Assessment of Aspiration Risk UsingFlexible Endoscopic Evaluation of Swallowing With Sensory Testing; Guest Blog by Dr. Eric Bicker
Flexible Endoscopic Evaluation of Swallowing with Sensory Testing (FEESST) is approved by the United States Food and Drug Administration (FDA) to assess quantitatively laryngopharyngeal sensory perception related to deglutition. Sensory discrimination testing during FEESST is conducted via delivered air pulses to the laryngopharyngeal musculature infiltrated by the internal branch of the superior laryngeal nerve (ISLN). Jafari, Prince, Kim, and Paydarfar (2003) implied that the afferent nerve transmission from the ISLN was essential for a functional pharyngeal swallow, specifically in supplying information to primary efferent neural functions that control adduction of the laryngeal musculature during the pharyngeal phase of the swallow. Their research proposed that ISLN damage was a major factor in the development of dysphagia and aspiration.
During the FEESST procedure protocol, as described in Aviv and Murray (2005), a flexible endoscope is passed transnasally, along the floor of the nose, past the velopharyngeal port and into the hypopharynx. Sensory discrimination thresholds during FEESST are obtained bilaterally by endoscopically providing air pulse stimuli directly anterior to the arytenoid cartilage at the juncture of the aryepiglottic fold because this mucosa in the laryngopharynx is innervated by the ISLN. The stimulus is designed to trigger a laryngeal adductor reflex (LAR) via direct stimulation of the ISLN (Aviv et al., 1993). Ludlow, Van Pelt, and Koda (1992) found that stimulation of this mucosa elicited the LAR, which was an involuntary, concise closure of the true vocal cords. Aviv et al. (1999) found that this airway defense LAR was maintained by brainstem function. Once the air-pulse testing is done, the patient is then fed food and liquid consistencies mixed with green or
blue food coloring for contrast while the pharyngeal phase of the swallow is assessed evaluating food, liquid, and secretions.
FEESST assessments are performed with patients who demonstrate dysphagia, a difficulty in swallowing, as defined by Logemann (1998). Clinical experience has shown that the presence of dysphagia might place the patient at risk for tracheal aspiration. As described by Marik and Kaplan (2003), the event of tracheal aspiration occurs when a bolus, particulate matter, or patient secretions enter the trachea. Research has shown that further airway entry into the lungs because of tracheal aspiration can become a catalyst for infection and pneumonia (Kalra, Ramsey, & Smithard, 2003). FEESST was designed to obtain data that is more objective regarding laryngopharyngeal sensation, when compared to the clinical bedside swallow evaluation, which is a more subjective evaluation.
Clinical practice has shown that instrumental assessment is especially important in those patients who have silent penetration when the bolus enters the larynx at or above the level of the true vocal cords without a sensory clearing response. As discovered by Logemann (1998), the same importance for instrumental assessment holds true for the identification of silent aspiration, when the bolus enters the trachea without a sensory clearing response. Aviv et al. (1996) suggested that the importance of sensory discrimination testing in these patients might be significant because decreased sensation in the laryngopharynx could contribute to dysphagia and aspiration. Sensory loss in the laryngopharynx might be a catalyst in dysphagia and aspiration, presuming that, if the patient did not sense a bolus or secretions within the laryngopharynx, regular upper airway shielding reflexes might be deficient. Research has shown that patients with more severe sensory
loss in the throat with FEESST have shown a higher frequency and occurrence of silent aspiration into the trachea, suggesting that there is some association between the sensory nerve for the laryngopharynx (ISLN) and the sensory nerve for the trachea (recurrent laryngeal nerve RLN), which are both branches of cranial nerve X, the vagus nerve (Blicker, 2008).
Written by Dr Eric Blicker MA CCC-SLP.D BRS-S
Eric's ASHA approved CE Provider website can be found here: WWW.CEUALLIEDHEALTH.COM
Amy Reinstein, M.S., CCC - SLP