Bolus aggregation in the oropharynx does not depend on gravity

OBJECTIVE

To determine whether bolus aggregation in the oropharynx (before swallowing) depends on gravity.

DESIGN

Before-during trial, with subjects serving as their own controls.

SETTING

Hospital radiology suite.

PARTICIPANTS

Five asymptomatic adult volunteers.

INTERVENTIONS

Videofluorography was performed while subjects ate soft and hard foods containing barium, first seated upright and then kneeling face down (quadruped position).

MAIN OUTCOME MEASURES

Duration of food processing in the oral cavity, bolus aggregation in the valleculae, and pharyngeal swallow.

RESULTS

Transport of chewed solid food from the oral cavity to the oropharynx (stage II transport) typically started several seconds before onset of swallow, regardless of head position or initial food consistency. Bolus aggregation in the valleculae (between the epiglottis and the tongue) began an average of 1.7 +/- 2.5sec before the onset of the pharyngeal swallow (p < .001). Stage II transport was driven by tongue-palate contact.

CONCLUSIONS

Transport of chewed solid food from the oral cavity to the pharynx is driven actively by tongue-palate contact and does not depend on gravity. A bolus may accumulate in the valleculae for several seconds before the swallow.

Kinetic magnetic resonance imaging analysis of swallowing: a new approach to pharyngeal function

The emergence of turbo-FLASH MR sequences allows us to acquire five 10-mm sections each second and thus to catch images of the soft tissues during function. One can trace the pathway of a liquid between the tongue, the soft palate, the epiglottis and the pharyngeal apparatus and analysis the role of the anatomic structures during swallowing. Restricted to the sagittal plane for the purpose of this preliminary study, this technique can be extended to the other planes to provide a three-dimensional analysis of oropharyngeal function or dysfunction.

Predictors of aspiration pneumonia: how important is dysphagia?

Aspiration pneumonia is a major cause of morbidity and mortality among the elderly who are hospitalized or in nursing homes. Multiple risk factors for pneumonia have been identified, but no study has effectively compared the relative risk of factors in several different categories, including dysphagia. In this prospective outcomes study, 189 elderly subjects were recruited from the outpatient clinics, inpatient acute care wards, and the nursing home care center at the VA Medical Center in Ann Arbor, Michigan. They were given a variety of assessments to determine oropharyngeal and esophageal swallowing and feeding status, functional status, medical status, and oral/dental status. The subjects were followed for up to 4 years for an outcome of verified aspiration pneumonia. Bivariate analyses identified several factors as significantly associated with pneumonia. Logistic regression analyses then identified the significant predictors of aspiration pneumonia. The best predictors, in one or more groups of subjects, were dependent for feeding, dependent for oral care, number of decayed teeth, tube feeding, more than one medical diagnosis, number of medications, and smoking. The role that each of the significant predictors might play was described in relation to the pathogenesis of aspiration pneumonia. Dysphagia was concluded to be an important risk for aspiration pneumonia, but generally not sufficient to cause pneumonia unless other risk factors are present as well. A dependency upon others for feeding emerged as the dominant risk factor, with an odds ratio of 19.98 in a logistic regression model that excluded tube-fed patients.

Effects of bolus volume on oropharyngeal swallowing: an electrophysiologic study in man

OBJECTIVE

Different variables of oropharyngeal swallowing change in response to bolus volume and consistency as determined by manometric/videofluoroscopic studies. But the subject is debatable especially from the physiologic point of view. No electrophysiologic studies are available on human subjects.

METHODS

The effects of bolus volume and viscosity on different variables of oropharyngeal swallowing were investigated using electrophysiologic methods. Mechanical upward and downward laryngeal movements and submental electromyographic (SM-EMG) activity of the laryngeal elevator muscles were recorded during dry and 3-, 10-, and 20-ml water swallowing in 14 normal subjects. Cricopharyngeus (CP) muscle was investigated during 3- and 10-ml water swallowing in 10 normal subjects. Semisolid and liquid swallowing were compared in eight normal subjects.

RESULTS

The total duration of SM-EMG, time necessary for larynx elevation, CP-EMG pause related with upper esophageal sphincter opening and swallowing variability (jitter) all increased significantly with increasing bolus volume. Laryngeal superior relocation time and CP-EMG pause were shorter for semisolid swallowing compared with swallowing the same amount of liquid.

CONCLUSION

The duration of SM-EMG activity, laryngeal upward-downward movements, and CP-EMG pause are affected by sensory inputs such as volume and viscosity of the bolus swallowed. The results indicate that sensory input modifies the central swallowing pattern although basic events remain the same in normal human subjects.

Valve obturation of the nasopharynx

Complete obturation of the nasopharynx can cause functional problems with breathing and swallowing due to obstruction of the nasal airway. A technique is described whereby a one way valve was incorporated in an obturator to allow normal nasal inspiration whilst maintaining an oropharyngeal seal during swallowing and speech.

Function of upper esophageal sphincter during swallowing: the grabbing effect

This study investigated deglutitive axial force developed within the pharynx, upper esophageal sphincter (UES), and cervical esophagus. Position and deglutitive excursion of the UES were determined using combined manometry and videofluoroscopy in eight healthy volunteers. Deglutitive clearing force was quantified with a force transducer to which nylon balls of 6- or 8-mm diameter were tethered and positioned within the oropharynx, hypopharynx, UES, and cervical esophagus. Axial force recordings were synchronized with videofluoroscopic imaging. Clearing force was dependent on both sphere diameter (P < 0.05) and location, with greater force exhibited in the hypopharynx and UES compared with the oropharynx and esophagus (P < 0.05). Within the UES, the onset of traction force coincided with passage of the pharyngeal clearing wave but persisted well beyond this. On videofluoroscopy, the persistent force was associated with the aboral motion of the ball caught within the UES. Force abated with gradual slippage of the UES around the ball. The force attributable to the combination of UES contraction and laryngeal descent was named the grabbing effect. The grabbing effect functions to transfer luminal contents distal to the laryngeal inlet at the end of the pharyngeal swallow, presumably acting to prevent regurgitation and/or aspiration of swallowed material.

Neuronal activation of the hypothalamic magnocellular system in response to oropharyngeal stimuli in the rat

The present study was designed to delineate the neuronal site, the nature, and the gastrointestinal origin of the stimulation of the hypothalamic magnocellular system induced by the ingestion of sweetened condensed milk. Concomitant localization of the c-fos protein (Fos) with either arginine-vasopressin (AVP) mRNA or oxytocin (OT) mRNA in the paraventricular nucleus of the hypothalamus (PVH) and the supraoptic nucleus (SON) revealed that the hypothalamic neurons containing AVP and OT were activated following ingestion of sweetened condensed milk. Expression of c-fos mRNA was also determined in rats implanted with a gastric cannula that allowed for real, sham, and gastric feeding of sweetened condensed milk. The results provide evidence that the stimulation of the PVH and SON induced by sweetened condensed milk originate from oropharyngeal stimuli. Indeed, in real-and sham-fed rats, the postprandial levels of c-fos mRNA in the PVH and SON were significantly higher than the preprandial values, whereas there was no early postprandial rise in c-fos mRNA levels within the magnocellular division of the PVH and SON after gastric feeding. The results of this study also suggested that the stimulation of the PVH and SON induced by sweetened condensed milk was related to the hypertonicity of the milk, indeed, ingestion of an hypertonic solution of sucrose with a carbohydrate content close to that of sweetened condensed milk led to a stimulation of the PVH and SON that was comparable to that induced by the milk, whereas ingestion of an isotonic solution of sucrose did not trigger any significant activation of the PVH and SON. Taken together, the present results indicate that magnocellular neurosecretory neurons are sensitive to oropharyngeal stimuli and further support the view of the existence of oropharyngeal osmoreceptors.

Oral sensory discrimination of fluid viscosity

This study was designed to investigate the ability of normal young adult volunteers to sensorially identify Newtonian fluids of specified viscosities. Twenty subjects, 10 men and 10 women between the ages of 18 and 29 years participated. Seven stimuli, consisting of combinations of corn syrup and water, with viscosities ranging from 2 to 2,240 centipoise (cP) were prepared and characterized using a coaxial rotational viscometer. Subjects were presented with two anchor stimuli representing the extremes of the range of viscosities as a basis from which the experimental stimuli were judged. The seven experimental stimuli were randomly presented to each subject 10 times. The accuracy with which the subjects identified the viscosity of the fluid was significant at p < 0.01. The pattern of response was not significantly different across subjects nor gender. There were no differences in performance throughout the duration of the study. The repeat presentation of the anchor points did not significantly affect performance. Further research on oral perception of viscosity, and the processes that mediate changes in swallow physiology resulting from changes in viscosity is required.

[A simple method for improvement of the measurement of respiratory impedance in humans by increasing oropharyngeal impedance using cheek and mouth floor clamps]

It is known, that the upper airway (oropharyngeal) impedance (Z(op)) influences the measured input impedance of the respiratory system (Zrs). This investigation deals with simple methods reducing the artefact caused by Z(op). The following methods have been examined: (1) Supporting the cheeks with fingers, (2) supporting the cheeks and the floor of the mouth with fingers and (3) using a new mechanical clamp for the cheeks and the floor of the mouth. The effect of these procedures on Zrs, were investigated on two subjects. Also Z(op) has been estimated during a voluntary closure of the glottis (VALSALVA manoeuvre). The impedance has been assessed as well with forced sine shaped oscillations as with the pulsatile technique. All three procedures show, compared to measurements without any support, an increase of the Zrs, especially at high values. The highest increase has been obtained while using the clamp (up to 50%). The varied impedance must be placed in parallel to Zrs, because Z(op) increases even more than Zrs. So, by applying the clamp the subjects is better coupled to the measuring system. The clamp is easy to handle, leads to more exact values, and increases the inter- and intra-individual reproducibility.

Cranial nerve modulation of human cortical swallowing motor pathways

Animal data indicate that cortical swallowing pathways can be modulated by cranial nerve afferent stimulation. We therefore studied the effects of human trigeminal and vagal nerve excitation on the corticofugal pathways to the oropharynx and esophagus, using electromagnetic stimulation. Unilateral stimulation of either the trigeminal or vagus nerve evoked two distinct reflex electromyographic responses in the pharynx and esophagus, an early response (latency range 19-30 ms) and a late response (latency range 42-72 ms). In the mylohyoid muscles, however, only a single response was seen (latency range 36-64 ms). Cortical stimulation also evoked electromyographic responses in the mylohyoid muscles, pharynx, and esophagus, with latencies of 8.5 +/- 0.3, 9.3 +/- 0.3, and 10.1 +/- 0.4 ms, respectively. When either trigeminal or vagus nerve stimulation preceded cortical stimulation, the cortically evoked responses were facilitated, with maximal effects at interstimulation intervals of 30-200 ms for pharynx and esophagus (P < 0.02) and at interstimulation intervals of 50-100 ms for mylohyoid muscles (P < 0.05). Our results demonstrate that stimulation of human cranial nerve afferent fibers facilitates cortical swallowing motor pathways.

A comparison of nasal resistance in white Caucasians and blacks

Total nasal resistance was measured in 42 white caucasian and 32 black healthy adults by both anterior and posterior rhinomanometry after using a nasal decongestant. The nasal airway resistance was found to be lower in the blacks compared to the caucasians by both anterior and posterior methods. The mean total nasal airway resistance was 0.136 Pa/ cm3/s in the blacks and 0.179 Pa/cm3/s in the caucasians by the anterior method, and 0.134 Pa/cm3/s and 0.161 Pa/cm3/s, respectively, by the posterior method. These differences were highly statistically significant.

The distribution and origin of keratin 20-containing taste buds in rat and human

Sections of tissues containing lingual and extra-lingual taste buds were evaluated with monoclonal antibodies against cytokeratins. In the caudal third of the rat's tongue, keratin 20 immunoreactivity was restricted to taste buds, whereas keratins 7, 8, 18, and 19 were expressed in vallate and foliate taste buds and in cells of salivary ducts that merge with these taste epithelia. Hence, antibodies against keratin 20 most clearly distinguished differentiated taste cells from all other cells. In rat epiglottis, taste buds and isolated bipolar cells were keratin-20-positive. In rat nasopalatine papilla and palate, antibodies against keratin 20 identified Merkel cells, none of which was near to the keratin-20-negative taste buds. Nor were Merkel cells present at epiglottal taste buds or the keratin-20-negative fungiform taste buds or elsewhere in rat tongue. Hence, Merkel cells make no contribution to rat fungiform, epiglottal, nasopalatine, or palatal taste buds. Human and rat keratin-20-positive tissues are reported to be endodermal derivatives with the exception of Merkel cells and luminal urothelial cells. In rats the distribution of keratin-20-positive taste buds was in full agreement with the classical view that the posterior third of the tongue is derived from endoderm (keratin-20-positive taste buds), whereas the anterior two-thirds of the tongue is derived from stomadeal ectoderm (keratin-20-negative taste buds). The equally intense keratin 20 immunoreactivity of human fungiform and vallate taste buds violates this traditional rostro-caudal segregation and suggests that endodermally derived tissues may be present in the tip of the human tongue.

Anatomy, physiology, and development of feeding

Dysphagia in infants and children is usually only one part of a broad spectrum of complex medical, health, and developmental problems. As etiologies vary, so do prognoses. Increased survival rates of infants in recent years have been accompanied by an increased prevalence of neurologic, cardiorespiratory, and structural impairments that can affect nutritional status and feeding function. Knowledge of anatomy, physiology, and normal development of feeding skills is basic to the assessment and management of pediatric dysphagia.

A method of studying adaptive changes of the oropharynx to variation in mandibular position in patients with obstructive sleep apnoea

The aim of this study was to develop a method of studying the effects of mandibular advancement on oropharyngeal airway dimensions in the sagittal plane in conscious, supine patients. Six white, dentate, male patients with proven obstructive sleep apnoea had sagittal fluoroscopic recordings taken in the resting supine position. Images were recorded at four frames per second as the mandible was advanced with the teeth in contact to maximum protrusion and then opened. Software in the fluoroscopic imaging system permitted measurement of the change in mandibular position together with oropharyngeal airway dimensions expressed as the narrowest dimension observable in the post-palatal and post-lingual sites. Plotting of airway dimensions during mandibular advancement enabled estimation of the degree of protrusion associated with maximal airway benefits. Progressive mandibular advancement produced variable adaptive changes in the post-palatal and post-lingual regions of the oropharynx. The amount of airway opening appeared to be related to the horizontal and vertical relationships of the face and to the dimensions of the soft palate. The changes in post-palatal and post-lingual airway dimensions were not always identical, despite the observation that both tongue and soft palate were seen to move in unison, with close contact being maintained between the two structures. Jaw opening resulted in synchronous posterior movement of both tongue and soft palate, with consequent narrowing of oropharyngeal airspace. Fluoroscopy is a simple method of assessing upper airway changes with mandibular advancement in the conscious patient. The technique should facilitate the selection of subjects for whom mandibular advancement would seem advantageous. The nature of the adaptive response is dependent on individual structural variation. It is suggested that, where artificial mandibular advancement with dental devices is considered beneficial, jaw opening should be kept to a minimum.

Upper airway size and collapsibility in snorers: evaluation with digital fluoroscopy

This study addressed the question of whether there are any differences in the size and collapsibility of the upper airway measured by digital fluoroscopy, between snorers and controls whilst they were awake and breathing normally; and whether there are any correlations between these measurements and other clinical data. The dynamic changes of the upper airway size were evaluated using digital fluoroscopy in 33 patients and 16 normal controls. The measurements were compared with findings in an overnight sleep study, including a static-charge-sensitive bed (SCSB) and oximeter recordings. The minimum anteroposterior dimension at the velopharyngeal level was smaller in patients with partial upper airway obstruction than in controls (p<0.005); patients with complete obstruction did not differ from the controls. The velopharyngeal airways were also more collapsible in patients with severe partial obstruction (p<0.01) than in controls. At the oropharyngeal and hypopharyngeal levels, the dimensions and the collapsibilities were similar in patients and controls. The velopharyngeal collapsibility correlated with body mass index (p<O.001), whereas the airway size did not. The velopharyngeal collapsibility was more pronounced in patients with frequent episodes of arterial oxyhaemoglobin desaturation during sleep. Velopharyngeal collapsibility associated with high body mass index was the important determinant of nocturnal breathing disturbances. Digital fluoroscopy displays the dynamic changes of the upper airways throughout the respiratory cycle.

Bacterial attachment to oropharyngeal epithelial cells in breastfed newborns

On day 2 post partum, swab samples were obtained from the oropharyngx of 20 healthy, breast-fed babies. The samples were examined for aerobes (culture on agar plates), for bacterial coating with the immunoglobulins SIgA, IgG and IgM (immunofluorescence assay), for bacterial attachment to epithelial cells (fluorescence microscopy of acridine orange stained material, and scanning electron microscopy). alpha-Hemolytic streptococci grew almost exclusively in the oropharynx, while 32% (median value) of the epithelial cells showed bacterial attachment in abundance, viz. > 50 attached bacteria per cell, 66% (median value) of the bacteria showed positive reactivity when treated with anti-human SIgA serum. 72% (median value) of the bacteria were coated with IgG, but no IgM coating of the bacteria could be detected. Newborns do not possess IgA antibodies, as only IgG is able to pass the placental barrier. The SIgA-rich colostrum is capable of coating the oropharyngeal bacteria of breast-fed babies during their first days after birth. However, despite abundant SIgA-coating, bacteria still succeed in attaching to the epithelial cells of the oropharynx. This finding hints that factors other than SIgA impede the bacterial/cellular adhesion mechanism.

Oropharyngeal accommodation to swallow volume

BACKGROUND & AIMS

The oropharyngeal swallow accommodates a range of bolus volumes with substantial impact on its dynamic radiographic appearance despite being a nearly reflexive sequence. The aim of this study was to analyze the mechanism of volume accommodation.

METHODS

Coordination of the glossopalatal junction, velopharyngeal junction, laryngeal vestibule, and upper esophageal sphincter (UES) and intraluminal pharyngeal dimensions were measured from biplane videofluoroscopic swallowing studies in 8 volunteers during 1- and 20-mL swallows. These measurements were applied to three-dimensional reconstructions of the pharyngeal swallow, permitting analysis of their effect on intraluminal volume and propulsive function.

RESULTS

Dividing the pharyngeal swallow into periods of reconfiguration, sustained reconfiguration, and offset of reconfiguration, volume accommodation occurred by a 0.2-second prolongation of reconfiguration, preserving the coordination of the onset and offset events. Augmented reconfiguration increased the dimensions of the pharyngeal chamber, caused more rapid bolus expulsion, and increased UES distention. However, maximal transphincteric flow per unit area across the UES was constant, showing its compliance.

CONCLUSIONS

Volume accommodation is accomplished by augmenting and prolonging pharyngeal reconfiguration from a respiratory to deglutitive pathway. This modification in the timing of neurally mediated events is amplified by its mechanical consequences, resulting in the different cineradiographic appearance and propulsive attributes of large and small volume swallows.

Dynamic reconstruction of the oropharyngeal swallow using computer based animation

The oropharyngeal swallow was modeled with computer based animation using data from biplane videofluorographic and dynamic CT images of 10 ml liquid swallows of a volunteer subject. Tracings of oropharyngeal structures from synchronized, magnification adjusted, images of the posterior-anterior, lateral, and cross-sectional planes were aligned in three dimensions with graphics animation software. Twenty oropharyngeal configurations were created at 1/15 second intervals to dynamically illustrate the swallow. These three-dimensional reconfigurations could be sequenced into an animation routine. Software analysis of the model permitted quantification of structural movement and intrapharyngeal volume across time. Such analyses can be used to detail both the efficacy of individual functional elements of the swallow as well as global pump function. It is hoped that modeling the oropharyngeal swallow will be useful to analyze mechanisms of dysphagia and the mechanics of compensatory therapeutic strategies.

Technique for measurement of oropharyngeal clearance in the elderly

In elderly patients, gram negative bacterial colonization often preceeds nosocomial pneumonia. As we propose that a critical factor influencing this change from normal to gram negative predominance is an alteration in oral clearance, we designed this study to validate a technique for measurement of oropharyngeal clearance in a large number of nursing home residents. We modified a protocol of La Force et al who utilized an atomizer to radiolabel oropharyngeal secretions. We determined the output per spray of a DeVILBISS model 152 atomizer and found that 3 sprays of 5 mCi of 99mTc-HSA in 4 ml saline delivered 263 microCi in 0.21 ml. To measure clearance, we designed a portable, collimated ratemeter. It has a lead lined tapered aluminium frame 15 cm high, originating from a 7.5 cm rectangular base which is fitted to the scintillator. On the bench we demonstrated that this collimator, used to confine detection to the face, did not alter sensitivity and linearity of the ratemeter in our specific experimental conditions. When the ratemeter was collimated and its window off, its sensitivity was 5 times greater than the gamma camera with no loss of linearity. However, distance had a significant effect on the ratemeter's sensitivity whereas it had little effect on the gamma camera. Finally, in thirteen patients we assessed the ratemeter's accuracy in measurement of oropharyngeal clearance by comparing curves obtained simultaneously from the ratemeter and gamma camera. While each curve had its own characteristics, both devices provided remarkably similar data and there were no significant differences (r = 0.967, p < 0.0001). We conclude that oropharyngeal clearance can be conveniently and accurately studied in elderly patients at the bedside with a collimated ratemeter. The high sensitivity provides a measure of clearance with low levels of radioactivity exposure, allowing repeated studies over time.

Effects of two breath-holding maneuvers on oropharyngeal swallow

This study quantified the effects of the supraglottic maneuver (SGM) and super supraglottic maneuver (SSGM) on laryngeal and pharyngeal movements before and during swallow. Simultaneous videofluoroscopic and videoendoscopic examinations of oropharyngeal swallowing were performed in eight healthy volunteers with and without maneuvers. Data analysis compared 1) temporal relationships of oropharyngeal events, 2) airway conditions at the time of selected oropharyngeal events, and 3) biomechanical computer analysis of swallowing events. Using these maneuvers, normal subjects produced earlier cricopharyngeal opening, prolonged pharyngeal swallow, some degree of laryngeal valving before swallow, and change in extent of vertical laryngeal position before swallow. These changes are more successful and maintained longer with the SSGM than the SGM. We concluded that breath-holding maneuvers alter not only airway conditions before swallow but also both the temporal relationships and biomechanical events during oropharyngeal swallow.

Normal adult swallowing of liquid and viscous material: scintigraphic data on bolus transit and oropharyngeal residues

Scintigraphic data are provided for 20 normal control subjects, 39-65 years of age. Each subject swallowed 10 cc of water and 10 cc of a more viscous material (1,100 centipoise) consisting of apple juice thickened with Thick-It, a commercial food thickener. The test substances were combined with 2.5 mCi Tc-99m sulfur colloid. Scintigraphic data were acquired in dynamic mode for 10 sec at 25 frames/sec as the subject swallowed. Time-activity (TA) data were used to compute transit times, percentage residues in the mouth and pharynx, percent ingested, and a derived swallow efficiency score. The liquid was ingested in a single swallow by all subjects, and 9 cc was actually transferred to the esophagus. In contrast, for the viscous material, 11/20 subjects performed a second clearing swallow within the 10-sec interval. On the first swallow with the viscous substance, an average of 7 cc was transferred to the esophagus. Scintigraphy offers an excellent technique for determining natural and preferred volumes for swallowing a variety of bolus consistencies, since it can quantify the volume of each swallow or partial swallow. In this group of subjects the oral discharge time was shorter with the viscous material than with the water, but the pharyngeal transit times were not significantly different for the two bolus consistencies. Numerical efficiency scores were lower for the viscous material, indicating that such a measure is bolus dependent.

Influence of gravity and body position on normal oropharyngeal swallowing

The influence of gravity, if any, on pharyngeal bolus transport is unknown. The aim of the present study was to evaluate the effect of gravity and body position on the radiological and manometric events during the normal oropharyngeal swallow. In eight healthy male volunteers, we performed simultaneous videoradiography and manometry, using a manometry catheter incorporating a perfused sleeve measuring upper esophageal sphincter pressure and three solid-state transducers recording pharyngeal pressures. Swallows of 5 and 10 ml of barium were performed in three different body positions: upright, horizontal, and 30 degrees head down (inverted). Hypopharyngeal intrabolus pressure increased significantly in the horizontal and inverted positions compared with upright, P = 0.0001. This resulted in increased maximal sphincter diameters during bolus flow (P = 0.0001) and shorter duration of sphincter opening (P = 0.03). As a result, transsphincteric flow increased in the horizontal and inverted positions, P = 0.04. Total swallowing duration, oral and pharyngeal transit time, pharyngeal peristaltic amplitude and duration, the length of the bolus in the pharynx, and excursions of the hyoid and larynx were unaffected by body position. We conclude that intrabolus pressure is an important determinant of upper esophageal sphincter opening in the healthy oropharynx and that gravity does not influence pharyngeal bolus transport. The healthy upper esophageal sphincter has residual opening capacity that can be demonstrated by altering body posture.

Deglutitive tongue force modulation by volition, volume, and viscosity in humans

BACKGROUND/AIMS

Deglutitive tongue biomechanics are complex, involving bolus containment, loading, and propulsion. This study aimed to quantify the modulation of deglutitive pulsive and clearing tongue forces in varied swallowing conditions.

METHODS

Oropharyngeal pressure and force were recorded using sensing bulbs and strain-gauge manometry in 8 volunteers during swallows of varied volume and viscosity. Volitional modulation was explored with forceful and attenuated swallows.

RESULTS

Temporal analysis confirmed that bulb recordings corresponded to tongue pulsive force, and the strain-gauge recordings measured tongue clearing pressure. Volition was the most potent modifier of both tongue pulsive force and clearing pressure with values showing a fourfold increase from attenuated to forceful swallows. Bolus viscosity also induced an increase of tongue pulsive force and clearing pressure by the oral tongue. Volitional control as well as adaptation to viscosity was greatest on the anterior and middle part of the oral tongue. There was no force adaptation with increased bolus volume.

CONCLUSIONS

Tongue pulsive force and clearing pressure during swallow showed substantial modulation for bolus viscosity that can be reproduced by volitional control. The anterior two thirds of the tongue showed both greater forces and greater modulation than did the tongue base.

Physiology of oropharyngeal swallow in the cat: a videofluoroscopic and electromyographic study

The majority of animal studies of deglutition have examined electrically stimulated swallows in sedated animals. This present investigation examined oropharyngeal and cervical esophageal swallow physiology in three awake normal domestic cats using concurrent electromyography (EMG) and videofluorography (VFG). Hooked wire electrodes were surgically implanted into six oropharyngeal muscles in each cat. During collection of VFG and EMG data, each cat ate barium-impregnated cat food while the fluorography tube focused on a lateral view of the oral cavity, pharynx, and cervical esophagus. A number of significant differences in the physiology of swallowing were found between the cat and human adult. The oral stage of swallow is much longer in the cat with bolus accumulation in the valleculae. Duration and components of the pharyngeal stage of swallow are much faster, and the pharyngeal stage occurs earlier in relation to bolus passage through the cricopharyngeus. In addition, the cat exhibits a marked superior constrictor bulge at the onset of the pharyngeal contractile wave and summation of the peristaltic waves in the esophagus, whereas the human adult does not. Feline swallow physiology is more similar to that of the human infant than that of human adults.