Effect of aging, position, and temperature on the threshold volume triggering pharyngeal swallows

The effects of simulated gastroesophageal reflux on infant pig oropharyngeal feeding physiology

The neural connectivity among the oral cavity, pharynx, and esophagus is a critical component of infant feeding physiology. Central integration of oral and pharyngeal afferents alters motor outputs to structures that power swallowing, but the potential effects of esophageal afferents on preesophageal feeding physiology are unclear. These effects may explain the prevalence of oropharyngeal dysphagia in infants suffering from gastroesophageal reflux (GER), though the mechanism underlying this relationship remains unknown. Here we use the validated infant pig model to assess the impacts of simulated GER on preesophageal feeding parameters. We used high-speed videofluoroscopy and electromyography to record bottle-feeding before and following the infusion of a capsaicin-containing solution into the lower esophagus. Sucking parameters were minimally affected by capsaicin exposure, such that genioglossus activity was unchanged and tongue kinematics were largely unaffected. Aspects of the pharyngeal swallow were altered with simulated GER, including increased thyrohyoid muscle activity, increased excursions of the hyoid and thyroid per swallow, decreased swallow frequency, and increased bolus sizes. These results suggest that esophageal afferents can elicit changes in pharyngeal swallowing. In addition, decreased swallowing frequency may be the mechanism by which esophageal pathologies induce oropharyngeal dysphagia. Although recent work indicates that oral or pharyngeal capsaicin may improve dysphagia symptoms, the decreased performance following esophageal capsaicin exposure highlights the importance of designing sensory interventions based upon neurophysiology and the mechanisms underlying disordered feeding. This mechanistic approach requires comprehensive data collection across the entirety of the feeding process, which can be achieved using models such as the infant pig.NEW & NOTEWORTHY Simulated gastroesophageal reflux (GER) in an infant pig model resulted in significant changes in pharyngeal swallowing, which suggests that esophageal afferents are centrally integrated to alter motor outputs to the pharynx. In addition, decreased swallow frequency and increased bolus sizes may be underlying mechanisms by which esophageal pathologies induce oropharyngeal dysphagia. The infant pig model used here allows for a mechanistic approach, which can facilitate the design of intervention strategies based on neurophysiology.

Videofluoroscopic analysis of the laryngeal movement of older adults in swallowing

Even without diseases that cause dysphagia, physiological swallowing function declines with age, increasing the risk of aspiration. This study analyzed age-related changes in laryngeal movement in older adults. The study population consisted of 10 volunteers in their 80s and six in their 20s. A videofluoroscopic study of 3 and 10 mL barium swallows was performed laterally using a digital fluorographic. The recorded images were retrieved to a personal computer and analyzed frame-by-frame using video analysis software. The movement of the larynx during swallowing, barium's pharyngeal transit time (PTT), and laryngeal elevation delay time (LEDT) were analyzed. Results were compared between the 20s and 80s age groups using statistical analyses. The PTT was shorter in the 20s than in the 80s age group. The PTT was significantly longer in the 80s group than in the 20s for both 3 and 10 mL barium swallows. LEDT in the 80s was statistically significantly longer than that in the 20s for the 10 ml barium. No statistically significant differences were found; however, there was a tendency for the 80s group to have more types of laryngeal movement velocity peaks. In this study, LEDT was prolonged in the 80s with 10 ml barium swallowing than in the 20s. Two peak patterns of laryngeal elevation during swallowing were observed. The velocity peaks showed a two-peak pattern when the patients were in their 80s and when the barium volume was tested at 10 mL. Our results suggest that aging's effect on swallowing relates to laryngeal elevation.

Pharyngeal biorhythms during oral milk challenge in high-risk infants: Do they predict chronic tube feeding?

BACKGROUND

Eating difficulties are common in high-risk neonatal intensive care unit (NICU) infants; mechanisms remain unclear. Crib-side pharyngo-esophageal motility testing is utilized to assess contiguous swallowing physiology, and cross-system interplay with cardio-respiratory rhythms. Aims were to: (1) identify whether distinct pharyngeal rhythms exist during oral milk challenge (OMC), and (2) develop a chronic tube feeding risk prediction model in high-risk infants.

METHODS

Symptomatic NICU infants (N = 56, 29.7 ± 3.7 weeks birth gestation) underwent pharyngo-esophageal manometry with OMC at 40.9 ± 2.5 weeks postmenstrual age (PMA). Exploratory cluster data analysis (partitioning around k-medoids) was performed to identify patient groups using pharyngeal contractile rhythm data (solitary swallows and swallows within bursts). Subsequently, (a) pharyngeal-esophageal, cardio-respiratory, and eating method characteristics were compared among patient groups using linear mixed models, and (b) chronic tube feeding prediction model was created using linear regression.

RESULTS

Three distinct patient groups were identified with validity score of 0.6, and termed sparse (high frequency of solitary swallows), intermediate, or robust (high swallow rate within bursts). Robust group infants had: lesser pharyngeal and esophageal variability, greater deglutition apnea, pharyngeal activity, and esophageal activity (all p < 0.05), but less frequent heart rate decreases (p < 0.05) with improved clinical outcomes (milk transfer rate, p < 0.001, and independent oral feeding at discharge, p < 0.03). Chronic tube feeding risk = -11.37 + (0.22 × PMA) + (-0.73 × bronchopulmonary dysplasia) + (1.46 × intermediate group) + (2.57 × sparse group).

CONCLUSIONS

Robust pharyngeal rhythm may be an ideal neurosensorimotor biomarker of independent oral feeding. Differential maturation of cranial nerve-mediated excitatory and inhibitory components involving foregut, airway, and cardiac rhythms distinguishes the physiologic and pathophysiologic basis of swallowing and cardio-respiratory adaptation.

Clinical determinants and neural correlates of presbyphagia in community-dwelling older adults

Background

“Presbyphagia” refers to characteristic age-related changes in the complex neuromuscular swallowing mechanism. It has been hypothesized that cumulative impairments in multiple domains affect functional reserve of swallowing with age, but the multifactorial etiology and postulated compensatory strategies of the brain are incompletely understood. This study investigates presbyphagia and its neural correlates, focusing on the clinical determinants associated with adaptive neuroplasticity.

Materials and methods

64 subjects over 70 years of age free of typical diseases explaining dysphagia received comprehensive workup including flexible endoscopic evaluation of swallowing (FEES), magnetoencephalography (MEG) during swallowing and pharyngeal stimulation, volumetry of swallowing muscles, laboratory analyzes, and assessment of hand-grip-strength, nutritional status, frailty, olfaction, cognition and mental health. Neural MEG activation was compared between participants with and without presbyphagia in FEES, and associated clinical influencing factors were analyzed. Presbyphagia was defined as the presence of oropharyngeal swallowing alterations e.g., penetration, aspiration, pharyngeal residue pooling or premature bolus spillage into the piriform sinus and/or laryngeal vestibule.

Results

32 of 64 participants showed swallowing alterations, mainly characterized by pharyngeal residue, whereas the airway was rarely compromised. In the MEG analysis, participants with presbyphagia activated an increased cortical sensorimotor network during swallowing. As major clinical determinant, participants with swallowing alterations exhibited reduced pharyngeal sensation. Presbyphagia was an independent predictor of a reduced nutritional status in a linear regression model.

Conclusions

Swallowing alterations frequently occur in otherwise healthy older adults and are associated with decreased nutritional status. Increased sensorimotor cortical activation may constitute a compensation attempt to uphold swallowing function due to sensory decline. Further studies are needed to clarify whether the swallowing alterations observed can be considered physiological per se or whether the concept of presbyphagia may need to be extended to a theory with a continuous transition between presbyphagia and dysphagia.

Swallowing and aspiration during sleep in patients with obstructive sleep apnea versus control individuals

Study Objectives

There are only a few reports on voluntary swallowing during sleep; therefore, this study aimed to propose a method for observing voluntary swallowing during sleep using polysomnography. The frequency of voluntary swallowing during sleep and the factors related to swallowing and aspiration during sleep were investigated.

Methods

Polysomnography records of 20 control subjects and 60 patients with obstructive sleep apnea (OSA) (mild, moderate, and severe groups; n = 20 each) were collected. Simultaneous increases in the electromyographic potentials of the submental and masseter muscles, termed coactivation, and declining oronasal airflow (SA) were extracted as “swallowing.” The cough reflex that occurred during sleep was extracted as “aspiration.” The frequency of swallowing events was compared among the different OSA severity groups. Subsequently, a multivariate regression analysis was performed.

Results

The average frequency of coactivation with SA in control subjects was 4.1 events/h and that without SA was 1.7 events/h. These frequencies increased with the severity of OSA during non-REM sleep. The distance of the hyoid to the Frankfurt plane was associated with the frequency of coactivation with (β = 0.298, p = 0.017) as well as without SA (β = 0.271, p = 0.038). The frequency of coactivation without SA was associated with aspiration (B = 0.192, p = 0.042).

Conclusions

Our data provide new insights into the relationship between swallowing and aspiration during sleep. We found that the longer the distance from the hyoid bone to the Frankfurt plane, the higher the coactivation without SA, which could lead to aspiration during sleep.

Clinical Trials

Retrospective observational study of swallowing during sleep in obstructive sleep apnea patients using polysomnography, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000050460, UMIN000044187.

Effects of age and gender on swallowing activity assessed by electromyography and laryngeal elevation

BACKGROUND

Quantitative assessment of swallowing function is necessary to prevent swallowing impairment due to ageing. Though surface electromyography (EMG) has been widely used to measure swallowing activity, the relationship between EMG results and swallowing function is unclear.

OBJECTIVE

This study examined the relationship between the temporal characteristics of muscle activity and laryngeal elevation (LE) during swallowing.

METHODS

This study analysed 60 healthy volunteers in two age groups (young, between 20 and 38 years; old, between 65 and 75 years), each containing the same number of male and female participants. Surface EMG signals were recorded from the suprahyoid and infrahyoid muscle groups (SH-EMG and IH-EMG, respectively). LE was measured using an array of pressure sensors. The participants swallowed 3 mL of water under three swallowing speed conditions: fast, normal and slow swallowing. The EMG duration, EMG time intervals before and after the onset of LE (pre-LE and post-LE intervals, respectively), and the LE velocity were analysed.

RESULTS

Both EMG duration and the post-LE interval of IH-EMG were significantly longer in the older group. As for the gender effect, the pre-LE interval of SH-EMG was significantly longer and the LE velocity was significantly higher in men than in women. Furthermore, there was a negative correlation between pre-LE interval and LE velocity in the fast swallowing condition.

CONCLUSION

Though ageing slightly prolonged the muscle activity time, gender influenced swallowing activity in a more complex manner. Therefore, it is important to take gender into account when examining swallowing function with increasing age.

Assessment of the risk of malnutrition due to aspiration pneumonia and oral feeding difficulty

Introduction

Introduction: many patients with acute-phase swallowing disorders experience malnutrition, which can be caused by oral intake difficulties. Many diseases can cause swallowing difficulties such as aspiration pneumonia, and it is, therefore, necessary to consider the risk of malnutrition during oral feeding therapy in patients with aspiration pneumonia. Objectives: we aimed to evaluate the risk of malnutrition in patients with aspiration pneumonia and other diseases. Methods: the participants comprised 62 patients (45 males, 17 females) with acute-phase swallowing disorders who underwent speech therapy (ST) for swallowing rehabilitation. The patients were divided into four groups: 1) oral feeding with pneumonia, 2) parenteral feeding with pneumonia, 3) oral feeding without pneumonia, and 4) parenteral feeding without pneumonia. The serum albumin and total protein levels were measured to evaluate malnutrition, and swallowing ability was assessed using the Fujishima grade. Results: at the time of ST initiation, serum albumin levels were significantly higher in the oral feeding with pneumonia and oral feeding without pneumonia groups than in the parenteral feeding with pneumonia and parenteral feeding without pneumonia groups. The Fujishima grades differed significantly between the pneumonia/parenteral feeding group and the non-pneumonia/parenteral feeding group. Conclusions: patients with difficulty in swallowing due to aspiration pneumonia were at higher risk of malnutrition than were those without these difficulties. These findings suggest that the nutritional status of parenterally fed patients who developed pneumonia may be inherently poorer than that of orally fed patients.

How addition of peach gel particles to yogurt affects oral behavior, sensory perception and liking of consumers differing in age

Addition of particles to foods, such as fruit pieces to dairy products or vegetable pieces to soup, is a convenient approach to alter nutritional composition, appearance, perception and acceptance. The aim of this study was to investigate the effect of addition of peach gel particles to yogurt on oral behavior, sensory perception and liking of consumers differing in age. One homogeneous yogurt and seven yogurts with peach gel particles were prepared. The added peach gel particles varied in size, fracture stress, or concentration. Oral behavior of n = 62 healthy Dutch, young adults (21 ± 2 years) and n = 62 healthy Dutch elderly (70 ± 5 years) participants was characterized by video recordings. Yogurts' sensory properties and liking were scored on nine-point scales. Elderly consumed yogurts with higher number of chews and longer consumption time leading to lower eating rate than young adults. Addition of particles, regardless of characteristics, increased number of chews, consumption time, and decreased eating rate up to 60% for both consumer groups, with an average decrement of 110 g/min for young and of 63 g/min for elderly consumers. With increasing peach gel hardness and concentration, the number of chews and consumption time increased while eating rate decreased. Peach gel particle size did not affect oral behavior. Sensory perception of yogurts with added peach gel particles was similar for healthy young adult and healthy elderly. Only small differences in sensory perception were observed between the young adults and elderly for flavor attributes, crumbliness, juiciness, and perceived particle size. Similarly, minor differences in liking of a few yogurts with peach pieces were observed between both consumer groups. Thus, healthy ageing seems to affect sensory perception of semi-solid foods to a limited extent only. We conclude that changes in food texture by addition of particles can be used as a strategy to steer eating rate and potentially impact food intake of young adult and elderly consumers while maintaining or enhancing food palatability. Additionally, particle characteristics can be modified to target specific consumer groups that might differ in eating capabilities.

The Importance of Extensional Rheology in Bolus Control during Swallowing

Thickened fluids are commonly used in the medical management of individuals who suffer swallowing difficulty (known as dysphagia). Previous studies have shown that the rheological properties of a liquid affect the flow behavior of the bolus in swallowing, such as pharyngeal transit time. While there is no doubt that shear rheology is a highly important factor for bolus flow, it is suspected that extensional properties of a liquid bolus also plays an important role in swallowing, due to elongation of the bolus as it flows through the oropharynx. Our aim in this work was to observe the effect of extensional viscosity on pharyngeal transit time and elongation of the bolus during swallowing. Eight samples of thickened liquid barium that were shear-controlled, but varied in extensional viscosity and two samples that were extensional-controlled, but varied in shear viscosity were swallowed by eight healthy individuals. Data were collected under lateral view of videofluoroscopy swallow study (VFSS); measures of pharyngeal transit time and the ratio of the length to the width of the bolus on the frame of Upper Esophageal Sphincter (UES) opening were taken from the VFSS recordings. It was observed that the pharyngeal transit time generally increases when the fluids are thickened to higher IDDSI consistency. Additionally, higher extensional viscosity fluids reduced the elongation of the bolus during swallowing, thus potentially reducing the risk of post-swallow residue due to bolus breakage. This study confirmed the relevance of the extensional viscosity of the bolus in swallowing.

The Adult Ts65Dn Mouse Model of Down Syndrome Shows Altered Swallow Function

There are increased risks for deglutition disorders in people with Down syndrome (DS). Although mouse models have been used to study the biological underpinnings of DS in other areas, relatively little is known about swallowing phenotypes in these models. We hypothesized that swallowing performance would be affected in adult mouse models of DS, relative to typical control mice. Videofluoroscopic swallow studies (VFSS) were conducted on adults of two mouse models of DS: Ts65Dn and Dp(16)1Yey, and evaluated in comparison with age-matched controls. Relative to other groups, adult Ts65Dn showed significantly slower swallow rates, longer inter-swallow intervals (ISI), and greater numbers of jaw excursion cycles preceding each swallow. In contrast, adult Dp(16)1Yey mice showed swallowing performance similar to control mice. Exploratory quantitative analyses of the intrinsic tongue (transverse muscle), and extrinsic tongue muscles [genioglossus (GG), styloglossus (SG), and hyoglossus (HG)] showed no significant differences between genotype groups in myosin heavy chain isoform profiles. Collectively, these findings suggest that while swallowing is typical in adult Dp(16)1Yey, swallowing in adult Ts65Dn is atypical due to unknown causes. The finding that adult Ts65Dn may have utility as a model of dysphagia provides new opportunities to elucidate biological underpinnings of dysphagia associated with DS.

Respiratory-Swallow Pattern Following Total Laryngectomy

The goal of this study was to further characterize respiratory patterns in total laryngectomees with attention to respiratory-swallow pattern as it relates to presence/absence of tracheoesophageal puncture (TEP) and bolus consistency. It was hypothesized that participants with TEP would exhibit respiratory-swallow patterns that were significantly different than those without TEP and that bolus consistency (thin or solid) would modulate respiratory-swallow pattern. Data were collected from 12 adults (8 male), aged 46-67 years (mean 57) status post total laryngectomy (1-30 years; average 6 years). Those actively receiving chemoradiation, with history of esophageal cancer, with neurologic disease, with history of lung cancer, with known or suspected recurrence of head and neck cancer (HNC), or with severe cognitive deficits were excluded. Laryngectomy participants were asked to swallow three sips of water and three bites of graham cracker. Submental surface EMG activity was used to detect swallows and a custom stoma mask in line with a pneumotachograph measured airflow during the swallows. Non-parametric Mann-Whitney test for differences was used to detect significance for our dependent variables, TEP or bolus consistency and independent variables, respiratory-swallow pattern. Laryngectomee's showed preference for swallow during inspiration which is inconsistent with the expiratory pattern preference found in healthy adults with intact larynges by McFarland et al. (Respir Physiol Neurobiol 234:89-96, 2016) but consistent with the pattern preference for inspiration (or non-dominant respiratory-swallow phase pattern) found in the HNC population at-large by Brodsky et al. (J Appl Physiol 112(10):1698-1705, 2012). No significant difference was found in swallow pattern with regards to presence/absence of TEP or bolus consistency.

Swallowing Kinematic Differences Across Frozen, Mixed, and Ultrathin Liquid Boluses in Healthy Adults: Age, Sex, and Normal Variability

PURPOSE

The aim of this study was to examine the effects of frozen and mixed-consistency boluses on the swallowing physiology of younger and older adults. We also aimed to quantify factors that lead to increased variability in swallowing outcomes (i.e., age, sex, bolus type).

METHOD

Forty-one healthy adults (18-85 years old) swallowed 5 blocks of 5 different boluses: 10-ml ultrathin liquid, a teaspoon of iced barium, a teaspoon of room-temperature pudding, a teaspoon of frozen pudding, and ultrathin barium with chocolate chips. All data were recorded with videofluoroscopy and underwent detailed timing kinematic measurements.

RESULTS

Neither barium ice nor frozen pudding sped up swallow responses. Many healthy adults initiated swallowing with the bolus as deep as the pyriform sinuses. Swallowing temporal kinematics for ultrathin liquid consistencies are most different from all others tested, requiring the best possible physiological swallowing performance in younger and older healthy individuals (i.e., faster reaction times, longer durations) compared with other bolus types tested. In each measure, older adults had significantly longer durations compared with the younger adults. More variability in swallowing kinematics were seen with age and laryngeal vestibule kinematics.

CONCLUSION

This study provides important contributions to the literature by clarifying normal variability within a wide range of swallowing behaviors and by providing normative data from which to compare disordered populations.

Characterization of pharyngeal peristaltic pressure variability during volitional swallowing in healthy individuals

BACKGROUND

Recent technological advances incorporated in high resolution manometry have justifiably heightened interest in manometric evaluation of the pharynx. Despite this interest, from both physiologic and clinical perspective there remain a number of unanswered questions regarding the magnitude of variability of pharyngeal pressure phenomena. Therefore, the aim of the present study was to characterize in healthy individuals the inter-subject and recording-site specific variability of pharyngeal peristaltic pressure phenomena.

METHODS

We studied 32 healthy subjects (age: 21-83 years,20 under 35 years) during dry,5 and 10 mL water swallows ×3. Pharyngeal peristaltic pressures were recorded using a high resolution (HR) manometric system and a catheter assembly with 36 circumferential sensors spaced at 1 cm intervals positioned trans-nasally to traverse the pharynx, UES and proximal esophagus.

KEY RESULTS

Both site-specific pressure data and the Pharyngeal contractile integral (PhCI) showed wide dispersion ranging between values under 50 mm Hg to over 300 mm Hg and 100-600 mm Hg/cm/s,respectively. There was also wide range of dispersion of data for both the standard deviations and the coefficient of variation for all sites (P=.001). The coefficient of variation for PhCI ranged between 0.02 and 0.25 representing data dispersion of 2-25 percent of the mean among subjects (P=.001). Position, age and volume of swallowed fluid did not influence the magnitude of variability.

CONCLUSIONS

Deglutitive Pharyngeal peristalsis generates pressures with significant degree of site-related and inter-subject variability. This variability is not influenced by age, position and volume of swallowed fluid.

Pharyngeal peristaltic pressure variability, operational range, and functional reserve

The present understanding of pharyngeal motor function remains incomplete. Among the remaining gaps of knowledge in this regard is the magnitude of variability of pharyngeal peristaltic pressure amplitude. Although variability can pose difficulty in interpretation of manometric findings, its magnitude can inform the operational range and reserve of the pharyngeal contractile function. We aimed to define the intra- and intersubject and intersession variability of select pharyngeal manometric parameters and, using this information, determine the number of swallow repetitions for acquiring reliable pharyngeal manometric data. We recorded pharyngeal peristalsis in 10 healthy subjects (age: 50 ± 25 yr, 5 women) by high-resolution manometry during two separate sessions of 20 sequences of 0.5-ml water swallows. Two-way ANOVA showed significant variation in the mean peak peristaltic pressure value across sites (P < 0.0001) as well as within the data at each site (P < 0.0001). Similarly, the pharyngeal contractile integral exhibited significant inter- (P = 0.003) and intrasubject (P < 0.001) variability. The Shapiro-Wilk normality test showed mixed results, in that some sites showed normally distributed data, whereas others did not. A robust Monte Carlo simulation showed that the nominal sample size was different for various tested metrics. For a power of 0.8, commonly accepted as an adequate threshold for acceptable statistical power, the optimal sample size for various peristaltic parameters ranged between 3 and 15. There is significant intra- and intersubject variability in site-specific and integrated parameters of pharyngeal peristalsis. The observed variance indicates a significant operational range and reserve in pharyngeal contractile function while necessitating parameter-specific sample size for reliable results.NEW & NOTEWORTHY Intra- and intersubject variability are significant and different at various sites within the contractile pharynx. In addition, significant swallow-to-swallow and subject-to-subject variability exists in pharyngeal contractile integral. The range of intrasubject variability indicates the existence of broad operational range and reserve. Lastly, our variability studies informed Monte Carlo and power analyses, yielding estimates of sample size that would ensure accurate representation of pressure metric variability.

Effects of age and viscosity on food transport and breathing-swallowing coordination during eating of two-phase food in nursing home residents

AIM

When eating food that contains both liquid and solid phases, the liquid component frequently enters the hypopharynx before swallowing and can increase the risk of aspiration. Thus, we examined whether the initial viscosity of mixed consistency food could alter pre-swallow food transport and breathing-swallowing coordination in older adults.

METHODS

Fiberoptic endoscopy was recorded while 18 healthy young adults and 19 older adults ate 5 g of steamed rice combined with 3 mL of blue-dye water. Liquid viscosity was set at three levels by the addition of a thickening agent (0 wt%, thin; 2 wt%, thicker; 4 wt%, higher-viscosity, respectively). We measured the timing of swallow initiation and its corresponding respiratory phase for each participant.

RESULTS

For thin mixed consistency food, whereas the timing of swallow initiation was comparable between young and older participants, swallowing was initiated during inspiration significantly more often in older participants (31.6 %) than in young participants (5.6 %). In contrast, the timing of swallow initiation was delayed in older participants for thicker and higher-viscosity foods, although swallowing was commonly initiated during expiration in both groups.

CONCLUSIONS

In older adults, we observed that swallow initiation function was preserved for thin mixed consistency samples, but breathing-swallowing coupling was diminished. For higher-viscosity foods, swallow initiation was delayed in this group, but breathing-swallowing coordination was not disturbed, probably as a result of the slow bolus flow into the hypopharynx. Thus, it appears the initial viscosity of mixed consistency food profoundly affects food transport before swallowing as well as breathing-swallowing coordination in nursing home residents. Geriatr Gerontol Int 2017; 17: 2171-2177.

The Effect of Capsaicin-Containing Food on the Swallowing Response

The purpose of this study was to determine the effect of regular ingestion of capsaicin-containing food that is easily available in everyday life on the latency of the swallowing response (LSR). Pickled Napa cabbage was selected as the food for the present study. One portion (10 g) of pickled Napa cabbage provides 1.5 µg of capsaicin. Participants ingested pickled Napa cabbage (10 g) before every meal for 20 days (days 1-20). LSR was measured pre-intervention (day 0) and post-intervention (day 21). The participants then followed their regular diet, without foods containing red pepper, from day 21 to day 27, and LSR was measured on day 28 (follow-up LSR). Sixteen elderly participants (two male, 14 female; age 81.6 ± 9.39 years) and 10 young participants (all female; age 21.6 ± 0.52 years) participated in the study. The pre-intervention LSR was 2.04 ± 1.60 s in elderly participants and 1.27 ± 0.27 s in young participants. In the elderly group, the post-intervention LSR (day 21) was 1.47 ± 1.05  the follow-up LSR (day 28) was 1.99 ± 1.80 s (p = 0.044 and 0.502, respectively, compared to pre-intervention). In the young group, the post-intervention and follow-up LSR values were 1.07 ± 0.20 s and 1.04 ± 0.10 s, respectively (p = 0.016 and 0.038, respectively, compared to pre-intervention). Swallowing function was improved by pickled Napa cabbage containing capsaicin, but capsaicin supplementation may need to be maintained to have an ongoing effect.

Isolated pharyngeal swallow exists during normal human feeding

Swallowing is one of the basic activities in humans. The pharynx functions as an airway and a food channel, and a pharyngeal swallow usually occurs after bolus transport from the oral cavity. However, direct fluid infusion through a catheter into the hypopharynx produces a pharyngeal swallow without the oral stage in experimental situations. The purpose of this study was to examine whether a pharyngeal swallow, which is not accompanied by bolus transport, can occur during normal human feeding. Fifty-three healthy volunteers (25-89 years) were recorded, via videofluoroscopic examination of swallowing, during 3 different swallowing trials: command swallow of 10 ml liquid barium, chew-swallow of corned beef, and chew-swallow of a mixture of corned beef and liquid barium. Subsequently each swallow was classified as being either a consecutive pharyngeal swallow (CPS), following transport, or an isolated pharyngeal swallow (IPS), without immediately prior transport. The location of the bolus at swallow initiation was also noted. Of 307 trials, 681 swallows were identified, which included 43 IPS and 638 CPS. IPS only occurred as the first swallow of a trial, but the frequency of IPS did not differ between 28 younger (< 60 years) and 25 older (≥ 60 years) people. Of the three food types, IPS occurred more frequently with the mixed food than with liquid. These results suggest that IPS may represent an airway protective mechanism. In conclusion, IPS occurs in normal swallowing during a daily eating situation. Swallowing is more complex than a simple reflex.

Videofluoroscopic Validation of a Translational Murine Model of Presbyphagia

Presbyphagia affects approximately 40% of otherwise healthy people over 60 years of age. Hence, it is a condition of primary aging rather than a consequence of primary disease. This distinction warrants systematic investigations to understand the causal mechanisms of aging versus disease specifically on the structure and function of the swallowing mechanism. Toward this goal, we have been studying healthy aging C57BL/6 mice (also called B6), the most popular laboratory rodent for biomedical research. The goal of this study was to validate this strain as a model of presbyphagia for translational research purposes. We tested two age groups of B6 mice: young (4-7 months; n = 16) and old (18-21 months; n = 11). Mice underwent a freely behaving videofluoroscopic swallow study (VFSS) protocol developed in our lab. VFSS videos (recorded at 30 frames per second) were analyzed frame-by-frame to quantify 15 swallow metrics. Six of the 15 swallow metrics were significantly different between young and old mice. Compared to young mice, old mice had significantly longer pharyngeal and esophageal transit times (p = 0.038 and p = 0.022, respectively), swallowed larger boluses (p = 0.032), and had a significantly higher percentage of ineffective primary esophageal swallows (p = 0.0405). In addition, lick rate was significantly slower for old mice, measured using tongue cycle rate (p = 0.0034) and jaw cycle rate (p = 0.0020). This study provides novel evidence that otherwise healthy aging B6 mice indeed develop age-related changes in swallow function resembling presbyphagia in humans. Specifically, aging B6 mice have a generally slow swallow that spans all stages of swallowing: oral, pharyngeal, and esophageal. The next step is to build upon this foundational work by exploring the responsible mechanisms of presbyphagia in B6 mice.

INFLUENCE OF AGE ON SWALLOWS OF A HIGHLY VISCOUS LIQUID BOLUS

Background Swallow function has a decline with aging, mainly in those over 80 years old. In the population over 69 years, about 11% of subjects reported symptoms indicative of significant dysphagia. Objectives Our objective was to evaluate the hypothesis that older asymptomatic subjects before 80 years old have compensations to sustain a safe and efficient swallow, at least with swallows of liquid bolus. Methods We performed videofluoroscopic evaluation of swallows in 55 normal volunteers, a younger group with 33 subjects (16 men and 17 women) aged 19 to 55 years, mean 35.5±9.8 years, and an older group with 22 subjects (15 men and 7 women) aged 56 to 77 years, mean 64.8±6.8 years. The subjects swallowed in duplicate 5 mL and 10 mL of liquid barium with a pH of 7.9, density of 1.82 g/cm3, and viscosity of 895 cp. Results The mean duration of pharyngeal transit, pharyngeal clearance, upper esophageal sphincter opening, hyoid movement and oral-pharyngeal transit were longer in the younger group compared with the older group. The relation between pharyngeal clearance duration and hyoid movement duration was similar in younger and older subjects, for 5 mL and 10 mL bolus volumes. Conclusions On average, a highly viscous liquid bolus crosses the pharynx faster in older subjects (56-77 years old) than in younger subjects (19-55 years old), which suggested an adaptation to the aging process to maintain a safe swallow.

Evaluation of the location of capsules swallowed with food during the pharyngeal phase triggering in asymptomatic adults

OBJECTIVE: To assess the location of hard gelatin capsules in the pharyngeal phase triggering among asymptomatic adults. INTRODUCTION: The location of the bolus during the pharyngeal phase triggering provides information about the sensorimotor model of the beginning of deglutition onset. PURPOSE: To evaluate the location of hard gelatin capsules in the pharyngeal phase triggering among asymptomatic adults. METHODS: A videofluoroscopy swallowing study was carried out in 60 subjects (14 male and 46 female participants) aged between 27 and 55 years, who were evaluated with hard gelatin capsules #00 and #3 containing barium sulfate, swallowed with liquid food and pudding, in free volume. The first laryngeal elevation movement was the criterion to locate the pharyngeal phase triggering. Statistical analysis was based on the McNemar test. RESULTS: Capsule #3 presented higher percentage of location in the tongue dorsum compared to capsule #00, and capsule #00 presented higher percentage of location in the tongue base and vallecula compared to capsule #3. There was a difference between different capsules swallowed with liquid (p=0.016) and pudding (p=0.037). CONCLUSION: The capsule size influenced the location of the pharyngeal phase triggering. Smaller capsules started pharyngeal phase in the most anterior region (tongue dorsum) compared to larger capsules.

Presbyfagie: de invloed van het primair verouderingsproces op de slikfunctie

PRESBYPHAGIA: THE INFLUENCE OF PRIMARY AGING ON SWALLOWING FUNCTION: Elderly often get confronted with swallowing difficulties. It is important to differentiate between presbyphagia, which describes the influence of primary aging on swallow function and dysphagia, which is a pathological swallowing disorder caused by age related diseases and their treatment. In this literature overview the focus is on presbyphagia. The influence of primary aging on the oropharyngeal swallowing function and on other body functions that are indirectly related to swallowing will be discussed. From the literature we learn that in primary aging a number of functions stay preserved, a number of functions deteriorate, and some compensatory mechanisms are evident. The swallow safety as such however, stays preserved. To conclude with we discuss some clinical implications concerning both the detection of swallowing disorders in the elderly and the establishment of preventive action for the healthy elderly.

The effect of bilateral superior laryngeal nerve lesion on swallowing: a novel method to quantitate aspirated volume and pharyngeal threshold in videofluoroscopy

The purpose was to determine the effect of bilateral superior laryngeal nerve (SLN) lesion on swallowing threshold volume and the occurrence of aspiration, using a novel measurement technique for videofluoroscopic swallowing studies (VFSS) in infant pigs. We used a novel radiographic phantom to assess volume of the milk containing barium from fluoroscopy. The custom made phantom was firstly calibrated by comparing image intensity of the phantom with known cylinder depths. Secondly, known volume pouches of milk in a pig cadaver were compared to volumes calculated with the phantom. Using these standards, we calculated the volume of milk in the valleculae, esophagus and larynx, for 205 feeding sequences from four infant pigs feeding before and after had bilateral SLN lesions. Swallow safety was assessed using the tested and validated IMPAS (Dysphagia 28(2):178-187, 2013). The log-linear correlation between image intensity values from the phantom filled with barium milk and the known phantom cylinder depths was strong (R (2) > 0.95), as was the calculated volumes of the barium milk pouches. The threshold volume of bolus in the valleculae during feeding was significantly larger after bilateral SLN lesion than in control swallows (p < 0.001). The IMPAS score increased in the lesioned swallows relative to the controls, indicating substantially impaired swallowing (p < 0.001). Bilateral SLN lesion dramatically increased the aspiration incidence and the threshold volume of bolus in valleculae. The use of this phantom permits quantification of the aspirated volume of fluid, allowing for more accurate 3D volume estimation from 2D X-ray in VFSS.

Aspiration Induced by Remifentanil

Background:

Remifentanil is widely used for monitored anesthesia care in spontaneously breathing patients. However, the authors’ previous studies have shown that remifentanil induces subjective swallowing difficulties, which may increase the risk of aspiration.

Methods:

Twenty-five healthy volunteers participated in a double-blind, randomized, crossover trial at the University Hospital in Örebro, Örebro, Sweden. The volunteers were studied on two different occasions during which they received either remifentanil with an effect-site target concentration of 3 ng/ml or saline over 1 h. A radionuclide tracer was infused simultaneously into the nasopharynx at a rate of 0.1 ml/min. Aspiration was determined by lung scans, and subjective swallowing difficulties and grip strength were evaluated. The primary outcome was the difference in occurrence of aspiration between remifentanil and placebo treatments. The secondary outcomes were differences in swallowing difficulty and grip strength and the association between aspiration and swallowing difficulty.

Results:

During remifentanil and placebo infusion, 48 and 12% of the volunteers aspirated, respectively, difference: 36% (95% CI, 10 to 62%). A similar significant difference was found for swallowing difficulties but not for the association between aspiration and swallowing. No difference was found in grip strength between the two treatments.

Conclusions:

Remifentanil infusion at concentrations used in monitored anesthesia care increases the incidence of aspiration. However, the subjective swallowing difficulty induced by remifentanil is not indicative of the aspiration risk.

The normative range for and age and gender effects on the Sydney Swallow Questionnaire (SSQ)

The Sydney Swallow Questionnaire (SSQ) is a validated measure of the symptomatic severity of oral-pharyngeal dysphagia. Up until now no normative ranges have been established for the questionnaire. This is a limitation in its utility as it makes it difficult to use the tool to identify the prevalence and burden of oral-pharyngeal dysphagia in the general population or within patient populations. The study's aim was to derive the normative range of dysphagia scores for the SSQ and to determine whether, in nondysphagic individuals, there are any age or gender effects on these scores. The questionnaire was administered to 73 eligible nondysphagic individuals who had been screened for any dysphagia or conditions that might predispose them to dysphagia. The frequency distribution of SSQ scores was first examined for normality and appropriate transformations performed before determining the upper limit of normal. Of the 73 healthy participants, 45 were male, and the cohort had a mean age of 58.6 years (range = 22.0-82.1 years). No statistically significant relationship between SSQ scores and either age (r s[73] = 0.140, p = 0.239) or gender (r pb[73] = 0.021, p = 0.857) was found. The mean total SSQ score (maximum possible score = 1,700) was 59.0 (SD = 56.7; range = 2-241). The frequency distribution of scores was non-normal and markedly skewed. After a Box-Cox transformation to normalise the distribution, the calculated upper limit of the reference interval was 234 with a 90 % CI of [193, 277]. The SSQ scores in a nondysphagic population are not influenced by age or gender. These data complement the existing reliability and validation data and thereby improve the overall utility of the SSQ in the context of future studies of oral-pharyngeal dysphagia prevalence, efficacy, and outcome.

Video-endoscopic comparison of swallowing waxy rice mochi and waxy wheat mochi: improvement of a traditional Japanese food that presents a choking hazard

Mochi is highly cohesive and adhesive, and easy to choke on. Many of the fatal suffocation accidents with mochi occur in the elderly aged 65 years or older. These circumstances prompted us to investigate a special property of waxy wheat which is similar in texture to waxy rice, but is less cohesive and adhesive. We compared the differences in chewing and swallowing movements associated with eating waxy rice mochi and waxy wheat mochi between healthy adults and healthy elderly. Healthy elderly chewed mochi more and longer than healthy adults. Although there was no difference in the number of chewing cycles or total duration of chewing between the two types of mochi, waxy wheat mochi was easier to chew and left less pharyngeal residue. These findings lead us to suggest that waxy wheat mochi is promising as a food that is easy to swallow and difficult to choke on.

Effect of aging on hypopharyngeal safe volume and the aerodigestive reflexes protecting the airways

OBJECTIVES/HYPOTHESIS

Studies on young volunteers have shown that aerodigestive reflexes are triggered before the maximum volume of fluid that can safely collect in the hypopharynx before spilling into the larynx is exceeded (hypopharyngeal safe volume [HPSV]). The objective of this study was to determine the influence of aging on HPSV and pharyngo-glottal closure reflex (PGCR), pharyngo-UES contractile reflex (PUCR), and reflexive pharyngeal swallow (RPS).

STUDY DESIGN

Comparison between two groups of different age ranges.

METHODS

Ten young (25 ± 3 standard deviation [SD] years) and 10 elderly (77 ± 3 SD years) subjects were studied. PGCR, PUCR, and RPS were elicited by perfusing water into the pharynx rapidly and slowly. HPSV was determined by abolishing RPS with pharyngeal anesthesia.

RESULTS

Frequency-elicitation of PGCR and PUCR were significantly lower in the elderly compared to the young during slow water perfusion (47% vs. 97% and 40% vs. 90%, respectively, P < .001). RPS was absent in five of the 30 (17%) slow injections in the elderly group. In these elderly subjects, HPSV was exceeded and laryngeal penetration of the water was seen. The threshold volume to elicit PGCR, PUCR, and RPS was significantly lower than the HPSV during rapid injections. Except for RPS, these volumes were also significantly lower than HPSV during slow injections.

CONCLUSIONS

PGCR, PUCR, and RPS reflexes are triggered at a threshold volume significantly lower than the HPSV in both young and elderly subjects. Lower frequency-elicitation of PGCR, PUCR, and RPS in the elderly can predispose them to the risks of aspiration.

Temporal measurements of deglutition in dynamic magnetic resonance imaging versus videofluoroscopy

OBJECTIVES

We undertook to provide data regarding temporal measurements of swallow function obtained by dynamic magnetic resonance imaging in a midsagittal plane and to compare these values to normative fluoroscopy data.

METHODS

Seventeen healthy female volunteers with no swallowing complaints underwent turbo-fast low-angle-shot magnetic resonance imaging with a 3-T scanner while swallowing liquid and pudding boluses delivered via syringe. Ninety sequential images were acquired with a temporal resolution of 113 ms per frame for each swallow. The imaging was performed in the midsagittal plane. The analyses focused on oral and pharyngeal transit times.

RESULTS

All subjects tolerated the protocol without complaints or adverse events. The mean (+/- SD) oral transit times for liquids and pudding were measured as 0.25 +/- 0.09 second and 0.25 +/- 0.13 second, respectively. This difference was not statistically significant (p = 0.74). The mean pharyngeal transit times for liquids and pudding were measured as 0.84 +/- 0.16 second and 1.11 +/- 0.21 seconds, respectively. This difference achieved statistical significance (p < 0.0001). The intrarater and inter-rater reliabilities for the measurements were excellent.

CONCLUSIONS

This sequence provided a high degree of temporal resolution of deglutition in the midsagittal plane. Furthermore, the temporal measurements acquired with dynamic magnetic resonance imaging were reliable and were relatively consistent with those of previous studies done with videofluoroscopy.

Swallowing frequency in elderly people during daily life

Disuse atrophy of swallowing-related organs due to an excessive decrease in swallowing frequency is suspected to occur in patients with poor oral intake, especially elderly people. However, swallowing frequency in daily life has not previously been examined in the elderly. This study examined swallowing frequency in elderly people and compared these findings to those in a younger population and differences in the degree of activity in daily life. (i) We compared swallowing frequency in 20 elderly people (82·0 ± 8·3 year) and 15 healthy young people (26·5 ± 3·5 year). (ii) 20 elderly people were divided into two groups according to the degree of activity in daily life: a semi-bedridden group and bedridden group; the swallowing frequency was compared between these groups. (i) The swallowing frequency in the elderly people was 2-19 times per hour and the mean was 9·4 ± 4·9, and that in the healthy young people was 16-76 times per hour and the mean was 40·7 ± 19·5. Swallowing frequency in elderly people was significantly lower than that in young healthy people (P < 0·0001). (ii) The swallowing frequency in bedridden group was 2-11 times per hour and the mean was 6·8 ± 3·3, and that in semi-bedridden group was 3-19 times per hour and the mean was 11·9 ± 5·1. Swallowing frequency in bedridden group was significantly lower than that in semi-bedridden group (P < 0·05). These results indicate that in daily life, elderly people tend to swallow less frequently than young people. In addition, swallowing frequency was lower in elderly subjects with a low degree of activity in daily life.

The effect of unilateral superior laryngeal nerve lesion on swallowing threshold volume

OBJECTIVES/HYPOTHESIS

The superior laryngeal nerve (SLN) is the major sensory nerve for the upper larynx. Damage to this nerve impacts successful swallowing. The first aim of the study was to assess the effect of unilateral SLN lesion on the threshold volume sufficient to elicit swallowing in an intact pig model; this volume was defined radiographically as the maximum bolus area visible in lateral view. The second aim was to determine if a difference existed between ipsilateral and contralateral function as a result of unilateral sensory loss, measured as the radiologic density of fluid seen in the valleculae. Finally, we determined whether there was a relationship between the threshold volume and the occurrence of aspiration after a unilateral SLN lesion.

STUDY DESIGN

Repeated measures animal study.

METHODS

Four female infant pigs underwent unilateral SLN lesion surgery. The maximum vallecular bolus area in lateral view and the relative vallecular density on each side in the dorsoventral view were obtained from videofluoroscopic recordings in both the prelesion control and postlesion experimental states.

RESULTS

In lateral view, the lesioned group had a larger maximum bolus area than the control group (P < .001). Although occasional left-right asymmetry in the dorsoventral view was observed, the vallecular densities were, on average, equal on both the left (intact) and right (lesioned) sides (P > .05). A bigger maximum bolus area did not predict aspiration in the lesioned group (P > .05).

CONCLUSIONS

Unilateral SLN lesions increased the swallowing threshold volume symmetrically in right and left valleculae, but the increased threshold may not be the main mechanism for the occurrence of aspiration.

Effect of viscosity on food transport and swallow initiation during eating of two-phase food in normal young adults: a pilot study

When eating food containing both liquid and solid phases (two-phase food), the liquid component frequently enters the hypopharynx before swallowing, which may increase the risk of aspiration. We therefore tested whether preswallow bolus transport and swallow initiation would change as the viscosity of two-phase food was increased. Fiberoptic endoscopy was recorded while 18 adult subjects ate 5 g of steamed rice with 3 ml of blue-dye water. Liquid viscosity was set at four levels by adding a thickening agent (0, 1, 2, and 4 wt%, respectively). We measured the timing of the leading edge of the food reaching the base of the epiglottis, as well as the location of the leading edge at swallow initiation. As viscosity increased, the leading edge of the food reached the epiglottis significantly later during chewing and was higher in the pharynx at swallow onset. The time after the leading edge reached the epiglottis did not vary among the viscosities of the two-phase food. This study found that the initial viscosity of two-phase food significantly altered oropharyngeal bolus flow and the timing of swallow initiation. Accordingly, increased two-phase food viscosity may delay food entry into the pharynx and be of use in dysphagic diets.

Evaluation of volitional and reflexive swallowing in elderly patients with a history of pneumonia

OBJECTIVES

Precise assessment of the risk of aspiration is critical in older patients with a history of pneumonia. However, the currently popular videofluoroscopic and videoendoscopic examinations of swallowing only evaluate volitional swallowing. A method for quantitative analysis of reflexive swallowing is not yet available.

METHODS

We evaluated volitional swallowing in the sitting position by videoendoscopic examination and then measured the volume of injected water that triggered reflexive swallowing in the supine position in 54 patients with a history of pneumonia and 24 control patients of a similar age who had no history of pneumonia.

RESULTS

The volume of injected water that triggered reflexive swallowing was larger in the pneumonia group than in the control group (mean, 1.64 +/- 0.61 mL versus 0.71 +/- 0.28 mL; p < 0.001). Both impaired volitional swallowing and impaired reflexive swallowing independently correlated with a history of pneumonia.

CONCLUSIONS

The endoscopic supine swallow-evoking test ("ESSET") may detect previously omitted risk factors for aspiration in patients who can volitionally swallow.

Development of a swallowing frequency meter using a laryngeal microphone

Disuse atrophy of swallowing-related organs is suspected when decreased swallowing frequency is seen in the elderly. However, swallowing frequency has not been examined in elderly people during daily life. We developed a swallowing frequency meter containing a laryngeal microphone that does not restrict the subject's ability to perform daily activities. In this study, the utility of the meter was assessed. Experiment 1: The ability of the meter to detect swallowing was examined. The subject was instructed to swallow saliva or foods at a voluntarily pace. During these procedures, swallowing events were simultaneously recorded by the meter, self-enumeration and videofluorography. As a result, all of the swallowing events identified by the meter coincided with the swallowing events identified by self-enumeration and videofluorography. Experiment 2: Swallowing sounds display various patterns both between and within individuals. Therefore, we examined the concordance rate between the number of swallowing events counted by the meter and that counted by self-enumeration in 15 subjects over a longer period than in experiment 1. The concordance rates calculated by two examiners between the meter and self-enumeration were 96·8 ± 4·5% and 98·9 ± 3·3% at rest and 95·2 ± 4·5% and 96·1 ± 4·1% during meals, respectively. Our findings indicate that this meter is useful for measuring the frequency of swallowing during daily situations.

Adaptation of swallowing hyo-laryngeal kinematics is distinct in oral vs. pharyngeal sensory processing

Before a bolus is pushed into the pharynx, oral sensory processing is critical for planning movements of the subsequent pharyngeal swallow, including hyoid bone and laryngeal (hyo-laryngeal) kinematics. However, oral and pharyngeal sensory processing for hyo-laryngeal kinematics is not fully understood. In 11 healthy adults, we examined changes in kinematics with sensory adaptation, sensitivity shifting, with oropharyngeal swallows vs. pharyngeal swallows (no oral processing), and with various bolus volumes and tastes. Only pharyngeal swallows showed sensory adaptation (gradual changes in kinematics with repeated exposure to the same bolus). Conversely, only oropharyngeal swallows distinguished volume differences, whereas pharyngeal swallows did not. No taste effects were observed for either swallow type. The hyo-laryngeal kinematics were very similar between oropharyngeal swallows and pharyngeal swallows with a comparable bolus. Sensitivity shifting (changing sensory threshold for a small bolus when it immediately follows several very large boluses) was not observed in pharyngeal or oropharyngeal swallowing. These findings indicate that once oral sensory processing has set a motor program for a specific kind of bolus (i.e., 5 ml water), hyo-laryngeal movements are already highly standardized and optimized, showing no shifting or adaptation regardless of repeated exposure (sensory adaptation) or previous sensory experiences (sensitivity shifting). Also, the oral cavity is highly specialized for differentiating certain properties of a bolus (volume) that might require a specific motor plan to ensure swallowing safety, whereas the pharyngeal cavity does not make the same distinctions. Pharyngeal sensory processing might not be able to adjust motor plans created by the oral cavity once the swallow has already been triggered.

Functional MRI of swallowing: from neurophysiology to neuroplasticity

Swallowing is a complex neurogenic sensorimotor process involving all levels of the neuraxis and a vast number of muscles and anatomic structures. Disruption of any of these anatomic or functional components can lead to swallowing disorders (also known as dysphagia). Understanding the neural pathways that govern swallowing is necessary in diagnosing and treating patients with dysphagia. Functional MRI (fMRI) is a prevalent and effective neuroimaging method that has been used to study the complex neurophysiologic control of swallowing in vivo. This article presents a summary of the research studies that have used fMRI to study the neural control of swallowing in normal subjects and dysphagic patients, and to investigate the effects of swallowing treatments on neuroplasticity. Methodologic challenges and caveats are discussed, and a case study of a pre-posttreatment paradigm is presented to highlight potential future directions of fMRI applications in swallowing research and clinical practice.

Pharyngeal airway protective reflexes are triggered before the maximum volume of fluid that the hypopharynx can safely hold is exceeded

Aerodigestive reflexes triggered by pharyngeal stimulation can protect the airways by clearing fluid from the pharynx. The objective of this study was to determine the relationship between the maximum capacity of fluid that can safely dwell in the hypopharynx [hypopharyngeal safe volume (HPSV)] before spilling into the larynx and the threshold volumes required to trigger pharyngoglottal closure reflex (PGCR), pharyngo-upper esophageal sphincter contractile reflex (PUCR), and reflexive pharyngeal swallow (RPS). Twenty-five healthy volunteers (mean age 24 yr, 8 males) were studied in the semi-inclined supine position. PGCR, PUCR, and RPS were elicited using techniques of concurrent upper esophageal sphincter manometry and pharyngo-laryngoscopy. The hypopharynx was then anesthetized to abolish RPS. HPSV was determined by infusing water in the pharynx, and perfusion was stopped when the infusate reached the superior margin of the interarytenoid fold. The threshold volumes for triggering PGCR, PUCR, and RPS by slow and rapid injections before pharyngeal anesthesia were 0.18 ± 0.02 and 0.09 ± 0.02 ml; 0.20 ± 0.020 and 0.13 ± 0.04 ml; and 0.61 ± 0.04 and 0.4 ± 0.06 ml, respectively. All of the above volumes were significantly smaller than the HPSV (0.70 ± 0.06 ml, P < 0.01) except for the threshold volume to elicit RPS during slow perfusion, which was not significantly different (P = 0.23). We conclude that pharyngeal aerodigestive reflexes are triggered by both slow and rapid pharyngeal perfusion of water at significantly smaller volumes than the maximum capacity of the hypopharynx to safely hold contents without spilling into the airway. These reflexes thereby aid in prevention of aspiration.

Protective role of aerodigestive reflexes against aspiration: study on subjects with impaired and preserved reflexes

BACKGROUND & AIMS

Direct evidence to support the airway protective function of aerodigestive reflexes triggered by pharyngeal stimulation was previously demonstrated by abolishing these reflexes by topical pharyngeal anesthesia in normal subjects. Studies have also shown that these reflexes deteriorate in cigarette smokers. Aim of this study was to determine the influence of defective pharyngeal aerodigestive reflexes on airway protection in cigarette smokers.

METHODS

Pharyngoglottal Closure reflex; PGCR, Pharyngo-UES Contractile reflex; PUCR, and Reflexive Pharyngeal Swallow; RPS were studied in 15 healthy non-smokers (24.2±3.3 SD y, 7 males) and 15 healthy chronic smokers (27.3±8.1, 7 males). To elicit these reflexes and to evaluate aspiration, colored water was perfused into the hypopharynx at the rate of 1 mL/min. Maximum volume of water that can safely dwell in the hypopharynx before spilling into the larynx (Hypopharyngeal Safe Volume; HPSV) and the threshold volume to elicit PGCR, PUCR, and RPS were determined in smokers and results compared with non-smokers.

RESULTS

At baseline, RPS was elicited in all non-smokers (100%) and in only 3 of 15 smokers (20%; P<.001). None of the non-smokers showed evidence of laryngeal spillage of water, whereas 12 of 15 smokers with absent RPS had laryngeal spillage. Pharyngeal anesthesia abolished RPS reflex in all non-smokers resulting in laryngeal spillage. The HPSV was 0.61±0.06 mL and 0.76±0.06 mL in non-smokers and smokers respectively (P=.1).

CONCLUSIONS

Deteriorated reflexive pharyngeal swallow in chronic cigarette smokers predispose them to risks of aspiration and similarly, abolishing this reflex in non-smokers also results in laryngeal spillage. These observations directly demonstrate the airway protective function of RPS.

Reduced somatosensory activations in swallowing with age

Understanding the neural functional organization of swallowing in healthy elders is essential in diagnosing and treating older adults with swallowing difficulties. The primary aims of this investigation were to identify the neural activation sites of different components of deglutition in healthy elders using functional Magnetic Resonance Imaging (fMRI) and to investigate age differences in the neural control of swallowing. Ten young (age range 19-25 years of age) and nine older (age range 66-77 years of age) right-handed healthy individuals were scanned in a 3-Tesla MRI scanner. Subjects were visually cued for both a "Swallow" task and for component/control tasks ("Prepare to swallow," "Tap your tongue," and "Clear your throat"). Behavioral interleaved gradient (BIG) methodology was used to address movement related artifacts. Between-group comparisons revealed statistically stronger activations in the primary somatosensory cortex of young adults during the motor tasks examined. Both groups showed activations in the major motor areas involved in the initiation and execution of movement; however, areas involved in sensory processing, sensorimotor integration and/or motor coordination and control, showed reduced or limited activity in the elderly. Potential implications of these findings for clinical practice are discussed.

Voluntary versus spontaneous swallowing in man

This review examines the evidence regarding the clinical and neurophysiological differences between voluntary and spontaneous swallows. From the clinical point of view, voluntary swallow (VS) occurs when a human has a desire to eat or drink during the awake and aware state. Spontaneous swallow (SS) is the result of accumulated saliva and/or food remnants in the mouth. It occurs without awareness while awake and also during sleep. VS is a part of eating behavior, while SS is a type of protective reflex action. In VS, there is harmonized and orderly activation of perioral, lingual, and submental striated muscles in the oral phase. In SS, the oral phase is bypassed in most cases, although there may be partial excitation. Following the oral phase, both VS and SS have a pharyngeal phase, which is a reflex phenomenon that protects the upper airway from any escape of food and direct the swallowed material into the esophagus. This reflexive phase of swallowing should not be confused with SS. VS and SS are similar regarding their dependence on the swallowing Central Pattern Generator (CPG) at the brainstem, which receives sensory feedback from the oropharynx. There are differences in the role of the corticobulbar input between VS and SS.

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.

Review: treatment of gastroesophageal reflux disease in the elderly

The prevalence of gastroesophageal reflux disease (GERD) increases with age; older patients are more likely to develop severe disease. Common symptoms of GERD in the elderly include dysphagia, vomiting, and respiratory problems. Older patients are more likely to require aggressive therapy, and usually their management is compounded by the presence of comorbidities and consumption of various medications. Proton pump inhibitors are the mainstay of GERD treatment in the elderly because of their profound and consistent acid suppressive effect. Overall, proton pump inhibitors seem to be safe for both short- and long-term therapy in elderly patients with GERD. Antireflux surgery may be safe and effective in a subset of elderly patients with GERD.