Amplitude-integrated EEG and range-EEG modulation associated with pneumatic orocutaneous stimulation in preterm infants

Abstract

Objective: Controlled somatosensory stimulation strategies have demonstrated merit in developing oral feeding skills in premature infants who lack a functional suck, however, the effects of orosensory entrainment stimulation on electrocortical dynamics is unknown. The objective of the study was to determine the effects of servo-controlled pneumatic orocutaneous stimulation presented during gavage feedings on the modulation of amplitude-integrated electroencephalogram (aEEG) and range electroencephalogram (rEEG) activity.

Study design: Two-channel EEG recordings were collected during 180 sessions that included orocutaneous stimulation and non-stimulation epochs among 22 preterm infants (mean gestational age=28.56 weeks) who were randomized to treatment and control 'sham' conditions. The study was initiated at around 32 weeks post-menstrual age. The raw EEG was transformed into aEEG margins, and rEEG amplitude bands measured at 1-min intervals and subjected to a mixed models statistical analysis.

Result: Multiple significant effects were observed in the processed EEG during and immediately following 3-min periods of orocutaneous stimulation, including modulation of the upper and lower margins of the aEEG, and a reorganization of rEEG with an apparent shift from amplitude bands D and E to band C throughout the 23-min recording period that followed the first stimulus block when compared with the sham condition. Cortical asymmetry also was apparent in both EEG measures.

Conclusion: Orocutaneous stimulation represents a salient trigeminal input, which has both short- and long-term effects in modulating electrocortical activity, and thus is hypothesized to represent a form of neural adaptation or plasticity that may benefit the preterm infant during this critical period of brain maturation.

Figure 1

Preterm infant with aEEG and pneumatically pulsed stimulation through a regular Philips AVENT BPA-free Soothie silicone pacifier coupled to the digitally-controlled handpiece of the NTrainer System. EEG signals derived from hydrogel electrodes placed at C3-P3, and C4-P4 were recorded on a bedside aEEG monitor (BRM3; Natus Medical Incorporated, San Carlos, California USA).

Figure 2

Bi-hemispheric aEEG (C3-P3, and C4-P4) on a preterm infant (32 wks PMA). Indexed events (#56, 58, and 60) represent the onset of 3-minute pulsed orocutaneous stimulation periods interleaved with 5.5 minute no-stimulus periods. Note the presence of aEEG amplitude modulation in the electrophysiological record during somatosensory stimulation.

Figure 3

Mean aEEG measures (maxima, mean, and minima) sampled from the left hemisphere (C3-P3), right hemisphere (C4-P4), and the crosshead montage pooled among all preterm infants during pulsed orocutaneous (NT-On) and sham pacifier stimulation conditions (PAC-On) (significant Bonferroni pairwise comparisons indicated, •• p<.0001).

Figure 4

rEEG amplitude bands sampled from the left hemisphere (C3-P3) in preterm infants during pulsed orocutaneous and blind ‘sham’ pacifier stimulation conditions. NT-On indicates the pneumatically charged pacifier is in the mouth, NT-Off indicates the charged pacifier is out of the mouth, sham PAC-On indicates the regular Soothie pacifier is in the mouth, and sham PAC-Off indicates the regular Soothie pacifier is out of the baby’s mouth. Significant Bonferroni pairwise contrasts between orosensory entrainment and sham pacifier stimulation conditions indicated by horizontal bars (* p<.001, ** p=.020).

Figure 5

rEEG amplitude bands sampled from the right hemisphere (C4-P4) in preterm infants during oral pulsed orocutaneous and blind ‘sham’ pacifier stimulation conditions. NT-On indicates the pneumatically charged pacifier is in the mouth, NT-Off indicates the charged pacifier is out of the mouth, sham PAC-On indicates the regular Soothie pacifier is in the mouth, and sham PAC-Off indicates the regular Soothie pacifier is out of the baby’s mouth. Significant Bonferroni pairwise contrasts between orosensory entrainment and sham pacifier stimulation conditions indicated by horizontal bars (* p<.001).

Figure 6

rEEG amplitude bands sampled from the crosshead montage (P3–P4) in preterm infants during pulsed orocutaneous and blind ‘sham’ pacifier stimulation conditions. NT-On indicates the pneumatically charged pacifier is in the mouth, NT-Off indicates the pneumatically-charged pacifier is out of the mouth, sham PAC-On indicates the regular Soothie pacifier is in the mouth, and sham PAC-Off indicates the regular Soothie pacifier is out of the baby’s mouth. Significant Bonferroni pairwise contrasts between orosensory entrainment and sham pacifier stimulation conditions indicated by horizontal bars (* p<.001).