Non-Invasive Estimation of Skeletal Muscle Oxygen Consumption Rate and Microvascular Reactivity in Chronic Stroke Survivors using Near Infrared Spectroscopy.

BACKGROUND:Understanding post-stroke changes in skeletal muscle oxidative metabolism and microvascular reactivity could help create therapeutic targets that optimize rehabilitative interventions. Due to disuse atrophy, we hypothesized that basal muscle oxygen consumption rate and microvascular endothelial function would be impaired in the tibialis anterior (TA) muscle of the affected leg of chronic stroke survivors compared to the non-affected leg and vs. matched controls. METHODS:Fifteen chronic stroke survivors (10 female) and 15 matched controls (9 female) completed this study. A near infrared spectroscopy oximeter measured tissue oxygen saturation (StO2) of the TA in both legs of stroke survivors and the dominant leg of controls. A cuff was placed around the thigh and inflated to 225 mmHg for five minutes while StO2 was continuously measured. The rate of change in StO2 was calculated during cuff occlusion and immediately post-cuff release. RESULTS:The rate of oxygen desaturation was similar between the legs of the stroke survivors (paretic -0.12±0.04 %∙s-1 vs non-paretic -0.16±011 %∙s-1; p=0.49), but the paretic leg had a reduced desaturation rate vs. controls (-0.25±0.18%∙s-1; p=0.007 vs. paretic leg). After cuff release, there was a greater oxygen resaturation rate in the non-paretic leg compared to the paretic leg (3.13±2.08 %∙s-1 vs. 1.60±1.11 %∙s-1, respectively; p=0.01). The control leg had a similar resaturation rate vs. the non-paretic leg (control = 3.41±1.79%∙s-1; p=0.69) but was greater than the paretic leg (p=0.003). CONCLUSION:The TA in the paretic leg had an impaired muscle oxygen consumption rate and reduced microvascular endothelial function compared to controls.