Effect of breast milk olfactory experience on physiological indicators in very low birth weight infants: a randomized clinical trial.

Very low birth weight infants (VLBWI) often demonstrate instability in their physiological indicators, such as bradycardia, apnea, and desaturation. According to reports, the provision of positive sensory stimulation by parents in the NICU can alleviate distress and improve the stability of physiological indicators in preterm infants. Our objective was to assess the effect of breast milk sniffing on the physiological parameters of infants with very low birth weight. A prospective, single-center, randomized controlled trial was conducted. One hundred and twenty very low birth weight infants were enrolled according to specific criteria and were randomly assigned into two groups, with 60 infants in each group, using a block randomization principle. Use a gauze pad or breast milk pad soaked in breast milk to give the infant the opportunity to smell the scent of breast milk. This experience began after the withdrawal of invasive mechanical ventilation in very low birth weight (VLBW) infants, with the infants being positioned on their side and the soaked spill pads placed 2-3 cm near the infant's nose. The pads were changed every two hours to ensure that the infants received a continuous breast milk sniffing experience. The control group received standard care without the experience of breast milk sniffing. The stability of physiological indicators (heart rate, respiration, transcutaneous pulse oximetry) was assessed from the day of weaning from invasive mechanical ventilation until discharge in both groups. A narrower range of fluctuation was observed across all physiological indicators in the intervention group, indicating a more stable pattern compared to the control group. Although no significant difference was found in heart rate variability (50.35 ± 9.61 vs. 48.03 ± 10.2, t=-1.320, P = 0.187), a significant difference was noted in the average heart rate between the two groups (155.65 ± 6.80 vs. 153.58 ± 4.22, t=-2.141, P = 0.032). While there was no significant difference in the average respiratory rate between the two groups (53.40 ± 0.96 vs. 53.36 ± 0.92, t=-1.499, P = 0.134), a statistically significant difference was identified in the range of respiratory rate variability (7.64 ± 6.13 vs. 7.28 ± 1.98, t=-2.123, P = 0.034). Furthermore, although no statistically significant differences in average oxygen saturation values were observed between the groups, it was suggested that measurements within the intervention group exhibited relatively greater stability. The significance of the breast milk sniffing experience in stabilizing physiological indicators in very low birth weight infants has been demonstrated, and it may hold promise for future research.Trial registration: ClinicalTrials.gov ID: NCT05406804, registered on 06/06/2022.