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

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.

Effect of systemic alcohol and nicotine on airway protective reflexes

OBJECTIVES

Injection of water into the pharynx induces contraction of the upper esophageal sphincter (UES), triggers the pharyngo-UES contractile reflex (PUCR), and at a higher volume, triggers an irrepressible swallow, the reflexive pharyngeal swallow (RPS). These aerodigestive reflexes have been proposed to reduce the risks of aspiration. Alcohol ingestion can predispose to aspiration and previous studies have shown that cigarette smoking can adversely affect these reflexes. It is not known whether this is a local effect of smoking on the pharynx or a systemic effect of nicotine. The aim of this study was to elucidate the effect of systemic alcohol and nicotine on PUCR and RPS.

METHODS

Ten healthy non-smoking subjects (8 men, 2 women; mean age: 32+/-3 s.d. years) and 10 healthy chronic smokers (7 men, 3 women; 34+/-8 years) with no history of alcohol abuse were studied. Using previously described techniques, the above reflexes were elicited by rapid and slow water injections into the pharynx, before and after an intravenous injection of 5% alcohol (breath alcohol level of 0.1%), before and after smoking, and before and after a nicotine patch was applied. Blood nicotine levels were measured.

RESULTS

During rapid and slow water injections, alcohol significantly increased the threshold volume (ml) to trigger PUCR and RPS (rapid: PUCR: baseline 0.2+/-0.05, alcohol 0.4+/-0.09; P=0.022; RPS: baseline 0.5+/-0.17, alcohol 0.8+/-0.19; P=0.01, slow: PUCR: baseline 0.2+/-0.03, alcohol 0.4+/-0.08; P=0.012; RPS: baseline 3.0+/-0.3, alcohol 4.6+/-0.5; P=0.028). During rapid water injections, acute smoking increased the threshold volume to trigger PUCR and RPS (PUCR: baseline 0.4+/-0.06, smoking 0.67+/-0.09; P=0.03; RPS: baseline 0.7+/-0.03, smoking 1.1+/-0.1; P=0.001). No similar increases were noted after a nicotine patch was applied.

CONCLUSIONS

Acute systemic alcohol exposure inhibits the elicitation PUCR and RPS. Unlike cigarette smoking, systemic nicotine does not alter the elicitation of these reflexes.

Oropharyngeal dysphagia

Although the aging process per se can produce measurable changes in the normal oropharyngeal swallow, these changes alone are rarely sufficient to cause clinically apparent dysphagia. The causes of oropharyngeal dysphagia in the elderly are predominantly neuromyogenic, with the most common cause being stroke. The evaluation of oropharyngeal dysphagia in the elderly involves early exclusion of structural abnormalities, detection of aspiration by videofluoroscopy which might dictate early introduction of nonoral feeding, and exclusion of underlying systemic and neuromyogenic causes that have specific therapies in their own right. Such conditions include Parkinson disease, myositis, myasthenia, and thyrotoxicosis. Management is best delivered by a multidisciplinary team involving physician, speech pathologist, nutritionist and, at times, a surgeon.

Brain stem control of the phases of swallowing

The phases of swallowing are controlled by central pattern-generating circuitry of the brain stem and peripheral reflexes. The oral, pharyngeal, and esophageal phases of swallowing are independent of each other. Although central pattern generators of the brain stem control the timing of these phases, the peripheral manifestation of these phases depends on sensory feedback through reflexes of the pharynx and esophagus. The dependence of the esophageal phase of swallowing on peripheral feedback explains its absence during failed swallows. Reflexes that initiate the pharyngeal phase of swallowing also inhibit the esophageal phase which ensures the appropriate timing of its occurrence to provide efficient bolus transport and which prevents the occurrence of multiple esophageal peristaltic events. These inhibitory reflexes are probably partly responsible for deglutitive inhibition. Three separate sets of brain stem nuclei mediate the oral, pharyngeal, and esophageal phases of swallowing. The trigeminal nucleus and reticular formation probably contain the oral phase pattern-generating neural circuitry. The nucleus tractus solitarius (NTS) probably contains the second-order sensory neurons as well as the pattern-generating circuitry of both the pharyngeal and esophageal phases of swallowing, whereas the nucleus ambiguus and dorsal motor nucleus contain the motor neurons of the pharyngeal and esophageal phases of swallowing. The ventromedial nucleus of the NTS may govern the coupling of the pharyngeal phase to the esophageal phase of swallowing.

Gastroesophageal scintigraphy in the evaluation of adult patients with chronic cough due to gastroesophageal reflux disease

OBJECTIVE

The aim of this study was to evaluate the findings of gastroesophageal scintigraphy (GES) with late lung imaging in adult patients with chronic cough due to gastroesophageal reflux disease and a group of healthy participants.

METHODS

Fifty-five patients with chronic cough with reflux symptoms, and a control group of 12 healthy participants were examined. All patients had reflux esophagitis documented by upper gastrointestinal endoscopy and histology. All participants underwent laryngoscopic examination and GES. The correlation between gastroesophageal reflux and several related variables was evaluated.

RESULTS

Overall, 51 patients (92.7%) had positive GES findings for pathologic reflux; 19 (37.2%) of these patients had proximal reflux; and the remaining 32 (62.7%) had distal reflux. The frequency, duration, and percentage volume of gastric content of reflux episodes were significantly greater in patients with proximal reflux than in patients with distal reflux (P<0.0001). No statistically significant differences were seen between proximal reflux and distal reflux patients in terms of pulmonary function parameters, duration of cough, and reflux symptoms scores. However, severe grade (B and C) of esophagitis and the posterior laryngitis were more common in the patients with proximal reflux. Late lung imaging demonstrated evidence of pulmonary aspiration in only three of 51 (6%) patients.

CONCLUSION

Our study suggests that GES with late lung imaging objectively showed the presence of pathologic distal and/or proximal reflux, but rarely pulmonary aspiration, in the majority of chronic cough patients with gastroesophageal reflux disease. As the chronic cough patients with proximal reflux have more severe reflux characteristics, this examination may be effective in screening and following up these patients.

The videofluorographic swallowing study

This article describes the evidence for the physiologic foundation and interpretation of the videofluorographic swallowing study (VFSS). The purpose and clinical efficacy of VFSS are explained. Standardization of the VFSS procedure, protocol, interpretation, and reporting is highlighted as a critical step in future clinical practice and research. Individualized evidenced-based rehabilitation strategies are presented as key components that are systematically applied during the VFSS procedure and integrated into the swallowing management plan. A new tool that has been developed and tested for the quantification of swallowing impairment is introduced.

Manometric evidence for a phonation-induced UES contractile reflex

The mechanism against entry of gastric content into the pharynx during high-intensity vocalization such as seen among professional singers is not known. We hypothesized that phonation-induced upper esophageal sphincter (UES) contraction enhances the pressure barrier against entry of gastroesophageal contents into pharynx. To determine and compare the effect of phonation on luminal pressures of the esophagus and its sphincters, we studied 17 healthy volunteers (7 male, 10 female) by concurrent high-resolution manometry and voice analysis. We tested high- and low-pitch vowel sounds. Findings were verified in six subjects by UES manometry using a water-perfused sleeve device. Eight of the volunteers (2 male, 6 female) had concurrent video fluoroscopy with high-resolution manometry and voice recording. Fluoroscopic images were analyzed for laryngeal movement. To define the sex-based effect, subgroup analysis was performed. All tested phonation frequencies and intensities induced a significant increase in UES pressure (UESP) compared with prephonation pressure. The magnitude of the UESP increase was significantly higher than that of the distal esophagus, the lower esophageal sphincter (LES), and the stomach. Concurrent videofluoroscopy did not show posterior laryngeal movement during phonation, eliminating a purely mechanical cause for phonation-induced UESP increase. Subgroup analysis demonstrated phonation-induced UESP increases in males that were significantly greater than those of females. Phonation induces a significant increase in UESP, suggesting the existence of a phonation-induced UES contractile reflex. UESP increase due to this reflex is significantly higher than that of the distal esophagus, LES, and stomach. The phonation-induced UESP increase is influenced by sex.

Sensory and instrumental analysis for slipperiness and compliance of food during swallowing

In spite of its importance, there have been few attempts to evaluate the sensory attributes of the food bolus during swallowing. In the current study, the slipperiness, the degree of slide for the food bolus through the mucosal surface of the oro-pharynx, and the compliance, how easily the shape of a food bolus can be transformed for automatic and comfortable swallowing, were derived among several sensory attributes related to the swallowing. Therefore, the study aims were twofold: (1) to develop the methods of sensory and instrumental analyses for determining the slipperiness and compliance of the food bolus during swallowing and (2) to examine the appropriateness of the newly designed devices by correlating the data between the sensory and instrumental analyses. Six commercial food products were evaluated by 10 trained panelists for each attribute. The devices for assessing each attribute were developed in consideration of the oro-pharyngeal movements. The sensory and instrumental analyses showed high correlation and regression coefficients as well as intensity differences of the 6 samples for each attribute. In conclusion, the slipperiness and the compliance were suitable for acquiring a better understanding of the sensory attributes of the food bolus during swallowing, and the newly developed devices showed a high potential for determining those attributes.

Safety and feasibility of evaluating airway-protective reflexes during sleep: new technique and preliminary results

BACKGROUND

The airway is vulnerable to aspiration during sleep. The integrity of aerodigestive-protective reflexes during sleep has not been studied previously because of a lack of adequate techniques.

OBJECTIVE

To determine the safety and the feasibility of a new technique to elicit pharyngoglottal closure reflex (PGCR), pharyngo-upper-esophageal sphincter (UES) pressure contractile reflex (PUCR), and reflexive pharyngeal swallow (RPS) during sleep.

SETTING

Outpatient sleep laboratory.

DESIGN AND INTERVENTION

PGCR, PUCR, and RPS were elicited in 3 subjects by injecting colored water into the pharynx through a specially designed UES manometry catheter to which a thin videoendoscope was taped. This assembly was passed transnasally and positioned to obtain UES-pressure recordings and adequate endoscopic glottic views. Sleep was monitored by polysomnography, and all modalities were synchronized by using a timer. Subjects were evaluated while awake and during stage I sleep.

RESULTS

All subjects were monitored for 3 hours of natural sleep, during which several periods of stage I sleep were observed. While awake, PGCR, PUCR, and RPS were elicited in all subjects. During sleep, PGCR was present in all, PUCR in 2, and RPS in 2 (1 after arousal) subjects. Threshold volumes for reflex elicitation were not significantly different between the awake state and stage I sleep. None of the subjects exhibited laryngeal penetration or aspiration.

LIMITATIONS

Small numbers of subjects were studied only in stage I sleep.

CONCLUSIONS

When using the above technique, it is safe and feasible to study aerodigestive reflexes during sleep. Preliminary data suggest that PGCR, PUCR, and RPS can be elicited during sleep.

Swallowing function and upper airway sensation in obstructive sleep apnea

The objective of this study was to determine whether impaired upper airway (UA) mucosal sensation contributes to altered swallowing function in obstructive sleep apnea (OSA). We determined UA two-point discrimination threshold (2PDT) and vibratory sensation threshold (VST) in 15 men with untreated OSA and 9 nonapneic controls (CL). We then assessed swallowing responses to oropharyngeal fluid boluses delivered via a catheter. The threshold volume required to provoke swallowing and the mean latency to swallowing were determined, as was the phase of the respiratory cycle in which swallowing occurred [expressed as percentage of control cycle duration (%CCD)] and the extent of prolongation of the respiratory cycle after swallowing [inspiratory suppression time (IST)]. 2PDT and VST were significantly impaired in OSA patients compared with CL subjects. 2PDT was positively correlated with swallowing latency and threshold volume in CL subjects, but not in OSA patients. Threshold volume did not differ between the groups [median value = 0.1 ml (95% confidence interval = 0.1-0.2) for OSA and 0.15 ml (95% confidence interval = 0.1-0.16) for CL], whereas swallowing latency was shorter for OSA patients [3.3 (SD 0.7) vs. 3.9 (SD 0.8) s, P = 0.04]. %CCD and IST were similar for OSA patients and CL subjects. However, among OSA patients there was a significant inverse relation between VST and IST. These findings suggest that oropharyngeal sensory impairment in OSA is associated with an attenuation of inhibitory modulating inputs to reflex and central control of UA swallowing function.

The effect of bolus viscosity on swallowing function in neurogenic dysphagia

AIM

To assess the pathophysiology and treatment of neurogenic dysphagia.

METHODS

46 patients with brain damage, 46 with neurodegenerative diseases and eight healthy volunteers were studied by videofluoroscopy while swallowing 3-20 mL liquid (20.4 mPa s), nectar (274.4 mPa s) and pudding (3931.2 mPa s) boluses.

RESULTS

Volunteers presented a safe and efficacious swallow, short swallow response (< or =740 ms), fast laryngeal closure (< or =160 ms) and strong bolus propulsion (> or =0.33 mJ). Brain damage patients presented: (i) 21.6% aspiration of liquids, reduced by nectar (10.5%) and pudding (5.3%) viscosity (P < 0.05) and (ii) 39.5% oropharyngeal residue. Neurodegenerative patients presented: (i) 16.2% aspiration of liquids, reduced by nectar (8.3%) and pudding (2.9%) viscosity (P < 0.05) and (ii) 44.4% oropharyngeal residue. Both group of patients presented prolonged swallow response (> or =806 ms) with a delay in laryngeal closure (> or =245 ms), and weak bolus propulsion forces (< or =0.20 mJ). Increasing viscosity did not affect timing of swallow response or bolus kinetic energy.

CONCLUSIONS

Patients with neurogenic dysphagia presented high prevalence of videofluoroscopic signs of impaired safety and efficacy of swallow, and were at high risk of respiratory and nutritional complications. Impaired safety is associated with slow oropharyngeal reconfiguration and impaired efficacy with low bolus propulsion. Increasing bolus viscosity greatly improves swallowing function in neurological patients.

Optimal stimulus intensity and reliability of air stimulation technique for elicitation of laryngo-upper esophageal sphincter contractile reflex

To determine the optimal air stimulus intensity and duration for elicitation of the laryngo-upper esophageal sphincter (UES) contractile reflex, we studied 37 healthy volunteers 20 to 81 years of age. A sleeve device monitored the UES pressure. For laryngeal stimulation, we used an air stimulator unit (Pentax AP-4000) that incorporated a nasolaryngeal endoscope. The arytenoids and interarytenoid areas were stimulated at least three times by three different stimuli: 6-mm Hg air pulse with 50-ms duration, 10-mm Hg air pulse with 50-ms duration, and 6-mm Hg air pulse with 2-second duration. Of 1,165 air stimulations, 1,041 resulted in mucosal deflections. Of these, 451 resulted in an abrupt increase in UES pressure. The response/deflection ratio for 6-mm Hg stimulation with 2-second duration was significantly higher than those for air pulses with 50-ms duration (p < .001). We conclude that although the laryngo-UES contractile reflex can be elicited by an air pulse with 50-ms duration, this ultrashort stimulation is not reliable. Using longer-duration pulses (at least 2 seconds) improves the reliability of elicitation of the laryngo-UES contractile reflex.

Dysphagia in aging

Dysphagia is a common problem in older patients and is becoming a larger health care problem as the populations of the United States and other developed countries rapidly age. Changes in physiology with aging are seen in the upper esophageal sphincter and pharyngeal region in both symptomatic and asymptomatic older individuals. Age related changes in the esophageal body and lower esophageal sphincter are more difficult to identify, while esophageal sensation certainly is blunted with age. Stroke, Parkinson's disease, amyotrophic lateral sclerosis, Zenker's diverticula, and several other motility and structural disorders may cause oropharyngeal dysphagia in an older patient. Esophageal dysphagia can also be caused by both disorders of motility (achalasia, diffuse esophageal spasm, scleroderma and others) and structure (malignancy, strictures, rings, external compression, and others). Many of these disorders have an increased prevalence in older patients and should be sought with an appropriate diagnostic evaluation in older patients. The treatment of dysphagia in older patients is similar to that in younger patients, but more invasive therapies such as surgery may not be possible in some older patients making less aggressive medical and endoscopic therapy more attractive.

Structural displacements affecting pharyngeal constriction in nondysphagic elderly and nonelderly adults

This study investigated spatial displacement variables important to pharyngeal constriction and clearing in nondysphagic elderly subjects and a control group of nondysphagic younger adults. Height, weight, and body mass index (BMI) characteristics were determined for all subjects, who then underwent videofluoroscopic swallow studies. Measures obtained during swallow of a 20-cc bolus included hyoid and laryngeal displacement, unobliterated pharyngeal space at the point of maximum pharyngeal constriction, and pharyngeal width when maximally expanded during the swallow. Data were first examined to determine if elderly subjects with medical conditions common to an aged population differed from elderly subjects with no medical condition. No differences were identified and data for all elderly subjects were subsequently pooled for comparison to data for the nonelderly control group. Findings revealed no differences in maximum hyoid displacement between the groups. Significant differences were identified for larynx-to-hyoid approximation and for the measure representing unobliterated pharyngeal space at the point of maximum pharyngeal constriction. Elderly subjects did not elevate the larynx to the same extent, or clear the pharynx, as well as the younger control subjects. In addition, data suggested that the larynx was positioned lower and that the width of the pharynx maximally expanded was greater in elderly subjects. Implications of the data for swallowing function in the elderly are discussed.

Laryngo-upper esophageal sphincter contractile reflex in humans deteriorates with age

BACKGROUND & AIMS

Recent studies have shown the existence of several reflex connections between the aerodigestive and upper gastrointestinal tracts. Our aim was to study the effect of laryngeal stimulation on upper esophageal sphincter (UES) pressure and to determine the reproducibility of this effect.

METHODS

We studied 14 young and 10 elderly healthy nonsmoker volunteers and 7 patients with UES dysphagia using a concurrent manometric and video endoscopic technique. Three levels of laryngeal air stimulation were studied: 6 mm Hg/50 ms, 10 mm Hg/50 ms, and 6 mm Hg/2 s. Ten young subjects were studied twice.

RESULTS

For 6-mm Hg/2-s and 6-mm Hg/50-ms duration stimuli, the frequency of UES response to air stimulation as evidenced by mucosal deflection (response/deflection ratio) in the elderly volunteers was significantly lower compared with that of young subjects (P < 0.05). The response/deflection ratio of the 6-mm Hg/2-s stimulus was significantly higher than those induced by stimuli of shorter duration (P < 0.01). Poststimulation UES pressure was significantly higher than prestimulation pressure (P < 0.05) in both groups. The magnitude of the increase in poststimulation UES pressure in the elderly volunteers was similar to that of the young subjects. Findings were similar in repeated studies. Four of 7 dysphagic patients exhibited an abnormal response.

CONCLUSIONS

Afferent signals originating from the larynx reproducibly induce contraction of the UES: the laryngo-UES contractile reflex. This reflex is elicited most reliably by 6-mm Hg/2-s air stimulation. Frequency elicitation of this reflex decreases significantly with age while the magnitude of change in UES pressure remains unchanged, indicating a deleterious effect of aging on the afferent arm of this reflex. This reflex is altered in some dysphagic patients.

Mechanism of sequential swallowing during straw drinking in healthy young and older adults

Recent research has revealed differences between isolated and sequential swallowing in healthy young adults; however, the influence of normal aging on sequential swallowing has not been studied. Thus, the purpose of this investigation was to examine the effects of normal aging on deglutition during sequential straw drinking. Videofluoroscopic samples of two 10-s straw drinking trials were obtained for 20 healthy young men (age 29 +/- 3 years) and 18 healthy older men (age 69 +/- 7 years). Hyolaryngeal complex (HLC) movement patterns, leading edge of the bolus location at swallow onset, and occurrences of airway invasion were determined. Two HLC patterns were identified: (a). HLC lowering with the epiglottis returned to upright between swallows and (b). partially maintained HLC elevation with the epiglottis inverted between swallows. The bolus was frequently in the hypopharynx at swallow onset. Strong associations were identified between age and HLC pattern, age and leading edge of the bolus location, and HLC pattern and leading edge location. Laryngeal penetration was uncommon overall; however, it occurred more frequently in the older adults than in the young adults. A significant relation was identified between age and the average Penetration-Aspiration Scale score. Laryngeal penetration was associated with both HLC movement patterns and hypopharyngeal bolus location, particularly in older adults. Results indicate that subtle age-related differences are evident in healthy young and older adults with sequential straw drinking. These data suggest that specific inherent swallowing patterns may increase the risk of laryngeal penetration with normal aging.

Normal physiology of the aerodigestive tract and its effect on the upper gut

There is a close functional relation between the aerodigestive tract and the upper gastrointestinal tract. The pharynx and larynx are involved in respiration, speech, and deglutition. This article reviews the effects of reflexes emanating from the pharynx and larynx on the esophagus and its sphincters, as well as the effects of reflexes emanating from the esophagus on the larynx. Principally, reciprocal reflexes within these 2 regions result in protection of the airway against aspiration from above and below, either by swallowed or refluxed material. However, other reflexes appear to facilitate reflux of gastric content into the esophagus and inhibit esophageal motor function.

The nasogastric feeding tube as a risk factor for aspiration and aspiration pneumonia

PURPOSE OF REVIEW

Aspiration is one of the most common complications in enterally fed patients. The source of aspiration is due to the accumulation of secretions in the pharynx of reflux gastric contents from the stomach into the pharynx. The true prevalence of aspiration is difficult to determine because of vague definitions, poor assessment methods, and varying levels of clinical recognition.

RECENT FINDINGS

There is evidence in the literature showing that the presence of a nasogastric feeding tube is associated with colonization and aspiration of pharyngeal secretions and gastric contents leading to a high incidence of Gram-negative pneumonia in patients on enteral nutrition. However, other aspects may be equally important and should also be considered when evaluating a patient suspected of having aspiration and aspiration pneumonia. The mechanisms responsible for aspiration in patients bearing a nasogastric feeding tube are (1). loss of anatomical integrity of the upper and lower esophageal sphincters, (2). increase in the frequency of transient lower esophageal sphincter relaxations, and (3). desensitization of the pharyngoglottal adduction reflex.

SUMMARY

Sometimes it is possible to differentiate whether the aspirate is gastric or pharyngeal. The kind of bacterial contamination is, however, more difficult to establish. Oral or dental disease, antibiotic therapy, systemic illness or malnutrition and reduction of salivary flow are responsible for colonization of Gram-negative bacteria in oral and pharyngeal flora in nasogastric-tube-fed patients. The use of a nasogastric feeding tube and the administration of food increase gastric pH and lead to colonization of gastric secretions. It has also been suggested that gastric bacteria could migrate upward along the tube and colonize the pharynx.

Temporal coordination of pharyngeal and laryngeal dynamics with breathing during swallowing: single liquid swallows

The critical integration of timing and patterning between respiratory and swallowing events was studied with simultaneous videofluoroscopic and respiratory recording during single liquid swallows. Respiratory phase patterns and the onsets and durations of 12 predetermined swallowing events and associated respiratory activities were studied. Results showed four highly repeatable, temporally oriented sequences (clusters) of swallowing and related respiratory events. Two respiratory phase patterns were identified without statistically significant differences in frequency of occurrence between age, gender, or race. These findings will aid in the identification of normal and abnormal patterns of breathing and swallowing in patients with dysphagia.

Physiology of the aerodigestive system and aberrations in that system resulting in aspiration

BACKGROUND

Aspiration pneumonia remains a significant and often devastating problem in critically ill patients. It is unclear whether aspiration pneumonia occurs because of problems in the handling of oropharyngeal secretions or if the reflux of gastric contents is the major etiological factor. Additionally, the obvious breakdown of upper aerodigestive protective mechanisms in the critically ill patient population is largely unstudied. Finally, the impact and contribution of tubes, both endotracheal and nasoenteral, on aspiration pneumonia is unclear.

METHODS

A Medline literature search on scientific and review articles concerning the normal physiology of the aerodigestive tract and factors that compromised normal physiology was undertaken. Readings were supplemented by expert outside opinion from researchers in these fields and from the combined expertise from a multidisciplinary panel of experts assembled at a recent summit on aspiration pneumonia.

RESULTS

Changes in the normal physiology of the aerodigestive tract are vast and varied and dependent on the response to injury, iatrogenic interventions, and the use of nasoenteral and endotracheal tubes. The effects on gastric and esophageal motility are likely dynamic and represent an ongoing but changing risk of reflux for the patient. Nasoenteral and endotracheal tubes likely compromise upper aerodigestive protective mechanisms.

CONCLUSIONS

More research is needed on the functioning of the aerodigestive protective mechanisms in critically ill patients. Understanding of the dynamic changes in gastrointestinal motility will also be an important factor to decrease the incidence of aspiration pneumonia in this patient population.

Aging and intestinal motility: a review of factors that affect intestinal motility in the aged

Normal aging is associated with significant changes in the function of most organs and tissues. In this regard, the gastrointestinal tract is no exception. The purpose of this review is to detail the important age-related changes in motor function of the various parts of the gastrointestinal tract and to highlight some of the important motility changes that may occur, either in relation to common age-related disorders, or as a result of certain drugs commonly prescribed in the aged. A major confounding factor in the interpretation of motor phenomena throughout the gastrointestinal tract in this age group is the frequent coexistence of neurological, endocrinological and other disease states, which may be independently associated with dysmotility. Overall, current data are insufficient to implicate normal aging as a cause of dysmotility in the elderly. Normal aging is associated with various changes in gastrointestinal motility, but the clinical significance of such changes remains unclear. More important is the impact of various age-related diseases on gastrointestinal motility in the elderly: for example, long-standing diabetes mellitus may reduce gastric emptying in up to 50% of patients; depression significantly prolongs whole-gut transit time; hypothyroidism may prolong oro-caecal transit time; and chronic renal failure is associated with impaired gastric emptying. In addition, various, frequently used drugs in the elderly cause disordered gastrointestinal motility. These drugs include anticholinergics, especially antidepressants with an anticholinergic effect, opioid analgesics and calcium antagonists.

Presbyesophagus: a reappraisal

The gastrointestinal tract undergoes change with aging, and the esophagus is not exempt from those changes. Failure of peristalsis in the older esophagus was labeled "presbyesophagus" over 35 years ago. Modern manometric techniques and classification systems have challenged this concept, yet there are clearly age-related changes in the esophagus. The lower esophageal sphincter changes little. Esophageal peristalsis (body) is more likely to fail in older patients, but some of this failure may be caused by damage from gastroesophageal reflux disease. The pharynx and upper esophageal sphincter also undergo age-related changes in health and disease. The ability to sense events in the esophagus fails with aging, which may cause patients with severe mucosal disease to present with less severe symptoms. Failure of the esophagus thus does not appear to be an inevitable consequence of aging, but the esophagues does undergo change with aging, and these changes should be considered in evaluation of older patients with esophageal complaints.

Swallowing disorders in the elderly

Changes that occur as a natural part of senescence in the complex action of deglutition predispose us to dysphagia and aspiration. As the "baby-boomers" begin to age, the onset of swallowing difficulties will begin to manifest in a greater number of our population. Recent advances in the evaluation of normal and abnormal swallowing make possible more precise anatomical and physiological diagnoses. Coupled with an understanding of swallowing physiology, such detailed evaluation allows greater opportunity to safely manage dysphagia with directed therapy and appropriate surgical intervention. The current study is a discussion of the changes that occur in deglutition with normal aging, contemporary evaluation of swallowing function, and some of the common causes of dysphagia in elderly patients.

Acid peptic disease in the elderly

GERD and peptic ulcer disease are important diseases in the elderly. GERD presents similarly in the elderly and the young, although elderly patients may have less severe symptoms yet more severe mucosal disease and a higher prevalence of BE. Although the prevalence of H. pylori is falling, the elderly remain at risk for peptic ulcer because of the widespread use of NSAIDS. The presentation of peptic ulcer disease in the elderly can be subtle and atypical when compared with younger patients, leading to a delay in diagnosis. Because of comorbidity in the aged, peptic ulcer disease and its complications result in increased morbidity and mortality rates.

Esophageal disorders in the elderly

As the number of elderly in the population increases, decompensation of swallowing and airway protective mechanisms can create an increased health care burden. This article outlines the effect of aging on deglutitive function and esophageal and aerodigestive reflexes. Specific disorders in the elderly are discussed.

Cerebral cortical representation of reflexive and volitional swallowing in humans

The purpose of this study was to compare cerebral cortical representation of experimentally induced reflexive swallow with that of volitional swallow. Eight asymptomatic adults (24-27 yr) were studied by a single-trial functional magnetic resonance imaging technique. Reflexive swallowing showed bilateral activity concentrated to the primary sensory/motor regions. Volitional swallowing was represented bilaterally in the insula, prefrontal, cingulate, and parietooccipital regions in addition to the primary sensory/motor cortex. Intrasubject comparison showed that the total volume of activity during volitional swallowing was significantly larger than that activated during reflexive swallows in either hemisphere (P < 0.001). For volitional swallowing, the primary sensory/motor region contained the largest and the insular region the smallest volumes of activation in both hemispheres, and the total activated volume in the right hemisphere was significantly larger compared with the left (P < 0.05). Intersubject comparison showed significant variability in the volume of activity in each of the four volitional swallowing cortical regions. We conclude that reflexive swallow is represented in the primary sensory/motor cortex and that volitional swallow is represented in multiple regions, including the primary sensory/motor cortex, insular, prefrontal/cingulate gyrus, and cuneus and precuneus region. Non-sensory/motor regions activated during volitional swallow may represent swallow-related intent and planning and possibly urge.

Loss of secondary esophageal peristalsis is not a contributory pathogenetic factor in posterior laryngitis

Secondary esophageal peristalsis helps prevent the entry of gastric acid into the pharynx by clearing the refluxed gastric contents back into the stomach. Because the loss of this mechanism may contribute to the pathogenesis of reflux-induced laryngeal disorders, our aim was to study the frequency of stimulation and parameters of secondary esophageal peristalsis in patients with posterior laryngitis (PL). We studied 14 patients (45 +/- 5 years) with PL documented by videolaryngoscopy and 11 healthy controls (46 +/- 6 years). The upper esophageal sphincter (UES) pressure was monitored by a sleeve assembly incorporating an injection port 5 cm distal to the sleeve. The esophageal body and lower esophageal sphincter (LES) pressures were measured by an LES sleeve assembly. Primary esophageal peristalsis was induced by 5-mL water swallows. Secondary esophageal peristalsis was induced by abrupt injection of volumes of air, incrementally increased by 5 mL, into the esophagus. Secondary esophageal peristalsis could not be elicited by injection of any volume (up to 60 mL) in 3 PL patients and 2 controls. These 5 subjects had normal primary peristalsis. The threshold volume of air required to stimulate secondary esophageal peristalsis in PL patients (median, 15 mL) was similar to that of controls (median, 10 mL). The parameters of the secondary esophageal peristaltic pressure wave were similar in both groups, and in both groups, they were similar to those of primary peristalsis. The UES response to the injection of the threshold volume that induced secondary esophageal peristalsis in PL patients was contraction in 58% of the trials, partial relaxation in 3%, and no response in 39%. The findings were similar to those in the controls. The LES response to injection of the threshold volume was complete relaxation in both the PL patients and the controls. We conclude that the integrity of secondary esophageal peristalsis is preserved in PL patients.

Effect of mucosal anaesthesia on oropharyngeal swallowing

The effect of the topical anaesthesia of the oropharyngeal mucosae was studied in order to evaluate the role of the mucosal sensory receptors on the oropharyngeal swallowing in 12 adult volunteers. Laryngeal vertical movements were detected by a piezoelectric sensor and electromyography of the submental muscle complex were simultaneously recorded. All subjects were instructed to swallow doses of water, gradually increasing in quantity from 3-20 mL and any recurrence of the signals related to swallowing within 8 s was accepted as a sign of dysphagia and its limit value measured. Before the topical anaesthesia of the oropharyngeal mucosae by xylocaine puffs; the dysphagia limit was never observed with less than 20 mL water. During topical mucosal anaesthesia lasting 4-6 min among the subjects, the dysphagia limit was less than 20 mL water and the recurrence of swallows two or more times was mainly recorded with 3-5 mL water. Five of the subjects demonstrated the clinical and electrophysiological signs of laryngeal aspiration at the earlier period of the topical anaesthesia. It is concluded that the sensory inputs from the mucosal receptors are important to trigger voluntary swallowing and their absence or dysfunction may contribute to oropharyngeal dysphagia and laryngeal aspiration.

Deterioration of the pharyngo-UES contractile reflex in the elderly

OBJECTIVES/HYPOTHESIS

Deterioration of aerodigestive tract reflexes such as the esophagoglottal and pharyngoglottal closure reflexes and pharyngeal swallow has been documented in the elderly. However, the effect of aging on the contractile response of the upper esophageal sphincter (UES) to pharyngeal water stimulation has not been studied. The aim of this study was to characterize the pharyngo-UES reflex in the healthy elderly.

METHODS

We studied nine healthy elderly (77 +/- 1 y [SD]; four men, five women) and nine healthy young volunteers (26 +/- 2 y [SD]; four men, five women). AUES sleeve sensor was used to measure the pressure. We tested pharyngeal stimulation induced by rapid pulse and slow continuous injection of water.

RESULTS

The volume of water required to stimulate the pharyngo-UES contractile reflex by rapid pulse injection in the elderly (0.5 +/- 34 0.1 mL) was significantly higher than that in the young (0.1 +/- 0.02 mL) (P < .05). In contrast to young subjects, there was no pressure increase in resting UES pressure observed in the elderly for continuous pharyngeal water infusion. In both young and elderly, the threshold volume for the pharyngo-UES contractile reflex was significantly lower than that for pharyngeal swallows.

CONCLUSIONS

The pharyngo-UES contractile reflex deteriorates with aging. This deterioration is primarily due to abnormalities of the afferent limb of the reflex.

Reflex-mediated enhancement of airway protective mechanisms

The upper esophageal sphincter (UES) and lower esophageal sphincter (LES) comprise the basal mechanisms against entry of gastric content into the aerodigestive tract and the airway. There are, however, other mechanisms referred to here as "response mechanisms" that become activated after certain stimulation, such as distention of the esophagus or tactile/pressure stimulation of the pharyngeal wall, and result either in fortification of the UES barriers--i.e., esophago-UES, pharyngo-UES, and laryngo-UES contractile reflexes--or closure of the glottis--i.e., esophagoglottal and pharyngoglottal closure reflexes. In addition, there are other reflexes included among the response mechanisms--such as pharyngeal swallow and secondary peristalsis induced by pharyngeal stimulation by liquid and esophageal distention by refluxate--that result in pharyngeal and esophageal volume clearance, thus reducing the chance for contact of refluxate with the tracheal, bronchial, and glottal structures.

Pharyngeal acid reflux in patients with single and multiple otolaryngologic disorders

OBJECTIVE

This study was designed to determine the prevalence and characteristics of pharyngeal acid reflux (PAR) events in single and multiple otolaryngologic disorders.

METHODS

Sixty-seven patients with otolaryngologic symptoms and objective findings and 34 healthy control subjects were studied with an ambulatory 24-hour, 3-site pharyngoesophageal pH monitoring technique. Otolaryngologic diagnosis included isolated posterior laryngitis (PL) in 28 patients, isolated chronic rhinosinusitis (SIN) in 12, combined PL and SIN (PL+SIN) in 6, PL plus laryngotracheal stenosis (PL+LTS) in 12, and PL plus vocal cord nodules (PL+VCN) in 9.

RESULTS

PAR events were documented in 68% of patients with PL, 34% of patients with SIN, 67% of patients with PL+SIN, 67% of patients with PL+LTS, 78% of patients with PL+VCN, and 21% of controls. The prevalence of PAR events in patients with isolated PL as well as those with PL combined with other disorders was significantly higher than that in patients without PL and that in controls. As a group, patients with PL had a greater number of PAR events and acid exposure time than other patients and controls. Distal and proximal esophageal reflux parameters were not significantly different among groups.

CONCLUSIONS

The prevalence of PAR is significantly higher in patients with isolated PL compared to patients with other isolated otolaryngologic disorders and in controls. The prevalence of PAR in isolated otolaryngologic disorders other than PL is similar to that in healthy controls. The prevalence of PAR is significantly higher in patients with both PL and other otolaryngologic disorders than in controls and in patients with isolated otolaryngologic disorders.

Esophagopharyngeal acid regurgitation: dual pH monitoring criteria for its detection and insights into mechanisms

BACKGROUND & AIMS

A valid technique for the detection of esophagopharyngeal acid regurgitation would be valuable to evaluate suspected reflux-related otolaryngologic and respiratory disorders. The aim of this study was to derive pH criteria that optimally define esophagopharyngeal acid regurgitation and to examine patterns of regurgitation.

METHODS

In 19 healthy controls and 15 patients with suspected regurgitation, dual or quadruple pH sensors were used to monitor pharyngeal and esophageal pH. For each combination of the 2 variables, DeltapH and nadir pH, proportions of pH decreases that occurred during or independent of esophageal acidification were calculated to determine the likelihood that an individual pharyngeal pH decrease was a candidate regurgitation event or a definite artifact.

RESULTS

Overall, 92% of pharyngeal pH decreases of 1-2 pH units and 66% of pH decreases of this magnitude reaching a nadir pH of <4 were artifactual. Optimal criteria defining a pharyngeal acid regurgitation event were a pH decrease that occurred during esophageal acidification, had a DeltapH of >2 units, and reached a nadir of <4 units in less than 30 seconds. Regurgitation occurred more frequently in subjects in an upright (32 of 35) than in a supine (3 of 35 events; P </= 0.0001) position and was more frequently abrupt (synchronous with esophageal acidification) than delayed (P </= 0.05).

CONCLUSIONS

Accepted criteria for gastroesophageal reflux are not applicable to the detection of esophagopharyngeal acid regurgitation, and most regurgitation occurs abruptly and in upright position.

Impaired swallowing reflex in patients with obstructive sleep apnea syndrome

BACKGROUND

The swallowing reflex is well coordinated with breathing patterns in normal humans. However, patients with obstructive sleep apnea syndrome (OSAS) may have a swallowing disorder that reflects the abnormal function of nerves and muscles in the suprapharynx.

OBJECTIVE

To examine the relationship between the swallowing function and sleep-disordered breathing in patients with OSAS.

PARTICIPANTS

Twenty patients with OSAS with a mean (+/-SD) age of 53.4+/-8.9 years old, and 20 age-matched control subjects with a mean age of 51.4+/-9.1 years old.

METHODS

OSAS was diagnosed using the recordings of overnight polysomnography. The swallowing function in the subject was tested using a swallowing provocation test. The swallowing reflex was determined according to the following criteria: latent time (LT), the time following a bolus injection of distilled water at the suprapharynx to the onset of swallowing; inspiratory suppression time (IST), the time from the termination of swallowing to the next onset of inspiration; and threshold volume, the minimum volume of water (range, 0.4 to 2 mL) that could evoke the swallowing response.

RESULTS

Whereas the LT values in patients with OSAS were larger than the LT values in the control subjects, the IST values (which may reflect the switching mechanism from deglutition apnea to breathing) were actually shorter. In addition, a greater bolus volume was necessary to elicit swallowing in patients with OSAS than was necessary in the control subjects.

CONCLUSION

Patients with OSAS are likely to exhibit an impaired swallowing reflex, probably due to the perturbed neural and muscular function of the upper airways.

Relation of body position at the time of discovery with suspected aspiration pneumonia in poisoned comatose patients

OBJECTIVE

The left lateral decubitus position is generally accepted as the position of choice to protect against aspiration pneumonia in comatose poisoned patients. We studied the relationship between initial body position during coma and subsequent development of suspected aspiration pneumonia (SAP).

DESIGN

Observational, descriptive study.

SETTING

Toxicology intensive care unit in a university hospital.

PATIENTS

Acutely poisoned comatose patients admitted to our intensive care unit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Glasgow Coma Scale score (GCS) and body position were recorded in poisoned patients on discovery. Chest radiographs were examined for infiltrates suggesting SAP within 24 hrs of hospitalization. The prone positioned patients had a lower incidence of SAP than patients in the lateral decubitus and supine positions, despite similar GCS scores. Patients in the semi-recumbent position had an incidence of SAP similar to prone patients, but with higher GCS values.

CONCLUSIONS

The prone position appears to be associated with a lower incidence of SAP than the lateral decubitus position in comatose poisoned patients.

Effect of pharyngeal stimulation on the motor function of the esophagus and its sphincters

OBJECTIVE/HYPOTHESIS

Sensory impulses from the pharynx induce contraction of the upper esophageal sphincter (UES), relaxation of the lower esophageal sphincter (LES), and inhibition of peristalsis. To determine 1) the magnitude of UES contractile response to threshold volume of fluid that induces LES relaxation and 2) the effect of rapid pharyngeal air stimulation on LES resting pressure and its concurrent influence on the UES and progression of esophageal peristalsis.

METHODS

Eleven healthy volunteers (age, 31 +/- 2 y) were studied by concurrent UES, esophagealbody, and LES manometry.

RESULTS

At a threshold volume of 0.3 +/- 0.05 mL, injections of water into the pharynx directed posteriorly, resulted in complete LES relaxation. Duration of these relaxations averaged 19 +/- 1 seconds. In 10 of 11 subjects, these relaxations were accompanied by a simultaneous increase in UES resting tone that averaged 142% +/- 27% above preinjection values. Pharyngeal stimulation by rapid air injection resulted in complete LES relaxation in 8 of the 11 subjects (threshold volume, 14 +/- 6 mL). Five of 8 developed a concurrent mild increase in resting UES pressure (17% +/- 6% above preinjection values) (P < .05). Pharyngeal water injection inhibited the progression of the peristaltic pressure wave at all tested sites and in all subjects, but pharyngeal air injection in only 2 of the 11 studied subjects.

CONCLUSIONS

The inhibitory effect of pharyngeal water injection on LES resting pressure is accompanied by a substantial contractile effect on the UES. Although stimulation of the pharynx by rapid air injection may induce LES relaxation, its inhibitory effect on esophageal peristalsis and stimulatory effect on UES pressure are negligible compared with that of water injection.

Investigation of effects of anesthesia and age on aspiration in mice through LacZ gene transfer by recombinant E1-deleted adenovirus vectors

To examine the role of disturbed upper airway reflexes in aspiration, we administered 20 microliters of the adenovirus (Ad) vector Ad-CMV-LacZ or 20 microliters of phosphate buffered saline (PBS) intranasally to C57 black mice. We investigated expression of the LacZ gene by this Ad vector in the nostrils of each mouse, with or without anesthesia. Under anesthesia, LacZ gene expression was detected in the lungs of every mouse given the Ad vector. However, no LacZ gene expression was found in the trachea or lungs of mice given the Ad vector without anesthesia. In mice given PBS or wild-type adenovirus transnasally during anesthesia, there was no LacZ gene expression in the nostrils, trachea, or lungs, suggesting that with 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-gal) staining, blue-stained cells indicated transferred LacZ gene expression. These results suggested that aspiration of intranasal solution into lower airways was caused by disturbed upper airway reflexes during anesthesia. This process can be analyzed by the distribution of LacZ gene expression in airways. We next examined the effect of age on anesthesia-induced aspiration. Twenty-six-mo-old mice exhibited more LacZ gene expression in their lungs than did 6-mo-old mice at a concentration of 0.5 to 4.0% halothane in 100% oxygen. This suggests that light anesthesia may depress upper airway reflexes and cause aspiration in older animals. This novel model of aspiration, generated with the Ad-CMV-LacZ vector, may be useful for elucidating the mechanism of development of aspiration pneumonia in relation to age-related impairment of upper airway reflexes.

Pharyngoglottal closure reflex: identification and characterization in a feline model

Earlier studies in humans have shown that pharyngeal stimulation by water at a threshold volume induces a brief vocal cord adduction, i. e., pharyngoglottal closure reflex. The present study was undertaken to 1) develop a suitable animal model for physiological studies of this reflex and 2) delineate its neural pathway and effector organs. Studies were done in cats by concurrent videoendoscopy and manometry followed by electromyographic studies. At a threshold volume (0.3 +/- 0.06 ml), injection of water into the pharynx resulted in a brief closure of the vocal folds, closing the introitus to the trachea. Duration of this closure averaged 1.1 +/- 0.1 s. Bilateral transection of the glossopharyngeal nerve completely abolished this reflex but not swallows induced by pharyngeal water stimulation. The pharyngoglottal closure reflex is present in the cats. The glossopharyngeal nerve is the afferent pathway of this reflex, and the interarytenoid and lateral cricoarytenoid muscles are among its target organs.

Anatomy and physiology of swallowing in adults and geriatrics

Key anatomic and physiologic features that play an important role in normal and abnormal swallowing in the adult are described. Highlighted topics include the neurologic afferent and efferent control mechanisms, the effect of stroke on these mechanisms, and the upper and lower esophageal sphincters.

Mandible position and head posture: electromyography of sternocleidomastoids

A study was performed to evaluate relationships between mandible position, dynamics, muscle activity and head posture while swallowing by use of surface EMG and mandible kinesiograph on two population groups (118 pathologics and 31 controls). The study produced the following: 1. specific mandible dynamics with a very fast rising phase (0.3 sec) and longer phase of stabilization (1.5 sec); 2. more than 60% of the subjects presented deglutition at occlusion level, the others swallowing at a distance of 0.1-4.6 mm; 3. the whole muscle activity (temporals, masseters, digastrics, sternocleidomastoids) lasted 1.5 sec with no correlation of duration to age; 4. sternocleidomastoids fired at swallowing with an effort of one-half of temporals or masseters; 6. firing order presented a particular pattern: digastrics more often first, sternocleidomastoids more often last. No differences were found between the pathologics and controls. Findings suggest that the oral phase or mandible dynamic, and the stabilization phase or oropharyngeal phase of swallowing, has an individual role that is important in head postural equilibrium.

Characterization of the pharyngo-UES contractile reflex in humans

Preliminary human studies suggest the presence of an upper esophageal sphincter (UES) contractile reflex triggered by pharyngeal water stimulation. The purposes of this study were to further characterize this reflex and determine the threshold volume for its activation. We studied 10 healthy young volunteers by manometric technique before and after topical pharyngeal anesthesia. UES pressure responses to various volumes and temperatures of water injected into the pharynx were elucidated. At a threshold volume, rapid-pulse and slow continuous pharyngeal water injection resulted in significant augmentation of UES pressure in all volunteers. Threshold volume for inducing UES contraction averaged 0.1 +/- 0.01 ml for rapid-pulse injection and was significantly smaller than that for slow continuous injection (1.0 +/- 0.2 ml). UES pressure increase duration averaged 16 +/- 4 s. Augmentation of UES resting tone by injection of water with three different temperatures was similar. This augmentation was abolished after topical anesthesia. Conclusions were that stimulation of the human pharynx by injection of minute amounts of water results in a significant increase in resting UES pressure: the pharyngo-UES contractile reflex. The magnitude of pressure increase due to activation of this reflex is not volume or temperature dependent. Loss of pharyngeal sensation abolishes this reflex.