Nonlinear evolution of acoustic characteristics of bowel sounds in preterm infants

Introduction Gastrointestinal function can be assessed through bowel sounds, which objectively indicate gastrointestinal movement. However, the conventional method of abdominal auscultation has considerable limitations. This study aimed to investigate the evolutionary patterns of acoustic characteristics of bowel sounds in preterm infants, explore their variation with postmenstrual ages (PMAs), and quantify the association between PMA and bowel sound maturity to characterize the developmental trajectory of intestinal motility in preterm infants. Methods Twenty-seven preterm infants (gestational age: 30–36 + 6 weeks) were enrolled in this study. A convolutional neural network-based smart device was used to monitor bowel sounds 1–4 times weekly for ≥3 h from day 1 to 30 after birth. Parameters, including bowel rate (number of bowel sounds per minute), frequency, and number of durations >2 s per min, were collected. Loess regression and derivative analysis were employed to characterize the dynamic progression of the bowel sound parameters relative to PMA, whereas Mann–Whitney U or Kruskal–Wallis H tests were utilized to assess between-group differences. Results A nonlinear dynamic change was observed in the relationship between characteristic parameters of bowel sounds in preterm infants and PMA. A significant transition occurred at 33.1 weeks of PMA. The PMA groups showed a significant difference in both between-group and multiple comparisons ( P < 0.001). Conclusion Bowel sound parameters demonstrated a nonlinear evolution with PMA, with an inflection point at 33.1 weeks that was synchronized with the critical maturation period of the enteric nervous system/interstitial cells of Cajal network. These parameters may serve as objective markers for assessing the dynamic maturation of the gastrointestinal system in preterm infants.