Effects of a Sour Bolus on the Intramuscular Electromyographic (EMG) Activity of Muscles in the Submental Region

Induction of the Swallowing Reflex by Electrical Stimulation of the Posterior Oropharyngeal Region in Awake Humans

We designed an electrical stimulation system to safely and reliably evoke the swallowing reflex in awake humans, and then examined the neural control of reflex swallowing initiated by oropharyngeal stimulation. A custom-made electrode connected to a flexible stainless-steel coil spring tube was introduced into the pharyngeal region through the nasal cavity and placed against the posterior wall of the oropharynx. Surface electrodes placed over the suprahyoid muscles recorded the electromyogram during swallowing. Swallowing reflexes were induced several times by 30 s of repetitive electrical pulse stimulation (intensity: 0.2-1.2 mA, frequency: 10-70 Hz, pulse duration: 1.0 ms). The onset latency of the swallowing reflex was measured over the 10-70 Hz frequency range. In addition, the two time intervals between the first three swallows were measured. The onset latency of the swallowing reflex became shorter as the stimulus frequency increased up to ≤30 Hz. Once the frequency exceeded 30 Hz, there was no further reduction in the latency. This finding was consistent with those of previous studies in anesthetized animals. The time intervals between successive swallowing reflexes did not change with increased stimulus frequencies. Furthermore, prolonged stimulation often failed to elicit multiple swallowing reflexes. The frequency dependence of onset latency suggests that temporal summation of pharyngeal afferents is required to activate the medullary swallowing center. This reliable stimulation method may help in rehabilitation of dysphagic patients without causing aspiration.

Effects of club soda and ginger brew on linguapalatal pressures in healthy swallowing

Oral chemesthesis is the detection of chemicals that activate temperature and pain receptors in the oral mucosa. Presentation of orally chemesthetic input has been theorized to stimulate a faster, stronger swallow. We measured differences in peak linguapalatal swallowing pressures, pressure durations, and pressure adjustments in response to two volumes of water and carbonation (in Schweppes® Club Soda) and carbonation + gingerol (in Reed's Extra Ginger Brew) in 20 young adult women. There was a main effect of stimulus on linguapalatal swallowing pressure, F(6,74) = 6.247, p = 0.000, hp(2) = 0.536 (Reed's Extra Ginger Brew > Schweppes Club Soda > water). Rising and releasing linguapalatal pressure durations were greater for carbonation + gingerol and carbonation than for water. Our results add to the evidence that orally chemesthetic beverages influence greater neuromotor activity compared to water during the oral stage of swallowing. Our findings also suggest that there may be some benefit to the cumulative addition of chemosensory agents in a beverage. Clinically, this provides a theoretical basis for considering the use of these or chemically similar beverages as facilitating stimuli in patients who aspirate thin liquids.

Effects of olfactory and gustatory stimuli on the biomechanics of swallowing

We have previously documented increased amplitude of motor-evoked potentials (MEPs) from the submental muscles during volitional swallowing following simultaneous odor and tastant stimulation. The MEP denotes neural excitability from the motor cortex to the target muscle(s). However, it is unknown if changes in the MEP transfer to the swallowing muscles to facilitate improved swallowing. Thus, we sought to evaluate changes in the biomechanics of swallowing following stimulation protocols that are known to influence neural excitability. Sixteen healthy participants were exposed to low and high concentrations of lemon odor and tastant. The odor and tastant concentrations which produced the highest amplitude of submental electromyography (EMG) were then combined for simultaneous stimuli presentation. Outcome measures included EMG from the submental muscles, as well as lingual and pharyngeal manometry. Poststimulation results showed decreased midglossopalatal pressure at 30 min and decreased duration at anterior and midglossopalatal pressure and increased EMG duration at 60 min. This study strengthens the justification for the use of flavor in managing patients with dysphagia as long-term changes were present in the poststimulation period.

Effects of olfactory and gustatory stimuli on neural excitability for swallowing

This project evaluated the effects of olfactory and gustatory stimuli on the amplitude and latency of motor-evoked potentials (MEPs) from the submental muscles when evoked by transcranial magnetic stimulation (TMS). Sixteen healthy volunteers (8 males; age range 19-43) participated in the study. Lemon concentrate at 100% and diluted in water to 25% were presented separately as odor and tastant stimuli. Tap water was used as control. 15 trials of TMS-evoked MEPs triggered by volitional contraction of the submental muscles and volitional swallowing were measured at baseline, during control condition, during stimulus presentation, and immediately, 30-, 60-, and 90-min poststimulation for each of the four stimulus presentations. Experiments were repeated using the combined odor and tastant concentrations that most influenced the MEP independently. Differences in MEP amplitude measured during swallowing were seen at 30-, 60-, and 90-min poststimulation for simultaneous olfactory and gustatory stimulation as opposed to no differences seen at any point for stimuli presented separately. This study has shown that combined odor and tastant stimulation (i.e., flavor) can increase MEP amplitude during swallowing and that this enhancement of MEP can persist for at least 90min following stimulation. As increased MEP amplitude has been associated with improved swallowing performance, a follow-up study is underway to determine the biomechanical changes produced by altered MEPs to facilitate translation of these data to clinical dysphagia management.

Effects of taste solutions, carbonation, and cold stimulus on the power frequency content of swallowing submental surface electromyography

This study explored the effects of 5 taste solutions (citric acid, sucrose, sodium chloride, caffeine, and sodium glutamate) versus water on the power frequency content of swallowing submental surface electromyography (sEMG). Healthy subjects were presented with 5 ml of each of 5 tastants and water. Data were collected in 3 trials of the 5 tastants and water by using submental sEMG, which was then subjected to spectral analysis. Sour and salt taste solutions increased the spectrum-integrated values of the total power components. The spectrum-integrated values of low-frequency power (below 10 Hz) in the salt taste trial significantly increased, whereas those of high-frequency power (above 10 Hz) in the sour taste trial tended to increase. Neither pleasantness nor intensity of taste was related to these changes. This study also explored the effects of carbonation and cold stimulus on the power frequency content of continuous swallowing sEMG for 60-ml solutions. Carbonation significantly increased the spectrum-integrated value of the total power components by significantly increasing the high-frequency content. Cold stimulus significantly decreased the low-frequency content. In summary, this study reveals that taste, carbonation, and cold stimulus have qualitatively different influences on the power frequency content of swallowing sEMG.

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.

Quantitative contributions of the muscles of the tongue, floor-of-mouth, jaw, and velum to tongue-to-palate pressure generation

PURPOSE

The purpose of this investigation was to evaluate the relationship between tongue-to-palate pressure and the electromyography (EMG) measured from the mylohyoid, anterior belly of the digastric, geniohyoid, medial pterygoid, velum, genioglossus, and intrinsic tongue muscles. Methods Seven healthy adults performed tongue-to-palate pressure tasks at known percentages of their maximum pressure while intramuscular EMG was recorded from the muscles stated above. Multiple regression analysis was performed.

RESULTS

Predictors of pressure included the posterior fibers of the genioglossus, mylohyoid, anterior belly of digastric, medial pterygoid, and intrinsic tongue.

CONCLUSIONS

Increasing tongue-to-palate pressure coincides with increased muscle activity. Activation of the floor-of-mouth, tongue, and jaw closing muscles increased tongue-to-palate pressure. These findings support the use of a tongue-press exercise to strengthen floor-of-mouth muscles, tongue, and jaw-closing muscles.

Reabilitação em disfagia orofaríngea neurogênica: sabor azedo e temperatura fria

TEMA: reabilitação em disfagia orofaríngea neurogênica OBJETIVO: apresentar revisão de literatura sobre os controles neurofisiológicos da deglutição orofaríngea e a influência do sabor azedo e da temperatura fria no mecanismo da deglutição. CONCLUSÃO: quanto à questão do controle central da deglutição, ainda existem controvérsias em relação ao sabor azedo e a temperatura fria. Esses dois parâmetros provocam mudanças na dinâmica da deglutição, podendo trazer benefícios aos indivíduos acometidos por disfagia orofaríngea neurogênica. Porém, tais achados sugerem a necessidade de investigações futuras com populações randomizadas.

Oropharyngeal dysphagia and nutritional management

PURPOSE OF REVIEW

This review examines recent studies of the evaluation and treatment of oropharyngeal dysphagia as well as papers investigating oropharyngeal dysphagia and nutritional management.

RECENT FINDINGS

There continue to be difficulties in accurate diagnosis of some disorders in oropharyngeal swallow, accounting for the patient's dysphagic symptoms and in identifying optimal treatment strategies for each patient. The efficacy of new techniques for the treatment of oropharyngeal dysphagia have been examined in various populations. Exercise programs have been showing increased efficacy in particular patient groups.

SUMMARY

Articles in this past year have focused largely on identifying new procedures for assessment of oropharyngeal swallowing and defining treatment effects. Relatively little work has examined nutritional management in patients with oropharyngeal dysphagia. Most studies that have investigated nutritional management do not carefully define the patient's medical diagnosis or specific swallowing disorders. Similarly, those that study oropharyngeal dysphagia do not relate these data to nutritional management of these patients.

Clinical Measurement of Pharyngeal Surface Electromyography

Background. Dysphagia diagnosis is limited by our inability to evaluate the underlying neuromuscular pathology of swallowing. A novel approach using pharyngeal surface electromyography (PsEMG) has been reported in the literature. Objective. Three exploratory projects were undertaken to provide data toward the validation of PsEMG as a clinical measure of pharyngeal physiology. The first evaluates laterality of electrode placement in the pharynx. The second and third evaluate PsEMG using a circumferential and unidirectional electrode, respectively, during swallowing maneuvers. Methods. In experiment 1, a catheter housing 3 manometric sensors and 1 bipolar PsEMG electrode was randomly inserted in each nares of 10 participants. Moving jaw radiographs were taken, and the PsEMG electrode was measured in millimeters from midline. In experiments 2 and 3, the catheter was placed in 22 and 40 research participants, respectively. Waveform characteristics were collected during swallowing maneuvers. The 2 experiments differed by type of electrode (circumferential, unidirectional) and swallowing maneuver (noneffortful and effortful swallow; noneffortful, effortful, and tongue-hold swallow). Results. Midline electrode placement occurred on 20% of trials with deviation of up to 14.7 mm on all other trials. Maneuver-specific differences in amplitude were not detected with PsEMG; unacceptable levels of intrasubject and intersubject variability were identified. Temporal relationships of PsEMG and pharyngeal manometric pressure appeared appropriate. The unidirectional electrode revealed a unique bimodal PsEMG pattern that may reflect sequential contraction of muscles of the posterior pharyngeal wall. Conclusions. The current PsEMG design and procedures do not validly measure pharyngeal muscle activity. Recommendations for improved methods are provided.