Oxigenação tecidual periférica em indivíduos com doença arterial periférica de capacidades de caminhada distintas: um estudo exploratório

Abstract

Introduction: The restriction of blood flow caused by peripheral arterial disease (PAD) results in a decrease of up to 50% in walking capacity when compared to healthy peers. Limiting the ability to walk has previously been related to worse quality of life and lower levels of functional capacity. When considering perfusion, metabolism, and blood flow, the peripheral mechanisms that may affect the walking capacity of individuals with PAD are not yet fully understood. This study aimed to 1) compare peripheral tissue oxygenation and muscle metabolism in individuals with PAD with different walking capabilities and 2) evaluate which variables of peripheral tissue oxygenation and muscle metabolism have the potential to explain the variability in distance walked between performance levels. Methods: An exploratory cross-sectional study was conducted using baseline data from two randomized clinical trials. A non-probabilistic sample, regardless of gender and ethnicity, was composed of adults diagnosed with PAD recruited from the services of a public health institution. Tissue oxygenation was assessed using Near-Infrared Spectroscopy (NIRS) at rest and during the treadmill test at constant speed and incline (3.2 km/h, 10%). Participants' self-perception of their walking ability was collected using the Walking Impairment Questionnaire (WIQ). Data normality was checked using the Shapiro-Wilk test. For comparison between groups, participants were separated into three tertiles (T1, T2, and T3) according to the distance covered in the treadmill test and the mean WIQ score. One-way analysis of variance (one-way ANOVA) was used for comparisons between tertiles, and the Least Significant Difference (LSD) test was used to perform post hoc comparisons. Multiple linear regression (backward model) was performed considering walking distance in the treadmill test as the dependent variable. Results: Data from 72 individuals aged 65.83±9.06 years, with a mean ankle-brachial index of 0.65±0.14, mostly men (56.9%), former smokers (61.1%), and hypertensive (88.9%) were analyzed. There were no significant differences in baseline peripheral tissue oxygen saturation (StO2) values or delta StO2 values across all tertiles (p>0.05). After the occlusion maneuver, the reoxygenation rate and StO2 in hyperemia were significantly higher in T3 compared to T1 and T2 (p<0.05). In the treadmill test, the time to reach the lowest StO2 and the time to resist ischemia were significantly longer in T3 compared to T1 and T2 (p<0.05). Linear regression demonstrated that ischemia resistance time is the variable that appears to have the greatest influence on the distance covered (adjusted R2=0.83). Conclusion: The NIRS variables related to oxygenation and muscle metabolism have different behavior between individuals with better and worse walking ability. Factors such as microvascular, endothelial, and muscular dysfunction were decisive in reducing the walking capacity of individuals with PAD.