Dysphagia matters and endoscopic examination of patients with swallowing complaints is an important part of their evaluation. The 3 key adjuncts to flexible fiber optic laryngoscopy are (1) flexible endoscopic evaluation of swallowing, (2) assessment of pharyngeal squeeze, and (3) sensory testing. Patients undergoing flexible fiber optic laryngoscopy are then challenged with liquid or solid materials for intake. Fundamental clinical signs of swallowing parameters are noted. The threshold at which the laryngeal adductor reflex is triggered is believed to be helpful in predicting swallowing capacity. This report deals solely with adult dysphagia evaluation.
Key points
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In-office evaluation of dysphagia is a fundamental part of caring for patients with swallowing complaints. Patients with dysphagia must undergo examination of the main organs of swallowing: larynx, pharynx, and tongue.
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Although flexible fiber optic laryngoscopy itself is a powerful tool in assessing patients with swallowing difficulties, the addition of a few simple steps allows for FEES, a well-studied, simple, and intuitive test of swallowing function.
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Clinical evaluation of pharyngeal motor strength can be accomplished with the pharyngeal squeeze maneuver; this is performed in a matter of seconds during flexible fiber optic laryngoscopy and has a strong correlation with more involved and more invasive measures.
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FEESST includes S ensory T esting with the FEES component. Despite promising early studies, FEESST has not become a common or widely used tool in the evaluation of swallowing dysfunction.
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The presence of bilateral deficits as determined by FEESST is a powerful clinical indicator of poor swallowing.
Overview
Dysphagia contributes to the dominant causes of morbidity and mortality in patients cared for by otolaryngologists, including the leading cause of death in this group—aspiration pneumonia complicating stroke. The overall morbidity and medical complexity of these cases and the perceived lack of opportunities for surgical intervention many contribute to reluctance and even disinterest among some otolaryngologists in the detailed evaluation of patients with swallowing disorders. It is the rare dysphagia patient seen in the outpatient setting that will undergo surgery for that problem. Nonetheless, important decisions must be made with regard to the feeding status, diet, and airway safety of these patients. Even patients without overt swallowing complaints should, depending on their overall clinical scenario, undergo the simple tests characterized in this article. One common example of this is in patients with unilateral vocal fold paralysis. Although predominantly thought of as a voice problem, many of these patients have swallowing problems as well. Heitmiller and colleagues recently reported on modified barium swallow studies performed on patients with known unilateral vocal fold paralysis. In this report, 38% of the studies found aspiration with 12% finding laryngeal penetration, a significant fraction in any group. This emphasizes the value of evaluating swallowing function in all laryngology consultations.
No group of physicians is more appropriate or capable of caring for this often-challenging group than otolaryngologists; improving and mastering the in-office evaluation of dysphagia patients begins with knowledge and familiarity with the flexible endoscopic evaluation of swallowing (FEES) examination and the pharyngeal squeeze maneuver. Flexible endoscopic evaluation of swallowing sensory testing (FEESST) is also discussed an attractive but less commonly used adjunct.
Flexible Endoscopic Evaluation of Swallowing
The intuitive and embraceable nature of the FEES examination has been a key part of its attraction for clinicians evaluating dysphagic patients. What could be more fundamental than literally looking into the pharynx and larynx during swallowing and noting what happens with material presented to the patient to swallow? The FEES examination was introduced in 1988 by Langmore and colleagues in the journal Dysphagia .
Patient preparation and positioning
The FEES procedure is ideally done with the patient in the seated position, unreclined, and totally awake. Sometimes these important examinations are performed at the bedside for inpatients at acute or chronic care facilities where patients cannot sit up. If possible, the most ideal condition for safe oral intake (position, wakefulness) is reproduced for FEES testing. One of the many advantages that FEES testing has over the modified barium swallow (MBS) is the ability to obtain useful clinical information without transporting patients (often infirm, unstable, or needing to travel a great distance) to a hospital with MBS facilities.
Although most studies cited in this section advocate (and even insist) that no local anesthesia be applied topically to the nose, as is customary for other flexible fiber optic laryngoscopy (FFL) examinations, opinion on this does vary. The concern driving this proscription is that the presence of anesthetic sprayed in and through the nasal cavity may alter pharyngeal or laryngeal function.
In one study of healthy young controls, Rubin and colleagues were not able to identify any obvious motion abnormalities in patients before versus after the administration of topical anesthetic for FFL. This study was helpful, but without larger numbers and a study group that included patients with laryngeal and pharyngeal dysfunction, it is difficult to say that the presence of topical anesthesia is innocuous.
Recently, a large Cochrane Review was performed looking not at the possible impact of topicalization on function but rather on its utility and necessity in anesthetizing the nose for FFL in the first place. The authors found no compelling evidence supporting its use. Predictably, the lack of strong evidence one way or another was lacking. Finally, Suiter and Moorhead executed a helpful study examining the impact of the presence of a fiber optic scope in the pharynx (transnasally placed) on MBS findings. In a study of 14 normal subjects, ranging from ages 23–83 years, the presence of an FFL past the soft palate but above the epiglottis did not affect swallow duration, bolus clearance, or penetration/aspiration scale (PAS) scores. This finding helps of course, with concerns over the observer effect of FEES on swallowing function. This study has not been reproduced in a population of symptomatic patients.
Aging effects on penetration/aspiration
FEES is capable of discriminating changes that occur with age even in an asymptomatic population. Butler and colleagues studied a series of young adults and compared them with a similarly sized group of subjects with a mean age of 75 years. The PAS score was significantly different between the 2 groups, who also had longer dwell times and more residue. Butler and colleagues follow this up with a prospective study of a group of 76 older subjects (age 60 years and older) with no swallowing complaints; their group specifically looked at liquid type, bolus size, and delivery method (straw vs cup) in this investigation. Penetration was found in up to 83% of subjects, and aspiration was seen in 24% of those studied. It should be noted that this took many swallows in some cases to detect these events. Nonetheless, they did occur. The PAS scores were clearly worse with milk versus water swallows, larger volumes, and straw use. These findings should be considered in the interpretation of FEES examinations on dysphagic clinic patients.
What is the role of the FEES examination? FEES is good at detecting the presence of penetration, aspiration, pooling, retained secretions, and the effectiveness of coughing in a given patient. It is also good at detecting even small amounts of material passing superiorly into the nasopharynx during swallowing.
FEES technique
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The FEES begins with the patient in the seated position.
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If a videostroboscopy is indicated for other reasons, it should be performed first.
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Once the patient and team (often an otolaryngologist and a speech language pathologist) are ready, the pharyngeal squeeze maneuver is performed first.
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The oral intake challenges begin with water or ice chips.
Some clinics, such as the University of Washington Laryngology Program, use some food coloring to help with the identification of retained food or liquid; this method is useful for training purposes and also for patients and their families. The study itself does not require contrasting colors; Leder and colleagues showed nicely it is not necessary for most FEES examinations. This important study also found remarkable intra- and interrater reliability for FEES.
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If a patient does well with the ice chips or water, pureed consistencies and crackers or pretzels can be administered. Although caution is important in evaluating these patients, a reasonable challenge to their swallowing should be presented in this monitored, idealized setting.
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The presence of penetration or aspiration should be noted.
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Important details should also include noting any vallecular, pharyngeal wall, or pyriform residue.
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As in an MBS, the presence of an expert speech language pathologist (SLP) allows for the implementation of positioning strategies and compensation maneuvers such as head tuck and chin tuck to one side to assess the impact, if any, on swallowing efficiency and safety.
FEES is limited in assessing oral phase problems, although early spillage is easily detected. The MBS is superior to FEES in this regard. The MBS is also better at allowing for quantification of pharyngeal movement, including base of tongue and constrictor activity. The FEES is also limited in terms of describing upper esophageal sphincter (UES) segment transit. Nonetheless, it is an important and valuable adjunct to the clinical evaluation of patients with dysphagia. It requires no more tools than what are already present in most otolaryngologists’ offices. It adds little time and minimal discomfort to the patient’s evaluation. The FEES may be the only meaningful swallow evaluation available to a remote or difficult-to-move patient.
Pharyngeal Squeeze Maneuver
The pharyngeal squeeze maneuver (PSM) is basic: during FFL, the patient is asked to make high-pitched, strained phonation, preferably in a rising crescendo of effort. This will, in normal pharynges, result in obvious recruitment of the pharyngeal constrictor musculature. It is not a subtle finding.
This simple observation, first characterized and published by Bastian in 1991, has proven to be a useful adjunct to the in-office evaluation of dysphagia patients. What is potent about the PSM is the clinical information it provides in just a few seconds, with zero risk to the patient.
Specifically, Bastian, followed by many others, advocates that the following step is performed during FFL. At a point in the examination before any challenges (FEESST or FEES), “while maintaining a panoramic view, patients are asked to produce the highest pitch of which they are capable.” This is meaningful even in the presence of severe dysphonia, ie, it is not the sound produced that matters, it is the recruitment of the pharyngeal musculature.
What can we conclude about the PSM? What does it mean?
Investigators have proposed that its presence endoscopically serves as a reasonable surrogate for the formal testing of pharyngeal motor strength. The University of California Davis group has published extensively on this subject; one of the more important articles from this team compared the endoscopic PSM with the pharyngeal constriction ratio (PCR), a validated measure of pharyngeal strength as seen on contrast fluoroscopy.
PCR correlation with pharyngeal strength
The PCR had been shown previously to inversely correlate with pharyngeal strength, ie, low strength was associated with a higher PCR and vice versa When using the PCR as a reliable indicator of pharyngeal strength, the PSM was also found to be good. The average PCR for dysphagic patients was found to be 0.06 (low number reflecting a good PCR and, by inference, good motor strength in the pharynx), whereas the mean PCR for those dysphagic patients with an absent PSM was 0.31, a statistically significant difference from the PSM-positive group.
PSM as predictor of swallowing safety
Advocates have studied the utility of PSM (focusing on the assessment of pharyngeal motor function) compared with the information obtainable in studying pharyngeal and laryngeal sensory function. In a small but important series of clinical investigations, pharyngeal strength, as inferred from the PSM, serves as an important predictor of swallowing safety—perhaps even more so than tests of sensory function.
PSM qualitative realiability
The PSM has high interrater reliability when the test is treated as qualitative and as a simple question of present or absent. In an article from 2007, Rodriguez and colleagues studied a convenience sample of 40 patients undergoing FFL with PSM. When the reviewers were asked to categorize the findings for PSM as absent, diminished, or normal, there was weak interrater reliability. When the reviewers simply grouped the studies by normal or abnormal PSM, the reliability was high. Also, the laterality of the test is not reliably assessable (Peter Belafsky, personal communication, 2012).
Food textures in PSM
Specific textures have been studied in terms of the role of PSM in swallowing evaluation. Perlman reported an interesting prospective study of pureed food intake in 204 dysphagic patients. These patients underwent both FEES and sensory testing ( FEESST , see later discussion). The patients were divided into groups with normal, moderate, or severe sensory deficits based on their sensory testing. They were also categorized by the presence or absence of the pharyngeal squeeze. One striking finding was that patients did not show an increasing level of aspiration for pureed textures despite increasing levels of sensory disturbance. The authors concluded “the aspiration of pureed foods may depend more on muscle tone of the hypopharynx than on sensation.”
Another part of that study looked at similar questions with thin liquid challenges instead of purees. Setzen and colleagues published this study of 204 patients presented with 5-mL liquid boluses during FEES testing. Again, these patients also underwent sensory testing. In the thin liquid study, only 2% of the normal sensation/normal squeeze aspirated. This number increased to 29% with motor function impairment. Patients with a moderate decrease in sensation did not aspirate during their trials as long as motor function, as measured by the presence of a positive PSM, was intact. When the patients with moderate sensory impairment also had any motor impairment, most of them aspirated. Most strikingly, the rate of aspiration in patients with severe sensory impairment but intact motor function was 15% (5 of 33 patients); this increased to 100% (15 of 15) in patients with the same severe level of sensory impairment but a poor pharyngeal squeeze.
PSM related to Zenker’s diverticulum
Anecdotally, the author thinks that the presence of a positive PSM is important in counseling patients with Zenker’s diverticulum as to their swallowing outcomes postoperatively. Those with intact PSM are more likely to have immediate swallowing success in contrast to those who have already worn out the pharynx or have become malnourished. The presence of a weak pharynx and or significant bilateral pooling in a preoperative patient with Zenker’s diverticulum is an indication for a preoperative gastrostomy tube in many cases of Zenker’s diverticulum with advanced age or comorbidities.
Flexible Endoscopic Evaluation of Swallowing with Sensory Testing
Investigators have long searched for a minimally invasive, clinically feasible, reliable method to test laryngeal sensory function. Recent advances have included “SELSAP” (Surface-Evoked Laryngeal Sensory Action Potential) in which external, noninvasive electrodes are used to assess superior laryngeal nerve conduction as an indicator of laryngeal sensory function. Until this or other approaches are more refined, the current leading method in the measurement of laryngeal sensory function is the FEESST. Despite a valuable series of supporting articles and studies, FEESST continues to be of modest clinical utility to laryngologists and to otolaryngologists in general.
The fundamental concept driving the FEESST study is that stimulation of the supraglottic larynx, in this case by a small puff of air delivered in close proximity to the laryngeal mucosa, results in elicitation of the laryngeal adductor reflex (LAR). The LAR results in a brisk and easily identifiable closure response to stimulus. The response is noted for both the right and left side; the tests are quantified at various levels of air-puff pressure stimulation.
One typical scenario is to test patients at 3 mmHg on each side and determine the presence or absence of the LAR response. If an LAR is detected, it is noted as normal for this side. Further precision beyond the presence of eliciting an LAR at 3 mmHg is not clinically useful. If no LAR is seen at 3 mmHg, the stimulus is increased to 6 mmHg and retested. If this increase elicits a response, a mild impairment is noted. If no response is elicited at 6 mmHg, the air puff stimulus is set to 9 mmHg. Positive LAR at this level (in the absence of positivity less than this threshold) is recorded as a moderate impairment. No response to stimulus at 9 mmHg is documented as a severe sensory deficit. Both sides are tested. It should be emphasized that the presence of bilateral deficits as determined by FEESST is a powerful clinical indicator of poor swallowing.
Jonathan Aviv, MD, is a main driver of investigation and dissemination of information regarding FEESST. He and others have carefully and comprehensively categorized its safety as an in-office examination. Aviv’s impact can be readily discerned from this article’s reference list. His 2005 book, coauthored with Tom Murry, PhD, is also helpful as a compendium of knowledge and experience regarding FEESST.
The fundamentals of FEESST depend on measuring the presence or absence of the LAR after unilateral stimulation of the supraglottic mucosa by a discreet puff of air, in this case, as delivered through the channel in or alongside a flexible fiber optic laryngoscope. Both sides are tested for the elicitation threshold. The pressure of the air puff can be altered, and the lowest level at which the LAR is seen is noted; the higher air pressure needed, the more impairment of laryngeal sensory function.
One of Aviv’s early studies compared psychophysical testing (ie, asking the patient if they can feel the stimulus in the larynx/pharynx) with the FEESST’s dependence on the simple LAR. In this elegant study, 20 normal subjects and 80 dysphagic patients were scrutinized and found to have a remarkable correlation between the psychophysical testing and the FEESST, providing solid evidence that the FEESST was an excellent surrogate and, more importantly, could perhaps be used in patients who were not able to participate in the test from a behavioral standpoint.
FEESST in bedridden or incapacitated patients
The ability for FEESST to assess laryngeal and pharyngeal function in the absence of patient participation has been touted as a significant advantage in bedridden or otherwise incapacitated patients. Although this is true, only a fraction of these patients are likely to be safely swallowing. The presence of severe, particularly bilateral, defects in sensation are thought to be indicators for poor swallowing safety. As discussed in the FEES section, clinicians have expressed concern with the possible impact of nasal topical anesthesia on FEESST findings. Johnson and colleagues looked at this in an important study from 2003 in which 15 subjects underwent FEESST with and without topical decongestion and anesthesia; no difference was noted in stimulation thresholds. Once again, however, this study was done in normal volunteers, not in dysphagic patients.
Aviv and colleagues, through an important series of articles, established early that normal subjects had predictable LAR responses to air-puff stimulation. In a study of 20 healthy patients with a mean age of 34 and no symptoms related to swallowing, sensory thresholds for LAR elicitation were consistent (2.9 mmHg ± 0.7). Another study nicely established that laryngeal sensory function, as tested during FEESST, declines with age. In a test of 80 adults across a wide variety of ages:
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The mean threshold for eliciting the LAR was 2.60 mmHg
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For the 20- to 40-year-old subjects, the level was 2.06 mmHg
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For the 41- to 60-year-old group, the level was 2.44 mmHg
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In the subjects older than 60, the level was 2.97 mmHg
The older control group was not at threshold level for sensory deficit, but the trend with time was clearly shown.
FEESST in acute neurologic patients
Perhaps the strongest argument for the utility of the FEESST study is in acute neurologic patients. Aviv and colleagues, in 1997, studied a series of 20 patients who underwent both MBS and FEESST testing in the acute period after stroke. These patients were followed up prospectively for 2 years. Four of the 10 patients with no evidence of aspiration on initial MBS had pneumonia in the follow-up period; most of these patients had significant bilateral deficits on FEESST examination. Of the 5 patients who had no aspiration on MBS and also did not have sensory deficits on FEESST, none had pneumonia during the follow-up period. The authors advocated the use of FEESST as an “adjunct to MBS in guiding the dietary management of stroke patients with dysphagia.” In my opinion, these patients are different than many of the complex dysphagia patients that might be seen in a laryngologist or otolaryngologists’ office; the OTO patients are more likely to have mucosal damage or inflammation, be it from reflux, radiation, or other form of injury. In my experience, this makes performance and interpretation of FEESST less predictable and, in my hands, less reliable. In patients without significant changes to the surface of the larynx/pharynx, FEESST remains an attractive idea. Aviv, Murry and colleagues, and others have investigated FEESST as a modality to test patients with chronic cough and paradoxic vocal fold dysfunction. The utility of FEESST in characterizing underlying neuropathy in the presence of varying amounts of laryngeal inflammation remains an open question.
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