三个地方问一下，谢谢

The intracranial pressure is influenced by pCO2. A rise in pCO2 will result in brain blood vessel dilatation and then increase in the cerebral blood volume. In contrast, when the pCO2 drops, the blood vessel diameter decreases and results in decreased cerebral blood volume. Although hypocarbic strategy promotes transient decrease in ICP and considered one of the effective intracranial hypertension temporizing measures, hyperventilation carries a serious risk of significant reduction in cerebral blood flow (CBF) and cerebral ischemia. In addition, studies showed prolonged hypocapnia can lead to rebound ICP . For this reason the Brain Trauma Foundation changed recently their 2017 guidelines about hyperventilation and stated that “prolonged prophylactic hyperventilation with partial pressure of carbon dioxide in arterial blood (PaCO2) of 25 mm Hg or less is not recommended” (Level IIB).

The change in cerebral blood flow is independent of the pH as there is no change with metabolic acidosis and alkalosis. There is rapid CO2 equilibration between the arterial blood and CSF , and the change in pH of the CSF acts directly in the vasculature resulting in relaxation or contraction.

颅内压受二氧化碳分压的影响。二氧化碳分压升高会导致脑血管扩张，进而导致脑血容量增加。相反，当二氧化碳分压降低时，血管直径减小，导致脑血容量减少。虽然低碳酸策略促进颅内压的一过性下降，并被认为是有效的颅内压缓解措施之一，但过度换气存在脑血流量（CBF）显著减少和脑缺血的严重风险。此外，研究表明：长期低碳酸血症可导致颅内压反弹。为此，脑创伤基金会最近修改了2017年关于过度通气的指南，并表示“不建议在动脉血二氧化碳分压（PaCO2）小于或等于25 mmHg的情况下长期预防性过度通气”（IIB级）。

脑血流量的变化与PH无关，因为代谢性酸中毒和碱中毒没有变化。动脉血液和脑脊液之间存在快速的二氧化碳平衡，脑脊液pH值的变化直接作用于血管系统，导致舒张或收缩。

1.temporizing measures是缓解措施吗？temporize  vi. 拖延, 妥协, 调停; 迎合潮流。来自temporal,时间的，-ize,使。原义为打发时间，引申词义拖延时间。

2.The change in cerebral blood flow is independent of the pH as there is no change with metabolic acidosis and alkalosis. 脑血流量的变化与PH无关，因为代谢性酸中毒和碱中毒没有变化。既然代谢性酸碱没有变化，那出现呼吸性的变化（二氧化碳分变化了），pH一定会改变，怎么能说脑血流量的变化与PH无关？

是不是意思，单独的代谢性酸碱紊乱不会引起血流量的变化？

3.脑脊液pH值的变化直接作用于血管系统，导致舒张或收缩。也就是血液PH值导致脑脊液pH值的变化，脑脊液pH值的变化引起脑血管舒张或收缩，而不是脑血液中pH值的变化直接引起脑血管舒张或收缩？对吗