Cortical Oxygenation Changes during Gastric Tube Feeding in Moderate- and Late-Preterm Babies: A NIRS Study

Abstract

Smell and taste of food can trigger physiological responses facilitating digestion and metabolism of nutrients. Controlled experimental studies in preterm babies have demonstrated that smell activates the orbitofrontal cortex (OFC) but none have investigated the effect of taste stimulation. Using cotside Near-Infrared Spectroscopy (NIRS), we measured changes in OFC cerebral oxygenation in response to gastric tube feeds five and 10 days after birth in 53 assessments of 35 moderate- to late-preterm babies enrolled in a randomized trial. Babies were randomly assigned to receive smell and taste of milk before gastric tube feeds (intervention group, n = 16) or no exposure (control group, n = 19). The majority of babies were born at 33 weeks of gestation (range 32-34) and 69% were boys. No differences in OFC cerebral oxygenation were observed between control and intervention groups. Gastric tube feeds induced activation of the OFC (p < 0.05), but sensory stimulation alone with smell and taste did not. Boys, but not girls, showed activation of the OFC following exposure to smell of milk (p = 0.01). The clinical impact of sensory stimulation prior to tube feeds on nutrition of preterm babies, as well as the impact of environmental inputs on cortical activation, remains to be determined.

Keywords: cortical activation; milk; moderate and late preterm; near-infrared spectroscopy; nutrition; sensory stimulation; smell; taste; tube feeding.

Figure 1

Assessment sequence. Prefeeding consisted of baseline period (P0, five minutes); period 1 (P1, one minute), corresponding to smell exposure in intervention group; period 2 (P2, one minute), corresponding to taste exposure in intervention group; and feeding period (P3, duration according to feeding volume).

Figure 2

Lateral view representing optode position. Optodes were placed bilaterally with emitter (E) positioned anterior to T3/T4 and receiver (R) positioned anterior to F7/F8 according to the international 10–20 system.

Figure 3

Study flowchart. ¹ Total recruited at Auckland City Hospital during the study period.

Figure 4

Model estimates adjusted for sex, gestation, and baseline oxygenation. Values are mean with 95% confidence intervals. (A) Effect of laterality (control N = 18, intervention N = 14). (B) Effect of postnatal day (control N = 19, intervention N = 16). (C) Effect of sex (control N = 18, intervention N = 14). * Significant change from baseline. ^a,b Different letters represent significant differences among periods. ^§ Significant difference between assessment 1 and assessment 2. ^∆ Significant group difference. ^† Significant sex difference. Statistical significance taken as p < 0.05 for all comparisons. P1: period 1 (smell exposure in intervention group). P2: period 2 (taste exposure in intervention group). P3: period 3 (feeding period in both groups). O₂Hb = oxygenated hemoglobin.