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Interaction between primary afferent nerves in the elicitation of reflex swallowing.

In adult cats anesthetized with urethan, a number of observations were made that support the concept that some control over the rate of reflexly induced swallowing occurs in the intermediate network at the level of the nucleus of the solitary tract. It was shown that different nerves, e.g., the two superior laryngeal and glossopharyngeal nerves, when activated in sequence interact in such a manner as to facilitate reflex swallowing. It was also shown that the decrement in the reflex response observed to continuous stimulation of a primary afferent nerve, e.g., one superior laryngeal, can be reversed by switching the stimulation to another nerve either on the same or contralateral side. And finally, following discrete medullary lesions, it was observed that that portion of the nucleus of the solitary tract located 2 mm or more rostral to the rostralmost point of the dorsal medial sulcus appears to contain an integral component of the intermediate network that governs reflexly induced swallowing, whereas lesions restricted to the ventrolateral portion of the nucleus of the solitary tract have no effect on the reflex response.

Action Potentials↗

Fetal swallowing: response to systemic hypotension.

The fetal swallowing and endocrine responses to systemic hypotension were studied in five chronically instrumented ovine fetuses (125 +/- 2 days). Fetuses were prepared with bipolar electrodes inserted in the thyrohyoid muscle, nuchal esophagus, and thoracic esophagus, a flow probe surrounding the thoracic esophagus, and arterial and venous catheters. In response to an intravenous infusion of sodium nitroprusside, fetal mean arterial blood pressure decreased from 50.8 +/- 3.6 to 41.7 +/- 3.8 mmHg. Fetal plasma renin activity (5.0 +/- 1.4-25.1 +/- 10.3 ng.ml-1.h-1) and arginine vasopressin (5.6 +/- 4.5-26.3 +/- 21.0 pg/ml) increased, while fetal swallowing electromyogram activity (7.3 +/- 1.1-1.9 +/- 0.3 swallows/10 min) and esophageal flow (5.5 +/- 3.1-1.2 +/- 0.9 ml/10 min) significantly decreased during the nitroprusside infusion. These results indicate a suppression of fetal swallowing in response to systemic hypotension despite stimulation of the renin-angiotensin system.

Animals↗

Role of solitarial GABAergic mechanisms in control of swallowing.

The role of solitarial gamma-aminobutyric acid (GABA)-ergic mechanisms in deglutition was investigated in urethane-anesthetized rats. When applied to the dorsal extraventricular surface of the nucleus tractus solitarii (NTS), muscimol reversibly inhibited 1) buccopharyngeal swallows evoked by either electrical or chemical stimulation of the NTS and 2) esophageal peristalsis evoked by muscarinic agonists. Bicuculline (5-1,000 pmol) applied to the NTS surface evoked rhythmic swallowing, which was reversibly blocked by DL-2-amino-7-phosphonoheptanoic acid (5-500 pmol). Methscopolamine (5-100 pmol) applied at the same site abolished the esophageal component of the response. Intrasolitarial application of bicuculline at s-glutamate-responsive loci in the intermediate and central subnuclei gave rise to buccopharyngeal and esophageal responses, respectively, and to a concomitant facilitation of glutamate-evoked responses. In subliminal doses ejected at esophageal loci, bicuculline induced deglutitive esophageal peristalsis during elicitation of buccopharyngeal swallowing by chemical (kainate or norepinephrine) or electrical stimulation of the NTS. We conclude that solitarial GABA neurons exert a tonic inhibition of the medullary deglutitive pattern generator and control buccopharyngeal-esophageal coupling.

Animals↗

Central angiotensin induction of fetal brain c-fos expression and swallowing activity.

The present study examined physiological and cellular responses to central application of ANG II in ovine fetuses and determined the fetal central ANG-mediated dipsogenic sites in utero. Chronically prepared near-term ovine fetuses (130 +/- 2 days) received injection of ANG II (1.5 microg/kg icv). Fetuses were monitored for 3.5 h for swallowing activity, after which animals were killed and fetal brains were perfused for subsequent Fos staining. Intracerebroventricular ANG II significantly increased fetal swallowing in near-term ovine fetuses (1.1 +/- 0.2 to 4.5 +/- 1.0 swallows/min). The initiation of stimulated fetal swallowing activity was similar to the latency of thirst responses (drinking behavior) elicited by central ANG II in adult animals. ANG II evoked increased Fos staining in putative dipsogenic centers, including the subfornical organ, organum vasculosum of the lamina terminalis, and median preoptic nucleus. Intracerebroventricular injection of ANG II also caused c-fos expression in the fetal hindbrain. These results indicate that an ANG II-mediated central dipsogenic mechanism is intact before birth, acting at sites consistent with the dipsogenic neural network. Central ANG II mechanisms likely contribute to fetal body fluid and amniotic fluid regulation.

Angiotensin II↗

Effects of age, gender, bolus volume, and bolus viscosity on oropharyngeal pressure during swallowing.

Oropharyngeal pressure during swallowing was studied in a total of 40 healthy adult males and females in two age groups (21-27 yr and 62-75 yr). Effects of bolus volume, bolus viscosity, age, and gender were analyzed, and dry and bolus swallows were compared. The duration of the intrabolus pressure, reflecting the pressure exerted by the tongue on the bolus and preceding the generation of the pharyngeal pressure, was significantly affected by bolus volume. The duration of oropharyngeal pressure was affected by age, gender, and bolus type (bolus vs. dry swallow). Peak oropharyngeal pressure was not affected by any of the test factors, although there was a tendency for older subjects to have higher pressures than young subjects.

Adult↗

Hypoglossal neural activity during licking and swallowing in the awake rat.

1. Thirty-five neurons in the hypoglossal nucleus (mXII) of the rat were characterized during licking and swallowing in response to fluid stimulation in an awake, freely moving preparation. Simultaneously recorded electromyographic (EMG) recordings from a subset of oropharyngeal muscles were obtained to delineate both the lick cycle and the occurrence of swallows. Most mXII neurons discharged with rhythmic bursts in phase with licking. Twenty-six of the 35 mXII neurons had bimodal interspike interval (ISI) histograms, reflecting rhythmic bursts and the absence of spontaneous activity. Three mXII cells with unimodal ISI histograms were rhythmically active during licking but had some spontaneous activity. Of the remaining six cells with unimodal ISI histograms, five had nonbursting modes of activity. 2. Phase relationships between neural and EMG activity during licking were determined by cross-correlation and compared with distributions of cross-correlations between lingual and masticatory EMG activity. A bimodal distribution of cross-correlations was obtained by cross-correlating EMG activity between lingual protrudor muscles [genioglossus (GG) or geniohyoid (GH)] and masticatory jaw-opener activity [anterior digastric (AD)] and cross-correlating lingual retractor activity [styloglossus (STY)] with anterior digastric EMG. A similar bimodal distribution of cross-correlations obtained between mXII neuron activity and AD contractions suggested that the majority of mXII neurons (30/35) could be classified as protrudor- or retractor-related. Neurons classified as protrudor-related cells were located ventrally in mXII; cells classified as retractor-related were more dorsally located, consistent with anatomic and physiological descriptions of the myotopic organization of mXII. 3. Ten mXII protrudor-related neurons responded with a mean of 4.9 +/- 2.2 (SD) action potentials per lick cycle and preceded the peak jaw-opening phase of licking by a mean of 22.3 ms. In contrast, the activity of 20 retractor-related mXII neurons lagged the jaw-opening phase of licking by a mean of 55.9 ms, with a mean of 5.5 +/- 3.4 (SD) action potentials occurring per lick cycle. Five other mXII neurons exhibited nonrhythmic activity during licking and could not be classified as protrudor- or retractor-related on the basis of cross-correlations with the AD. 4. The occurrence of a swallow decreased the licking frequency by 21%, corresponding to an increase of approximately 43 ms in the period between AD contractions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Interobserver agreement on normal swallowing physiology as viewed by videoendoscopy.

This study examines the agreement of 2 observers in identifying selected normal oropharyngeal swallow events in the 1- and 5-ml swallows of 3 normal young adult males as identified by videoendoscopy at each of two endoscopic positions: (1) with the tip of the endoscope just at or below the tip of the uvula (high position), and (2) with the tip of the endoscope just below the tip of the epiglottis (low position), and thereby defines the needed focus for observer training in endoscopic assessment of swallowing. Overall, the more and less experienced examiners agreed on seeing or not seeing the onsets and terminations of the 12 events 83% of the time. Scope position affected observer agreement on several events while bolus volume did not.

Adult↗

Videofluoroscopic evaluation in the assessment of swallowing disorders in paediatric and adult populations.

Videofluoroscopic swallow studies (VFSS) are often considered the 'gold standard' technique to assess dysphagia. Despite this status, unanimous agreement has not been reached regarding the protocol for this procedure. Review of the literature reveals two main schools of thought. The first advocates a uniform, standardised protocol used with all patients. The second argues for functional, tailor-made studies, which aim to elicit a sample of swallowing representative of typical feeding patterns. This paper reviews the literature on VFSS methodology and evaluates the applicability of protocols to the paediatric population. Broadly speaking, adult protocols tend towards uniform procedures, whereas paediatric studies aim to be more individualised and tailor-made. Clinical recommendations based upon VFSS are examined in the light of validity and reliability issues. The need for standardisation of the VFSS procedure is highlighted. The question is raised whether it is possible to achieve uniformity and consistency between clinicians and still perform patient-centered, tailor-made VFSSs, which are truly representative of a patient's swallow function. It is revealed that dysphagia specialists should achieve greater consistency in the VFSS procedure before claiming to be implementing a 'gold standard' technique.

Adult↗

Relaxation of the lower-oesophageal sphincter during swallowing.

A rapid-pull through technique was used to measure lower oesophageal sphincter pressure before and immediately after swallowing. Often no high pressure zone could be detected after a swallow although sometimes an attenuated pressure profile persisted, associated with weakly developed peristalsis. The persistence of normal sphincter profiles was associated with failure of peristalsis or weak peristaltic pressure waves. Overall, there was a significant drop in mean sphincter pressure after swallowing.

Adult↗

Dysphagia after radiotherapy: endoscopic examination of swallowing in patients with nasopharyngeal carcinoma.

Dysphagia is a late sequela compromising the lives of more than one fourth of patients with nasopharyngeal carcinoma (NPC) who survive long after radiotherapy. By using fiberoptic endoscopic examination of swallowing as a modality for dysphagia evaluation, we were able to easily recognize the functional and anatomic changes in 31 dysphagic NPC patients. The majority of patients were found to aspirate after the act of swallowing (77.4%). Seventeen (54.8%) had tongue atrophy, and 9 (29%) had vocal cord palsy. Dysfunctions such as dry mouth (45.2%), velopharyngeal incompetence (58%), premature leakage (41.9%), delay or absence of swallow reflex (87.1%), poor pharyngeal constriction (80.6%), pharyngeal residue retention (83.9%), penetration or aspiration (93.5%), and silent aspiration (41.9%) were noted in these patients. Multiple dysfunctions were demonstrated in each patient. Abnormality of pharyngeal constriction and/or aberrant upper esophageal sphincter function played the major role in the postswallow aspiration of these irradiated NPC patients. Clinically compromised patients (weight loss of > or =5 kg in 1 year or pneumonia) had more of the above anatomic and functional impairments. The radiation dosage and volume bore no correlation to the time of symptom onset, or to the occurrence of functional changes.

Adult↗

Endoscopic evaluation of swallowing as an alternative to 24-hour pH monitoring for diagnosis of extraesophageal reflux.

Patients with symptoms of extraesophageal reflux may not be eager to undergo 24-hour pH probe monitoring for the sake of a definitive diagnosis. It has been anecdotally noted that extraesophageal reflux can be detected during an endoscopic swallowing evaluation. The purpose of this pilot study was to demonstrate that flexible endoscopic evaluation of swallowing with sensory testing (FEESST) can be implemented to identify and subsequently treat patients with extraesophageal reflux. Over a 6-month period, FEESST was prospectively performed in 20 healthy control subjects and in 20 patients with dysphagia. The dysphagic patients did not have a history of stroke or chronic neurologic disease. Attention was specifically directed toward noting the presence or absence of reflux into the laryngopharynx during the endoscopic swallowing evaluation. None of the control subjects were noted to have reflux during FEESST, but 18 of the 20 patients with dysphagia were found to have reflux during the evaluation; this difference was statistically significant (p < .001, Fisher's exact test). We conclude that FEESST is useful as a means of diagnosing extraesophageal reflux in patients with dysphagia.

Adult↗

Videofluoroscopic and manometric evaluation of swallowing function in patients with multiple system atrophy.

We investigated swallowing function of 29 patients with multiple system atrophy (MSA) by videofluoroscopy and manometry. Abnormal findings in videofluoroscopy were generally consistent with those in Parkinson's disease. Although findings of videofluoroscopy were not correlated with a history of aspiration pneumonia, severity of disease was significantly correlated with a history of aspiration pneumonia. Oropharyngeal and hypopharyngeal swallowing pressures of the patients were decreased to 73.9 +/- 48.4 mm Hg and 85.3 +/- 42.9 mm Hg, respectively, both of which were significantly different from the pressures of the control group. Incomplete relaxation of the upper esophageal sphincter was seen in 23.1% of the MSA patients, all of whom had had MSA for more than 5 years. In conclusion, patients with MSA are at risk for aspiration pneumonia as disease severity increases, and the swallowing function of patients with more than 5 years' duration of MSA should be routinely followed up with both videofluoroscopy and manometry.

Aged↗

Rehabilitation of swallowing after stroke.

Seven consecutive patients who had lost the ability to swallow saliva or ingest food following cerebrovascular accidents were subsequently taught to eat again. Five patients were restored to eating a regular diet and two showed improvement limited by their underlying conditions. Prior to swallowing rehabilitation, their nutrition had been maintained by tube feedings for periods of 5 months to 3.9 years. Patients were instructed in sucking, elevation of the larynx, and coordination of those functions. This method has not been reported previously for use in stroke patients. Oral feeding was initiated with ice chips and progressed to a normal diet. Speech also improved after regaining deglutition. The clinical evidence suggests that paralysis initiated the swallowing disability which persisted due to disuse of retrainable pharyngeal muscles. The reflex sequence of deglutition can be retaught if lost due to stroke.

Aged↗

Phonation and swallowing considerations in pediatric laryngotracheal reconstruction.

Experience with laryngotracheal reconstruction (LTR) has resulted in and continues to yield modifications and refinements in approach and technique with the goal to restore and maintain total laryngeal function. In addition to airway obstruction, the laryngeal functions of phonation and swallowing also may be affected by the underlying injury as well as by procedures designed to enlarge the airway. This paper discusses various problems encountered with phonation and swallowing in pediatric patients who underwent LTR and postoperative patients who were seen during the year July 1, 1990, through June 30, 1991. Phonation problems became apparent as long-term difficulties that persisted after tracheotomy decannulation. Swallowing was frequently a short-term perioperative problem while a stent was in place following LTR. The approaches and techniques that have been employed to treat, minimize, and prevent these problems are discussed.

Adolescent↗

Kinematic and dynamic characteristics of solid pellet movement during the pharyngeal phase of swallowing.

Information on solid particle movement through the pharynx, in addition to its physiologic importance, has relevance to the swallowing of medications in pill form. The purpose of this study was to determine the kinematics of a solid particle during the oral-pharyngeal phase of swallowing. We used a concurrent manometric-videofluoroscopic technique and identified two distinct zones of increasing bolus velocity, one at the tongue base and the other at the pharyngo-upper esophageal sphincter (UES) region. Velocity decreased significantly (p < .05), to 9.0 +/- 1.0 cm/s, while the bolus traversed the area located between the tip of the horizontal epiglottis and the pharyngeal wall. The velocity of the liquid barium bolus head was similar to that of the solid barium pellet. The average bolus tail velocity was relatively constant. The acceleration of the barium pellet was temporally associated with development of an incrementally decreasing pressure distal to the location of the pellet in the hypopharynx and across the UES. In conclusion, the kinematics of a solid particle are similar to those of the head of a liquid bolus, but both are different from bolus tail kinematics. During the pharyngeal phase of swallowing, the area located ahead of the bolus exhibits an incrementally decreasing pressure, caudally. This may facilitate bolus transport and contribute to airway protection.

Adult↗

Cause of eustachian tube constriction during swallowing in patients with otitis media with effusion.

In order to clarify the cause of the constriction of the eustachian tube during swallowing that is often seen in patients with otitis media with effusion, video endoscopy of the pharyngeal orifice of the eustachian tube was performed and superimposed with videograms of the tubal airflow and resistance, which were simultaneously examined by the forced response test. In children with otitis media with effusion (17 ears), when the eustachian tube constricted on the videogram on swallowing, the tubal orifice was found to be squeezed between an elevated soft palate and a hypertrophied adenoid (7/17), squeezed between an elevated soft palate and edema of the posterior lip (7/17), or blocked by nasal discharge (5/17). In adults with otitis media with effusion (7 ears), edema of the posterior lip (5/7) was the main cause of the constriction of the tubal orifice during swallowing. Inflammation in the nasopharynx and the pharyngeal portion of the eustachian tube was considered to be closely related to the tubal constriction, which represents a considerable part of the cause of tubal ventilatory dysfunction in otitis media with effusion.

Adult↗

Effectiveness of feeding tubes in nursing home residents with swallowing disorders.

BACKGROUND: Among nursing home residents who stop eating, a common decision for residents, caregivers, and families is the decision to begin tube feeding. This study examines the effectiveness of feeding tubes at reducing mortality among nursing home residents with swallowing disorders and feeding disabilities. METHODS: Data from a version of the Minimum Data Set+ (MDS +) encompassing three different states from calendar years 1993 and 1994 were analyzed. Residents were included in the study if they were not totally dependent on staff for eating upon their first assessment but became totally dependent on staff for eating and had a swallowing disorder at some point during their nursing home stay. We used a proportional hazard regression to examine the relationship of feeding tubes with mortality after total eating dependence occurred. RESULTS: Unadjusted Kaplan-Meier curves found that those with feeding tubes were less likely to die than comparable residents without feeding tubes (p < .001). Estimated survival at 1 year was 39% for those without feeding tubes and 50% for those with feeding tubes. The multivariate results indicated that feeding tubes were associated with a reduced risk of death (risk ratio, 0.71; 95% confidence interval, 0.59, 0.86). CONCLUSIONS: This study provides evidence that tube feeding can be life-prolonging, even if the gain in life is not substantial. Such information can be useful to nursing home staff, residents, and families when trying to decide whether to place a feeding tube in a resident with swallowing disorders and eating disabilities.

Activities of Daily Living↗

Barium swallow is a predictor of salivary fistula following laryngectomy.

Pharyngocutaneous salivary fistula after laryngectomy is a serious complication that can lead to prolonged hospitalization and increased patient morbidity. A postoperative barium swallow provides the surgeon with information regarding the integrity of the pharyngeal suture line. In an attempt to determine whether this information can be used to predict or prevent salivary fistula, we reviewed the records of 109 patients who underwent total laryngectomy, including 51 who had a barium swallow before they began oral intake. Ten patients (20%) demonstrated a sinus tract originating from the pharyngeal suture line. A clinical salivary fistula developed in all four patients with a sinus tract 2 cm or longer, but in only one of six patients with a tract shorter than 2 cm. Other factors predictive of salivary fistula included tumor stage, previous radiation therapy, and the presence of concurrent postoperative complications. A single fistula developed in the 58 patients not studied with barium. Information provided by postlaryngectomy barium swallow appeared to predict, but not prevent salivary fistula formation.

Adult↗