Dumais Valerie, Nault Patrice, Tsertsvadze Alexander, Forbes Thomas L
Department of General Surgery, The Ottawa Hospital, University of Ottawa, Ontario, Canada.
Wilderness Environ Med. 2011 Dec;22(4):309-15. doi: 10.1016/j.wem.2011.06.009. Epub 2011 Oct 14.
Hemodynamic changes in response to the hypoxic environment of high altitude are vascular bed-specific. The aim of the present study was to investigate diameter and blood flow changes in conduit vessels in response to hypobaric hypoxia.
Eleven healthy subjects ascending Mount Everest to base camp participated in this study. Vessel diameter and blood velocity for brachial, carotid, common femoral, superficial femoral, and deep femoral arteries were measured by portable Doppler ultrasound. Blood flow was calculated from these values. Measurements were taken at sea level, at increasing altitudes on ascent to base camp (1310 m, 3470 m, 5330 m), and repeated on descent to lower altitude (1310 m).
For all vessels except carotids, both vessel diameter and blood flow decreased between sea level and initial ascent to altitude, with subsequent persistence of these decreased values; there was no further significant change with continued ascent to higher altitude. Blood flow for all arteries (except carotids) increased significantly on descent to lower altitude, with an associated nonsignificant increase in velocity and decrease in diameter.
This study showed that there is vasoconstriction of limb conduit vessels at altitude, which persists upon descent to lower altitude. Blood flow in these vessels also decreases with initial exposure to high altitude, yet increases when returning to lower altitude, reflecting variations in blood velocity. Carotid arteries responded differently to the stimulus of hypobaria than limb conduit vessels; there was no change in diameter seen on ascent or descent, but there was a progressive decrease in blood flow on ascent, with no change on subsequent descent.
对高海拔低氧环境的血流动力学变化具有血管床特异性。本研究的目的是调查低压缺氧时传导血管的直径和血流变化。
11名攀登珠穆朗玛峰至大本营的健康受试者参与了本研究。通过便携式多普勒超声测量肱动脉、颈动脉、股总动脉、股浅动脉和股深动脉的血管直径和血流速度。根据这些值计算血流量。在海平面、攀登至大本营过程中海拔不断升高时（1310米、3470米、5330米）进行测量，并在下降至较低海拔（1310米）时重复测量。
除颈动脉外，所有血管的直径和血流量在海平面至初始海拔上升过程中均下降，且这些下降值随后持续存在；继续上升至更高海拔时无进一步显著变化。下降至较低海拔时，所有动脉（颈动脉除外）的血流量显著增加，同时速度有不显著增加，直径减小。
本研究表明，海拔高度时肢体传导血管会发生血管收缩，下降至较低海拔时这种收缩仍持续存在。这些血管的血流量在最初暴露于高海拔时也会减少，但返回较低海拔时会增加，反映出血流速度的变化。颈动脉对低压刺激的反应与肢体传导血管不同；上升和下降过程中直径无变化，但上升时血流量逐渐减少，随后下降时无变化。
