Assessing the relationship between the cerebral metabolic rate of oxygen and the oxidation state of cytochrome-c-oxidase

Abstract

Significance: Hyperspectral near-infrared spectroscopy (hsNIRS) combined with diffuse correlation spectroscopy (DCS) provides a noninvasive approach for monitoring cerebral blood flow (CBF), the cerebral metabolic rate of oxygen (CMRO2) and the oxidation state of cytochrome-c-oxidase (oxCCO). CMRO2 is calculated by combining tissue oxygen saturation (StO2) with CBF, whereas oxCCO can be measured directly by hsNIRS. Although both reflect oxygen metabolism, a direct comparison has yet to be studied.Aim: We aim to investigate the relationship between CMRO2 and oxCCO during periods of restricted oxygen delivery and lower metabolic demand.Approach: A hybrid hsNIRS/DCS system was used to measure hemodynamic and metabolic responses in piglets exposed to cerebral ischemia and anesthetic-induced reductions in brain activity.Results: Although a linear relationship was observed between CMRO2 and oxCCO during ischemia, both exhibited a nonlinear relationship with respect to CBF. In contrast, linear correlation was sufficient to characterize the relationships between CMRO2 and CBF and between the two metabolic markers during reduced metabolic demand.Conclusions: The observed relationship between CMRO2 and oxCCO during periods of restricted oxygen delivery and lower metabolic demand indicates that the two metabolic markers are strongly correlated.