Modulation of Upper Esophageal Sphincter (UES) Relaxation and Opening During Volume Swallowing.
Charles Cock, Corinne A Jones, Michael J Hammer and 2 others
PMID 27534548WHAT IT FOUND
In eight healthy adults, swallowing larger volumes changed how the upper esophageal sphincter opened.
At 20 ml, the bolus itself pushed the sphincter open before the submental muscles peaked. This suggests 20 ml exceeds the optimal single-swallow volume.
Key findings
01The duration of upper esophageal sphincter opening increased progressively across bolus volumes.
02At volumes over 10 ml, the peak of submental muscle activity shifted to occur after the upper esophageal sphincter reached its maximum opening.
03Swallowing 20 ml resulted in higher intrabolus distension pressures in the hypopharynx compared to smaller volumes.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study included only eight healthy participants, limiting the generalizability of these specific timing shifts to patients with dysphagia. No simultaneous radiology (videofluoroscopy) was used, so UES opening was inferred from admittance (impedance) rather than directly visualized. Hyolaryngeal elevation was not measured directly, so the relationship between hyoid movement and sphincter opening remains an inference based on EMG and pressure data. The study focused on liquid saline boluses; viscosity and other bolus properties were not tested.
Declared interests
Author TO owns a patent on AIMplot software, which may have been used for analysis. Other authors declared no conflicts of interest.
The easy way to misread this
Do not assume that 20 ml is a safe or standard bolus size for patients with dysphagia. This study shows that 20 ml exceeds the mechanically optimal volume even in healthy adults, relying on passive distension and higher pressures that may be dangerous or ineffective for patients with impaired sensation or strength.