Review of early development of near-infrared spectroscopy and recent advancement of studies on muscle oxygenation and oxidative metabolism

Abstract

Near-infrared spectroscopy (NIRS) has become an increasingly valuable tool to monitor tissue oxygenation (T_oxy) in vivo. Observations of changes in the absorption of light with T_oxy have been recognized as early as 1876, leading to a milestone NIRS paper by Jöbsis in 1977. Changes in the absorption and scatting of light in the 700-850-nm range has been successfully used to evaluate T_oxy. The most practical devices use continuous-wave light providing relative values of T_oxy. Phase-modulated or pulsed light can monitor both absorption and scattering providing more accurate signals. NIRS provides excellent time resolution (~ 10 Hz), and multiple source-detector pairs can be used to provide low-resolution imaging. NIRS has been applied to a wide range of populations. Continued development of NIRS devices in terms of lower cost, better detection of both absorption and scattering, and smaller size will lead to a promising future for NIRS studies.

Keywords: Exercise; Muscle; Oxidative metabolism; Oximetry; Tissue oxygenation.

Fig. 1

Changes in absorbance (optical density) in accordance to a wavelength. The optical density (absorption) increases at 760 nm when the oxygenated hemoglobin (O₂Hb) is deoxygenated (HHb). When blood volume increases, the line shifts to the upper (increase in absorbance) Copyright © 2017 Willingham and McCully from Ref. [14]

Fig. 2

Schematic illustration of main types of near-infrared (NIR) spectroscopy instrumentation. a NIR continuous wave spectroscopy with single-distance (NIR_SDCWS) or multi-distance (NIR_MDCWS). b NIR time-resolved spectroscopy (NIR_TRS). c NIR phase modulation spectroscopy (NIR_PMS)

Fig. 3

Schematic illustration of the volume of tissue being measured. a The volume of tissue being evaluated using continuous light and 3-cm separation distance was estimated to be ~ 4 cm³, when it is assumed that the volume of interest be a rotation body of the ellipse revolved across 180° or a hemisphere. b If a banana-like pattern is assumed rather than a hemisphere, the volume might be smaller

Fig. 4

The influence of subcutaneous adipose tissue thickness on the near-infrared signals (a). b Relationship between slope (S) of increase in muscle deoxy-[hemoglobin/myoglobin (Hb/Mb)] during the ischemia occlusion test and the subcutaneous adipose tissue thickness (ATT) for all subjects: S = 12.73–1.49·ATT (r = 0.71, P < 0.01). Note that the greater the ATT, the more the slope was attenuated. Open and closed circles denote the deoxygenation responses of the vastus lateralis (VL) and rectus femoris (RF) muscles at the distal sites, respectively. Open and closed squares denote the deoxygenation responses of the VL and RF muscles at the proximal sites, respectively a Copyright © 2000 The Amercian College of Sports Medicine. Adopted from Ref. [1]. b Copyright © The American Physiological Society. Reproduced by permission of the publisher. Adopted from Ref. [61]

Fig. 5

Changes in phosphocreatine (PCr) and oxygenation in human forearms during 15 min of arterial occlusion measured by near-infrared and ³¹P-magnetic resonance spectroscopy. No significant changes were found in pH or ATP throughout arterial occlusion Copyright © The American Physiological Society. Reproduced by permission of the publisher. Adopted from Ref. [77]

Fig. 6

a Changes in oxygenated hemoglobin (O₂Hb) and deoxygenated hemoglobin (HHb) during periods of cuff-induced ischemia. b NIRS O₂Hb kinetics during a series of arterial occlusions following 15-s electrical stimulation (E-Stim). c Slope values from NIRS O₂Hb recovery kinetics plotted over time and fit to exponential equation. In this equation, y is the relative rate of oxygen metabolism, End is the rate of oxygen metabolism at the end of exercise (S1), and Δ is the difference between the rates of resting oxygen metabolism and End. The rate constant, k, is used an index of muscle mitochondrial capacity. d NIRS set up for assessment of mitochondrial capacity in the gastrocnemius Copyright © 2017 Willingham and McCully from Ref. [14]