Preliminary evaluation of a new fibre-optic cerebral oximetry system.
A new system for measuring the oxygen saturation of blood within tissue has been developed, for a variety of patient monitoring applications. A particular unmet need is in the central nervous system, and this project aims to devise a means for measuring blood oxygen saturation in the brain tissue of patients recovering from neurosurgery or head injury. Coupling light sources and a photodetector to optical fibres results in a probe small enough to pass through a cranial bolt of the type already in use for intra-cranial pressure monitoring. The development and evaluation of a two-wavelength fibre-optic reflectance photoplethysmography (PPG) system are described. It was found that good quality red and near-infrared PPG signals could be obtained from the finger using a fibre-optic probe. Experiments were conducted to find the inter-fibre spacings that yield signals most suitable for calculating oxygen saturation. Reliable signals could be obtained for inter-fibre spacings between 2 mm and 5 mm, the latter being the size of the maximum aperture in the cranial bolt. A preliminary measurement from human brain tissue is also presented.
Phillips
J P
JP
Anaesthetic Laboratory, St Bartholomew's Hospital, London EC1A 7BE, UK. j.p.phillips@qmul.ac.uk
Langford
R M
RM
Kyriacou
P A
PA
Jones
D P
DP
D000669:Amplifiers, Electronic; D001923:Brain Chemistry / Q000502:physiology*; D006801:Humans; D007259:Infrared Rays; D008027:Light; D010092:Oximetry / Q000295:instrumentation* / Q000379:methods; D017156:Photoplethysmography / Q000295:instrumentation* / Q000379:methods; D012449:Safety; D012815:Signal Processing, Computer-Assisted; D012984:Software