Vascular responsiveness measured by tissue oxygen saturation reperfusion slope is sensitive to different occlusion durations and training status.

Abstract

What is the central question of this study? Is the near-infrared spectroscopy-derived measure of tissue oxygen saturation (StO2) reperfusion slope sensitive to a range of ischaemic conditions, and do differences exist between trained and untrained individuals? What is the main finding and its importance? The StO2 reperfusion rate is sensitive to different occlusion durations, and changes in the reperfusion slope in response to a variety of ischaemic challenges can be used to detect differences between two groups. These data indicate that near-infrared spectroscopy-derived measures of StO2, specifically the reperfusion slope following a vascular occlusion, can be used as a sensitive measure of vascular responsiveness. The reperfusion rate of near-infrared spectroscopy-derived measures of tissue oxygen saturation (StO2) represents vascular responsiveness. This study examined whether the reperfusion slope of StO2 is sensitive to different ischaemic conditions (i.e. a dose-response relationship) and whether differences exist between two groups of different fitness levels. Nine healthy trained (T; age 25±3years; maximal oxygen uptake 63.4±6.7mlkg-1 min-1 ) and nine healthy untrained men (UT; age 21±1years; maximal oxygen uptake 46.6±2.5mlkg-1 min-1 ) performed a series of vascular occlusion tests of different durations (30s, 1, 2, 3 and 5min), each separated by 30min. The StO2 was measured over the tibialis anterior using near-infrared spectroscopy, with the StO2 reperfusion slope calculated as the upslope during 10s following cuff release. The reperfusion slope was steeper in T compared with UT at all occlusion durations (P<0.05). For the T group, the reperfusion slopes for 30s and 1min occlusions were less than for all longer durations (P<0.05). The reperfusion slope following 2min occlusion was similar to that for 3min (P>0.05), but both were less steep than for 5min of occlusion. In UT, the reperfusion slope at 30s was smaller than for all longer occlusion durations (P<0.05), and 1min occlusion resulted in a reperfusion slope that was less steep than following 2 and 3min (P<0.05), albeit not different from 5min (P>0.05). The present study demonstrated that the reperfusion rate of StO2 is sensitive to different occlusion durations, and that changes in the reperfusion rate in response to a variety of ischaemic challenges can be used to detect differences in vascular responsiveness between trained and untrained groups.