title: Extra-cerebral oxygenation influence on near-infrared-spectroscopy-determined frontal lobe oxygenation in healthy volunteers: a comparison between INVOS-4100 and NIRO-200NX.
abstract: BACKGROUND
  Frontal lobe oxygenation (Sc O2 ) is assessed by spatially resolved near-infrared spectroscopy (SR-NIRS) although it seems influenced by extra-cerebral oxygenation. We aimed to quantify the impact of extra-cerebral oxygenation on two SR-NIRS derived Sc O2 .
  
  
  METHODS
  Multiple regression analysis estimated the influence of extra-cerebral oxygenation as exemplified by skin oxygenation (Sskin O2 ) on Sc O2 in 21 healthy subjects exposed to whole-body exercise in hypoxia (Fi O2  = 12%; n = 10) and normoxia (n = 12), whole-body heating, hyperventilation (n = 21), administration of norepinephrine with and without petCO2 -correction (n = 15), phenylephrine and head-up tilt (n = 7). Sc O2 was assessed simultaneously by NIRO-200NX (Sniro O2 ) and INVOS-4100 (Sinvos O2 ). Arterial (Sa O2 ) and jugular bulb oxygen saturations (Sj O2 ) were obtained.
  
  
  RESULTS
  The regression analysis indicated that Sinvos O2 reflects 46% arterial, 14% jugular, 35% skin and 4% oxygenation of tissues not interrogated. Sinvos O2 follows a calculated estimate of cerebral capillary oxygenation (r = 0·67; P<0·0001). In contrast, the NIRO-200NX-determined Sc O2 did not correlate with the estimate of cerebral oxygenation (r = 0·026; P = 0·71).
  
  
  CONCLUSIONS
  For all interventions, 35% of the INVOS-4100 signal reflected extra-cerebral oxygenation while, on the other hand, NIRO-200NX did not follow changes in a calculated estimate of cerebral capillary oxygenation. Thus, the NIRO-200NX and INVOS-4100 do not provide for unbiased evaluation of the cerebral signal.
authors.affiliation: Department of Anaesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; Zürich Centre for Integrative Human Physiology, University of Zürich, Zürich, Switzerland.
authors.forename: Henrik
authors.initials: H
authors.lastname: Sørensen
authors.forename: Peter
authors.initials: P
authors.lastname: Rasmussen
authors.forename: Christoph
authors.initials: C
authors.lastname: Siebenmann
authors.forename: Morten
authors.initials: M
authors.lastname: Zaar
authors.forename: Morten
authors.initials: M
authors.lastname: Hvidtfeldt
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Ogoh
authors.forename: Kohei
authors.initials: K
authors.lastname: Sato
authors.forename: Matthias
authors.initials: M
authors.lastname: Kohl-Bareis
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.forename: Carsten
authors.initials: C
authors.lastname: Lundby
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001785:Blood Gas Monitoring, Transcutaneous / Q000295:instrumentation*; D002560:Cerebrovascular Circulation; D004867:Equipment Design; D005625:Frontal Lobe / Q000098:blood supply* / Q000378:metabolism*; D064368:Healthy Volunteers; D006801:Humans; D006979:Hyperthermia, Induced; D006985:Hyperventilation / Q000097:blood / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000503:physiopathology; D008297:Male; D009638:Norepinephrine / Q000008:administration & dosage; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010656:Phenylephrine / Q000008:administration & dosage; D011187:Posture; D011237:Predictive Value of Tests; D011897:Random Allocation; D015203:Reproducibility of Results; D012867:Skin / Q000098:blood supply* / Q000378:metabolism*; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation*; D018667:Tilt-Table Test; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010656:Phenylephrine; D010100:Oxygen; D009638:Norepinephrine
keywords: cerebral oxygenation; cutaneous oxygenation; humans; jugular vein; monitoring