Measurement of tongue-artificial nipple contact force in infants with sucking difficulties

Infants are known to suckle and ingest breast milk by wrapping the tongue around a nipple, writhing the tongue, and pressing the nipple. However, the dynamic mechanisms of tongue movement are still obscure, and factors related to sucking difficulties of infants are not well understood. We developed an artificial nipple installed with small cantilever-type sensors and directly measured the force applied on the nipple by the tongue. Small force sensors were arranged within the artificial nipple in a two-dimensional matrix of 3 × 2 to measure the force at 6 points. Subjects were 20 healthy infants (Group A) and 5 infants who had difficulty sucking (Group B). The latter could not breastfeed well and were fed from bottles or tubes. Informed consent was provided by the parents or guardians. The measured maximum force at the tip of the nipple was 1.4 ± 0.4 N and 1.2 ± 0.3 N (mean ± SD) in Groups A and B, respectively. At the base of the nipple, the maximum force recorded was 0.8 ± 0.5 N and 0.3 ± 0.3 N (mean ± SD), respectively, showing a statistically significant difference (p<0.05). The sucking period was 0.6 ± 0.1 s (mean ± SD) in both groups. The difference in time necessary to reach the maximum forces between the sensors at the tip and base was 39.7 ± 28.8 ms (mean ± SD) and 37.2 ± 75.9 ms in Groups A and B, respectively.