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.

The effects of ultrasound and shockwave treatment on muscle regional oxygen saturation using near-infrared spectroscopy

“…It is a non-invasive technique that uses the differential absorption properties of haemoglobin to evaluate tissue oxygenation. This method has been used primarily as a research tool to assess dynamic changes in the status of tissue oxyhaemoglobin, deoxyhaemoglobin, total blood (haemoglobin) volume and the oxidation state of the copper moiety of mitochondrial cytochrome c oxidase (cytochrome a, a3) in brain and muscle [21,24,32]. The measurement is based on the relative ease with which near infrared light (700-1000 nm) penetrates through biological tissues, including bone, skin and muscle and allows for detection of changes in light-absorbing chromophores (haemoglobin, myoglobin and cytochrome c oxidase) in human in vivo [25,33].…”

“…It is assumed that changes in haemoglobin and myoglobin oxygenation are an expression of the difference between the amount of oxygen delivered and consumed by tissues, an thus of metabolic changes occurring in them [25,32,34]. Unfortunately, a common problem in the use of NIRS is difficulties in interpretation that result from diversity of indices and their units being used in measuring equipment.…”

“…In the case of the apparatus being used by us, this index is rSO2 expressed in %. Despite some limitations, many researchers believe that, due to the possibility of non-invasive and direct assessment of rSO2 in muscle capillary vessels, NIRS provides valuable information to evaluate the tissue condition [22,26,28,32], owing to which NIRS can be an important tool for the objective assessment of physical training, planning of possible therapeutic strategies, and creation of rehabilitation protocols [24,35]. We did not find, however, any reports on the use of NIRS to assess the effect of physical therapy treatments and therefore an attempt was made to evaluate the suitability of its application to assess the treatments, being by design of hyperaemic and trophic nature.…”

Near-Infrared Spectroscopy Screening to Allow Detection of Pathogenic Mitochondrial DNA Variants in Individuals with Unexplained Abnormal Fatigue: A Preliminary Study

“…The changes in deoxyhemoglobin and deoxymyoglobin (deoxy[Hb + Mb]) during ICCP (i.e., the mean of the highest 10 s value) were expressed relative to the arterial occlusion amplitude to reduce possible influences of forearm adipose tissue thickness and eventual deconditioning effects. 6…”

Combined surface electromyography, near-infrared spectroscopy and acceleration recordings of muscle contraction: The effect of motion

“…Being well-known, MBLL has been widely described in numerous publications. 14,15 The general idea is that the absorption of the tested sample is proportional to the concentration of the absorber, its extinction coe±cient and the path length of light traveling through the sample.…”