Analysis of the Changes in the Oxidation of Brain Tissue Cytochrome c Oxidase in Traumatic Brain Injury Patients during Hypercapnoea: a Broadband NIRS Study

Using broadband near-infrared spectroscopy (NIRS) and cerebral microdialysis (MD) we investigated cerebral cellular metabolism and mitochondrial redox states, following hypercapnoea in 6 patients with traumatic brain injury (TBI). In all patients hypercapnoea increased intracranial pressure and cerebral blood flow velocity measured with transcranial Doppler. Despite the likely increase in cerebral oxygen delivery, we did not see an increase in the oxidation status of cytochrome-c-oxidase [oxCCO] in every patient. Analysis of the NIRS data demonstrated two patterns of the changes; Group A (n=4) showed an increase in [oxCCO] of 0.34(±0.34)µM and Group B (n=2) a decrease of 0.40(±0.41)µM. Although no obvious association was seen between the Δ[oxCCO] and the MD measured changes in lactate and pyruvate concentrations, further work using model informed data interpretation may be helpful in understanding the multimodal signals acquired in this heterogeneous patient group.