Pre-pharyngeal Swallow Effects of Recurrent Laryngeal Nerve Lesion on Bolus Shape and Airway Protection in an Infant Pig Model.
Francois D H Gould, B Yglesias, J Ohlemacher and 1 others
PMID 27873091WHAT IT FOUND
In infant pigs whose recurrent laryngeal nerve was injured, swallows that protected the airway had smaller boluses before swallowing.
Bolus shape differed by pig and injury. The authors suggest testing controlled milk volume in future human work.
Key findings
01After the recurrent laryngeal nerve was injured, airway protection was worse, and bolus shape before the swallow differed by pig, by injury, and by how safe the swallow was.
02Bolus area was smaller after nerve injury, and this was most visible in swallows that did not enter the airway.
03Tongue shape and bolus area did not explain all bolus shape differences; bolus shape still varied with injury and airway safety after those variables were accounted for.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
This was a laboratory study in five infant pigs, not a clinical study in human infants. Only 188 selected swallows were analysed, and the airway safety scores used were 1, 2, and 7, so the sample was not balanced across all possible swallow outcomes. Between-pig variation was very high; one pig never aspirated after injury, and one pig was removed from tongue-shape analysis because its outline fit poorly. Bolus and tongue shapes were measured from two-dimensional lateral video frames, so head movement and projection of a three-dimensional bolus could distort the shape findings. The analysis captured one frame before the epiglottis moved, so differences may reflect timing of tongue movement rather than a true difference in tongue or bolus shape. The study did not test a treatment; controlled milk volume delivery is only a proposed future investigation.
Declared interests
No author conflicts of interest were reported. The article is listed as supported by NIH extramural research.
The easy way to misread this
Do not use the bolus-shape findings to change how you feed a human infant with recurrent laryngeal nerve injury. The study was in pigs, did not test controlled milk volume, and had large between-pig variation.