What happens to your body at the top of Mount Everest - Andrew Lovering

翻译人员: Frank Wang

If someone teleported from sea level to the top of Mt. Everest,

一个人如果从海平面 瞬移到珠穆朗玛峰顶上，

things would go bad fast.

其身体情况会迅速恶化。

At an altitude of 8,848 meters,

在 8848 米的海拔高度上，

barometric pressure is approximately 33% of what it is at sea level.

大气压只有海平面高度的三分之一，

This means there's significantly less oxygen in the air,

这意味着空气中的氧气极度稀少，

and our teleported individual would likely suffocate in minutes.

而这个可怜的人 在几分钟内就会窒息。

However, for people that make this same journey over the course of a month,

但是，那些花一个月攀登到山顶的人

it's possible to survive at the peak for hours.

却能够在山顶上存活好几个小时。

So what can happen to our bodies in just one month

所以，在这短短的一个月当中 我们的身体究竟发生了什么，

that allows us to endure this incredible altitude?

让我们能够忍受 这高得不可思议的海拔？

Let’s imagine you’re one of the 5.8 billion people

假设你是住在 海平面 500 米以内的

living less than 500 meters above sea level.

那 58 亿人中的一个。

When you take a breath at this altitude,

在这个海拔高度深吸一口气，

your lungs fill up with air composed of numerous gases and compounds.

由多种气体和化合物组成的空气 就会充满你的肺，

Most important among these are oxygen molecules,

其中最重要的就是氧分子，

which bind to the hemoglobin in your red blood cells.

氧分子与红细胞中的血红蛋白结合，

Blood then circulates throughout your body,

这样一来，当血液在体内循环，

bringing essential oxygen to all your cells.

至关重要的氧气 就会抵达所有细胞。

But as altitude increases, the air starts to get thinner.

但当海拔升高， 空气也随之变得稀薄，

The relative amounts of each compound remain the same

空气中每种化合物的相对含量

well into the upper atmosphere,

并不会随着海拔升高而改变。

but overall, there is less oxygen for our bodies to absorb.

但总的来说， 供身体吸收的氧分子越来越少。

And if you ascend to altitudes above 2,500 meters,

当你爬升到 2500 米以上的海拔时，

the resulting oxygen deprivation can cause a form of altitude sickness

随之而来的缺氧 会造成一种高海拔疾病，

known as AMS,

即 “AMS” （急性高山症），

often causing headaches, fatigue and nausea.

通常表现为头疼、疲乏、恶心。

Fortunately, AMS only happens when we ascend too fast,

幸运的是，急性高山症 只会在海拔上升过快时发生，

because our bodies have numerous ways of adapting to high altitudes.

因为人体针对高海拔 有无数的应对机制。

Within minutes or even seconds of reaching altitudes of 1,500 meters,

如果在几分钟甚至几秒钟内 到达 1500 米以上的海拔，

carotid chemoreceptors in your neck sense your blood’s low oxygen pressure.

脖子里的颈动脉化学感受器 就会察觉到血液氧气压力过低，

This triggers a response that increases the rate and depth of your breathing

触发生理反应， 使呼吸更快更用力，

to counteract the lack of oxygen.

从而弥补氧气的缺乏。

Your heart rate also increases

同时心率也会加快，

and your heart contracts more tightly to pump additional blood with each beat,

心脏会更加用力地收缩， 在每次跳动时带动更多的血液，

quickly moving oxygenated blood around your body.

让充了氧的血液 在人体里更快速地运转。

All these changes happen relatively fast, and if you were to keep ascending,

这些变化的发生相对较快， 而且如果你还在继续爬升，

your heart rate and breathing would speed up accordingly.

你的心跳和呼吸都会相应地加快。

But if you stayed at this altitude for several weeks,

但如果你在这个海拔 停留上几个星期，

you could reap the benefits of some longer-term adaptations.

你可能会因为长期适应 而获得一些好处。

Within the first few days above 1,500 meters,

在 1500 米以上停留的最开始几天，

the volume of plasma in your blood decreases,

人体血液内血浆的含量会减少，

which increases the concentration of hemoglobin.

引起血红蛋白浓度的增加。

Over the next two weeks, your hemoglobin levels will continue to rise,

接下来的两个星期里 血红蛋白水平会持续增长，

allowing your blood to carry even more oxygen per milliliter.

使得每毫升血液 能够运输更多的氧气，

Paired with your high heart rate,

再加上高心率，

this new hemoglobin-rich blood efficiently distributes oxygen throughout your body.

这种新的高血红蛋白血液 高效地将氧气运送到人体各处，

So much so that the volume of blood being pumped with each heartbeat

从而使每次心跳带动的血液

can return to normal levels.

回到正常水平。

Over this same time, your breathing also increases even further

同时，你的呼吸也会继续加快，

in a process called ventilatory acclimatization.

这种过程被称为 “通气习服” 。

After this several weeks of extended acclimatization,

这种适应过程持续几个星期之后，

your body has made enough significant changes to climb even higher.

你的身体就做好足够的准备 能够继续向上爬了。

However, you’ll still have to spend additional time acclimating along the way,

但是，你在攀爬的过程中 还需要花额外的时间适应环境。

often climbing back down to recover before ascending even higher.

在继续向上爬之前 人们常常暂时下山，进行恢复。

Because the summit of Everest isn't just high,

因为珠穆朗玛峰不止是一座高山，

it’s the highest place on Earth.

它还是世界上最高的山。

And at altitudes above 3,500 meters, our bodies are under incredible stress.

在 3500 米以上的海拔 你将承受巨大的压力，

Arteries and veins in the brain dilate to speed up blood flow,

大脑里的动脉和静脉都会膨胀 以加快血液流速。

But our smallest blood vessels, called capillaries,

但我们最小的血管， 也就是毛细血管，

remain the same size.

仍然保持原状。

This increased pressure can cause blood vessels to leak,

增加的压力会使这些血管破裂，

and fluid to build up in the brain.

还会导致液体在大脑内积聚。

A similar issue can occur in the lungs,

肺部也会受到类似的威胁，

where low oxygen causes blood vessels to constrict,

肺部血管会在低氧环境下收缩

leading to more leaking vessels and fluid buildup.

进而破裂，使更多液体积聚。

These two conditions— known as HACE and HAPE, respectively—

这两种情况分别被称为 HACE 和 HAPE ，

are incredibly rare,

它们非常罕见，

but can be life-threatening if not dealt with quickly.

但如果不及时处理 可能会危及生命。

Some Tibetans and South Americans with family histories

一些中国西藏和南美地区的人，

of living at high altitude

其祖先生活在高海拔地区，

have genetic advantages that can prevent minor altitude sickness,

所以本身就能抵抗 一些轻型的高海拔症状。

but even they aren’t immune to these severe conditions.

但即使是这些人， 也可能遭遇严重状况。

[1978年来 近200名登山者 在无额外供氧的前提下登顶珠穆朗玛]

Yet despite these risks, climbers over the last century

虽然风险巨大， 但在过去的一个世纪里，

have proved people can go higher than scientists ever thought possible.

登山者们已经证明， 人类能比科学家预测的爬得更高，

Pushing past their body’s limitations,

这些登山者不断挑战身体极限，

these climbers have redefined what humanity can adapt to.

重新定义了人类对环境的适应能力。