Longitudinal Changes in Aerodigestive Responses to Varying Nipple Properties in Infant Pigs

Abstract

Coordination of respiration and swallowing is critical for survival in infant mammals and changes throughout infant maturation. Infants show sensorimotor feeding responses to changes in physical properties of nipples. Commercial nipples are promoted as improving aerodigestive coordination. However, it is unknown how nipple properties influence coordination of respiration and swallowing. Furthermore, how infant-nipple interactions change throughout maturation is not well understood. We designed and manufactured four silicone nipples of the same shape that varied in two parameters: nipple opening diameter and nipple stiffness. We used our validated infant pig model to test the impact of nipple parameters on aerodigestive coordination throughout ontogeny. We recorded videofluoroscopy and simultaneous chest plethysmography on six infant pigs at age 7 and 17 days when feeding on each of the four nipples presented in a randomized order. We measured the time between a swallow and the closest inspiration, and the length of the respiratory cycles during feeding. Larger nipple opening diameter resulted in shorter delay between swallow and onset of inspiration regardless of stiffness or pig age. In young pigs, respiratory cycle length was shorter when feeding on nipples with large diameter openings. In older pigs, there was a nipple-stiffness interaction such that respiratory cycle length increased with opening diameter in soft nipples but decreased with opening diameter in hard nipples. Nipple opening diameter has a pervasive effect on swallow-breathing coordination in freely feeding infants, but infant maturation modifies responses to nipple properties.

Keywords: breathing; infant; nipple; swallow.

Figure 1

Representative trace of 15 s of plethysmography recorded from a pig while feeding on milk from a nipple. Voltage increases as chest circumference increases, so increases in voltage indicate inhalation. Gray shaded areas indicate inspiratory phases. White background indicates inspiratory phases. Vertical doted lines mark the time of swallows as identified from simultaneous videofluoroscopy. Adapted from Gould et al. (2023).

Figure 2

Violin plots of swallow inspiration delay by diameter size. Horizontal lines in the violin plots represent medians. Points represent means. Brackets with asterisks indicate posthoc significant pairwise differences. See Table 1 for statistical analysis. Data for 530 swallows across six pigs and four nipple types.

Figure 3

Violin plots of respiration cycle length for different combinations of nipple opening diameter and nipple stiffness on day 7 and day 17. Top row are respiration cycles that do not contain a swallow, bottom row are respiration cycles that do. Horizontal lines in the violin plots are medians. Points are group means. Brackets indicate significant pairwise differences as determined by posthoc tests. Data for 1349 respiratory cycles for six pigs.