Diffuse Optical Spectroscopy Assessment of Resting Oxygen Metabolism in the Leg Musculature

• Type of Material: Article
• Authors: Scott E. Boebinger, Emory University; Rowan O. Brothers, Emory University; Sistania Bong, Emory University; Bharat Sanders, Emory University; Courtney McCracken, Kaiser Permanente; Lena Ting, Emory University; Erin Buckley, Emory University
• Language: English
• Date: 2021-08-01
• Publisher: MDPI AG
• Publication Version: Final Published Version
• Copyright Statement: © 2021 by the authors.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.3390/metabo11080496
• Title of Journal or Parent Work: Metabolites
• Volume: 11
• Issue: 8
• Grant/Funding Information: This research was funded by NIH R01 HD46922 (L.H.T.) and R21 HL138062 (EMB). This material is additionally based upon work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 1937971 (S.E.B. and R.O.B.). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
• Keywords: blood flow; oxygen metabolism; near-infrared spectroscopy; muscle; diffuse correlation spectroscopy
• Research Categories: Physics, Optics; Biology, Anatomy

Abstract

We lack reliable methods to continuously assess localized, resting-state muscle activity that are comparable across individuals. Near-infrared spectroscopy (NIRS) provides a low-cost, non-invasive means to assess localized, resting-state muscle oxygen metabolism during venous or arterial occlusions (VO2VO and VO2AO, respectively). However, this technique is not suitable for continuous monitoring, and its utility is limited to those who can tolerate occlusions. Combining NIRS with diffuse correlated spectroscopy (DCS) enables continuous measurement of an index of muscle oxygen metabolism (VO2i). Despite the lack of previous validation, VO2i is employed as a measure of oxygen metabolism in the muscle. Here we characterized measurement repeatability and compared VO2i with VO2VO and VO2AO in the medial gastrocnemius (MG) in 9 healthy adults. Intra-participant repeatability of VO2i, VO2VO, and VO2AO were excellent. VO2i was not significantly correlated with VO2AO (p = 0.15) nor VO2VO (p = 0.55). This lack of correlation suggests that the variability in the calibration coefficient between VO2i and VO2AO/VO2VO in the MG is substantial across participants. Thus, it is preferable to calibrate VO2i prior to every monitoring session. Important future work is needed to compare VO2i against gold standard modalities such as positron emission tomography or magnetic resonance imaging.