Quantification of cyclical oscillations in cerebral blood volume in human neonates using near-infrared spectroscopy

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The purpose of this study was to investigate the oscillations of oxy- and deoxy-hemoglobin ([oxyHb] and [deoxyHb]) in healthy preterm and term infants by using near-infrared topography and to determine the change in spontaneous oscillation in the developing brain. The subjects were 10 healthy term infants (gestational week : 37-40 weeks, birth weight : 2358-3400g), aged 9 to 12 days, and 11 preterm infants (gestational week : 23-34 weeks, birth weight : 474-2048g), aged 36-73 days (37-46 weeks of postconceptional age).We used 24-channel near-infrared topography to measure changes in [oxyHb] and [deoxyHb] in the bilateral temporal cortices of infants during quiet sleep at 24 measurement positions with interoptode distance of 20 mm. Spontaneous oscillations of cerebral hemodymanics were observed in all of the infants. To focus on the slow fluctuations, data over a period of 180 sec (1801 data points) were selected from the channel among the 24 channels showing the smallest baseline shift … More in data. Power spectral analysis was then performed in these epochs. The power spectral density (PSD) was divided into 3 spectral windows (0.02-0.06,0.06-0.10, and 0.10-0.15 Hz). To compare the PSDs in term infants with those in preterm infants, the PSD was normalized as follows : PSD=(Area of spectral window/Total area of PSD)x100 (%).Cyclical fluctuations of [oxyHb] and [deoxyHb] in term infants were 3.1±0.6 (mean±SD) and 2.9±0.5 cycles/min in the left temporal region and 3.1±0.6 and 2.9±0.6 cycles/min in the right temporal region, respectively. Those at term in preterm infants were 3.9±0.6 and 4.1±0.7 cycles/min on the left side and 4.0±0.6 and 4.1±0.6 cycles/min on the right side, respectively. The difference between term infants and preterm infants was statistically significant at 0.02-0.06 and 0.06-0.10 Hz for [oxyHb] and [deoxyHb]. The term infants had significantly lower frequency than did the preterm infants (Term vs. preterm at 0.02-0.06 and 0.06-0.10 Hz:81±4 % and 69±15 % (p=0.017), and 16±4 % and 28±14 % (p=0.017), respectively). This study demonstrated a predominance of low frequency oscillations in [oxyHb] and [deoxyHb] less than 0.10 Hz in the temporal cortices in both term and preterm infants by near-infrared topography. Less