title: Capillary-oxygenation-level-dependent near-infrared spectrometry in frontal lobe of humans.
abstract: Brain function requires oxygen and maintenance of brain capillary oxygenation is important. We evaluated how faithfully frontal lobe near-infrared spectroscopy (NIRS) follows haemoglobin saturation (SCap) and how calculated mitochondrial oxygen tension (PMitoO2) influences motor performance. Twelve healthy subjects (20 to 29 years), supine and seated, inhaled O2 air-mixtures (10% to 100%) with and without added 5% carbon dioxide and during hyperventilation. Two measures of frontal lobe oxygenation by NIRS (NIRO-200 and INVOS) were compared with capillary oxygen saturation (SCap) as calculated from the O2 content of brachial arterial and right internal jugular venous blood. At control SCap (78%+/-4%; mean+/-s.d.) was halfway between the arterial (98%+/-1%) and jugular venous oxygenation (SvO2; 61%+/-6%). Both NIRS devices monitored SCap (P<0.001) within approximately 5% as SvO2 increased from 39%+/-5% to 79%+/-7% with an increase in the transcranial ultrasound Doppler determined middle cerebral artery flow velocity from 29+/-8 to 65+/-15 cm/sec. When SCap fell below approximately 70% with reduced flow and inspired oxygen tension, PMitoO2 decreased (P<0.001) and brain lactate release increased concomitantly (P<0.001). Handgrip strength correlated with the measured (NIRS) and calculated capillary oxygenation values as well as with PMitoO2 (r>0.74; P<0.05). These results show that NIRS is an adequate cerebral capillary-oxygenation-level-dependent (COLD) measure during manipulation of cerebral blood flow or inspired oxygen tension, or both, and suggest that motor performance correlates with the frontal lobe COLD signal.
authors.affiliation: Copenhagen Muscle Research Centre, Department of Anaesthesia, University of Copenhagen, Rigshospitalet, Copenhagen, Denmark. peter@prec.dk
authors.forename: Peter
authors.initials: P
authors.lastname: Rasmussen
authors.forename: Ellen A
authors.initials: EA
authors.lastname: Dawson
authors.forename: Lars
authors.initials: L
authors.lastname: Nybo
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: van Lieshout
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.forename: Albert
authors.initials: A
authors.lastname: Gjedde
mesh_terms: D000328:Adult; D000465:Algorithms; D001784:Blood Gas Analysis; D001842:Bone and Bones / Q000378:metabolism; D002196:Capillaries / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood; D002560:Cerebrovascular Circulation / Q000502:physiology; D005260:Female; D005385:Fingers / Q000502:physiology; D005625:Frontal Lobe / Q000098:blood supply / Q000378:metabolism*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009046:Motor Neurons / Q000502:physiology; D009068:Movement / Q000502:physiology; D018482:Muscle, Skeletal / Q000098:blood supply / Q000502:physiology; D010100:Oxygen / Q000097:blood*; D012039:Regional Blood Flow / Q000502:physiology; D019265:Spectroscopy, Near-Infrared; D016683:Supine Position / Q000502:physiology; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen