Intra- and Inter-Day Reliability of the NIRS Portamon Device after Three Induced Muscle Ischemias

Abstract

(1) Background: Near-infrared spectroscopy (NIRS) is an innovative and non-invasive technology used to investigate muscular oxygenation. The aim of this study is to assess the within- and between-session reliability of the NIRS Portamon (Artinis, Elst, Netherlands) device following three sets of induced muscle ischemia. (2) Methods: Depending on the experimental group (G1, G2 or G3), a cuff was inflated three times on the left upper arm to 50 mmHg (G1), systolic blood pressure (SBP) + 50 mmHg (G2) or 250 mmHg (G3). Maximum, minimum and reoxygenation rate values were assessed after each occlusion phase, using a Portamon device placed on the left brachioradialis. Reliability was assessed with intraclass correlation coefficient (ICC) value and ICC 95% confidence interval (CI-95%), coefficient of variation (CV) and standard error of measurement (SEM) (3) Results: Our results showed a good to excellent reliability for maximums and minimums within-session. However, the reoxygenation rate within sessions as well as measurements between sessions cannot predominantly show good reliability. (4) Conclusions: Multiple measurements of maximums and minimums within a single session appeared to be reliable which shows that only one measurement is necessary to assess these parameters. However, it is necessary to be cautious with a comparison of maximum, minimum and reoxygenation rate values between sessions.

Keywords: arterial occlusion; blood flow restriction; hyperemia; ischemic preconditioning; test–retest.

Figure 1

Participants were lying on a medical couch for the duration of the session in the dark and asked to avoid any movement which could disturb the signal. After a 15 min baseline period, the cuff placed on the left arm was inflated to induce three occlusion phases (O1, O2, O3) each of seven minutes. Each occlusion phase was followed by a reperfusion period (R1 = 10 min, R2 = 10 min, R3 = 20 min).

Figure 2

NIRS device placement illustration.

Figure 3

Example of tissue saturation index (TSI%), oxyhemoglobin concentration ([O₂Hb]) and deoxyhemoglobin concentration ([HHb]) responses during the whole protocol for a single participant in group 3 (G3: 250 mmHg). The dashed rectangle represents the last minute of the baseline, which is averaged to provide the baseline value of each parameter. When the cuff is inflated during occlusion phases (O1, O2, O3), both TSI% and [O₂Hb] decrease until their minimum, whereas [HHb] increases to its maximum. When the cuff is deflated at the beginning of reperfusions phases (R1, R2, R3), TSI% and [O₂Hb] rise until their maximum above the baseline value (hyperemia spike), whereas [HHb] reach its minimum.

Figure 4

Examples of Bland–Altman plots of the reliability across trials for TSI_max of participants belonging to the group 2 (G2): (a) between sessions (bias = 0.99, 95% CI = −4.53 to 6.52) (b) and within sessions (bias = −0.35, 95% CI = −2.21 to 1.52). The within-session trial comparison (b) shows a lower dispersion around the mean compared to between-session trial comparison (a).