Journal of Clinical Monitoring and Computing

, Volume 14, Issue 5, pp 353–360

Sensitivity of Near Infrared Spectroscopy to Cerebral and Extra-Cerebral Oxygenation Changes is Determined by Emitter-Detector Separation

  • T. J. Germon
  • P. D. Evans
  • A. R. Manara
  • N. J. Barnett
  • P. Wall
  • R. J. Nelson
Article

DOI: 10.1023/A:1009957032554

Cite this article as:
Germon, T.J., Evans, P.D., Manara, A.R. et al. J Clin Monit Comput (1998) 14: 353. doi:10.1023/A:1009957032554

Abstract

Objective. To examine the effect of two emitter-detector separations (2.7 and 5.5 cm) on the detection of changes in cerebral and extra-cerebral tissue oxygenation using near infrared spectroscopy (NIRS). Methods. Two NIR detectors were placed on the scalp 2.7 and 5.5 cm from a single NIR emitter. Changes in deoxyhaemoglobin (HHb), oxyhaemoglobin (O2Hb),oxidised cytochrome C oxidase (Cyt) and total haemoglobin (tHb) were recorded from each detector during the induction of cerebral oligaemia (transition from hypercapnia to hypocapnia) and scalp hyperaemia (following release of a scalp tourniquet). Results. Cerebral oligaemia (mean decrease in middle cerebral artery blood flow velocity of 44%) induced by a mean reduction in end tidal CO2 of 18 mmHg was accompanied by a significant increase in the spectroscopic signal for HHb and a decrease in the O2Hb signal. The signal change per unit photon path length detected at 5.5 cm was significantly greater for HHb (p = 0.007) than that detected at 2.7 cm. In contrast, the increase in all chromophores detected at 5.5 cm during scalp hyperaemia was significantly less than that detected at 2.7 cm (p < 0.001). Conclusions. The differing sensitivity of the proximal and distal channels to changes in cerebral and extra-cerebral oxygenation is compatible with theoretical models of NIR light transmission in the adult head and may provide a basis for spatially resolving these changes. The optimal emitter-detector separation for adult NIRS requires further investigation and may differ between individuals.

Near infrared spectroscopycerebral oxygenationoximeters

Copyright information

© Kluwer Academic Publishers 1998

Authors and Affiliations

  • T. J. Germon
    • 1
  • P. D. Evans
    • 2
  • A. R. Manara
    • 3
  • N. J. Barnett
    • 2
  • P. Wall
    • 2
  • R. J. Nelson
    • 1
  1. 1.Department of NeurosurgeryFrenchay HospitalFrenchayU.K.
  2. 2.European Product Development CentreJohnson & Johnson Medical LtdNewportU.K.
  3. 3.Department of AnaestheticsFrenchay HospitalFrenchayU.K.