In Vitro Comparisons of Near-Infrared Spectroscopy Oximeters: Impact of Slow Changes in Scattering of Liquid Phantoms.

Several cerebral oximeters based on near-infrared spectroscopy (NIRS) are commercially available that determine tissue oxygen saturation (StO2). One problem is an inconsistency of StO2 readings between different brands of instruments. Liquid blood phantoms mimicking optical properties of the neonatal head enable quantitative device comparisons. However, occasionally, the reduced scattering coefficient (μs') of these phantoms decreases over time. AIM: To investigate whether this decrease in μs' affects the validity of comparison of these devices. StO2 was measured by several NIRS oximeters simultaneously on a phantom, which exhibited a particularly strong decrease in μs'. We found that a decrease in μs' by ≤16% from baseline led to deviations in StO2 of ≤3%.