response to TES is poorly studied, especially in older adults.

MATERIALS AND METHODS

Physiological change in swallowing associated with no stimulation, sensory stimulation and motor stimulation was compared in 20 young adults versus 14 older adults. Lingua-palatal and pharyngeal manometric pressures assessed physiological swallowing effort.

RESULTS

Multivariate analyses identified interactions between age and stimulation amplitude on lingual and pharyngeal functions. Motor stimulation reduced anterior tongue pressure in both age groups but selectively reduced posterior lingua-palatal pressures in young adults only. Sensory stimulation increased base of tongue (BOT) pressures in older adults but decreased BOT pressures in young adults. Motor stimulation increased hypopharyngeal pressures in both groups.

CONCLUSION

Age and TES level interact in determining immediate physiological responses on swallow performance. A one-size-fit-all approach to TES in dysphagia rehabilitation may be misdirected.

Surface electrical stimulation for treating swallowing disorders after stroke: a review of the stimulation intensity levels and the electrode placements

Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing.