Abstract
The purpose of the study was to compare muscle oxygenation as measured by two portable, wireless near-infrared spectroscopy (NIRS) devices under resting and dynamic conditions. A recently developed low-cost NIRS device (MOXY) was compared against an established PortaMon system that makes use of the spatially resolved spectroscopy algorithm. The influence of increasing external pressure on tissue oxygen saturation index (TSI) indicated that both devices are stable between 2 and 20mmHg. However, above this pressure, MOXY reports declining TSI values. Analysis of adipose tissue thickness (ATT) and TSI shows a significant, nonlinear difference between devices at rest. The devices report similar TSI (%) values at a low ATT (<7 mm) (PortaMon minus MOXY difference is +1.1±2.8%) with the major subsequent change between the devices occurring between 7 and 10mm; at ATT values >10 mm the difference remains constant (-14.7±2.8%). The most likely explanation for this difference is the small source-detector separation (2.5cm) in the MOXY resulting in lower tissue penetration into muscle in subjects with higher ATT. Interday test-retest reliability of resting TSI was evaluated on five separate occasions, with the PortaMon reporting a lower coefficient of variation (1.8% to 2.5% versus 5.7% to 6.2%). In studies on male subjects with low ATT, decreases in the TSI were strongly correlated during isometric exercise, arterial occlusion, and incremental arm crank exercise. However, the MOXY reports a greater dynamic range, particularly during ischemia induced by isometric contraction or occlusion (Δ74.3% versus Δ43.7%; hyperemia MAX-occlusion MIN). This study shows that in this subject group both MOXY and PortaMon produce physiologically credible TSI measures during rest and exercise. However, the absolute values obtained during exercise are generally not comparable between devices unless corrected by physiological calibration following an arterial occlusion.
Highlights
The use of wearable devices or wearable biosensors, which allow the continuous monitoring of physiological signals, is important for better monitoring of active lifestyles and the diagnosis and treatment of diseases.[1]
There was a significant correlation between tissue saturation index (TSI) and external pressure for both MOXY and PortaMon devices [Fig. 1(a)], in both cases showing a drop in TSI with increasing pressure
The slope was significantly steeper for the MOXY than the PortaMon
Summary
The use of wearable devices or wearable biosensors, which allow the continuous monitoring of physiological signals, is important for better monitoring of active lifestyles and the diagnosis and treatment of diseases.[1]. A further measurement, tissue saturation index (TSI) represents muscle NIRS studies are relevant in the evaluation of exercise performance, exercise tolerance,[1] and exercise training adaptation that can influence the balance between muscle O2 delivery and muscle utilization.[5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
