Willie Christopher K, MacLeod David B, Smith Kurt J, Lewis Nia C, Foster Glen E, Ikeda Keita, Hoiland Ryan L, Ainslie Philip N
Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia - Okanagan, Kelowna, British Columbia, Canada.
Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina, USA.
J Cereb Blood Flow Metab. 2015 May;35(5):873-81. doi: 10.1038/jcbfm.2015.4. Epub 2015 Feb 18.
The effects of partial acclimatization to high altitude (HA; 5,050 m) on cerebral metabolism and cerebrovascular function have not been characterized. We hypothesized (1) increased cerebrovascular reactivity (CVR) at HA; and (2) that CO2 would affect cerebral metabolism more than hypoxia. PaO2 and PaCO2 were manipulated at sea level (SL) to simulate HA exposure, and at HA, SL blood gases were simulated; CVR was assessed at both altitudes. Arterial-jugular venous differences were measured to calculate cerebral metabolic rates and cerebral blood flow (CBF). We observed that (1) partial acclimatization yields a steeper CO2-H(+) relation in both arterial and jugular venous blood; yet (2) CVR did not change, despite (3) mean arterial pressure (MAP)-CO2 reactivity being doubled at HA, thus indicating effective cerebral autoregulation. (4) At SL hypoxia increased CBF, and restoration of oxygen at HA reduced CBF, but neither had any effect on cerebral metabolism. Acclimatization resets the cerebrovasculature to chronic hypocapnia.
部分适应高海拔（HA；5050米）对脑代谢和脑血管功能的影响尚未明确。我们假设：（1）在高海拔时脑血管反应性（CVR）增加；（2）二氧化碳对脑代谢的影响大于缺氧。在海平面（SL）时对动脉血氧分压（PaO2）和动脉血二氧化碳分压（PaCO2）进行调控以模拟高海拔暴露情况，而在高海拔时则模拟海平面的血气情况；在两个海拔高度均评估脑血管反应性。测量动脉 - 颈静脉差异以计算脑代谢率和脑血流量（CBF）。我们观察到：（1）部分适应使动脉血和颈静脉血中二氧化碳 - 氢离子关系更陡峭；然而（2）脑血管反应性并未改变，尽管（3）在高海拔时平均动脉压（MAP） - 二氧化碳反应性增加了一倍，这表明有效的脑自动调节。（4）在海平面时缺氧增加脑血流量，而在高海拔时恢复氧气则降低脑血流量，但两者对脑代谢均无任何影响。适应使脑血管系统重新调整至慢性低碳酸血症状态。
