Ter Minassian A, Beydon L, Ursino M, Gardette B, Gortan C, Richalet J P
Département d'Anesthésie-Réanimation, CHU d'Angers, France.
Wilderness Environ Med. 2001 Fall;12(3):175-83. doi: 10.1580/1080-6032(2001)012[0175:dsomca]2.0.co;2.
To explore cerebral hemodynamics in 8 healthy volunteers in a hypobaric chamber up to the altitude of Mount Everest after a progressive stepwise decompression to 8,848 m.
Physiological, clinical, and transcranial Doppler data were collected after at least 3 days at 5,000, 6,000, and 7,000 m and within 4 hours of reaching 8,000 m and returning to sea level.
Three subjects were excluded at 8,000 and 8,848 m because of acute neurological deficits. Heart rate increased; mean arterial pressure remained stable; PaO2 and PaCO2 decreased with altitude; hemoglobin (Hb) and hematocrit (Ht) increased; arterial O2 content decreased over 6,000 m; middle cerebral artery blood flow velocity (MCAv) increased only during acute exposure to 8,000 m; and the corresponding pulsatility (PI) and resistivity indices (RI) decreased over 5,000 m. PI and RI correlated with heart rate. The transient hyperemic response (THR) of MCAv to common carotid compression was depressed at 8,000 m.
At 8,000 m, the increase in MCAv seemed to reflect the normal hemodynamic response to acute hypoxia. The decrease of THR at this altitude could be an indication of impaired cerebral autoregulation. The role of impaired cerebral autoregulation in the genesis of acute neurologic deficits, observed at 8,000 m and above in 3 subjects, remains speculative.
在低压舱中对8名健康志愿者进行逐步减压直至珠穆朗玛峰海拔高度（8848米），以探索其脑血流动力学变化。
在海拔5000米、6000米和7000米至少停留3天后，以及到达8000米并返回海平面后4小时内，收集生理、临床和经颅多普勒数据。
在8000米和8848米时，3名受试者因急性神经功能缺损被排除。心率增加；平均动脉压保持稳定；随着海拔升高，动脉血氧分压（PaO₂）和动脉血二氧化碳分压（PaCO₂）降低；血红蛋白（Hb）和血细胞比容（Ht）升高；海拔超过6000米时，动脉血氧含量降低；仅在急性暴露于8000米时，大脑中动脉血流速度（MCAv）增加；海拔超过5000米时，相应的搏动指数（PI）和阻力指数（RI）降低。PI和RI与心率相关。在8000米时，MCAv对颈总动脉压迫的短暂充血反应（THR）减弱。
在8000米时，MCAv增加似乎反映了对急性缺氧的正常血流动力学反应。该海拔高度THR降低可能表明脑自动调节功能受损。在3名受试者中观察到的8000米及以上高度脑自动调节功能受损在急性神经功能缺损发生中的作用仍具有推测性。
