Relationship between relative cerebral blood flow, relative cerebral blood volume, and relative cerebral metabolic rate of oxygen in the preterm neonatal brain

Abstract

The mechanisms responsible for coupling between relative cerebral blood flow (rCBF), relative cerebral blood volume (rCBV), and relative cerebral metabolic rate of oxygen (rCMRO2), an important function of the microcirculation in preterm infants, remain unclear. Identification of a causal relationship between rCBF–rCBV and rCBF−rCMRO2 in preterms may, therefore, help to elucidate the principles of cortical hemodynamics during development. We simultaneously recorded rCBF and rCBV and estimated rCMRO2 by two independent acquisition systems: diffuse correlation spectroscopy and near-infrared spectroscopy, respectively, in 10 preterms aged between 28 and 35 weeks of gestational age. Transfer entropy was calculated in order to determine the directionality between rCBF–rCBV and rCBF−rCMRO2. The surrogate method was applied to determine statistical significance. The results show that rCBV and rCMRO2 have a predominant driving influence on rCBF at the resting state in the preterm neonatal brain. Statistical analysis robustly detected the correct directionality of rCBV on rCBF and rCMRO2 on rCBF. This study helps to clarify the early organization of the rCBV–rCBF and rCBF−rCMRO2 inter-relationship in the immature cortex.