Microvascular fluid filtration capacity (Kf) assessed with cumulative small venous pressure steps and with various degrees of tilt.
Microvascular fluid filtration capacity (Kf) assessed with cumulative small venous pressure steps and with various degrees of tilt.
复制标题
通过累积小静脉压力阶跃和不同倾斜度来评估微血管液体过滤能力（Kf）。
DOI：
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发表时间：
1997
影响因子：
4.2
通讯作者：
K. Messmer
中科院分区：
文献类型：
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作者：
F. Christ;J. Gamble;V. Baranov;A. Kotov;I. Gartside;I. Nehring;K. Messmer
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直立失调是经历极端重力的飞行员和长期暴露于微重力的宇航员中的常见现象。我们使用非侵入性静脉充血体积描记术（VCP）来研究微循环变化以及在不同倾斜度期间激活外周和中枢介导的保护机制的能力，我们将其用作直立挑战。
方法
这项研究得到了当地生物医学问题研究所伦理委员会的批准，在六名健康的 20 - 26 岁男性志愿者中进行。我们对大腿施加 6 - 8 个累积小静脉充血压力步骤 (8 mmHg)，并确定液体过滤能力 (Kf)、袖带压力 (Pcuff) 和测量的液体过滤 (Jv) 之间的线性关系。然后，我们测量了流体过滤 (Jv) 对不同累积倾斜度的响应，从 0 度开始，然后低头 -8 度 -15 度、-30 度 -15 度、-8 度、0 度，然后抬头 15 度、30 度、70 度、30 度、15 度和 0 度。每个倾斜阶段持续15分钟。通过测量应变计水平处右心房和小腿中部之间的垂直高度差来确定应变计水平处的静水负荷变化。在小累积压力步骤方案之前和之后以及每个倾斜步骤结束时测量肢体动脉血流量并进行肺功能测试。
结果
在累积压力步骤方案期间，血压（BP）和心率（HR）没有发生显着变化。然而，在倾斜过程中观察到 HR 增加，但仅在 30 度和 70 度时达到显着性。使用小累积压力步骤测量的平均 Kf 值为 3.25 +/- 0.5 (10(-3) ml.100 ml 组织(-1) mmHg(-1) = KfU），该值显着 (p < 0.005) 高于使用倾斜增加静水载荷获得的值 (0.98 +/- 0.2 KfU)。一名受试者的 Kf 值没有变化，在施加 70 度倾斜后出现血管迷走神经晕厥，心率 < 35 / 分钟，收缩压为 60 mmHg。在倾斜过程中，肢体血流量的测量显示没有显着变化。肺功能测量显示，在 35 度和 70 度抬头倾斜期间，只有呼气储备量 (ERV) 显着增加。所有其他参数均未改变。我们认为，这些 Kf 值的差异可以通过响应倾斜而激活中枢和外周介导的毛细血管前阻力变化来解释。我们怀疑，一名受试者经历的血管迷走神经晕厥反映了他无法激活这些保护性反射机制，亚临床静脉功能不全可能会加剧这种情况。我们相信这些结果表明 VCP 是确定直立性应激不耐受的有用工具。
UNLABELLED
Orthostatic dysregulation is a frequent phenomenon in pilots experiencing extreme G forces and after prolonged exposures to microgravity in cosmonauts. We used non-invasive venous congestion plethysmography (VCP) to study microcirculatory changes and the ability to activate peripheral and centrally mediated protective mechanisms during various degrees of tilt, which we used as an orthostatic challenge.
METHOD
The study, which was approved by the local ethical committee of the Institute of Biomedical Problems, was performed on six healthy 20 - 26 years old male volunteers. We applied 6 - 8 cumulative small venous congestion pressure steps (8 mmHg) to the thigh and determined the fluid filtration capacity (Kf), the linear relationship between cuff pressure (Pcuff) and measured fluid filtration (Jv). We then measured the fluid filtration (Jv) response to varying cumulative degrees of tilt, starting at 0 degrees followed by head down -8 degrees -15 degrees, -30 degrees -15 degrees, -8 degrees, 0 degrees, and then head up 15 degrees, 30 degrees, 70 degrees, 30 degrees, 15 degrees and 0 degrees. Each tilt stage was sustained for 15 minutes. The change in hydrostatic load, at the level of the strain gauge, was determined by measuring the difference in vertical height between the right atrium and mid calf at the level of the gauge. Limb arterial blood flow was measured and lung function tests were performed before and after the small cumulative pressure step protocol, as well as at the end of each tilt step.
RESULTS
No significant changes in blood pressure (BP) and heart rate (HR) occurred during the cumulative pressure step protocol. However, an increase in HR was observed during the tilt, but only reached significance at 30 degrees and 70 degrees. The mean Kf value measured with small cumulative pressure steps was 3.25 +/- 0.5 (10(-3) ml.100 ml tissue(-1) mmHg(-1) = KfU), which was significantly (p < 0.005) higher than the value obtained using tilt to increase the hydrostatic load (0.98 +/- 0.2 KfU). One subject had an unchanged Kf value and experienced vaso - vagal syncope following the imposition of 70 degrees tilt, with a heart rate < 35 / min and a systolic blood pressure of 60 mmHg. The measurement of blood flow in the limb showed no significant change during the tilt procedure. The lung function measurements revealed, that only expiratory reserve volume (ERV) did significantly increase during 35 degrees and 70 degrees head up tilt. All other parameters were unchanged. We suggest that the differences in these Kf values can be explained by the activation of both central and peripheral mediated changes in pre- capillary resistance in response to the tilt. We suspect, that the vaso - vagal syncope, experienced by one subject, reflected his inability to activate these protective reflex mechanisms, a situation that could be exacerbated by sub-clinical venous insufficiency. We believe that these results show that VCP is a useful tool for the determination of intolerance to orthostatic stress.