Cervical accelerometry in preterm infants with and without bronchopulmonary dysplasia

Abstract

Cervical accelerometry with digital signal processing (DSP) can identify signals that are consistently associated with swallowing during feeding of infants. It is shown that these signals, called initial discrete sounds (IDSs), become more uniform with advancing postmenstrual age (PMA) in healthy preterm infants. The objectives of this study were to determine if cervical accelerometry and DSP at a higher sample rate than previously used (22kHz versus 16kHz), in conjunction with a DSP software package that allows manipulation of the sound files, would improve the accuracy of the previously developed variance index (VI) method of analyzing accelerometric information. The modified VI method was then used to measure developmental differences in the IDS morphology of infants with and without bronchopulmonary dysplasia (BPD). VIs were calculated for 24 feeding studies of infants of between 32 and 39 weeks PMA: 12 studies on healthy preterm infants (n=10: three males, seven females; mean gestational age [GA] 28.6 weeks, SD 0.4; mean birthweight [BW] 1080g, SD 82; PMA mean 35.2 weeks, SD 0.6) and 12 studies on infants with BPD (n=7: five males, two females; GA 27.1 weeks, SD 0.4; BW 911g, SD 71; PMA 36.2 weeks, SD 0.6). There was a significant inverse correlation between VI and PMA for the healthy preterm group (r=0.66, m=–2.31/week, p=0.02). There was no significant correlation between VI and PMA for the BPD cohort. The VI of infants with BPD was significantly different from that of infants without BPD (p<0.007, multiple regression analysis, interaction PMA×Group). Additionally, using our modified VI technique, 100% of swallows were found to have the expected IDS signals.