Cerebral near infrared spectroscopy: emitter-detector separation must be increased

Timothy J Germon, PD Evans, NJ Barnett, P Wall, Alexander R Manara, Richard J Nelson

    Research output: Contribution to journalArticle (Academic Journal)peer-review

    132 Citations (Scopus)


    We have compared the effect of increasing optode separation (range 0.7-5.5 cm) on the sensitivity of near infrared spectroscopy (NIRS) to discrete reductions in scalp and cerebral oxygenation in 10 healthy men (mean age 32, range 26-39 yr) using multichannel NIRS. During cerebral oligaemia (a mean reduction in middle cerebral artery flow velocity of 47%) induced by a mean reduction in end-tidal PCO2 of 2.4 kPa, the decrease in oxyhaemoglobin detected by NIRS became significantly greater with increasing optode separation (P < 0.0001). In response to scalp hyperaemia induced by inflation and release of a pneumatic scalp tourniquet, increases in oxyhaemoglobin became significantly smaller with increasing optode separation (P < 0.0002). These results are consistent with theoretical models of the behaviour of NIR light in the adult head and support the concept of using multi-detector NIRS to separate intra- and extracranial NIR signal changes. However, the emitter-detector separation used by currently available cerebral oximeters is not large enough to provide optimal spatial resolution.
    Translated title of the contributionCerebral near infrared spectroscopy:emitter-detector separation must be increased
    Original languageEnglish
    Pages (from-to)831-837
    Number of pages7
    JournalBritish Journal of Anaesthesia
    Issue number6
    Publication statusPublished - Jun 1999


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