title: Normobaric hyperoxia does not change optical scattering or pathlength but does increase oxidised cytochrome C oxidase concentration in patients with brain injury.
abstract: We report the use of a novel hybrid near-infrared spectrometer for the measurement of optical scattering, pathlength and chromophore concentration in critically ill patients with brain injury. Ten mechanically ventilated patients with acute brain injury were studied. In addition to standard neurointensive care monitoring, middle cerebral artery flow velocity, brain lactate-pyruvate ratio (LPR) and brain tissue oxygen tension were monitored. The patients were subjected to graded normobaric hyperoxia (NBH), with the inspired fraction of oxygen increased from baseline to 60% then 100%. NBH induced significant changes in the concentrations of oxyhaemoglobin, deoxyhaemoglobin and oxidised-reduced cytochrome c oxidase; these were accompanied by a corresponding reduction in brain LPR and increase in brain tissue oxygen tension. No significant change in optical scattering or pathlength was observed. These results suggest that the measurement of chromophore concentration in the injured brain is not confounded by changes in optical scattering or pathlength and that NBH induces an increase in cerebral aerobic metabolism.
authors.affiliation: Institute of Neurology, University College London, 4 Brookfield Road, Queen Square, London, E9 5AH, UK. arnab.ghosh@ucl.ac.uk.|Neurocritical Care, University College Hospitals, Queen Square, London, UK. arnab.ghosh@ucl.ac.uk.
authors.forename: Arnab
authors.initials: A
authors.lastname: Ghosh
authors.affiliation: Medical Physics and Bioengineering, University College London, Malet Place, London, UK.
authors.forename: Ilias
authors.initials: I
authors.lastname: Tachtsidis
authors.affiliation: Medical Physics and Bioengineering, University College London, Malet Place, London, UK.
authors.forename: Christina
authors.initials: C
authors.lastname: Kolyva
authors.affiliation: Neurocritical Care, University College Hospitals, Queen Square, London, UK.
authors.forename: David
authors.initials: D
authors.lastname: Highton
authors.affiliation: Medical Physics and Bioengineering, University College London, Malet Place, London, UK.
authors.forename: Clare
authors.initials: C
authors.lastname: Elwell
authors.affiliation: Neurocritical Care, University College Hospitals, Queen Square, London, UK.|Medical Physics and Bioengineering, University College London, Malet Place, London, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology / Q000628:therapy; D002560:Cerebrovascular Circulation / Q000502:physiology; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005260:Female; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000378:metabolism; D019289:Pyruvic Acid / Q000378:metabolism; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; D019344:Lactic Acid; D019289:Pyruvic Acid; C100003:deoxyhemoglobin; D003576:Electron Transport Complex IV; D010100:Oxygen