Annular Flow in the Upper Esophageal Sphincter Demonstrated with Dynamic 320-row Area Detector Computed Tomography.
Yoko Inamoto, Eiichi Saitoh, Jeffrey B Palmer
PMID 33507395WHAT IT FOUND
Thin liquid swallows create an annular flow pattern in the upper esophageal sphincter, where liquid lines the wall and air flows through the center.
Thick liquids produce a plug flow pattern with no central air column. This distinction explains why intrabolus pressure readings differ by consistency.
Key findings
01Annular flow, defined as a ring of liquid surrounding a core of air, occurred in nearly every thin liquid swallow across all subjects.
02Annular flow was rarely seen in thick liquid swallows, which instead exhibited plug flow where the lumen was entirely filled by liquid.
03The presence of annular flow in thin liquids may explain lower intrabolus pressure readings at the distal sphincter, as manometry catheters may sit in the air core rather than the liquid.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study compared different people for thin versus thick liquids rather than testing the same person with both consistencies, so individual anatomical differences could influence results. Participants were scanned in a semi-reclining position, not upright, which may affect gravity-dependent flow dynamics. The study used healthy volunteers, so it is unknown if these flow patterns occur in patients with dysphagia. Radiation exposure limited the number of swallows and prevented within-subject comparison of consistencies.
Declared interests
Funding was provided by JSPS KAKENHI.
The easy way to misread this
Do not assume this study proves thick liquids are safer or more efficient for patients with dysphagia. It only describes flow physics in healthy volunteers. The difference in flow pattern does not automatically translate to a clinical outcome like reduced aspiration risk.