Non-invasive assessment of cerebral oxygenation: A comparison of retinal and transcranial oximetry

Abstract

BackgroundTo investigate the correlation between cerebral (SO2-transcranial), retinal arterial (SaO2-retinal) and venous (SvO2-retinal) oxygen saturation as measured by near-infrared spectroscopy (NIRS) and retinal oximetry respectively.MethodsPaired retinal and cerebral oxygen saturation measurements were performed in healthy volunteers. Arterial and venous retinal oxygen saturation and diameter were measured using a non-invasive spectrophotometric retinal oximeter. Cerebral oxygen saturation was measured using near-infrared spectroscopy. Correlations between SO2-transcranial and retinal oxygen saturation and diameter measurements were assessed using Pearson correlation coefficients. Lin’s concordance correlation coefficient (CCC) and Bland-Altman analysis were performed to evaluate the agreement between SO2-transcranial as measured by NIRS and as estimated using a fixed arterial:venous ratio as 0.3 x SaO2-retinal + 0.7 x SvO2-retinal. The individual relative weight of SaO2-retinal and SvO2-retinal to obtain the measured SO2-transcranial was calculated for all subjects.ResultsTwenty-one healthy individuals aged 26.4 ± 2.2 years were analyzed. SO2-transcranial was positively correlated with both SaO2-retinal and SvO2-retinal (r = 0.44, p = 0.045 and r = 0.43, p = 0.049 respectively) and negatively correlated with retinal venous diameter (r = -0.51, p = 0.017). Estimated SO2-transcranial based on retinal oximetry showed a tolerance interval of (-13.70 to 14.72) and CCC of 0.46 (95% confidence interval: 0.05 to 0.73) with measured SO2-transcranial. The average relative weights of SaO2-retinal and SvO2-retinal to obtain SO2-transcranial were 0.31 ± 0.11 and 0.69 ± 0.11, respectively.ConclusionThis is the first study to show the correlation between retinal and cerebral oxygen saturation, measured by NIRS and retinal oximetry. The average relative weight of arterial and venous retinal oxygen saturation to obtain the measured transcranial oxygen saturation as measured by NIRS, approximates the established arterial:venous ratio of 30:70 closely, but shows substantial inter-individual variation. These findings provide a proof of concept for the role of retinal oximetry in evaluating cerebral oxygenation.

Differences in Cerebral Tissue Oxygenation in Preterm Neonates Receiving Adult or Cord Blood Red Blood Cell Transfusions

“…Accordingly, preterm neonates who develop ROP may spend more time than controls in a condition of cerebral hyperoxia, defined as crSO 2 greater than 80% . On the other hand, also in healthy adult volunteers, there is a positive correlation between retinal arterial and venous oxygen saturation measured by spectrophotometric retinal oximetry and crSO 2 measured by NIRS . Intriguingly, Vesoulis et al demonstrated through NIRS monitoring of preterm neonates born before 30 weeks of gestation that low cFTOE but not high SpO 2 in the first 96 hours was a risk factor for severe ROP.…”

“… 30 On the other hand, also in healthy adult volunteers, there is a positive correlation between retinal arterial and venous oxygen saturation measured by spectrophotometric retinal oximetry and crSO 2 measured by NIRS. 31 Intriguingly, Vesoulis et al 32 demonstrated through NIRS monitoring of preterm neonates born before 30 weeks of gestation that low cFTOE but not high SpO 2 in the first 96 hours was a risk factor for severe ROP. Specifically, neonates who developed severe ROP spent 20% more time than those without severe ROP with cFTOE values less than 15% during a mean recording length of 36 hours, corresponding to an additional 40 minutes of hyperoxia exposure.…”

Anterior visual system imaging to investigate energy failure in multiple sclerosis

“…Retinal oximetry can distinguish venules from arteries and plot an oxygenation map of the retina. This is an improvement compared with cerebral NIRS, which calculates the average oxygenation in venules and arteries combined (Van Keer et al, 2018).…”

Retinal oxygen saturation as a non‐invasive estimate for mixed venous oxygen saturation and cardiac output

“…Recent studies have shifted the focus to applications beyond the eye, with increasing interest in using retinal oximetry as a non-invasive tool to monitor neurological and systemic diseases including chronic obstructive pulmonary disease, Eisenmenger syndrome, Alzheimer's Disease and Multiple Sclerosis (Einarsdottir et al 2018;Eliasdottir et al 2017;Mahajan & Votruba 2017;Palkovits et al 2013;Stef ansson et al 2017;Traustason et al 2011;Van Keer et al 2018;Willerslev et al 2016). Several studies have already demonstrated the ability of retinal oximetry to estimate systemic arterial blood saturation in humans, as measured using pulse oximetry, earlobe capillary blood or arterial blood gas samples (Choudhary et al 2013;Eliasdottir et al 2017;Man et al 2014;Palkovits et al 2013Palkovits et al , 2014Told et al 2018;Traustason et al 2011).…”