Suitability of the muscle O2 resaturation parameters most used for assessing reactive hyperemia: a near-infrared spectroscopy study

Abstract

Background There is a spectrum of possibilities for analyzing muscle O2 resaturation parameters for measurement of reactive hyperemia in microvasculature. However, there is no consensus with respect to the responsiveness of these O2 resaturation parameters for assessing reactive hyperemia. Objectives This study investigates the responsiveness of the most utilized muscle O2 resaturation parameters to assess reactive hyperemia in the microvasculature of a clinical group known to exhibit impairments of tissue O2 saturation (StO2). Methods Twenty-three healthy young adults, twenty-nine healthy older adults, and thirty-five older adults at risk of cardiovascular disease (CVD) were recruited. Near-infrared spectroscopy (NIRS) was used to assess StO2 after a 5-min arterial occlusion challenge and the following parameters were analyzed: StO2slope_10s, StO2slope_30s, and StO2slope_until_baseline (upslope of StO2 over 10s and 30s and until StO2 reaches the baseline value); time to StO2baseline and time to StO2max (time taken for StO2 to reach baseline and peak values, respectively); ∆StO2reperfusion (the difference between minimum and maximum StO2 values); total area under the curve (StO2AUCt); and AUC above the baseline value (StO2AUC_above_base). Results Only StO2slope_10s was significantly slower in older adults at risk for CVD compared to healthy young individuals (p < 0.001) and to healthy older adults (p < 0.001). Conversely, time to StO2max was significantly longer in healthy young individuals than in older adult at CVD risk. Conclusions Our findings suggest that StO2slope_10s may be a measure of reactive hyperemia, which provides clinical insight into microvascular function assessment.

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

“…In their study, Soares et al (2019) showed that after 5 min occlusion at 250 mmHg at the arm, the NIRS reperfusion slope calculated for the forearm (flexor digitorum superficialis muscle) showed a value of 1.77 ± 0.60%•s −1 for TSI% [41], which is slightly higher than our findings for G3 (1.37 ± 0.33%•s −1 ). On the flexor carpi radialis muscle, a reoxygenation rate of 1.24 ± 0.41%•s −1 was found after 5 min occlusion at 250 mmHg [42], and, interestingly, results on leg measurements match our findings on forearm measurements, with 1.32 ± 0.38 [24] and 1.60 ± 0.80%•s −1 [27] for tibialis anterior.…”

Association between Femoral Artery Flow-Mediated Dilation and Muscle Oxygen Saturation Parameters in Healthy, Young Individuals

“…As a result, by-products from the energetic metabolism can induce microvascular vasodilation, increasing the blood flow velocity in the upstream artery, which results in an increased FMD response. A previous study from our Laboratory failed to show a correlation between the brachial artery FMD and muscle StO 2 parameters during ischemia [ 10 ]. These divergent findings reinforce that the macro and microvascular response observed in the brachial artery should not be extrapolated to the other arteries present in the body’s other segments (i.e., lower limb).…”

“…From a mechanical perspective, the magnitude of ischemia induced by cuff occlusion depends on the oxidative capacity of muscles experiencing oxygen deprivation. When a muscle extracts a high oxygen level during cuff occlusion, a more robust magnitude of ischemia is generated [ 10 , 17 ]. As a result, by-products from the energetic metabolism can induce microvascular vasodilation, increasing the blood flow velocity in the upstream artery, which results in an increased FMD response.…”

“…The reperfusion magnitude (%) was calculated as the difference between the highest and lowest StO 2 value during the reperfusion period. The muscle StO 2 parameters during the occlusion and reperfusion phases were used to measure the muscle oxygen extraction (ischemia magnitude) and microvascular responsiveness, respectively [ 10 ].…”

“…Near-infrared spectroscopy (NIRS) assesses muscle oxygen saturation (StO 2 ) since NIRS determines changes in oxygenated and deoxygenated hemoglobin in the microcirculation [ 8 ]. During the VOT, the muscle StO 2 parameters during the cuff occlusion and disocclusion are established as a measurement of the magnitude of tissue ischemia and reperfusion, respectively [ 9 , 10 ]. Given that previous studies have found a positive correlation between the FMD response and the parameters of muscle StO 2 during reperfusion [ 5 , 6 ], the FMD assessment and NIRS analysis have been combined to better understand the crosstalk between macro- and microvascular responsiveness in many clinical populations [ 4 , 6 , 11 ].…”