Bauer Andreas, Demetz Florian, Bruegger Dirk, Schmoelz Martin, Schroepfer Sebastian, Martignoni André, Baschnegger Heiko, Hoelzl Josef, Thiel Manfred, Choukér Alexander, Peter Klaus, Gamble John, Christ Frank
Clinic for Anaesthesiology, Ludwig-Maximilians University Munich, Marchioninistr. 15, 81377 Munich, Germany.
Clin Sci (Lond). 2006 Feb;110(2):207-15. doi: 10.1042/CS20050217.
The role of microvascular fluid shifts in the adaptation to hypobaric hypoxia and its contribution to the pathophysiology of AMS (acute mountain sickness) is unresolved. In a systematic prospective study, we investigated the effects of hypobaric hypoxia and physical exercise alone, and in combination, on microvascular fluid exchange and related factors. We used computer-assisted VCP (venous congestion plethysmography) on the calves of ten altitude-acclimatized volunteers. We investigated the effects of: (i) actively climbing to an altitude of 3196 m, (ii) airlifting these subjects to the same altitude, and (iii) exercise at low altitude. CFC (capillary filtration capacity), Pvi (isovolumetric venous pressure) and Qa (calf blood flow) were assessed before and after each procedure and then repeated after an overnight rest. Measurements of CFC showed no evidence of increased microvascular permeability after any of the procedures. Pvi was significantly decreased (P<0.001) from 20.3+/-4.4 to 8.9+/-4.3 mmHg after active ascent, and was still significantly lower (P=0.009) after overnight rest at high altitude (13.6+/-5.9 mmHg). No such changes were observed after the passive ascent (16.7+/-4.0 mmHg at baseline; 17.3+/-4.5 mmHg after passive ascent; and 19.9+/-5.3 mmHg after overnight rest) or after exercise at low altitude. After the active ascent, Qa was significantly increased. We also found a significant correlation between Qa, Pvi and the number of circulating white blood cells. In conclusion, we found evidence to support the hypothesis that increased microvascular permeability associated with AMS does not occur in acclimatized subjects. We also observed that the microvascular equilibrium pressure (Pvi) fell in inverse relation to the increase in Qa, especially in hypoxic exercise. We hypothesize that this inverse relationship reflects the haemodynamic changes at the microvascular interface, possibly attributable to the flow-induced increases in endothelial surface shear forces.
微血管液体转移在适应低压缺氧中的作用及其对急性高原病（AMS）病理生理学的影响尚未明确。在一项系统性前瞻性研究中，我们调查了低压缺氧和单独及联合体育锻炼对微血管液体交换及相关因素的影响。我们对十名适应高原环境的志愿者的小腿进行了计算机辅助静脉充血体积描记法（VCP）。我们研究了以下情况的影响：（i）主动攀登至3196米的海拔高度；（ii）将这些受试者空运至相同海拔高度；（iii）在低海拔进行锻炼。在每个程序前后评估毛细血管滤过能力（CFC）、等容静脉压（Pvi）和小腿血流量（Qa），并在过夜休息后重复测量。CFC测量结果显示，在任何程序后均无微血管通透性增加的证据。主动攀登后，Pvi从20.3±4.4显著降低至8.9±4.3 mmHg（P<0.001），在高海拔过夜休息后仍显著较低（13.6±5.9 mmHg，P=0.009）。被动攀登后（基线时为16.7±4.0 mmHg；被动攀登后为17.3±4.5 mmHg；过夜休息后为19.9±5.3 mmHg）或在低海拔锻炼后未观察到此类变化。主动攀登后，Qa显著增加。我们还发现Qa、Pvi与循环白细胞数量之间存在显著相关性。总之，我们发现有证据支持以下假设：在适应环境的受试者中，与AMS相关的微血管通透性增加不会发生。我们还观察到微血管平衡压力（Pvi）与Qa的增加呈反比下降，尤其是在缺氧运动中。我们推测这种反比关系反映了微血管界面的血流动力学变化，可能归因于血流引起的内皮表面剪切力增加。
