The Natural Swallow: Factors Affecting Subject Choice of Bolus Volume and Pharyngeal Swallow Parameters in a Self-selected Swallow.
Sophia M Colevas, Lily N Stalter, Corinne A Jones and 1 others
PMID 34687378WHAT IT FOUND
Healthy adults choose a consistent, comfortable sip volume averaging 16.66 mL.
Swallowing this self-selected volume requires lower peak pressures in the tongue base and upper esophagus than swallowing a fixed 10 mL bolus, suggesting it is a more efficient mechanical action.
Key findings
01The mean self-selected swallow volume was 16.66 mL, with males choosing larger volumes than females.
02Self-selected swallows generated significantly lower maximum pressure in the velopharynx and tongue base compared to 10 mL syringe-delivered swallows when volume was adjusted.
03Within-subject variability for self-selected volume was low, indicating individuals consistently choose a similar sip size.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The study was conducted in a structured clinical environment with a catheter in the nose, which may not reflect true day-to-day natural swallowing behavior. Participants were required to hold the bolus in their mouth until cued to swallow, which is not how people naturally drink. The study used barium sulfate, which tends to result in smaller sip volumes than water, potentially underestimating the natural volume choice. The analysis compared self-selected volumes to a fixed 10 mL volume, making it difficult to isolate the effect of volume choice from the effect of the delivery method (cup/straw vs. syringe).
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not assume that lower peak pressures in self-selected swallows indicate a weaker or pathological swallow. The study suggests these lower pressures are a sign of greater mechanical efficiency, as the body uses less force to move a comfortable volume than it does to force a standardized, potentially unnatural volume.