The effect of stiffness and hole size on nipple compression in infant suckling

Abstract

During infant feeding, the nipple is an important source of sensory information that affects motor outputs, including ones dealing with compression of the nipple, suction, milk bolus movement, and swallowing. Despite known differences in behavior across commercially available nipples, little is known about the in vivo effects of nipple property variation. Here we quantify the effect of differences in nipple stiffness and hole size on an easily measured metric representing infant feeding behavior: nipple compression. We bottle-fed 7-day old infant pigs (n = 6) on four custom fabricated silicone nipples. We recorded live X-ray fluoroscopic imaging data of feeding on nipples of two levels of hardness/stiffness and two hole sizes. We tested for differences in nipple compression at the nipple's maximum compression across different nipple types using a mixed model analysis of variance. Stiffer nipples and those with smaller holes were compressed less than compliant nipples and nipples with larger holes (p < 0.001). We also estimated the force applied on the nipple during feeding and found that more force was applied to the compliant nipple with disproportionately larger strains. Our results suggest that infant pigs' nipple compression depends on material type and hole size, which is likely detected by the infant pigs' initial assessment of compressibility and flow. By isolating nipple properties, we demonstrated a relationship between properties and suckling behavior.Our results suggest that sensory information affects feeding behaviors and may also inform clinical treatment of poor feeding performance.

Nipple properties affect sensorimotor integration during bottle feeding in an infant pig model

“…For each of the stiffness ratings, nipples were designed with a large hole size (2.0 π mm 2 CSA) and a small hole size (0.5 π mm 2 CSA), corresponding to a four‐fold difference in passive flow rates (2.44 ± 0.19 mL/s for the small hole and 8.33 ± 0.00 mL/s for the large hole). Young's modulus values and passive flow rates were experimentally determined for each nipple type (Adjerid et al, 2022).…”

“…Previous research illustrates the potential for suction generation modification depending on variation in sensation (Mayerl et al, 2021). For instance, suction generation can be modified through nipple material properties, where nipple stiffness impacts the force applied to the nipple during nutritive sucking (Adjerid et al, 2022). Continued research on the effect of nipple stiffness integrated with passive flow rate is essential to understand the neurophysiology of infant feeding.…”

Exploring the interaction of viscosity and nipple design on feeding performance in an infant pig model

“…The pigs were monitored for their first 24 h as they were trained to feed on milk replacement formula (Solustart Pig Milk Replacement, Land o' Lakes, Arden Mills, MN) from a bottle. The pigs were trained on a nipple bottle system (Adjerid et al, 2023) using a custom‐made training nipple comprising 20A hardness silicone (Smooth‐on Inc. Macungie, PA). All animal care and experimental conditions were approved under the IACUC protocol # 17‐04‐071.…”

“…We found, by measuring the muscles that move the jaw relative to the timing of suck phase, or tongue movement, that changes in the nipple disrupted the coordination between the jaw and tongue. Preparing the proper combination of viscosity and nipple type is not straightforward, especially given the wide variety of commercially available bottle nipples (Adjerid et al, 2023). Communication regarding the totality of the feeding system, at all levels of the infant's care, will be important to ensure good outcomes for the infant.…”

“…How to cite this article: Howe, S., Steer, K., Johnson, M., Adjerid, K., Edmonds, C., German, R., & Mayerl, C. (2023).…”