Rosenberry Ryan, Trojacek Darian, Chung Susie, Cipher Daisha J, Nelson Michael D
Department of Kinesiology, University of Texas at Arlington, Arlington, Texas.
College of Nursing, University of Texas at Arlington, Arlington, Texas.
Am J Physiol Regul Integr Comp Physiol. 2019 Oct 1;317(4):R530-R538. doi: 10.1152/ajpregu.00157.2019. Epub 2019 Jul 17.
Reactive hyperemia is an established, noninvasive technique to assess microvascular function and a powerful predictor of all-cause and cardiovascular morbidity and mortality. Emerging evidence from our laboratory suggests a close link between reactive hyperemia and the metabolic rate of the ischemic limb and the existence of large interindividual differences contributing to markedly different stimuli to vasodilate. Here we relate forearm tissue desaturation (i.e., the ischemic stimulus to vasodilate, measured by near-infrared spectroscopy) to brachial artery hyperemic velocity and flow (measured using duplex ultrasound) across a wide range of ischemic stimuli. Twelve young and 11 elderly individuals were prospectively studied. To recapitulate conventional vascular occlusion testing, reactive hyperemia was first assessed using a standard 5-min occlusion period. Then, to evaluate the dose dependence of tissue ischemia on reactive hyperemia, we randomly performed 4-, 6-, and 8-min cuff occlusions in both groups. In all cases, peak velocity, as well as the 5-s average velocity, immediately after the cuff occlusion was significantly higher in the young than the elderly group; however, tissue desaturation was also much more pronounced in the young group ( < 0.05), representing a greater ischemic stimulus. Remarkably, when reactive hyperemia was adjusted for the ischemic vasodilatory stimulus, group differences in reactive hyperemia were abrogated. Together, these data challenge conventional interpretations of reactive hyperemia and show that the ischemic stimulus to vasodilate varies across individuals and that the level of reactive hyperemia is often coupled to the magnitude of tissue desaturation.
反应性充血是一种成熟的、非侵入性的评估微血管功能的技术，也是全因发病率和心血管发病率及死亡率的有力预测指标。我们实验室的新证据表明，反应性充血与缺血肢体的代谢率之间存在密切联系，而且个体间存在很大差异，这导致血管舒张刺激明显不同。在此，我们研究了在广泛的缺血刺激范围内，前臂组织去饱和（即通过近红外光谱测量的血管舒张缺血刺激）与肱动脉充血速度和血流量（使用双功超声测量）之间的关系。对12名年轻人和11名老年人进行了前瞻性研究。为了重现传统的血管闭塞测试，首先使用标准的5分钟闭塞期评估反应性充血。然后，为了评估组织缺血对反应性充血的剂量依赖性，我们在两组中随机进行了4分钟、6分钟和8分钟的袖带闭塞。在所有情况下，袖带闭塞后立即出现的峰值速度以及5秒平均速度，年轻人组显著高于老年人组；然而，年轻人组的组织去饱和也更为明显（<0.05），这代表着更大的缺血刺激。值得注意的是，当根据缺血性血管舒张刺激对反应性充血进行调整后，反应性充血的组间差异消失。总之，这些数据挑战了对反应性充血的传统解释，并表明血管舒张的缺血刺激因人而异，而且反应性充血的程度通常与组织去饱和的程度相关。
