Transmittance Mode of Time-Resolved Near-Infrared Spectroscopy for Monitoring Deeper Cerebral Tissues in Extremely Low-Birth-Weight Infants

AimTo investigate the potential of the transmittance mode of time-resolved near-infrared spectroscopy, in which the source and detector probes are placed on the bilateral temporal region of the head, compared with the conventional reflectance mode in extremely low-birth-weight (ELBW) infants.MethodsDifferences in cerebral tissue oxygen saturation (StO2) and cerebral blood volume (CBV) between the two modes were evaluated. Linear regression was performed to investigate contributing factors to StO2 and CBV.ResultsForty-nine ELBW infants (median gestational age, 24.9 weeks; mean birthweight, 672 g), including nine intraventricular haemorrhage (IVH) cases, were evaluated at a median of 14.0 days of age. StO2 and CBV values were significantly lower in the transmittance mode than in the reflectance mode. IVH was a significant contributor to StO2 and CBV. Two out of four cases with IVH grade 3 had larger ventricular dilations and showed outliers towards low StO2.ConclusionThe transmittance mode detected lower StO2 in ELBW infants as compared to the reflectance mode, especially in IVH cases. This was either due to the optical effects of the IVH itself and/or large dilated ventricles.