In vivo validation of cerebral near-infrared spectroscopy: a review

Abstract

We summarize the available in vivo validation of cerebral near-infrared spectroscopy (NIRS) oximetry to inform future in vivo validation strategies. In particular, to establish a way forward in the assessment of NIRS instrumentation for future randomized trials, a systematic literature search is performed. The records are screened and abstracts are assessed to select studies fulfilling our inclusion criteria. Twenty-two pediatric and 28 adult studies are analyzed after exclusion of three articles in each group. All studies compare regional cerebral tissue oxygenation measured by cerebral NIRS to invasive measurement of central or jugular venous oxygen saturation. In studies without Bland-Altman plots, we extracted data from scatter plots enabling estimation of mean difference (MD), standard deviation (SD), and limits of agreement (LOA). To assess the agreement between rStO 2 (regional cerebral tissue oxygenation) estimated by NIRS and by blood samples, weighted averages of the MDs and SDs from each study are calculated. We found a fair agreement between the overall mean of cerebral tissue oxygenation and the mean of a reference value measured by co-oximetry whatever NIRS instrument or site of blood sampling used. Cerebral oxygenation overestimates the reference at low values, some instruments apparently more than others. Thus, a high degree of scatter and a lack of a good reference method complicate in vivo validation of NIRS. It is difficult to draw any firm conclusions despite the large number of studies, and the result of this review leaves us questioning if more of such validation studies of cerebral NIRS oximetry are really needed. Furthermore, the combination of lack of validation and poor repeatability is an important issue when designing a randomized clinical trial of implementing cerebral NIRS oximetry into clinical care.

The Various Oximetric Techniques Used for the Evaluation of Blood Oxygenation

“…A major difficulty of validating the cerebral oxygenation NIRS technology is the absence of acceptable and reliable methods for the measurement of cerebral tissue oxygenation to compare NIRS with [ 135 ]. In several studies, NIRS-derived cerebral StO 2 readings were compared to oxygen saturation in the jugular vein (SjO 2 ), which drains venous blood from one of the brain hemispheres.…”

“…In several studies, NIRS-derived cerebral StO 2 readings were compared to oxygen saturation in the jugular vein (SjO 2 ), which drains venous blood from one of the brain hemispheres. Both NIRS StO 2 and invasive SjO 2 decreased during induced hypoxia, though the deviations between the values of the two parameters were significant [ 100 , 135 ]. In the study of Rosenthal et al [ 136 ], NIRS StO 2 correlated with SjO 2 when the latter was measured in blood drained from the hemisphere with the NIRS probe site (r = 0.60, p < 0.001), but not with SjO 2 measured in the jugular vein that drains blood from the contralateral hemisphere.…”

“…As StO 2 is the mean oxygen saturation in the entire blood in tissue, arterial and venous, cerebral StO 2 readings were compared to a weighted mean of oxygen saturation in blood extracted from the jugular vein and a systemic artery (SavO 2 ) [ 114 , 115 , 135 ], and the comparison rendered smaller deviations than those found for SjO 2 . The weight of the cerebral arterial and venous blood is generally based on the assumption that the venous-to-arterial blood volume ratio of the cerebral tissue is 70:30, as was found by PET measurements [ 137 ]: SavO 2 = 0.3SaO 2 + 0.7SjO 2 .…”

Frequency-Domain Techniques for Cerebral and Functional Near-Infrared Spectroscopy

“…These enormous practical advantages of non-invasive diffuse optical imaging, combined with a strong sensitivity to cerebral hemodynamics and oxygenation, compensate intrinsic limitations in penetration depth and spatial resolution, and account for the large number of applications and the growing interest in this technology. Several review articles cover a variety of topics in cerebral near-infrared spectroscopy (NIRS), including a historical overview (Ferrari and Quaresima, 2012), description of instrumentation and methodology (Scholkmann et al, 2014b), clinical applications (Irani et al, 2007;Smith, 2011;Obrig, 2014;Yang et al, 2019), brain oximetry in newborns and adults (Wolf et al, 2012;Nielsen, 2014;la Cour et al, 2018), and critical perspectives (Fantini et al, 2018;Quaresima and Ferrari, 2019).…”

A Mini-Review on Functional Near-Infrared Spectroscopy (fNIRS): Where Do We Stand, and Where Should We Go?

“…(Japan). Today, more than 10 brain oximeters with Food and Drug Administration (FDA) and/or European Union (EU) approval are commercially available and utilized worldwide mainly in cardiac surgery and neonatal intensive care units [10][11][12][13]. The present mini-review does not cover the present and future applications of oximetry.…”