Sucking versus swallowing coordination, integration, and performance in preterm and term infants

Abstract

Mammalian infants must be able to integrate the acquisition, transport, and swallowing of food in order to effectively feed. Understanding how these processes are coordinated is critical, as they have differences in neural control and sensitivity to perturbation. Despite this, most studies of infant feeding focus on isolated processes, resulting in a limited understanding of the role of sensorimotor integration in the different processes involved in infant feeding. This is especially problematic in the context of preterm infants, as they are considered to have a pathophysiological brain development and often experience feeding difficulties. Here, we use an animal model to study how the different properties of food acquisition, transport, and swallowing differ between term and preterm infants longitudinally through infancy in order to understand which processes are sensitive to variation in the bolus being swallowed. We found that term infants are better able to acquire milk than preterm infants, and that properties of acquisition are strongly correlated with the size of the bolus being swallowed. In contrast, behaviors occurring during the pharyngeal swallow, such as hyoid and soft palate movements, show little to no correlation with bolus size. These results highlight the pathophysiological nature of the preterm brain and also demonstrate that behaviors occurring during oral transport are much more likely to respond to sensory intervention than those occurring during the 'pharyngeal phase'.

Increased viscosity of milk during infant feeding improves swallow safety through modifying sucking in an animal model

“…Suck amplitude and length were measured following published protocols at the time of maximal suck generation (Geddes, Kent, Mitoulas, & Hartmann, 2008; Mayerl, Edmonds, Catchpole, et al, 2020). In short, suck amplitude was measured as the maximum dorsoventral distance between the hard palate and tongue during a suck cycle, and suck length was calculated as the distance from the nipple to the location of the tongue‐soft palate seal at the frame of maximum suck amplitude using ImageJ (Figure 1, Schneider, Rasband, & Eliceiri, 2012).…”

“…During feeding, infants use suction to acquire milk, and then move their tongue in a wave posteriorly to transport it to the valleculae (Elad et al, 2014; German et al, 1992). Tongue movements and suction generation during this process have been demonstrated to respond to sensory feedback (Mayerl et al, 2020), and infants use different neuromotor patterns and suction generation capacities depending on nipple properties and milk flow (Inoue, Sakashita, & Kamegai, 1995; Moral et al, 2010). After milk arrives in the valleculae, a swallow is triggered by sensory fibers associated with the internal superior laryngeal nerve (SLN) when a threshold volume is attained (Ding et al, 2013; Lang, Medda, Babaei, & Shaker, 2014), and the resulting swallow is thought to be primarily reflexive (Miller, 2008).…”

“…However, different parts of the system vary in their sensitivity to sensory feedback. For example, movements of the tongue during swallowing are highly sensitive to bolus volume, whereas the movements of the hyoid and soft palate are less so (Mayerl, Edmonds, Catchpole, et al, 2020). This is most likely due to the reflexive nature of the pharyngeal swallow, with modulations in function arising in structures associated with food transport prior to swallowing.…”

“…Temporally, clinical videofluoroscopic recordings of infants are often limited to 15 fps to limit radiation exposure (Layly et al, 2020). This resolution is insufficient to measure the movements of the structures involved in sucking and swallowing, as an entire swallow can occur in less than 0.5 s, resulting in only four frames being acquired (Mayerl, Edmonds, Catchpole, et al, 2020).…”

Nutritional Management and Recommendation for Preterm Infants: A Narrative Review

“…33 Preterm infants are also lacking in reflexes for sucking and swallowing that could lead to feeding difficulties. 34 Periodic breathing can be seen in preterm and term infants. However, it occurs more often in preterm infants.…”