“The effects of endoscope placement in the hypopharynx on swallowing-related measures in healthy adults” by Rebecca H. Affoo, Ciara Nellenbach, Joe Chomchai, and Nicole Rogus‐Pulia.

There is nothing quite like the release of a new FEES-related research article to get a group of FEES SLPs excited! At Carolina Speech Pathology, we are dedicated to serving our patients and customers with the highest quality of care. To ensure that our team delivers Reliable Excellence with every FEES, our Education and Clinical Departments complete thorough article reviews, organize an internal journal club, and update company practices, policies, and processes when indicated. Quite a feat in the ever-evolving world of dysphagia!

When completing dysphagia imaging, it is imperative that the clinician understands the wide variances that can occur within healthy swallowers in order to prevent over-diagnosing and inappropriately treating “problems” that are actually within a normal range. In the same vein, this article explores the potential impact that endoscope placement may have on the following swallowing-related measures: salivary flow rate, spontaneous swallow frequency, and masticatory efficiency. Let’s break down these measures to see how each relates to swallow function.


Saliva wears many hats in keeping us healthy and happy, including: lubricating and binding food to assist with transport into and through the esophagus, protecting esophageal mucosa from damage during food and liquid transport, solubilization of foods so that we can taste them, flushing of food debris to keep the mouth clean, destruction of bacteria and prevention of overgrowth of oral microbial populations, and initiation of starch digestion (Tiwari, 2011). Saliva is secreted in response to: chewing and other movements of oro-facial structures, mucosal dryness, and taste, smell, and visual stimuli (and, auditory stimuli if we are hanging out with Pavlov’s dogs).


The article notes that previous studies have shown that as the volume of saliva increases in the oral cavity, humans will respond by spontaneously swallowing more frequently. Mean SSF is cited for healthy young adults and healthy older adults.


Saliva also results in less effort required during mastication, and therefore fewer chewing cycles. This occurs as saliva lines the oral cavity with viscoelastic proteins, softens dry foods, and helps with transport through the oral cavity.


The aim of the study was to determine if transnasal passage of a FEES endoscope into the hypopharynx results in changes in SSF, salivary flow rate (SFR) and/or masticatory efficiency. The study was completed with 15 healthy participants between 20-63 years of age and occurred in 3 parts.

Part 1

Each participant was given a 5-minute habituation period, then baseline assessment of the measures was completed:

  • Spontaneous swallow frequency was collected over a 5 minute period, without informing the participants.
  • Salivary flow rate was collected using the draining method, requiring the participants to tilt their heads forward and not swallow, with expectoration of pooled saliva into a receptacle for measurement.
  • Masticatory effort was measured using The Test of Masticating and Swallowing Solids (TOMASS).

Part 2

“A distal chip, flexible endoscope with a 3.1 mm diameter insertion tube was inserted transnasally into the hypopharynx using a hypoallergenic, water-based lubricant.” The above measures were again collected with the endoscope in place, however it is not noted if a 5 minute habituation period was also used following endoscope placement.

Part 3

The endoscope was removed from the hypopharynx, and SSF was collected for 10 minutes and a final SFR was collected for 5 minutes.


Salivary flow rate: Significantly increased during endoscope placement in the hypopharynx as well as following endoscope removal, compared to baseline.

Spontaneous swallow frequency: Not significantly different with endoscope in place or following removal.

Masticatory efficiency: Total mastication time and number of masticatory cycles required to eat a cracker were significantly decreased with the endoscope in the hypopharynx as compared to baseline.

  • The mean of mastication time decreased by 7.5 seconds with the endoscope in place (25.5 seconds with endoscope, 33 seconds without endoscope)
  • The mean masticatory cycles decreased by 6 chew cycles with endoscope in place (30.5 cycles with endoscope, 36.5 cycles without endoscope)


Compared to TOMASS normative data from Huckabee, 2017 – Saltine Cracker

Age 20-40:

  • Masticatory time mean:
    • Males: 23.42 seconds
    • Females: 26.4 seconds
  • Masticatory cycles mean:
    • Males: 30.8
    • Females: 40.3

Age 40-60

  • Masticatory time mean:
    • Males: 28.04
    • Females: 36.41
  • Masticatory cycles mean:
    • Males: 34.3
    • Females: 53.4

Age 60-80

  • Masticatory time mean:
    • Males: 30.66
    • Females: 37.71
  • Masticatory cycles mean:
    • Males: 41.5
    • Females: 39.5

Conclusions from the normative data include: “when evaluating patients against the normative sample, attention should be paid to age and sex categorization.”


Surprisingly, spontaneous swallow frequency did not increase even with higher levels of salivary flow, which contradicts former studies. The article notes that perhaps in healthy individuals, increased salivary secretions may not be the only factor that influences spontaneous swallow frequency. The article suggests that the transnasal passage of an endoscope does stimulate salivary flow rate which may also result in improved masticatory efficiency.


Bruss & Sajjad (2023) define the hypopharynx as: “the portion of the pharynx where the cavity diverges anteriorly into the larynx and posteriorly into the esophagus. It contains three main structures: the posterior pharyngeal wall, pyriform sinuses, and the post-cricoid area.” While the article describes that endoscope placement occurred within this inferior portion of the pharynx, endoscope placement during FEES is predominantly higher in the pharynx, at the level of the oropharynx (also known as the “pre-swallow position”). Endoscope advancement into the hypopharynx may occur briefly during a FEES (also known as the “post-swallow position”) to allow for quick assessment of the laryngeal vestibule and trachea, then is immediately retracted to the oropharynx.


Assessment of endoscope placement on swallowing-related measures is an important area of research in order for clinicians to consider the impact of equipment interference when interpreting results. Further studies could consider a larger sample size with focus on endoscope placement within the oropharynx, the predominant area for scope placement during FEES. Studies could also incorporate both age and sex categorization, as the Huckabee normative data shows consistent and significant influences of age and sex on raw data measures and derived measures. Comparison to normative confidence intervals may also assist with identifying if changes in measures that occur with endoscope placement are great enough to fall outside of the range of normal. For example, the confidence interval for masticatory time in males ages 40-60 ranges from 15.46 seconds to 40.62 seconds. With such a wide range of normal, the shift in measures may not necessarily fall outside of a normal range, and would be interesting to further explore.

Written by Lyndsay Parker, M.S., CCC-SLP
Edited by Selena Reece, M.S., CCC-SLP, BCS-S


Affoo RH, Nellenbach C, Chomchai J, Rogus-Pulia N. The effects of endoscope placement in the hypopharynx on swallowing-related measures in healthy adults. Eur Arch Otorhinolaryngol. 2023 Jul 7. doi: 10.1007/s00405-023-08114-6. Epub ahead of print. PMID: 37414941.

Bruss DM, Sajjad H. Anatomy, Head and Neck: Laryngopharynx. [Updated 2023 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK549913/

Huckabee ML, McIntosh T, Fuller L, Curry M, Thomas P, Walshe M, McCague E, Battel I, Nogueira D, Frank U, van den Engel-Hoek L, Sella-Weiss O. The Test of Masticating and Swallowing Solids (TOMASS): reliability, validity and international normative data. Int J Lang Commun Disord. 2018 Jan;53(1):144-156. doi: 10.1111/1460-6984.12332. Epub 2017 Jul 5. PMID: 28677236.

Tiwari M. Science behind human saliva. J Nat Sci Biol Med. 2011 Jan;2(1):53-8. doi: 10.4103/0976-9668.82322. PMID: 22470235; PMCID: PMC3312700.