Fiberoptic endoscopic evaluation of swallowing is a technique that allows for the assessment of pharyngeal dysphagia and the implementation of rehabilitation interventions with the goal of promoting safe and efficient swallowing. An overview of the equipment needed for the laryngoscopic evaluation, how to conduct the examination, what can be visualized endoscopically, diagnostic parameters, the implementation of therapeutic strategies, and suggestions for future research are discussed herein.
The use of flexible fiberoptic transnasal laryngoscopy to visualize swallowing function is becoming increasingly common in settings in which a practical and less resource intensive alternative is desired for the objective assessment of patients with dysphagia. The use of flexible laryngoscopy to assess swallowing was first reported by Langmore and colleagues and Bastian . In the 20 years since these initial reports, FEES has become a validated technique to evaluate the pharyngeal swallow . These studies have demonstrated that FEES and the videofluoroscopic swallowing study (VFSS) (ie, modified barium swallow) have equivalent sensitivity and specificity in detecting the critical variables of delay in triggering the swallow reflex, pharyngeal residue after the swallow, as well as laryngeal penetration and tracheal aspiration of various consistencies of foods and liquids.
A comprehensive swallow evaluation has two purposes: (1) to assess dysphagia; and, (2) when appropriate, to make recommendations and implement strategies to allow for safe eating. A complete FEES examination includes surveying anatomic structures at rest and in motion, identifying the presence and management of oropharyngeal secretions, and evaluating the consequences of swallowing various consistencies of foods and liquids. If dysphagia is identified, implementation of various therapeutic interventions is performed (with the endoscope in place) to determine if postural (eg, head position), dietary (eg, bolus volume and consistency), and behavioral changes (eg, effortful swallow or two swallows per bolus) are successful in promoting safer and more efficient oral alimentation.
History of the laryngoscopic swallowing evaluation
The development of improved camera technology capable of interfacing with arrayed bundles of ever smaller flexible optical fibers has permitted visualization of anatomic areas that were previously too remote to be inspected routinely for the determination of potential medical conditions. The first of these instruments was a flexible transoral gastroscope patented in 1956. In less than 10 years, Sawashima and Hirose reported the development of a smaller flexible array of optical fibers designed specifically to view the pharynx and larynx . Continued improvements in camera and fiberoptic technologies have resulted in improved laryngoscopic imaging, such as the evolution from analog to digital signals and the recent development of the digital “chip tip” camera that rivals the images achieved with rigid telescopes. During the past 20 years, an ever increasing body of research has described the use of flexible laryngoscopy in patients presenting with dysphagia. The purposes of this article are to explain the use of flexible fiberoptic laryngoscopy in the assessment of swallowing, to review relevant findings, and to stimulate further research.
Purposes of dysphagia testing
The response to a consultation for the evaluation of a patient with suspected dysphagia should always include a complete medical review and clinical assessment. If the clinical evaluation does not provide sufficient information to allow for confident patient management, an instrumental assessment should be performed . The goals of the two most popular instrumental assessments (ie, FEES and VFSS) are similar in construct. In the course of these examinations the clinician attempts to identify normal and abnormal anatomy relative to swallow function; to discern discrete physiologic structural movements associated with the swallow; to determine the temporal coordination of structural movements relative to bolus advancement; to assess the trajectory of the bolus through the pharynx; to ascertain bolus residue patterns; and, when indicated, to implement appropriate therapeutic interventions. Fig. 1 shows simultaneous comparisons of VFSS (on the left) and FEES (on the right) showing spillage into the vallecula and pyriform sinuses bilaterally.
The endoscopist is alert to the major salient findings of penetration of food and liquid into the laryngeal and tracheal airways as well as the retention of food and liquid in the pharynx after the initial swallow has been completed. During the examination the clinician will make adjustments to bolus volume, viscosity, and rate of delivery, as well as adjustments in positioning and implementation of maneuvers to determine if these changes have a positive effect on the safety or efficiency of the swallow. The ultimate goals are improved nutrition and hydration for the maintenance and enhancement of quality of life.
The examination is typically tailored to meet the needs of the individual patient. The American Speech-Language-Hearing Association has developed a comprehensive triad of documents related to the performance of FEES, that is, reports on the knowledge and skills for speech-language pathologists performing endoscopic assessment of swallowing and the role of the speech-language pathologist in the performance and interpretation of the endoscopic evaluation of swallowing technical report and guidelines . Readers are encouraged to familiarize themselves with the information provided in these reports.
Purposes of dysphagia testing
The response to a consultation for the evaluation of a patient with suspected dysphagia should always include a complete medical review and clinical assessment. If the clinical evaluation does not provide sufficient information to allow for confident patient management, an instrumental assessment should be performed . The goals of the two most popular instrumental assessments (ie, FEES and VFSS) are similar in construct. In the course of these examinations the clinician attempts to identify normal and abnormal anatomy relative to swallow function; to discern discrete physiologic structural movements associated with the swallow; to determine the temporal coordination of structural movements relative to bolus advancement; to assess the trajectory of the bolus through the pharynx; to ascertain bolus residue patterns; and, when indicated, to implement appropriate therapeutic interventions. Fig. 1 shows simultaneous comparisons of VFSS (on the left) and FEES (on the right) showing spillage into the vallecula and pyriform sinuses bilaterally.
The endoscopist is alert to the major salient findings of penetration of food and liquid into the laryngeal and tracheal airways as well as the retention of food and liquid in the pharynx after the initial swallow has been completed. During the examination the clinician will make adjustments to bolus volume, viscosity, and rate of delivery, as well as adjustments in positioning and implementation of maneuvers to determine if these changes have a positive effect on the safety or efficiency of the swallow. The ultimate goals are improved nutrition and hydration for the maintenance and enhancement of quality of life.
The examination is typically tailored to meet the needs of the individual patient. The American Speech-Language-Hearing Association has developed a comprehensive triad of documents related to the performance of FEES, that is, reports on the knowledge and skills for speech-language pathologists performing endoscopic assessment of swallowing and the role of the speech-language pathologist in the performance and interpretation of the endoscopic evaluation of swallowing technical report and guidelines . Readers are encouraged to familiarize themselves with the information provided in these reports.
Endoscopic equipment
The flexible laryngoscope is constructed to cast a “cold” light delivered from a halogen or xenon light source. The light travels along fiberoptic bundles which traverse the length of the scope. Depending on the configuration, the light is diffused through one or two lenses at the tip of the scope to illuminate the area of interest. An analog laryngoscope has a separate lens on the distal end of the scope that collects the reflected image and projects it along another bundle of light fibers to the eyepiece. The endoscopist can visualize the image by looking directly through the eyepiece or by using a chip camera, which converts the image to a video signal allowing the image to be viewed on a monitor and recorded on a video recorder. A digital chip tip scope also requires a bundled array of light fibers to illuminate the anatomy of interest but does not have an eyepiece for viewing. Instead, the image is captured on an optical chip and then projected to a video display/recorder. Ideally, when performing the laryngoscopic swallowing examination the endoscopist should be freed from viewing the image through the eyepiece. With the chip camera in place, patient positioning becomes less restrictive because close proximity of the patient and endoscopist is no longer a necessity. In addition, the image is much larger on the video monitor, allowing for better identification of potential abnormalities. It is advantageous to record the study on video tape or via digital format for archiving and later review .
Many fine flexible laryngoscopes on the market are suitable for the performance of FEES. The typical laryngoscope has a flexible insertion shaft that is approximately 40 cm long, with the diameters ranging from 3.2 to 4.0 mm. Smaller pediatric laryngoscopes with diameters ranging from 1.6 to 2.2 mm provide diminished but nonetheless adequate illumination capabilities for good visualization of the anatomic structures, swallow physiology, and bolus flow patterns of interest. The operation of the angulation lever on the control portion of the scope adjusts the degree of deflection. The distal tip of the scope deflects greater than 90 degrees to allow dynamic control of the image being viewed. Generally, the FEES examination rarely requires deflection beyond 90 degrees.
Laryngoscopic visualization of the pharyngeal swallow
The scope is gently inserted transnasally along the path of least resistance in the most patent naris. This path is generally along the nasal floor below the middle turbinate or between the inferior and middle turbinates. Once a passage has been determined, the scope is continuously inserted until the nasopharyngeal vault is visualized. The clinician should position the scope just anterior to the vomer bone, which demarcates the point where the hard and soft palate articulate. It is at this point that velar function should be assessed initially. The patient is then instructed to breath through the nose or hum, causing the velum to drop and opening the velopharyngeal port. At this point the angulation control lever is manipulated to angle the scope downward and allow for insertion into the nasopharynx to view the base of tongue and laryngeal inlet. After insertion, rotation of the endoscope clockwise or counter-clockwise and deflection of the endoscope tip permits the endoscopist to view the entire pharynx and larynx.
For the observation of general swallowing function, the distal end of the scope is placed superior to the epiglottis at the level of the uvula. This position allows for a view of the base of tongue, posterior pharyngeal wall, lateral pharyngeal walls, epiglottis, vallecula, larynx, and pyriform sinuses. It is important to remember that the endoscopic image is reversed, that is, the right side in the image is actually the left side anatomically and the left side in the image is actually the right side anatomically. As the scope is advanced further into the pharynx, fewer structures peripheral to the larynx are included in the field of view. The scope may be advanced to the tip of the epiglottis for optimal viewing of the pyriform sinuses, laryngeal vestibule, and subglottis, that is, the anterior tracheal wall. This location is the ideal position to observe airway closure patterns during the swallow. The typical depth of placement of the laryngoscope to view adequately swallow function and aspiration is no greater than 15 cm from the tip of the nares.
Despite concern that the presence of the flexible portion of the laryngoscope in the pharynx may have a deleterious effect on pharyngeal swallow physiology, this has been shown not to be true. Suiter and Moorhead reported that the presence of a flexible fiberoptic endoscope in the pharynx during swallowing in 14 normal adults did not significantly affect pharyngeal swallow physiology in three swallow duration measures, the number of swallows necessary to clear the bolus, or Penetration-Aspiration Scale (PAS) scores.
During the examination, the laryngoscope is placed transnasally and advanced through the nasopharynx and positioned with the objective lens between the distal nasopharynx and midpharynx, with adjustments in the depth of placement to optimize the visualization of findings throughout the examination. The field of view obtainable with the laryngoscope includes only a fraction of the area that can be viewed with the fluoroscopic image; therefore, consideration should be given to the clinical signs and symptoms that the patient presents with when choosing between FEES and VFSS for the assessment of swallow. A typical fluoroscopic image will include the oral cavity, pharynx, and portions of the striated esophagus. Flexible laryngoscopy allows for the visualization of the anatomy and biomechanical movements that are immediately in front of the objective lens. The oral, upper esophageal, and esophageal stages of the swallow will not be visualized during this procedure. During the height of the pharyngeal swallow there is a brief period when the image is obliterated due to the apposition of tissue, usually the base of the tongue or velum to posterior pharyngeal wall, around the objective lens. In exchange for these disadvantages, the skilled endoscopist will be rewarded with an unequaled view of airway protective patterns and a sensitive tool for detecting laryngeal penetration and aspiration as well as an invaluable mechanism for biofeedback and patient education. Fig. 2 shows a FEES image of diffuse spillage of liquid (milk) into the vallecula and pyriform sinuses bilaterally.
Indications for the laryngoscopic evaluation of swallowing
Following a carefully conducted clinical examination (eg, a brief assessment of cognitive status and an oral-peripheral examination), the clinician should determine the field of view necessary to most completely reveal the pathophysiology of the suspected dysphagia. If questions regarding oral stage impairments cannot be answered following the clinical examination or if there is a suspicion of an esophageal component to the dysphagia, a fluoroscopic evaluation should be performed.
Numerous clinical signs and symptoms of dysphagia can be confidently assessed by employing the flexible laryngoscope. Ideal candidates are patients with hypernasality and suspected nasal regurgitation, laryngeal penetration, or aspiration before the swallow is initiated, abnormal vocal quality, and increased swallowing difficulty over the duration of a meal secondary to fatigue. The practical reasons for employing laryngoscopy are more numerous given that a single clinician can perform the examination at bedside and on short notice. Among the practical reasons for choosing laryngoscopy are the testing of individuals who may have safety issues associated with radiation exposure (eg, women with confirmed or possible pregnancy or patients with radiation limitations) and the retesting of individuals with documented dysphagia on the endoscopic or fluoroscopic evaluation . Because many patients may experience difficulty while being transported to the radiology suite, the laryngoscopic evaluation may be less taxing for bedridden or weak patients, patients with open wounds, contractures, fractures, or pain, and patients with quadriplegia or ventilator dependency. Additionally, patients who are morbidly obese, who require special positioning, or who are wheel chair dependent are challenging to assess via fluoroscopy. In the authors’ experience, the greatest opportunities to apply the practicalities of the laryngoscopic evaluation are in patients who are in the intensive care unit, who are heavily monitored, or who are ventilatory dependent. Contraindications for the procedure include cases of acute facial fracture, recent refractory epistaxis, bilateral obstruction of the nasal passages, severe agitation, and possible inability to cooperate with the examination.
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