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

譯者: Camila Lin 審譯者: Yi-Ping Cho (Marssi)

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

如果有人突然從海平面高度 瞬間移動到聖母峰的山頂，

things would go bad fast.

事情就會立刻惡化。

At an altitude of 8,848 meters,

在海拔 8848 公尺的地方，

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

大氣壓力約為海平面高度的三分之一。

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

這意味著空氣中的氧氣大量減少，

and our teleported individual would likely suffocate in minutes.

而我們這位剛瞬間移動的朋友， 可能會在幾分鐘內窒息。

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

然而，如果有人花上一個月， 從海平面逐漸爬上山頂，

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

就可能在山峰上存活幾個小時。

So what can happen to our bodies in just one month

所以，在這一個月中， 我們的身體發生了甚麼變化，

that allows us to endure this incredible altitude?

讓我們能承受如此高海拔的環境？

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

讓我們想像一下： 你是 58 億人中的其中一人，

living less than 500 meters above sea level.

住在海拔五百公尺以下的地方。

When you take a breath at this altitude,

當你在這種海拔高度呼吸時，

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

你的肺部充滿了由多種氣體 與化合物組成的空氣。

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.

氧分子會和紅血球中的血色素結合，

Blood then circulates throughout your body,

血液會在我們體內循環，

bringing essential oxygen to all your cells.

為所有細胞帶去必要的氧氣。

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

然而，隨著海拔升高，空氣也更稀薄。

The relative amounts of each compound remain the same

雖然在較高處，

well into the upper atmosphere,

空氣的組成比例仍大體相同，

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

但整體而言，能讓我們 身體吸收的氧氣變少了。

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

而如果你抵達超過 海拔 2500 公尺的地方，

the resulting oxygen deprivation can cause a form of altitude sickness

隨之而來的缺氧， 會導致一種高海拔疾病，

known as AMS,

也就是為人所知的「急性高山症」。

often causing headaches, fatigue and nausea.

症狀通常包含頭痛、疲勞和噁心。

Fortunately, AMS only happens when we ascend too fast,

幸運的是，急性高山症只在 我們上升太快時發生，

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

因為我們的身體有 許多適應高海拔的方法。

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

若在幾分鐘、甚至是幾秒鐘內， 抵達海拔 1500 公尺的地方，

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

脖子中的頸動脈體能偵測出 身體裡的血氧濃度下降。

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

這會讓我們的呼吸加快、加深，

to counteract the lack of oxygen.

以抵銷缺氧的影響。

Your heart rate also increases

你的心跳也會加快，

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

心臟的收縮力道也會增強， 以便每次都輸出更多血液，

quickly moving oxygenated blood around your body.

迅速將攜氧的血液送到身體各處。

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

這些變化都發生得相對快速， 而如果你還繼續往上走，

your heart rate and breathing would speed up accordingly.

你的心跳數和呼吸也會隨之加快。

But if you stayed at this altitude for several weeks,

但如果你在同高度海拔待上幾星期，

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

你就能獲得長期適應高海拔的好處。

Within the first few days above 1,500 meters,

你待在高於海拔 1500 公尺處的前幾天，

the volume of plasma in your blood decreases,

血液中的血漿體積會變小，

which increases the concentration of hemoglobin.

血紅素的濃度因而上升。

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

在接下來的兩個禮拜， 你的血紅素濃度會持續上升，

allowing your blood to carry even more oxygen per milliliter.

讓每毫升的血液能攜帶更多氧氣。

Paired with your high heart rate,

這富含血紅素的血液 和你提高的心率相互合作，

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

就能有效地將氧氣送到全身。

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

由於氧氣已經夠多， 所以心臟每次輸出的血液總量

can return to normal levels.

會和普通狀態下一樣多。

Over this same time, your breathing also increases even further

同時，你的呼吸進一步增強，

in a process called ventilatory acclimatization.

進入所謂呼吸適應的過程。

After this several weeks of extended acclimatization,

經過延長至數週的適應期後，

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

你的身體已有了顯著的改變， 能讓你爬到更高的地方。

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

然而，在攀爬過程中， 你仍必須花額外的時間適應高度，

often climbing back down to recover before ascending even higher.

通常在爬到更高處之前， 必須先下山恢復身體。

Because the summit of Everest isn't just high,

因為聖母峰不只是高，

it’s the highest place on Earth.

而是全世界最高的地方。

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

而在超過海拔 3500 公尺的地方， 我們的身體會承受驚人的壓力。

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

大腦中的動脈和靜脈會擴張， 以加速血液流動，

But our smallest blood vessels, called capillaries,

但我們身體中最纖細的微血管，

remain the same size.

仍然維持相同形狀。

This increased pressure can cause blood vessels to leak,

增加的壓力可能會造成血管滲漏，

and fluid to build up in the brain.

讓水分積於腦中造成腦水腫。

A similar issue can occur in the lungs,

同樣的問題也可能發生在肺部，

where low oxygen causes blood vessels to constrict,

低濃度血氧可能會導致血管收縮，

leading to more leaking vessels and fluid buildup.

讓更多血液滲進肺部並堆積。

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

這兩個症狀稱為 「高山症腦水腫」和「 高山症肺水腫」，

are incredibly rare,

雖然都相當罕見，

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

但如果不及時處理，就可能危及性命。

Some Tibetans and South Americans with family histories

有些累世居住於高海拔地區的 西藏人和南美洲人，

of living at high altitude

have genetic advantages that can prevent minor altitude sickness,

具有預防輕微高山症的基因優勢，

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

但就算是他們， 面對如此嚴峻的環境也會受影響。

Yet despite these risks, climbers over the last century

然而，即使存在這些風險， 上個世紀的登山者

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

已經證明人類能抵達 超乎科學家預估的高處。

Pushing past their body’s limitations,

他們突破身體的極限，

these climbers have redefined what humanity can adapt to.

重新定義了人類的適應力。