The influence of chemical gustatory stimuli and oral anaesthesia on healthy human pharyngeal swallowing

Trigeminal innervation and tactile responses in mouse tongue

The neural basis of tongue mechanosensation remains largely mysterious despite the tongue's high tactile acuity, sensitivity, and relevance to ethologically important functions. We studied terminal morphologies and tactile responses of lingual afferents from the trigeminal ganglion. Fungiform papillae, the taste-bud-holding structures in the tongue, were convergently innervated by multiple Piezo2+ trigeminal afferents, whereas single trigeminal afferents branched into multiple adjacent filiform papillae. In vivo single-unit recordings from the trigeminal ganglion revealed lingual low-threshold mechanoreceptors (LTMRs) with distinct tactile properties ranging from intermediately adapting (IA) to rapidly adapting (RA). The receptive fields of these LTMRs were mostly less than 0.1 mm2 and concentrated at the tip of the tongue, resembling the distribution of fungiform papillae. Our results indicate that fungiform papillae are mechanosensory structures and suggest a simple model that links functional and anatomical properties of tactile sensory neurons in the tongue.

Trigeminal innervation and tactile responses in mouse tongue

The mammalian tongue is richly innervated with somatosensory, gustatory and motor fibers. These form the basis of many ethologically important functions such as eating, speaking and social grooming. Despite its high tactile acuity and sensitivity, the neural basis of tongue mechanosensation remains largely mysterious. Here we explored the organization of mechanosensory afferents in the tongue and found that each lingual papilla is innervated by Piezo2 + trigeminal neurons. Notably, each fungiform papilla contained highly specialized ring-like sensory neuron terminations that asymmetrically circumscribe the taste buds. Myelinated lingual afferents in the mouse lingual papillae did not form corpuscular sensory end organs but rather had only free nerve endings. In vivo single-unit recordings from the trigeminal ganglion revealed lingual low-threshold mechanoreceptors (LTMRs) with conduction velocities in the Aδ range or above and distinct adaptation properties ranging from intermediately adapting (IA) to rapidly adapting (RA). IA units were sensitive to both static indentation and stroking, while RA units had a preference for tangential forces applied by stroking. Lingual LTMRs were not directly responsive to rapid cooling or chemicals that can induce astringent or numbing sensations. Sparse labeling of lingual afferents in the tongue revealed distinct terminal morphologies and innervation patterns in fungiform and filiform papillae. Together, our results indicate that fungiform papillae are mechanosensory structures, while suggesting a simple model that links the functional and anatomical properties of tactile sensory neurons in the tongue.

Comparing Taste Perception Across Modalities in Healthy Adults: Liquids Versus Dissolvable Taste Strips

Taste stimulation has rehabilitative value in dysphagia management, as it activates salient underlying afferent pathways to swallowing which may evoke feedforward effects on swallow biomechanics. Despite its potential beneficial effects on swallow physiology, taste stimulation's clinical application is limited for persons unsafe to orally consume food/liquid. This study aimed to create edible, dissolvable taste strips matched to flavor profiles previously used in research assessing taste's effects on swallowing physiology and brain activity, and to evaluate how similar their perceived intensity and hedonic, or palatability, ratings were between their liquid counterparts. Plain, sour, sweet-sour, lemon, and orange flavor profiles were custom-made in taste strips and liquid modalities. The generalized Labeled Magnitude Scale and hedonic generalized Labeled Magnitude Scale were used to assess intensity and palatability ratings for flavor profiles in each modality. Healthy participants were recruited and stratified across age and sex. Liquids were rated as more intense than taste strips; however, there was no difference in palatability ratings between the modalities. There were significant differences across flavor profiles in intensity and palatability ratings. Collapsed across liquid and taste strip modalities, pairwise comparisons revealed all flavored stimuli were rated as more intense than the plain profile, sour was perceived as more intense and less palatable than all other profiles, and orange was rated as more palatable than sour, lemon, and plain tastants. Taste strips have useful implications for dysphagia management, as they could offer safe and patient-preferred flavor profiles to potentially provide advantageous swallowing and neural hemodynamic responses.

Feel it or deal with it: Oral perception and aspiration risk in early stroke

BACKGROUND

Sensation and perception impairments are significant problems faced by individuals with early-stage stroke. Sensory inputs needed in swallowing guide the perceptual process with the involvement of cognitive functions. In the absence of sensory input, bolus perception may be altered, and swallowing safety may be compromised.

OBJECTIVES

This study aims to evaluate the oral perception of volume change and the aspiration risk of individuals with stroke and determine the relationship between oral perception and aspiration risk.

METHODS

Total participants were 35. The Gugging Swallowing Screening Test (GUSS) was used to determine individuals' risk of aspiration and divide them into groups 'aspiration risk' and 'non-aspiration risk'. The Oral Perception of Liquid Volume Changes Test (OPLVCT) was used to determine the level of oral perception.

RESULTS

The groups were statistically similar in terms of age and other descriptives. When the OPLVC test was examined, the scores of the aspiration risk group were significantly lower (p < .001). In addition, a moderate negative correlation was found between aspiration risk and the OPLVC scores (r: -0.502; p < .001).

CONCLUSION

In this study, a relationship was found between aspiration risk and oral perception. It also revealed that individuals with stroke who are at risk of aspiration have low oral perception abilities. Based on these results, it was concluded that these individuals cannot reliably determine the maximum volume of liquid to be consumed without assistance. We suggest that evaluations and training of oral perception should be added to the rehabilitation of individuals with stroke.

The effect of taste on swallowing: A scoping and systematic review

Consuming foods and liquids for nutrition requires the coordination of several muscles. Swallowing is triggered and modified by sensory inputs from the aerodigestive tract. Taste has recently received attention as a potential modulator of swallowing physiology, function, and neural activation; additionally, taste impairment is a sequela of COVID-19. This review presents factors impacting taste and swallowing, systematically summarizes the existing literature, and assesses the quality of included studies. A search was conducted for original research including taste stimulation, deglutition-related measure(s), and human participants. Study design, independent and dependent variables, and participant characteristics were coded; included studies were assessed for quality and risk of bias. Forty-eight articles were included after abstract and full-text review. Synthesis was complicated by variable sensory components of stimuli (taste category and intensity, pure taste vs. flavor, chemesthesis, volume/amount, consistency, temperature), participant characteristics, confounding variables such as genetic taster status, and methods of measurement. Most studies had a high risk of at least one type of bias and were of fair or poor quality. Interpretation is limited by wide variability in methods, taste stimulation, confounding factors, and lower-quality evidence. Existing studies suggest that taste can modulate swallowing, but more rigorous and standardized research is needed.

Evidence of intermediate reticular formation involvement in swallow pattern generation, recorded optically in the neonate rat sagittally sectioned hindbrain

Swallow is a primitive behavior regulated by medullary networks, responsible for movement of food/liquid from the oral cavity to the esophagus. To investigate how functionally heterogeneous networks along the medullary intermediate reticular formation (IRt) and ventral respiratory column (VRC) control swallow, we electrically stimulated the nucleus tractus solitarius to induce fictive swallow between inspiratory bursts, with concurrent optical recordings using a synthetic Ca²⁺ indicator in the neonatal sagittally sectioned rat hindbrain (SSRH) preparation. Simultaneous recordings from hypoglossal nerve rootlet (XIIn) and ventral cervical spinal root C1-C2 enabled identification of the system-level correlates of 1) swallow (identified as activation of the XIIn but not the cervical root) and 2) Breuer-Hering expiratory reflex (BHE; lengthened expiration in response to stimuli during expiration). Optical recording revealed reconfiguration of respiration-modulated networks in the ventrolateral medulla during swallow and the BHE reflex. Recordings identified novel spatially compact networks in the IRt near the facial nucleus (VIIn) that were active during fictive swallow, suggesting that the swallow network is not restricted to the caudal medulla. These findings also establish the utility of using this in vitro preparation to investigate how functionally heterogeneous medullary networks interact and reconfigure to enable a repertoire of orofacial behaviors.NEW & NOTEWORTHY For the first time, medullary networks that control breathing and swallow are recorded optically. Episodic swallows are induced via electrical stimulation along the dorsal medulla, in and near the NTS, during spontaneously occurring fictive respiration. These findings establish that networks regulating both orofacial behaviors and breathing are accessible for optical recording at the surface of the sagittally sectioned rodent hindbrain preparation.

Influence of Thermal and Gustatory Stimulus in the Initiation of the Pharyngeal Swallow and Bolus Location Instroke

INTRODUCTION/OBJECTIVE

The aim of this study is to analyze the influence of sour taste and cold temperature in the initiation of the pharyngeal swallow (IPS) and bolus location at pharyngeal swallow onset in individuals after stroke.

METHODS

Cross-sectional prospective study. The study included 52 individuals with unilateral ischemic stroke. Each individual was assessed by videofluoroscopic swallowing study with 5ml of paste bolus offering four different stimuli (natural, cold, sour, and sour-cold). The individuals were divided into two groups according to the offer sequence. Group 1 (G1) - received a randomized sequence of stimuli (24 individuals), and Group 2 (G2) -the stimuli were offered in the following order: natural, cold, sour, and sour-cold(28 individuals). The IPS time and bolus location at pharyngeal swallow onset were analyzed. The bolus location at pharyngeal swallow onset was defined using six different levels.

RESULTS

Individuals in G1 did not show a significant difference in IPS time between stimuli. However, individuals in G2 presented a significantly shorter IPS time with the sour and sour-cold stimuli than with natural or cold stimuli. The bolus location at pharyngeal swallow onset did not show significant difference between stimuli in both groups. On the other hand, in the G2 it was observed higher frequency of swallowing with sour-cold stimulus at level 1 (the bolus head was located in any region between the fauces pillar and the point where the tongue crosses the inferior border of the mandible).

CONCLUSION

The sour and sour-cold stimuli influenced the IPS time when they were offered in a sequential order. Moreover, both the IPS time and bolus location at pharyngeal swallow onset were not influenced by the sour and sour cold-bolus when offered in a random sequence.

Experience of speech pathology and nutritional monitoring of oral feeding in older people from a community-based approach

ABSTRACT Purpose: to describe the changes in the body composition and swallowing of an older-people group from a community-based speech therapy and nutrition program. Methods: a pre-experimental study of a single group was carried out, with prospective timing and pre-post evaluation for three months. The Body Mass Index (BMI), percentage of body fat (%BF), percentage of muscle mass (%MM), percentage of visceral fat (%VF), swallowing performance, and Swallowing Quality of Life (Swall-QoL) were evaluated. The Spearman correlation coefficient and the Mann-Whitney U test were used, significance level p<0.05. Results: 13 older people participated in the study. The average age of the group was 73.8 years (SD= 4.6). The BMI (pre=28.17; post=28.38), %BF (pre=38.5; post=38.7), %MM (pre=24.8; post=24.9) and %VF (pre=14.3; post=14.8) did not present significant differences (p>0.05). The scores obtained in the deglutition test was pre=19.15 and post=18.9. An association between BMI and VF (Rho=0.74; p=0.02) was detected. Conclusion: the program represented a community-based instance of health promotion focus on oral feeding of older people.

Lasting modulation of human cortical swallowing motor pathways following thermal tongue stimulation

BACKGROUND

Thermal tactile oropharyngeal stimulation has been clinically used to facilitate swallowing initiation in dysphagic patients. We previously demonstrated that thermal stimulation applied to the oral cavity provokes an immediate excitability in pharyngeal motor cortex. The aim of the current study was to investigate whether thermal stimulation can produce longer lasting effects on the corticopharyngeal neural pathway.

METHODS

Healthy volunteers (n = 8/12) underwent baseline pharyngeal motor evoked potential (PMEP) measurements evoked by transcranial magnetic stimulation. In the first experiment, subjects received thermal stimulation alternating 30 seconds of 15 and 36°C applied to the tongue surface for either 10 minutes, 5 minutes, or sham. In the second experiment, one of three intermittent thermal stimulus patterns was delivered: cold (alternating 30 seconds of 15 and 36°C), warm (continuous 36°C), or hot (alternating 30 seconds of 45 and 36°C) for 10 minutes. In both experiments, PMEP were remeasured every 15 minutes up to 60 minutes following thermal stimulation.

KEY RESULTS

Repeated measures ANOVA for each stimulus time in the first experiment showed a significant increased change in PMEP amplitude at 30 minutes following only 10-minute stimulation compared with sham (P < .05). In the second experiment, we found that cold stimulation was more effective than the other stimulation (P < .05) at increasing PMEP amplitudes.

CONCLUSIONS AND INFERENCES

Ten-minute cold stimulation on the tongue can induce a delayed (30 minutes) increase in pharyngeal cortical excitability, providing a clinically useful therapeutic window for its application in dysphagic patients.

Targeting Chemosensory Ion Channels in Peripheral Swallowing-Related Regions for the Management of Oropharyngeal Dysphagia

Oropharyngeal dysphagia, or difficulty in swallowing, is a major health problem that can lead to serious complications, such as pulmonary aspiration, malnutrition, dehydration, and pneumonia. The current clinical management of oropharyngeal dysphagia mainly focuses on compensatory strategies and swallowing exercises/maneuvers; however, studies have suggested their limited effectiveness for recovering swallowing physiology and for promoting neuroplasticity in swallowing-related neuronal networks. Several new and innovative strategies based on neurostimulation in peripheral and cortical swallowing-related regions have been investigated, and appear promising for the management of oropharyngeal dysphagia. The peripheral chemical neurostimulation strategy is one of the innovative strategies, and targets chemosensory ion channels expressed in peripheral swallowing-related regions. A considerable number of animal and human studies, including randomized clinical trials in patients with oropharyngeal dysphagia, have reported improvements in the efficacy, safety, and physiology of swallowing using this strategy. There is also evidence that neuroplasticity is promoted in swallowing-related neuronal networks with this strategy. The targeting of chemosensory ion channels in peripheral swallowing-related regions may therefore be a promising pharmacological treatment strategy for the management of oropharyngeal dysphagia. In this review, we focus on this strategy, including its possible neurophysiological and molecular mechanisms.

Variations in the amplitude and duration of hyolaryngeal elevation during swallow: Effect of sour and carbonated liquid bolus

BACKGROUND

Altering sensory properties of food is relevant to the management of swallowing disorders. The current investigation aimed to examine the influence of sour and carbonated stimuli on measures of hyolaryngeal elevation.

METHOD

Sixty healthy adults in the age range of 18 to 35 years were assessed using Digital Accelerometry Swallowing Imaging (DASI) while swallowing 5 ml of neutral, sour and carbonated liquid bolus.

RESULTS

Sour stimulus was significantly different with higher amplitude and longer durational measures of hyolaryngeal elevation compared to the two other stimuli.

CONCLUSION

Sour stimulus facilitates better hyolaryngeal elevation, which implicates its usage in dysphagia management.

Gustatory function in persons with cerebral palsy

Gustatory function is closely related to chewing and swallowing; however, there are currently no reports regarding gustatory function in persons with cerebral palsy (CP). The aim of this study was to compare the gustatory function between persons with CP and healthy controls. We investigated sweet, salty, sour and bitter tastes using the whole-mouth method and measured the electrogustometric thresholds in the chorda tympani nerve area. Twelve participants with CP (6 women and 6 men) for whom gustatory testing was possible at our facilities, and 17 age-matched controls (9 women and 8 men) were included. The mean age ± standard deviation was 58.6 ± 8.1 years and 58.5 ± 8.7 years in subjects with CP and controls, respectively. Taste detection and identification were significantly worse in persons with CP compared with the controls. Taste identification was more impaired than taste detection. At the highest concentration, taste identification was impossible 11 times out of 48 (12 persons × 4 kinds of tastes) in persons with CP but such a deficit was not observed in 68 attempts (17 persons × 4 kinds of tastes) involving controls. The electrogustometric thresholds were not significantly different between the groups. Gustatory function associated with chewing and swallowing is worse in persons with CP compared to the controls.

Genetic Taster Status as a Mediator of Neural Activity and Swallowing Mechanics in Healthy Adults

As part of a larger study examining relationships between taste properties and swallowing, we assessed the influence of genetic taster status (GTS) on measures of brain activity and swallowing physiology during taste stimulation in healthy men and women. Twenty-one participants underwent videofluoroscopic swallowing study (VFSS) and functional magnetic resonance imaging (fMRI) during trials of high-intensity taste stimuli. The precisely formulated mixtures included sour, sweet-sour, lemon, and orange taste profiles and unflavored controls. Swallowing physiology was characterized via computational analysis of swallowing mechanics plus other kinematic and temporal measures, all extracted from VFSS recordings. Whole-brain analysis of fMRI data assessed blood oxygen responses to neural activity associated with taste stimulation. Swallowing morphometry, kinematics, temporal measures, and neuroimaging analysis revealed differential responses by GTS. Supertasters exhibited increased amplitude of most pharyngeal movements, and decreased activity in the primary somatosensory cortex compared to nontasters and midtasters. These preliminary findings suggest baseline differences in swallowing physiology and the associated neural underpinnings associated with GTS. Given the potential implications for dysphagia risk and recovery patterns, GTS should be included as a relevant variable in future research regarding swallowing function and dysfunction.

Quantitative assessment of oral phase efficiency: validation of the Test of Masticating and Swallowing Solids (TOMASS)

BACKGROUND

The Test of Masticating and Swallowing Solids (TOMASS) has been developed to provide clinicians with objective data regarding the efficiency of oral phase function and solid bolus ingestion.

AIMS

To determine if the TOMASS will detect changes in the oral phase of swallowing imposed by topical anaesthesia, thus providing validation of its clinical utility.

METHODS & PROCEDURES

Per the standard protocol, 10 healthy participants ate one-quarter of an Arnotts Salada^TM biscuit. The number of bites per cracker, number of masticatory cycles, number of swallows and total time taken were recorded at baseline, following application of topical oral anaesthetic; this was additionally compared with a post-anaesthetic condition. Median and interquartile range (IQR) were calculated. Wilcoxon signed-rank tests were conducted to evaluate trial effect, and Friedman's tests were used to detect differences in the number of bites, number of swallows, number of chews and time taken to eat the crackers.

OUTCOMES & RESULTS

Results indicated that the number of both bites and swallows did not significantly change across conditions (χ²(2) = 0.105, p = 0.949, χ²(2) = 1.357, p = 0.507); however, the number of chews for the anaesthetic condition was significantly higher when compared with the baseline (p = 0.02) and post-anaesthesia conditions (p = 0.02). Further, the durations of ingestion in the anaesthetic condition were significantly longer than the baseline (p = 0.01) and post-anaesthesia (p = 0.01) conditions. Across all measures, there were no differences between baseline and post-anaesthesia conditions.

CONCLUSIONS & IMPLICATIONS

Although further exploration is required, these early data suggest the TOMASS is a sensitive measure in the evaluation of the oral-phase preparation of solid textures.

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.

WATER INGESTION DYNAMICS IN PATIENTS WITH ACHALASIA: INFLUENCE OF SEX AND AGE

BACKGROUND

Achalasia is a disease that affects esophageal bolus transit due to the absence of esophageal peristaltic contractions and impaired or absent relaxation of the lower esophageal sphincter.

OBJECTIVE

The objective of this investigation was: a) to evaluate the dynamics of water ingestion in patients with achalasia, idiopathic or caused by Chagas' disease; b) to evaluate the influence of sex and age on water ingestion dynamics.

METHODS

The investigation was conducted with 79 patients with achalasia (27 idiopathic and 52 Chagas' disease) and 91 healthy volunteers, all evaluated by the water-drinking test. The individuals drank, in triplicate, 50 mL of water without interruption. The time and the number of swallows for this task were counted. We also measured: (a) inter-swallow interval - the time to complete the task, divided by the number of swallows during the task; (b) swallowing rate - volume drunk divided by the time; (c) volume per swallow - volume drunk divided by the number of swallows.

RESULTS

Patients with achalasia took longer to ingest all the volume (mean 12.2 seconds) than healthy controls (mean 5.4 seconds), had greater number of swallows, longer interval between swallows, lower swallowing rate (5.2 mL/s vs 10.9 mL/s in controls) and lower volume per swallow (9.1 mL vs 14.4 mL in controls, P<0.01). Among healthy volunteers, women had a shorter interval between swallows and lower volume per swallow compared with men, and in the achalasia group, women had a longer interval between swallows and lower ingestion rate. No difference in the drinking test results was found between younger and older subjects in achalasia or control group. Also, no differences were observed between patients with Chagas' disease and those with idiopathic achalasia, or between patients with increased and normal esophageal diameter.

CONCLUSION

Patients with achalasia have difficulty in ingesting water, taking a longer time to complete the task, which is influenced by sex but not by age or severity of the disease.

Cold thermal oral stimulation produces immediate excitability in human pharyngeal motor cortex

BACKGROUND

Current strategies of swallowing therapy include facilitation of swallowing initiation by sensory modulation. Although thermal tactile oral stimulation is a common method to treat dysphagic patients to improve swallowing movement, little is known about the possible mechanisms. This study is aimed to investigate whether thermal oral (tongue) stimulation can modulate the cortico-pharyngeal neural motor pathway in humans.

METHODS

Eighteen healthy volunteers participated and were intubated with an intraluminal catheter for recording pharyngeal electromyography. Each participant underwent baseline transcranial magnetic stimulation (TMS) cortico-pharyngeal motor evoked potential (MEP) measurements bilaterally. MEPs were then measured during thermal stimulation over the dorsal tongue, applied using the Peltier device at three different temperatures; 45°C, 37°C, and 15°C, in a pre-ordered manner. Each of the three temperatures was given twice with a 5-min resting time between each trial. Averaged MEP amplitude changes were analyzed using ANOVA and post-hoc t-tests.

KEY RESULTS

Two-way repeated measures ANOVA with factors of Temperature × Trial in amplitude of MEP demonstrated a significant effect of Temperature both in the stronger (F_2,34  = 5.775, P = .007) and weaker (F_2,34  = 4.771, P = .017) pharyngeal hemispheres. Subsequent post-hoc tests showed the significant increase in pharyngeal MEPs at 15° compared to 37° in both hemispheres (P < .05).

CONCLUSIONS & INFERENCES

Cold oral stimulation was able to induce significant changes in pharyngeal cortical excitability, demonstrating evidence for a sensorimotor interaction between oral and pharyngeal cortical areas.

Topical Anesthesia for Endoscopic Office-based Procedures of the Upper Aerodigestive Tract

OBJECTIVE

Over the last two decades, an increase in office-based procedures under topical anesthesia in laryngology and head and neck oncology has occurred. Adequate anesthesia in the nasal cavity, pharynx, and larynx is essential for successful performance of these procedures. Our goal is to provide an objective summary on the available local anesthetics, methods of application, local secondary effects, efficacy, and complications.

MATERIAL AND METHODS

A descriptive review of literature on topical anesthesia for office-based procedures in laryngology and head and neck oncology was performed.

RESULTS

Lidocaine is the most applied and investigated topical anesthetic. Topical anesthesia results in decreased sensory function without impairing motor function of the pharynx and larynx. For the nasal cavity, cotton pledgets soaked in anesthetic spray and decongestant, or anesthetic gel, are effective. For the pharynx, anesthetic spray is the most frequently used and effective method. For the larynx, applying local anesthesia through a catheter through the working channel of the endoscope or anesthetic injection through the cricothyroid membrane is effective. Studies comparing the most effective application methods for each anatomical site are lacking. Complications of topical lidocaine administration are rare.

CONCLUSIONS

By properly applying topical anesthesia to the upper aerodigestive tract, several surgical procedures in laryngology and head and neck oncology can be performed in the outpatient clinic under topical anesthesia instead of the operating room under general anesthesia. Lidocaine is the most investigated anesthetic, with adequate efficacy and few complications. Studies that determine the most effective application methods are still wanting.

Difficulties in thickened water ingestion in healthy subjects

BACKGROUND

For some patients with dysphagia who have airway aspiration, it is not possible to drink water as a thin liquid, as they need their water to be thickened.

OBJECTIVE

To evaluate in healthy volunteers the difficulties and dynamics of ingestion of thickened water.

METHOD

In 94 healthy volunteers aged 18-67 years, the ingestion of 100 mL of water with consistencies of thin liquid and thickened with 1.2 g (nectar-thick), 2.4 g (honey-thick) and 3.6 g (pudding-thick) of a commercial thickener with maltodextrin, xanthan gum and potassium chloride was evaluated. The volunteers drank in a random sequence 100 mL of each consistency. The duration and the number of swallows to drink the volume were measured. The interval between swallows, the flux of ingestion and the volume of each swallow were calculated. After each test, the individual was asked about the sensation during drinking, with ten as the best sensation and zero as the worst sensation, and about the difficulty to swallow each consistency.

STATISTICAL ANALYSIS

The analysis was done using a linear model with mixed effects.

RESULTS

The time to ingest the volume increased (liquid: 5.8 s; nectar: 7.9 s; honey: 9.5 s; pudding: 12.7 s; p < 0.01), the flux of ingestion decreased (liquid: 20.3 mL/s; nectar: 15.6 mL/s; honey: 13.4 mL/s; pudding: 10.6 mL/s; p < 0.01), the sensation worsened (liquid: 9.7; nectar: 5.7; honey: 4.3; pudding: 2.8), and the difficult of ingestion increase with the increase of the water consistency. Individuals with dental prosthesis (n = 11) had a decrease in the flux of ingestion with 3.6 g of thickener (prosthesis: 11.1 mL/s, no prosthesis: 6.8 mL/s, p = 0.05) and a decrease in the volume in each swallow (prosthesis: 17.6 mL, no prosthesis: 10.5 mL).

CONCLUSIONS

There is some difficulty to drink thickened water. The use of dental prosthesis cause further difficulties.

Diverging lesion and connectivity patterns influence early and late swallowing recovery after hemispheric stroke

Knowledge about the recovery of oral intake after hemispheric stroke is important to guide therapeutic decisions, including the administration of enteral tube feeding and the choice of the appropriate feeding route. They aimed to determine the localization and connectivity of lesions in impaired recovery versus recovered swallowing after initially dysphagic stroke. Sixty-two acute ischemic hemispheric stroke patients with impaired oral intake were included in a prospective observational cohort study. Voxel-based lesion-symptom mapping and probabilistic tractography were used to determine the association of lesion location and connectivity with impaired recovery of oral intake ≥7 days (indication for early tube feeding) and ≥4 weeks (indication for percutaneous endoscopic gastrostomy feeding) after stroke. Two distinct patterns influencing recovery of swallowing were recognized. Firstly, impaired recovery of oral intake after ≥7 days was significantly associated with lesions of the superior corona radiata (65% of statistical map, P < 0.05). The affected fibers were connected with the thalamus, primary motor, and supplemental motor areas and the basal ganglia. Secondly, impaired recovery of oral intake after ≥4 weeks significantly correlated with lesions of the anterior insula (54% of statistical map, P < 0.05), which was connected to adjacent operculo-insular areas of deglutition. These findings indicate that early swallowing recovery is influenced by white matter lesions disrupting thalamic and corticobulbar projection fibers. Late recovery is determined by specific cortical lesions affecting association fibers. This knowledge may help clinicians to identify patients at risk of prolonged swallowing problems that would benefit from enteral tube feeding. Hum Brain Mapp 38:2165-2176, 2017. © 2017 Wiley Periodicals, Inc.

Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network

Sour stimuli have been shown to upregulate swallowing in patients and in healthy volunteers. However, such changes may be dependent on taste-induced increases in salivary flow. Other mechanisms include genetic taster status (Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Weiffenbach JM. Physiol Behav 82: 109-114, 2004) and differences between sour and other tastes. We investigated the effects of taste on swallowing frequency and cortical activation in the swallowing network and whether taster status affected responses. Three-milliliter boluses of sour, sour with slow infusion, sweet, water, and water with infusion were compared on swallowing frequency and hemodynamic responses. The sour conditions increased swallowing frequency, whereas sweet and water did not. Changes in cortical oxygenated hemoglobin (hemodynamic responses) measured by functional near-infrared spectroscopy were averaged over 30 trials for each condition per participant in the right and left motor cortex, S1 and supplementary motor area for 30 s following bolus onset. Motion artifact in the hemodynamic response occurred 0-2 s after bolus onset, when the majority of swallows occurred. The peak hemodynamic response 2-7 s after bolus onset did not differ by taste, hemisphere, or cortical location. The mean hemodynamic response 17-22 s after bolus onset was highest in the motor regions of both hemispheres, and greater in the sour and infusion condition than in the water condition. Genetic taster status did not alter changes in swallowing frequency or hemodynamic response. As sour taste significantly increased swallowing and cortical activation equally with and without slow infusion, increases in the cortical swallowing were due to sour taste.

Oropharyngeal swallowing in chronic renal failure

OBJECTIVE

To characterize the oropharyngeal swallowing profile of patients with chronic renal failure.

METHODS

A cross-sectional clinical study involving 20 adults diagnosed with chronic renal failure in hospital stay was conducted. The evaluation of swallowing was performed by videofluoroscopy, and characterization of findings was based on effectiveness and safety parameters. Functional Oral Intake Scale (FOIS) was also applied.

RESULTS

On videofluoroscopy, 16 patients presented changes in oral and pharyngeal patterns, three individuals presented impairment at the pharyngeal phase, and only one individual presented changes only at the oral phase of swallowing. Furthermore, videofluoroscopy showed penetration and tracheal aspiration in 30% of the sample. Before the videofluoroscopy, four individuals (20%) were at level 5 of FOIS scale, whereas 16 individuals (80%) were at level 7. After adjustments of the oral diet consistency because of safety and swallowing effectiveness, FOIS classification was six individuals at level 1, seven at level 4, four at level 5, and three at level 6.

CONCLUSION

The characterization of oropharyngeal swallowing profile in chronic renal patients showed abnormalities at oral and pharyngeal phase, including penetration and tracheal aspiration, which requires oral intake changes.

POSTFUNDOPLICATION DYSPHAGIA CAUSES SIMILAR WATER INGESTION DYNAMICS AS ACHALASIA

BACKGROUND

- After surgical treatment of gastroesophageal reflux disease dysphagia is a symptom in the majority of patients, with decrease in intensity over time. However, some patients may have persistent dysphagia.

OBJECTIVE

- The objective of this investigation was to evaluate the dynamics of water ingestion in patients with postfundoplication dysphagia compared with patients with dysphagia caused by achalasia, idiopathic or consequent to Chagas' disease, and controls.

METHODS

- Thirty-three patients with postfundoplication dysphagia, assessed more than one year after surgery, together with 50 patients with Chagas' disease, 27 patients with idiopathic achalasia and 88 controls were all evaluated by the water swallow test. They drunk, in triplicate, 50 mL of water without breaks while being precisely timed and the number of swallows counted. Also measured was: (a) inter-swallows interval - the time to complete the task, divided by the number of swallows during the task; (b) swallowing flow - volume drunk divided by the time taken; (c) volume of each swallow - volume drunk divided by the number of swallows.

RESULTS

- Patients with postfundoplication dysphagia, Chagas' disease and idiopathic achalasia took longer to ingest all the volume, had an increased number of swallows, an increase in interval between swallows, a decrease in swallowing flow and a decrease in water volume of each swallow compared with the controls. There was no difference between the three groups of patients. There was no correlation between postfundoplication time and the results.

CONCLUSION

- It was concluded that patients with postfundoplication dysphagia have similar water ingestion dynamics as patients with achalasia.

Differential response properties of peripherally and cortically evoked swallows by electrical stimulation in anesthetized rats

We compared onset latency, motor-response patterns, and the effect of electrical stimulation of the cortical masticatory area between peripherally and cortically evoked swallows by electrical stimulation in anesthetized rats. The number of swallows and the motor patterns were determined using electromyographic recordings from the thyrohyoid, digastric, and masseter muscles. The onset latency of the first swallow evoked by electrical stimulation of the cortical swallowing area (Cx) was significantly longer than that evoked by stimulation of the superior laryngeal nerve (SLN). The duration of thyrohyoid burst activity associated with SLN-evoked swallows was significantly longer than that associated with either Cx-evoked or spontaneous swallows. Combining Cx with SLN stimulation increased the number of swallows at low levels of SLN stimulation. Finally, A-area (the orofacial motor cortex) stimulation inhibited Cx-evoked swallows significantly more than it inhibited SLN-evoked swallows. These findings suggest that peripherally and cortically evoked swallows have different response properties and are affected differently by the mastication network.

The interactions between different tastes on initiation of reflex swallow elicited by electrical stimulation in humans

The act of eating is a source of pleasure for people and is a major factor in maintaining a good quality of life. Several types of products for dysphagia patients are available to decrease aspiration of food that often accompanies daily food intake. The final goal of these products is to improve the ease of forming a food bolus and/or the safety of the swallowing process; however, tastes of products are not a major concern with initiation of swallowing. In the present study, we investigated the effect of bitter taste stimuli (quinine) and the combination of quinine and umami (monosodium glutamate: MSG) applied to the oropharynx on reflex swallows evoked by electrical stimulation to the oropharyngeal mucosa. Each of the distilled water (DW), quinine and quinine-MSG mixture solution (volume of each solutions, 100 µl) was applied 1 s prior to electrical stimulation. No swallow was evoked when each of the solutions was applied without electrical stimulation. The application of DW and lower concentration of quinine (<100 µM) did not affect the latency of reflex swallow, but 100 µM quinine application increased the latency of the reflex swallow. In addition, application of quinine-MSG mixture solution counteracted the increase in latency induced by quinine application alone. These findings suggest that MSG enhances the initiation of swallowing along with its well-known increase in appetite stimulation. Adding MSG might be effective when creating food to promote swallowing.

Using sensory properties of food to trigger swallowing: a review

The effect of food consistency on swallowing function has been widely studied, and it is well recognized that by delaying the flow of the food bolus, thickened liquids can help in the management of swallowing dysfunction. However, fewer studies have been carried out on the impact of food sensory properties and related liking on swallowing function. This paper reviews the role of taste, olfaction, and trigeminal perceptions on swallowing function and highlights the need for a deeper investigation of this aspect of patient diet modification.

Brain and behavioral effects of swallowing carbonated water on the human pharyngeal motor system

Chemical stimulation of the swallowing network with carbonation and citric acid has been investigated, showing potential benefits on swallowing of dysphagic patients. Despite this, the underlying mechanisms for these effects are not fully understood. Here we investigated the effects of 5 ml liquid bolus swallows of carbonated, citric acid, and still water on a swallowing reaction-time tasks paradigm in 16 healthy adults (8 male, mean age 33 ± 3.7 yr, protocol 1). We then investigated the net effects of "sensory bolus interventions" (40 repeated swallows every 15 s) of the three different liquid boluses on corticobulbar excitability, as examined with single-pulse transcranial magnetic stimulation (TMS) in 16 participants (8 female, mean age 33 ± 3.7 yr, protocol 2). The findings showed that a larger number of correctly timed swallows (within a predetermined time window) was accomplished mainly with carbonated liquids (z = -2.04, P = 0.04 vs. still water, protocol 1). Both carbonated and citric acid liquid interventions with 40 swallows increased corticobulbar excitability of the stronger pharyngeal projection, suggesting a similar modulatory pathway for the effects on swallowing. However, carbonation showed superiority (P = 0.04, F = 4.75, 2-way ANOVA), with the changes lasting up to 60 min following the intervention. These results hold significance for future further and in-depth physiological investigations of the differences between different stimuli on swallowing neural network.

Patient-centred pharmaceutical design to improve acceptability of medicines: similarities and differences in paediatric and geriatric populations

Patient acceptability of a medicinal product is a key aspect in the development and prescribing of medicines. Children and older adults differ in many aspects from the other age subsets of population and require particular considerations in medication acceptability. This review highlights the similarities and differences in these two age groups in relation to factors affecting acceptability of medicines. New and conventional formulations of medicines are considered regarding their appropriateness for use in children and older people. Aspects of a formulation that impact acceptability in these patient groups are discussed, including, for example, taste/smell/viscosity of a liquid and size/shape of a tablet. A better understanding of the acceptability of existing formulations highlights opportunities for the development of new and more acceptable medicines and facilitates safe and effective prescribing for the young and older populations.

Informing a realistic laboratory erosion-testing regime--observations

OBJECTIVES

To measure aspects of fizzy drink consumption in a social environment to inform the development of a laboratory testing regime.

METHODS

This was an observational study in which participants were invited to attend one of four pizza and soft drink parties. All such foods and drinks were served in an air conditioned room at a temperature of 24°C. All drinks were at a temperature of 4°C and each participant was asked to spit out, into graduated cups, their first and second sips. Both the temperature and volume of these were measured. Upon completion of the party the volume of drinks consumed was determined. Video footage of the experiment was recorded for subsequent analysis to determine sip count and the elapsed time period between first and last sip. These values were compared to the analogous measured value of expectorated volume in order to assess the usefulness of video observation in the context of this work.

RESULTS

The mean expectorated beverage temperature was 14.9±2.0°C. The mean time spent drinking was 44.2±17.4 minutes with a mean consumption rate of 13.3±6.0 ml/min. Only the sip volume and sip count per can values were significantly different between sexes (P<0.05) with females displaying lower values for volume and a higher sip count. There was close agreement between the sip volume values observed and calculated using video observation derived parameters.

CONCLUSIONS

Several human drinking behaviour values were reported in this study and these will be of value in the development of more realistic laboratory erosion-testing regimes. It is concluded, within the limitations of this work, that (1) there are differences in the drinking behaviour of males and females with respect to sip volume and count, (2) the intraoral rise in temperature of a 4°C beverage is lower than that used in previous laboratory simulations and (3) the values derived from video observation agree with those measured directly validating this technique for use in further studies.

CLINICAL SIGNIFICANCE

The work provides valuable quantitative data on which to base simulated laboratory erosion work. Perhaps the most significant finding is that sipped beverages attain a temperature of only 14.9°C.

Analysis of carbonated thin liquids in pediatric neurogenic dysphagia

BACKGROUND

Aspiration of liquids is a serious complication of neurological impairments such as traumatic brain injury or stroke. Carbonated liquids have been examined as a possible alternative to thickened liquids to help reduce aspiration in cases of dysphagia in adults, but no published literature to the best of our knowledge has evaluated this technique in children. If carbonated liquids result in safer swallowing in children, they could provide a preferred alternative to thickened liquids.

OBJECTIVE

This pilot study examined whether carbonated thin liquids (CARB) improved swallowing compared to non-carbonated thin liquids (NOCARB) for children with neurogenic dysphagia.

MATERIALS AND METHODS

Twenty-four children admitted to a level I trauma center for acute neurological injury/disease were evaluated via videofluoroscopic swallow studies. Four descriptive outcome measures were contrasted.

RESULTS

CARB significantly decreased pooling (P = 0.0006), laryngeal penetration/aspiration (P = 0.0044) and Penetration-Aspiration Scale scores (P = 0.0127) when compared to NOCARB. On average, CARB improved scores on the Penetration-Aspiration Scale by 3.7 points for participants who aspirated NOCARB. There was no significant difference in pharyngeal residue noted between CARB and NOCARB (P = 0.0625).

CONCLUSION

These findings support the hypothesis that carbonated thin liquids may provide an alternative to thickened liquids for children with neurogenic dysphagia. Implications for future research and clinical practice are discussed.

Oral perception of liquid volume changes with age

Bolus volume has been widely studied, and research has demonstrated a variety of physiological impacts on swallowing and swallowing disorders. Oral perception of bolus volume has not, to our knowledge, been investigated in association with normal ageing processes. Research suggests many sensory changes with age, some within the oral cavity, and changes in swallowing function with age have been defined. The role of perception in oropharyngeal deglutition with age requires further investigation. The purpose of this study was to establish the psychophysical relationship between liquid volume and oral perception and examine changes with age. Healthy young and older adults were prospectively assessed using a magnitude estimation task differentiating five volumes of water delivered randomly to the oral cavity. Results suggest a fourfold increase in liquid volume is required by older participants to perceive an approximate twofold increase in the perception of volume compared with younger healthy adults. Sensory receptors in the oral cavity provide a feedback loop that modulates the swallowing motor response so that it is optimal for the size and consistency of the bolus. Changes in perception of bolus volume with age are consistent with other perceptual changes and may provide valuable information regarding sensorineural rehabilitation strategies in the future.

A framework for understanding shared substrates of airway protection

Deficits of airway protection can have deleterious effects to health and quality of life. Effective airway protection requires a continuum of behaviors including swallowing and cough. Swallowing prevents material from entering the airway and coughing ejects endogenous material from the airway. There is significant overlap between the control mechanisms for swallowing and cough. In this review we will present the existing literature to support a novel framework for understanding shared substrates of airway protection. This framework was originally adapted from Eccles' model of cough²⁸ (2009) by Hegland, et al.⁴² (2012). It will serve to provide a basis from which to develop future studies and test specific hypotheses that advance our field and ultimately improve outcomes for people with airway protective deficits.

ACIDIC AND NEUTRAL LIQUID INGESTION IN PATIENTS WITH GASTROESOPHAGEAL REFLUX DISEASE

Context Sour acidic liquid has a slower distal esophageal transit than a neutral liquid. Our hypothesis was that an acidic sour bolus has a different ingestion dynamic than a neutral bolus. Method In 50 healthy volunteers and 29 patients with gastroesophageal reflux disease (GERD), we evaluated the ingestion dynamics of 100 mL of acidic sour liquid (concentrated lemon juice, pH: 3.0) and 100 mL of water (pH: 6.8). The time to ingest the total volume, the number of swallows to ingest the volume, the interval between swallows, the flux of ingestion and the volume ingested in each swallow was measured. Results In both groups, healthy volunteers and patients in treatment for GERD, the acidic liquid took longer to be ingested, a higher number of swallows, a slower flux of ingestion and a smaller volume in each swallow than the neutral bolus. There was no difference between healthy volunteers and patients with GERD. The ingestion in women was longer than in men for acidic and neutral liquids. Conclusion Acidic liquid has a different dynamic of ingestion than the neutral liquid, which may be consequence of the slower transit through the distal esophageal body or an anticipation to drink a sour bolus. Patients with GERD have the same prolonged ingestion of the acidic liquid bolus as seen in healthy volunteers.

Barium versus nonbarium stimuli: differences in taste intensity, chemesthesis, and swallowing behavior in healthy adult women

PURPOSE

The authors examined the impact of barium on the perceived taste intensity of 7 different liquid tastant stimuli and the modulatory effect that these differences in perceived taste intensity have on swallowing behaviors.

METHOD

Participants were 80 healthy women, stratified by age group (<40; >60) and genetic taste status (supertasters; nontasters). Perceived taste intensity and chemesthetic properties (fizziness; burning-stinging) were rated for 7 tastant solutions (each prepared with and without barium) using the general Labeled Magnitude Scale. Tongue-palate pressures and submental surface electromyography (sEMG) were simultaneously measured during swallowing of these same randomized liquids. Path analysis differentiated the effects of stimulus, genetic taste status, age, barium condition, taste intensity, and an effortful saliva swallow strength covariate on swallowing.

RESULTS

Barium stimuli were rated as having reduced taste intensity compared with nonbarium stimuli. Barium also dampened fizziness but did not influence burning-stinging sensation. The amplitudes of tongue-palate pressure or submental sEMG did not differ when swallowing barium versus nonbarium stimuli.

CONCLUSIONS

Despite impacting taste intensity, the addition of barium to liquid stimuli does not appear to alter behavioral parameters of swallowing. Barium solutions can be considered to elicit behaviors that are similar to those used with nonbarium liquids outside the assessment situation.

Differences in swallowing between high and low concentration taste stimuli

Taste is a property that is thought to potentially modulate swallowing behavior. Whether such effects depend on taste, intensity remains unclear. This study explored differences in the amplitudes of tongue-palate pressures in swallowing as a function of taste stimulus concentration. Tongue-palate pressures were collected in 80 healthy women, in two age groups (under 40, over 60), stratified by genetic taste status (nontasters, supertasters). Liquids with different taste qualities (sweet, sour, salty, and bitter) were presented in high and low concentrations. General labeled magnitude scale ratings captured perceived taste intensity and liking/disliking of the test liquids. Path analysis explored whether factors of taste, concentration, age group, and/or genetic taste status impacted: (1) perceived intensity; (2) palatability; and (3) swallowing pressures. Higher ratings of perceived intensity were found in supertasters and with higher concentrations, which were more liked/disliked than lower concentrations. Sweet stimuli were more palatable than sour, salty, or bitter stimuli. Higher concentrations elicited stronger tongue-palate pressures independently and in association with intensity ratings. The perceived intensity of a taste stimulus varies as a function of stimulus concentration, taste quality, participant age, and genetic taste status and influences swallowing pressure amplitudes. High-concentration salty and sour stimuli elicit the greatest tongue-palate pressures.

Influence of the perceived taste intensity of chemesthetic stimuli on swallowing parameters given age and genetic taste differences in healthy adult women

PURPOSE

This study examined whether the perceived taste intensity of liquids with chemesthetic properties influenced lingua-palatal pressures and submental surface electromyography (sEMG) in swallowing, compared with water.

METHOD

Swallowing was studied in 80 healthy women, stratified by age group and genetic taste status. General Labeled Magnitude Scale ratings of taste intensity were collected for deionized water; carbonated water; 2.7% w/v citric acid; and diluted ethanol. These stimuli were swallowed, with measurement of tongue-palate pressures and submental sEMG. Path analysis differentiated stimulus, genetic taste status, age, and perceived taste intensity effects on swallowing. Signal amplitude during effortful saliva swallowing served as a covariate representing participant strength.

RESULTS

Significant differences (p < .05) in taste intensity were seen across liquids: citric acid > ethanol > carbonated water > water. Supertasters perceived greater taste intensity than did nontasters. Lingua-palatal pressure and sEMG amplitudes were correlated with the strength covariate. Anterior palate pressures and sEMG amplitudes were significantly higher for the citric acid stimulus. Perceived taste intensity was a significant mediator of stimulus differences.

CONCLUSION

These data provide confirmatory evidence that high-intensity sour stimuli do influence swallowing behaviors. In addition, taste genetics influence the perception of taste intensity for stimuli with chemesthetic properties, which modulates behavioral responses.

A novel objective sour taste evaluation method based on near-infrared spectroscopy

One of the most important themes in the development of foods and drinks is the accurate evaluation of taste properties. In general, a sensory evaluation system is frequently used for evaluating food and drink. This method, which is dependent on human senses, is highly sensitive but is influenced by the eating experience and food palatability of individuals, leading to subjective results. Therefore, a more effective method for objectively estimating taste properties is required. Here we show that salivary hemodynamic signals, as measured by near-infrared spectroscopy, are a useful objective indicator for evaluating sour taste stimulus. In addition, the hemodynamic responses of the parotid gland are closely correlated to the salivary secretion volume of the parotid gland in response to basic taste stimuli and respond to stimuli independently of the hedonic aspect. Moreover, we examined the hemodynamic responses to complex taste stimuli in food-based solutions and demonstrated for the first time that the complicated phenomenon of the "masking effect," which decreases taste intensity despite the additional taste components, can be successfully detected by near-infrared spectroscopy. In summary, this study is the first to demonstrate near-infrared spectroscopy as a novel tool for objectively evaluating complex sour taste properties in foods and drinks.

Coordination of cough and swallow: a meta-behavioral response to aspiration

Airway protections is the prevention and/or removal of material by behaviors such as cough and swallow. We hypothesized these behaviors are coordinated to respond to aspiration. Anesthetized animals were challenged with simulated aspiration that induced both coughing and swallowing. Electromyograms of upper airway and respiratory muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with rapid pharyngeal clearance. Phase restriction between cough and swallow was observed; swallow was restricted to the E2 phase of cough. These results support three main conclusions: 1) the cough and swallow pattern generators are tightly coordinated so as to generate a protective meta-behavior; 2) the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences; and 3) the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Coordination of cough and swallow: a meta-behavioral response to aspiration

Airway protections is the prevention and/or removal of material by behaviors such as cough and swallow. We hypothesized these behaviors are coordinated to respond to aspiration. Anesthetized animals were challenged with simulated aspiration that induced both coughing and swallowing. Electromyograms of upper airway and respiratory muscles together with esophageal pressure were recorded to identify and evaluate cough and swallow. During simulated aspiration, both cough and swallow intensity increased and swallow duration decreased consistent with rapid pharyngeal clearance. Phase restriction between cough and swallow was observed; swallow was restricted to the E2 phase of cough. These results support three main conclusions: 1) the cough and swallow pattern generators are tightly coordinated so as to generate a protective meta-behavior; 2) the trachea provides feedback on swallow quality, informing the brainstem about aspiration incidences; and 3) the larynx and upper esophageal sphincter act as two separate valves controlling the direction of positive and negative pressures from the upper airway into the thorax.

Lesion Location Predicts Transient and Extended Risk of Aspiration After Supratentorial Ischemic Stroke

Background and Purpose—

To assess the association of lesion location and risk of aspiration and to establish predictors of transient versus extended risk of aspiration after supratentorial ischemic stroke.

Methods—

Atlas-based localization analysis was performed in consecutive patients with MRI-proven first-time acute supratentorial ischemic stroke. Standardized swallowing assessment was carried out within 8±18 hours and 7.8±1.2 days after admission.

Results—

In a prospective, longitudinal analysis, 34 of 94 patients (36%) were classified as having acute risk of aspiration, which was extended (≥7 days) or transient (<7 days) in 17 cases. There were no between-group differences in age, sex, cause of stroke, risk factors, prestroke disability, lesion side, or the degree of age-related white-matter changes. Correcting for stroke volume and National Institutes of Health Stroke Scale with a multiple logistic regression model, significant adjusted odds ratios in favor of acute risk of aspiration were demonstrated for the internal capsule (adjusted odds ratio, 6.2; P <0.002) and the insular cortex (adjusted odds ratio, 4.8; P <0.003). In a multivariate model of extended versus transient risk of aspiration, combined lesions of the frontal operculum and insular cortex was the only significant independent predictor of poor recovery (adjusted odds ratio, 33.8; P <0.008).

Conclusions—

Lesions of the insular cortex and the internal capsule are significantly associated with acute risk of aspiration after stroke. Combined ischemic infarctions of the frontal operculum and the insular cortex are likely to cause extended risk of aspiration in stroke patients, whereas risk of aspiration tends to be transient in subcortical stroke.

Effect of a bitter bolus on oral, pharyngeal and esophageal transit of healthy subjects

CONTEXT

During swallowing, boluses stimulate sensory receptors of the oral, pharyngeal, laryngeal, and esophageal regions. Sweet and tasteless foods are more acceptable for swallowing than bitter foods. A bitter bolus is unpleasant for most subjects. Our hypothesis was that the ingestion of a bitter bolus might alter the oral behavior, pharyngeal and esophageal transit when compared to a sweet bolus.

OBJECTIVE

To evaluate whether the bitter taste of a liquid bolus causes alteration on oral, pharyngeal and/or esophageal transit in normal subjects in comparison with sweet bolus.'

METHOD

Scintigraphic evaluation of oral, pharyngeal and esophageal transit was performed in 43 asymptomatic subjects, 22 women and 21 men, ages 23-71 years, without problems with the ingestion of liquid and solid foods, and without digestive, cardiac or neurologic diseases. Each subject swallowed in random sequence and at room temperature 5 mL of a liquid bolus with bitter taste, prepared with 50 mL of water with 2 g of leaves of Peumus boldus, heated until boiling (boldus tea), and 5 mL of a liquid bolus with sweet taste, prepared with 50 mL of water with 3 g of sucrose, both labeled with 37 MBq of technetium phytate (Tc99m).

RESULTS

There was no difference between the bitter bolus and the sweet bolus in mouth, pharynx and esophageal transit and clearance duration and in the amount of residues.

CONCLUSION

A bitter bolus, considered an unpleasant bolus, does not alter the duration of oral, pharyngeal and esophageal phases of swallowing, when compared with a sweet bolus, considered a pleasant bolus.

The effect of barium on perceptions of taste intensity and palatability

Barium may affect the perception of taste intensity and palatability. Such differences are important considerations in the selection of dysphagia assessment strategies and interpretation of results. Eighty healthy women grouped by age (younger, older) and genetic taste status (supertaster, nontaster) rated intensity and palatability for seven tastants prepared in deionized water with and without 40 % w/v barium: noncarbonated and carbonated water, diluted ethanol, and high concentrations of citric acid (sour), sodium chloride (salty), caffeine (bitter), and sucrose (sweet). Mixed-model analyses explored the effects of barium, taster status, and age on perceived taste intensity and acceptability of stimuli. Barium was associated with lower taste intensity ratings for sweet, salty, and bitter tastants, higher taste intensity in carbonated water, and lower palatability in water, sweet, sour, and carbonated water. Older subjects reported lower palatability (all barium samples, sour) and higher taste intensity scores (ethanol, sweet, sour) compared to younger subjects. Supertasters reported higher taste intensity (ethanol, sweet, sour, salty, bitter) and lower palatability (ethanol, salty, bitter) than nontasters. Refusal rates were highest for younger subjects and supertasters, and for barium (regardless of tastant), bitter, and ethanol. Barium suppressed the perceived intensity of some tastes and reduced palatability. These effects are more pronounced in older subjects and supertasters, but younger supertasters are least likely to tolerate trials of barium and strong tastant solutions.