title: Influence of skin blood flow and source-detector distance on near-infrared spectroscopy-determined cerebral oxygenation in humans.
abstract: Most near-infrared spectroscopy (NIRS) apparatus fails to isolate cerebral oxygenation from an extracranial contribution although they use different source-detector distances. Nevertheless, the effect of different source-detector distances and change in extracranial blood flow on the NIRS signal has not been identified in humans. This study evaluated the extracranial contribution, as indicated by forehead skin blood flow (SkBF) to changes in the NIRS-determined cerebral oxyhaemoglobin concentration (O2 Hb) by use of a custom-made multidistance probe. Seven males (age 21 ± 1 year) were in a semi-recumbent position, while extracranial blood flow was restricted by application of four different pressures (+20 to +80 mmHg) to the left temporal artery. The O2 Hb was measured at the forehead via a multidistance probe (source-detector distance; 15, 22·5 and 30 mm), and SkBF was determined by laser Doppler. Heart rate and blood pressure were unaffected by application of pressure to the temporal artery, while SkBF gradually decreased (P<0·001), indicating that extracranial blood flow was manipulated without haemodynamic changes. Also, O2 Hb gradually decreased with increasing applied pressure (P<0·05), and the decrease was related to that in SkBF (r = 0·737, P<0·01) independent of the NIRS source to detector distance. These findings suggest that the NIRS-determined cerebral oxyhaemoglobin is affected by change in extracranial blood flow independent of the source-detector distance from 15 to 30 mm. Therefore, new algorithms need to be developed for unbiased NIRS detection of cerebral oxygenation.
authors.affiliation: Graduate school of Engineering, Toyo University, Kawagoe-shi, Saitama, Japan.
authors.forename: Ai
authors.initials: A
authors.lastname: Hirasawa
authors.forename: Shintaro
authors.initials: S
authors.lastname: Yanagisawa
authors.forename: Naoki
authors.initials: N
authors.lastname: Tanaka
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Funane
authors.forename: Masashi
authors.initials: M
authors.lastname: Kiguchi
authors.forename: Henrik
authors.initials: H
authors.lastname: Sørensen
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.forename: Shigehiko
authors.initials: S
authors.lastname: Ogoh
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000097:blood; D001783:Blood Flow Velocity; D002560:Cerebrovascular Circulation; D004867:Equipment Design; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D010092:Oximetry / Q000295:instrumentation / Q000379:methods*; D010100:Oxygen / Q000097:blood*; D010101:Oxygen Consumption; D010108:Oxyhemoglobins / Q000378:metabolism; D011237:Predictive Value of Tests; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012867:Skin / Q000098:blood supply*; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation; D013699:Temporal Arteries / Q000502:physiology*; D014159:Transducers; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010108:Oxyhemoglobins; D010100:Oxygen
keywords: deoxyhaemoglobin; extracranial blood flow; head cuff; oxyhaemoglobin; temporal artery