Huang S Y, Moore L G, McCullough R E, McCullough R G, Micco A J, Fulco C, Cymerman A, Manco-Johnson M, Weil J V, Reeves J T
J Appl Physiol (1985). 1987 Jul;63(1):395-400. doi: 10.1152/jappl.1987.63.1.395.
Cerebral blood flow increases at high altitude, but the mechanism of the increase and its role in adaptation to high altitude are unclear. We hypothesized that the hypoxemia at high altitude would increase cerebral blood flow, which would in turn defend O2 delivery to the brain. Noninvasive Doppler ultrasound was used to measure the flow velocities in the internal carotid and the vertebral arteries in six healthy male subjects. Within 2-4 h of arrival on Pikes Peak (4,300 m), velocities in both arteries were slightly and not significantly increased above sea-level values. By 18-44 h a peak increase of 20% was observed (combined P less than 0.025). Subsequently (days 4-12) velocities declined to values similar to those at sea level. At altitude the lowest arterial O2 saturation (SaO2) and the highest end-tidal PCO2 was observed on arrival. By day 4 and thereafter, when the flow velocities had returned toward sea-level values, hemoglobin concentration and SaO2 were increased over initial high-altitude values such that calculated O2 transport values were even higher than those at sea level. Although the cause of the failure for cerebral flow velocity to increase on arrival is not understood, the subsequent increase may act to defend brain O2 transport. With further increase in hemoglobin and SaO2 over time at high altitude, flow velocity returned to sea-level values.
在高海拔地区脑血流量会增加，但这种增加的机制及其在适应高海拔过程中的作用尚不清楚。我们推测，高海拔地区的低氧血症会增加脑血流量，进而保障向大脑输送氧气。我们使用无创多普勒超声测量了6名健康男性受试者颈内动脉和椎动脉的血流速度。在抵达派克斯峰（4300米）后的2 - 4小时内，两条动脉的血流速度较海平面时略有增加，但无显著差异。到18 - 44小时，观察到血流速度峰值增加了20%（合并P值小于0.025）。随后（第4 - 12天）血流速度降至与海平面时相似的值。在海拔高度时，到达时观察到最低的动脉血氧饱和度（SaO2）和最高的呼气末二氧化碳分压。到第4天及之后，当血流速度恢复到接近海平面的值时，血红蛋白浓度和SaO2较最初的高海拔值有所增加，以至于计算得出的氧输送值甚至高于海平面时的值。虽然到达时脑血流速度未能增加的原因尚不清楚，但随后的增加可能有助于保障脑部的氧输送。随着高海拔地区血红蛋白和SaO2随时间进一步增加，血流速度恢复到海平面值。
