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Title	Use of retinal oximetry in estimating cerebral tissue oxygenation
Abstract Nr.	1062

Purpose	To investigate the correlation between cerebral tissue oxygenation (SctO2) and retinal vessel oxygen saturation (SO2) using non-invasive spectroscopy in healthy individuals.
Methods	Retinal and cerebral oxygen saturations were measured in healthy volunteers using dual wavelength retinal oximetry and transcranial near-infrared spectroscopy (NIRS) respectively. Correlations between SO2 and SctO2 were analyzed using Pearson correlation coefficients. Multivariate analysis was performed to determine the relative contribution of the arterial and venous vessels to SctO2. Using this model, SctO2 was estimated based on retinal arterial and venous oxygen saturation. The measured and the predicted SctO2 were compared using Pearson correlation coefficients, paired sample t-test and Bland-Altman analysis.
Results	Twenty-one young healthy individuals aged 26.4±2.2 years were analyzed. SctO2 showed a significant positive correlation with both arterial and venous SO2 (r=0.442, P=0.045 and r=0.434 P=0.049 respectively). In multivariate analysis, the relative contribution of arterial and venous SO2 to SctO2 was significantly correlated with diastolic blood pressure, retinal venous oxygen saturation and retinal venous diameter (R2=0.60, P<0.001). The measured SctO2 (72.2±3.5%, range 67.3–80.1) correlated well with estimated SctO2 (72.2±2.6%, range 67.6–77.5) (r=0.774, P<0.001). Bland–Altman plots showed 95% agreement within ±6.8%.
Conclusion	In this pilot study, retinal oximetry showed promising as an estimate of cerebral tissue oxygenation as measured by NIRS.

Authors 1

Last name	VAN KEER
Initials	K
Department	UZ Leuven
City	Leuven

Authors 2

Last name	Abegão Pinto
Initials	L
Department	Faculty of Medicine of Lisbon University
City	Lisbon

Authors 3

Last name	Stalmans
Initials	I
Department	UZ Leuven
City	Leuven

Authors 4

Last name	Vandewalle
Initials	E
Department	UZ Leuven
City	Leuven