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Comparison of two spatially resolved NIRS oxygenation indices
Roy E Gagnon1, Andrew J Macnab, Faith A Gagnon
1Department of Pediatrics, Children's & Women's Health Centre, University of British Columbia, Vancouver, Canada. roy.gagnon@telus.net
Unlabelled:
We compared the percentage haemoglobin oxygenation indices from two near infrared spectrophotometers (NIRS) to determine whether the devices reported similar changes in response to induced changes in oxygenation.
Methods:
24 healthy juvenile swine undergoing cardiac bypass surgery had INVOS 5100 and NIRO-300 sensors applied to the brow. Induced events included circulatory arrest, altered blood flow rate, core cooling, and re-warming.
Results:
The average data collection was 4 hours 36 minutes and had an r = 0.82 mean correlation between the INVOS and NIRO. The total resting baseline collection from all trials (8,590 pairs) had a correlation of r = 0.62. The average relationship between the INVOS and NIRO was non-linear: an INVOS regional oxygen saturation index (rSO2) of 0% was equivalent to a NIRO tissue oxygenation index (TOI) of 36.2%; values were equal at 56.8%; and an (rSO2) of 100% was equivalent to a TOI 85.9%. There was good or excellent agreement (r > 0.5) between the (rSO2) and TOI patterns of change during induced events in 96% of trials. The INVOS and NIRO were most closely correlated when an attenuation filter was used to obtain identical emitter/detector separations.
Conclusions:
There was close agreement between the INVOS 5100 and NIRO-300 in response to major physiological change, although absolute values of (rSO2) and TOI were not identical. There was less agreement during baseline measurements or minimal physiologic change.