Interpretation of Near-Infrared Spectroscopy (NIRS) Signals in Skeletal Muscle

Abstract

Near-infrared spectroscopy (NIRS) uses the relative absorption of light at 850 and 760 nm to determine skeletal muscle oxygen saturation. Previous studies have used the ratio of both signals to report muscle oxygen saturation. Purpose: The purpose of this pilot study is to assess the different approaches used to represent muscle oxygen saturation and to evaluate the pulsations of oxygenated hemoglobin/myoglobin (O2heme) and deoxygenated hemoglobin/myoglobin (Heme) signals. Method: Twelve participants, aged 20–29 years, were tested on the forearm flexor muscles using continuous-wave NIRS at rest. Measurements were taken during 2–3 min rest, physiological calibration (5 min ischemia), and reperfusion. Ten participants were included in the study analysis. Results: There was a significant difference in pulse size between O2heme and Heme signals at the three locations (p < 0.05). Resting oxygen saturation was 58.8% + 9.2%, 69.6% + 3.9%, and 89.2% + 6.9% when calibrated using O2heme, the tissue oxygenation/saturation index (TSI), and Heme, respectively. Conclusion: The difference in magnitude of O2heme and Heme pulses with each heartbeat might suggest different anatomical locations of these signals, for which calibrating with just one of the signals instead of the ratio of both is proposed. Calculations of physiological calibration must account for increased blood volume in the tissue because of the changes in blood volume, which appear to be primarily from the O2heme signal. Resting oxygen levels calibrated with Heme agree with theoretical oxygen saturation.

Effects of Inspiratory Muscle Training on Muscle Oxygenation during Vascular Occlusion Testing in Trained Healthy Adult Males

“…The [HHb] and %TSI were used for the analyses. Both indexes were obtained from the sender at a distance of 40 mm, since this distance allows for greater penetration into the muscle [ 14 ]. Previously, [HHb] has been shown to be useful for measuring muscle oxidative metabolism; therefore, we used the calculation of the area under the deoxyhemoglobin curve (HHb AUC ) to observe this condition [ 15 ].…”

A Novel Methodology for the Synchronous Collection and Multimodal Visualization of Continuous Neurocardiovascular and Neuromuscular Physiological Data in Adults with Long COVID

“…NIRS measurements record absorbance of light at several wavelengths, where changes in absorbance in the region near 850 nm are ascribed to oxygenated hemoglobin (O2Hb), and absorbance in the region near 760 nm is attributed to deoxygenated hemoglobin (HHb) [39]. Combinations of the O2Hb and HHb are often reported to describe physiological events, including oxygen saturation (O2Hb/(O2Hb + HHb)) [40], hemoglobin difference (O2Hb-HHb) [41], and tissue saturation index (TSI) [42].…”

The effects of whole‐body vibration amplitude on glucose metabolism, inflammation, and skeletal muscle oxygenation

“…The thickness of adipose tissue superficial to the muscle belly of the gastrocnemius where the NIRS device was attached was determined using B-mode ultrasound (Logiq 7, GE Medical Systems). After correcting for blood volume change (Ryan et al, 2012), an estimate of muscle oxygen consumption (mVO 2 ) was obtained from the average of %Hbdiff signal during each minute of WBV and converted into milliliters of O 2 per minute per 100 g of tissue {m V O 2 [ml O 2 min −1 (100 g) − 1] = abs[([HbDi ff/2] × 60)/(10 × 1.04) × 4] × 22.4/1000}, assuming 22.4 L for the volume of gas (STPD) and 1.04 kg l−1 for muscle density [ (Lucero et al, 2018;Sanni & McCully, 2019)].…”