Reproducibility of cerebral near infrared spectroscopy in neonates

Near infrared spectroscopy (NIRS) allows to study cerebral hemodynamics and oxygenation in neonates, which may be useful for early detection of cerebral hypoxemia. So far this method is not reliable enough to be used clinically. Reproducibility is one of the prerequisites for reliable quantitative monitoring. The aim of this study was to assess the reproducibility of the NIRS parameters HbO(2) and HbD (oxygenated and deoxygenated hemoglobin concentration) and the derived NIRS parameters HbT (tissue hemoglobin concentration, HbT = HbO(2) + HbD) and rSO(2) (regional cerebral oxygen saturation, rSO(2) = HbO(2)/HbT). Two observers repeated a total number of 500 measurements in 25 neonates. Additionally, a baseline measurement was done to assess the physiological variation in every neonate. For all NIRS parameters, the inter-patient variance contributed most to the total variance, while the interobserver variance was the smallest variance component. The cerebral oxygen saturation parameter rSO(2) showed a good reproducibility, with an inter-measurement variance slightly but not significantly higher than the physiological baseline variation. The NIRS concentration parameters HbO(2), HbD, and HbT were less reproducible, with significant variation due to repeated sensor replacement. However, for cerebral oximetry rSO(2) is likely to be more important than the other NIRS parameters, so that NIRS has the potential to become a quantitative cerebral monitoring method.