title: Possible Influences on the Interpretation of Functional Domain (FD) Near-Infrared Spectroscopy (NIRS): An Explorative Study.
abstract: The influence of subcutaneous adipose tissue (ATT) and oxygen (O2) delivery has been poorly defined in frequency domain (FD) near-infrared spectroscopy (NIRS). Therefore, the aim of this study was to investigate the possible influence of these variables on all FD NIRS responses using a reliable protocol. Moreover, these influences were also investigated when using relative oxy- and deoxyhemoglobin and -myoglobin (oxy[Hb + Mb] and deoxy[Hb + Mb]) values (in %). A regression analysis was carried out for ATT and maximal-minimum oxy[Hb + Mb], deoxy[Hb + Mb], oxygen saturation (SmO2), and total hemoglobin (totHb) amplitudes during an incremental cyclic contraction protocol (ICCP) in a group of 45 participants. Moreover, the same analysis was carried out between subcutaneous ATT and the relative oxy- and deoxy[Hb + Mb] values (in %). In the second part of this study, a regression analysis was performed for peak forearm blood flow (FBF) during ICCP and the absolute and relative NIRS values in a group of 37 participants. Significant exponential correlation coefficients were found between ATT and deoxy[Hb + Mb] (r = 0.53; P < 0.001), oxy[Hb + Mb] (r = 0.57; P < 0.001), and SmO2 amplitudes (r = 0.57; P < 0.001). No significant relations were found between ATT and relative oxy[Hb + Mb] (r = 0.37; P = 0.07) and deoxy[Hb + Mb] (r = 0.09; P = 0.82). Significant positive correlation coefficients were found between force at exhaustion and maximal FBF (r = 0.66; P < 0.001), maximal differences in deoxy[Hb + Mb] (r = 0.353; P = 0.032) and totHb (r = 0.512; P = 0.002) while no significant correlation coefficients were found between these maximal force values and maximal differences in oxy[Hb + Mb] (r = -0.267; P = 0.111) and SmO2 (r = -0.267; P = 0.111). Significant linear correlation coefficients were found between FBF and deoxy[Hb + Mb] (r = 0.51; P = 0.001), oxy[Hb + Mb] (r = -0.50; P = 0.001), SmO2 (r = -0.54; P = 0.001), and totHb amplitude (r = 0.61; P < 0.001). No significant correlations were found when using relative oxy[Hb + Mb] (r = -0.01; P = 0.957) and deoxy[Hb + Mb] (r = -0.02; P = 0.895). Based on these findings, caution is advised when using NIRS values, as subcutaneous ATT and O2 delivery significantly influence NIRS measurements. To eliminate these influences, use of relative deoxy[Hb + Mb] is advised, especially in clinical settings or in people with a higher subcutaneous ATT layer.
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.
authors.forename: Bert M
authors.initials: BM
authors.lastname: Celie
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium Centre of Sports Medicine, Ghent University Hospital, Ghent, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Boone
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.
authors.forename: Jasmien
authors.initials: J
authors.lastname: Dumortier
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Derave
authors.affiliation: Department of Cardiology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Tine
authors.initials: T
authors.lastname: De Backer
authors.affiliation: Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium Centre of Sports Medicine, Ghent University Hospital, Ghent, Belgium jan.bourgois@ugent.be.
authors.forename: Jan G
authors.initials: JG
authors.lastname: Bourgois
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D008297:Male; D009211:Myoglobin / Q000032:analysis; D010100:Oxygen / Q000032:analysis*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D050151:Subcutaneous Fat / Q000098:blood supply / Q000737:chemistry; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D009211:Myoglobin; D010100:Oxygen
keywords: ATT; Blood flow; NIRS; Near-infrared spectroscopy; Physiological calibration; Subcutaneous adipose tissue thickness