

NEW & NOTEWORTHY Chemical sensory interventions alter swallow physiology, which is well-documented in adults but relatively unexplored in infants. Our results provide insight into the neural control of swallowing and capsaicin’s mechanism of action, and suggest that capsaicin may be beneficial in treating acute infant dysphagia.

The timing and extent of posterior tongue movement were only correlated with bolus size pre-capsaicin, which could imply that capsaicin fundamentally changes in relationships between tongue movements and bolus size. TPT and hyoid and thyroid excursions maintained relationships with bolus size post-capsaicin, suggesting that these variables are less sensitive to sensory intervention. Similarly, excursions of the hyoid, thyroid, and posterior tongue were unchanged. However, capsaicin did not change swallow frequency, the number of sucks prior to each swallow, nor total pharyngeal transit time (TPT). Furthermore, capsaicin improved performance when infant pigs swallowed more moderately sized boluses. We found that capsaicin application decreased maximal bolus sizes, which improved swallow safety. Using high-speed videofluoroscopy, we collected oropharyngeal kinematic data while pigs suckled on bottles, before and after applying capsaicin to the posterior tongue and valleculae. We explored the neurophysiological mechanism by which capsaicin improves swallow performance using an infant pig model with a unilateral iSLN lesion. The iSLN initiates the pharyngeal swallow, and a more sensitive iSLN should more readily elicit swallowing and improve swallow safety. One such treatment may be found in capsaicin, which activates the internal branch of the superior laryngeal nerve (iSLN). Because of this, sensory interventions have the potential to treat dysphagia. Sensorimotor feedback is critical to safe and effective swallowing.
