Muscle tissue oxygenation in individuals with peripheral arterial disease of different walking abilities: An exploratory study.

Background: Blood flow restriction caused by peripheral arterial disease (PAD) is reflected in reduced walking capacity. The peripheral mechanisms that may affect the walking capacity of individuals with PAD are not yet fully understood. This study aimed to 1) compare tissue oxygenation and muscle metabolism of individuals with PAD with different walking capacities and 2) evaluate which variables have the greatest potential to explain the variability in distance walked between performance levels.

Methods: The sample composed of adults diagnosed with PAD underwent evaluation of microvascular function in the gastrocnemius muscle through Near-Infrared Spectroscopy (NIRS) at two time points: (1) during the arterial occlusion maneuver; (2) on a treadmill test with constant speed and inclination (3.2 km/h, 10 %). The following NIRS parameters were selected: (1) percentage of peripheral tissue oxygen saturation (StO₂); (2) StO₂ delta; (3) reoxygenation rate; (4) time to reach lowest StO₂; (5) ischemia resistance time; (6) StO₂ in reactive hyperemia. Participants were divided into tertiles (T1, T2, and T3) according to the walking distance in the treadmill test. One-way analysis of variance (ANOVA) was used for comparisons between tertiles and multiple linear regression was used for association analyses.

Results: There were no significant differences between tertiles in baseline values or delta StO₂. The reoxygenation rate and StO₂ in hyperemia of the occlusion maneuver, as well as the time to reach the lowest StO₂ and the ischemia resistance time in the treadmill test, were significantly higher in T3 than in T1 and T2 (p < 0.05). Linear regression demonstrated that the ischemia resistance time is the variable that appears to have the greatest influence on the distance walked (adjusted R² = 0.83).

Conclusion: Better walking performance was associated with better dynamic response capacity to ischemia. Factors such as microvascular, endothelial, and muscular dysfunction appear to be decisive in reducing the walking capacity of individuals with PAD.