听力文摘：为什么高海拔会引起头痛？（在线收听）

Why Does Altitude Cause Headache?

为什么高海拔会引起头痛？

Mountain climbers face many dangers as they brave the cold winds and icy slopes and jagged cliffs of the peaks they climb. But one of the most serious dangers they face is all in their heads–literally.

当勇敢面对冷风，冰坡和参差不齐的悬崖时，登山运动员面临着很多危险。但是其中一个他们面临最严峻的危险就是他们的头。

Why does altitude cause headache? Since the air is thinner, there is less oxygen in the blood, so blood flow to the brain increases. The extra blood can cause blood vessels to swell and tissues to press on the sensitive membrane that surrounds the brain, resulting in a headache.

为什111么高海拔会引起头痛？随着大气越来越薄，血液中的氧气越来越少，因此流到大脑中的血液就会增多。多余的血会使血管膨胀，挤压敏感的在大脑周围细胞膜，导致头痛。

But not everyone develops a headache at moderately high altitudes, partly because the low oxygen content of the air causes the climber to breath more often, forcing carbon dioxide out of the blood.

但并不是每个人都会在适度的高海拔感到头痛，部分是由于大气中低氧引起攀登者常常喘不过气，驱使二氧化碳离开血液。

The body reacts to the lowered carbon dioxide content of the blood by decreasing blood flow to the brain. An individual’s susceptibility to altitude-induced headache, as well as the severity of the headache, depends on whether the overall blood flow to the brain increases or decreases.

血液中的二氧化碳少了，身体中流入大脑中的血液就会减少。一个个体对于海拔降低引起头痛的敏感性和头痛的严重性，取决于全面流入大脑中的血液是增多了还是减少了。

At high altitudes, usually over 10,000 feet, an unrelated condition known as high-altitude cerebral edema, or HACE, can develop. HACE occurs when parts of the brain become waterlogged.

在高海拔，常常超过3000米，一种不相关的高海拔脑水肿情况出现。当大脑的部分浸满水的时候脑水肿就会出现。

Unlike altitude-induced headache, which occurs in over ninety percent of the people who ascend to 11,000 feet, HACE is a rare disorder. Characterized by mental confusion, hallucinations, and a drunken stagger, HACE is almost always fatal if descent is not immediate.

当海拔超过3300米，90%的人会出现海拔降低的头痛，与此不同的是，脑水肿是一种罕见的混乱。其特征是精神混乱，幻觉和酒醉后的蹒跚。如果下降的不够及时，那么脑水肿几乎是致命的。