The relation of leg venous function and structure to orthostatic hypotension in humans

背景和目的：尽管进行了广泛的研究，但心血管健康或年龄对立位的影响仍不确定。小腿静脉顺应性可能是决定与立位改变相关的心血管应激的关键因素。防止液体进入腿部可显著降低对立位应激源的反射反应。在以前久坐不动的老年人和年轻人中，运动训练会在多大程度上影响静脉顺应性和对立位应激的耐受性，目前尚不清楚。用静脉充血体积描记术(VCPG)评价人小腿整个静脉系统(包括小静脉到大静脉)的顺应性(Halliwill等，J.Appl.Physiol)。1999)，已经在几个应用研究中使用。利用B型超声(US)，我们已经提出了一种类似的技术，即DERI…，用于使用US图像来估计中等静脉血管(即，腓静脉)的顺应性因此，我们研究：1.人体腿部静脉顺应性与立位耐力的关系。连续10天耐力训练对小腿静脉顺应性的影响。其次，为了明确与静脉共用有关的静脉血管功能，我们考察了：3.缺血握力运动对人体小腿静脉顺应性的影响。结果：耐受组与不耐受组静脉顺应性差异无统计学意义。这一结果表明，腿部静脉顺应性不是人类立位不耐受的主要决定因素。静脉共用可降低心脏充盈压和血压；因此，心肺区域的动脉压力感受器(颈动脉和主动脉)和压力感受器必须适应，以在相当广泛的血流动力学条件下维持血压。连续10d耐力训练(60min，40%峰VO2)后，小腿静脉顺应性无明显变化。在缺血握力运动诱发的交感神经刺激(交感-兴奋性刺激)下至运动后缺血后的疲劳。与对照组相比，在交感神经刺激下，小腿体积一直较小。静脉顺应性在低PV时显著降低。这些数据表明人类交感静脉血管调节的存在。此外，静脉顺应性与下肢毛细血管滤过率呈负相关。较少

BACKGROUND AND PURPOSE: Despite extensive investigation, the effects of either cardiovascular fitness or age on orthostatic remain uncertain. Calf venous compliance may be a critical factor in determining the cardiovascular stress associated with change in orthostasis. Preventing fluid shifts into the legs markedly reduces reflex responses to an orthostatic stressor. The extent to which exercise training in a previously sedentary older and young population will affect venous compliance and tolerance to the orthostatic stress is unknown. An evaluation of the compliance of the whole venous system (including venule to large vein) in human calf was developed with a venous congested plethysmography (VCPG) (Halliwill, et al., J.Appl.Physiol. 1999) which has already been used in several application studies. Utilizing the B-mode ultrasonography (US), we have proposed a similar technique for estimating the compliance in medium venous vessels (i.e., Popliteal vein) using US images, which is deri … More ved from the CSA-venous pressure (Pv) relationship.Therefore, we investigate:1. The relation of leg venous compliance to orthostatic intolerance in humans.2. Effect of 10days successive endurance training on leg venous compliance.Secondly, to clearly define the venous vascular function concerning venous pooling, we examined:3. The effect of ischemic handgrip exercise on leg venous compliance in humans4. The relationship between venous compliance and capillary filtration in the lower limb.RESULT: Venous compliance was not different between tolerance and intolerance group. This result suggested that the leg venous compliance is not dominant determinant of the orthostatic intolerance in humans. Venous pooling decreases cardiac filling pressure and blood pressure (BP); therefore, arterial baroreceptors (carotid and aortic) and baroreceptors in the cardiopulmonary region must adapt to maintain BP over a fairly wide range of hemodynamic conditions. And no change in calf venous compliance was found after 10 days successive of endurance training (60 min, 40% peak Vo2). Under the sympathetic stimulation (sympatho-excitatory stimulation) induced by the ischemic handgrip exercise to fatigue followed post-exercise ischemia. Compared to the control, the calf volume was consistently smaller under the sympathetic stimulation. The venous compliance at lower Pv was significantly lower. These data shows to existence of sympathetic venous vascular regulation in humans. In addition, there is negative correlation was observed between venous compliance and capillary filtration in the lower limb. Less