Why can we survive much more, but not much less pressure?

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In summary, the conversation discusses the effects of pressure on humans and deep-sea fish. While humans can survive higher pressure in water due to the incompressibility of their bodies, they would die quickly in a vacuum due to the lack of pressure to keep their bodies intact. Deep-sea fish also experience negative effects when brought to the surface due to changes in pressure. However, there are efforts being made to save these fish from barotrauma, which can occur when they are brought to the surface.
  • #1
greypilgrim
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Hi.

In water, pressure increases with roughly 1 atm per 10 m depth, yet some divers can reach more than 100 m. Why can humans survive more than 10 times the atmospheric pressure, but will die a horrible death within seconds when released into a vacuum (e.g. outer space, even with oxygen for breathing provided)?

Similar question: Why don't deep-sea fish experience all those nasty things such as bursting blood vessels when brought to the surface?
 
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  • #2
Think of all the air dissolved in one's blood suddenly forming expanding bubbles in the blood vessels and capillaries. Ugh!
 
  • #3
In vacuum the air in your lungs would be drained out (and you would suffocate), and perhaps your blood will start to flow off your skin because smaller veins will collapse
 
  • #4
greypilgrim said:
but will die a horrible death within seconds when released into a vacuum (e.g. outer space, even with oxygen for breathing provided)

Are you sure this is what happens? Within seconds?
 
  • #5
greypilgrim said:
Why don't deep-sea fish experience all those nasty things such as bursting blood vessels when brought to the surface?
They do. It is not exactly the same but they can easily suffer decompression sickness. Often their stomach becomes inverted and protrudes into their mouth.
 
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greypilgrim said:
Why can humans survive more than 10 times the atmospheric pressure, but will die a horrible death within seconds when released into a vacuum
Even much simpler systems will display this asymmetry. Consider the behavior of an inflated balloon: under pressure it compresses reversibly while in vacuum it bursts.

Humans are mostly liquid water, which is incompressible so that internal pressures can equalize against increased external pressure without doing irreparable structural damage (although a burst eardrum is seriously no fun). But being made of liquid water is a real handicap in a vacuum environment.
 
  • #7
greypilgrim said:
Why can humans survive more than 10 times the atmospheric pressure, but will die a horrible death within seconds when released into a vacuum (e.g. outer space, even with oxygen for breathing provided)?

Oh you'd puff up and swell a bit, but as long as you had a tight mask to provide air to breathe you would live for much, much longer than a few seconds. Human skin is airtight and would exert enough pressure to keep your insides on your insides without rupturing. Exposed tissue other than skin would likely suffer much worse. Your eyes, for example, would probably not fare very well in an extended spacewalk without protection. Without a mask, the saliva in your mouth would boil off and you'd lose consciousness in about 10-15 seconds as the oxygen is pulled from your blood through your lungs.

That's not to say that you'd be okay as long as you had a mask. I doubt you'd be able to survive for an extended period of time, but you'd last much longer than a few seconds.
 
  • #8
I have my information from this video, where that guy actually puts his arm in vacuum.
 
  • #9
A YouTube video is not a very reliable source.
 
  • #11
greypilgrim said:
In water, pressure increases with roughly 1 atm per 10 m depth, yet some divers can reach more than 100 m. Why can humans survive more than 10 times the atmospheric pressure, but will die a horrible death within seconds when released into a vacuum (e.g. outer space, even with oxygen for breathing provided)?
A lot happens to substances as the pressure drops toward zero. If you look at a phase diagram for, say, water, you will see that they tend to be displayed logarithmically.
Similar question: Why don't deep-sea fish experience all those nasty things such as bursting blood vessels when brought to the surface?
They do.

https://www.npr.org/sections/thesal...-are-learning-to-save-fish-that-get-the-bends

Caveat: I think the NPR article is wrong about barotrauma being the same as "the bends", but nevertheless they can get both.
 

1. Why can we survive much more pressure, but not much less pressure?

Our bodies have adapted to survive in a range of pressures, but there are limits to how much pressure our bodies can handle. Too much pressure can cause damage to our organs and tissues, while too little pressure can lead to serious health problems such as hypoxia (lack of oxygen) and decompression sickness.

2. How does our body adapt to high pressure environments?

When exposed to high pressure, our bodies activate physiological responses to help us survive. These include increased heart rate and blood pressure, changes in breathing patterns, and the release of hormones to constrict blood vessels and prevent blood from pooling in our extremities.

3. Why is it harder for our bodies to adapt to low pressure environments?

Our bodies are not equipped to handle low pressure environments, as they are used to functioning in a relatively stable atmospheric pressure. In a low pressure environment, there is less oxygen available for our bodies to use, and the lack of pressure can also cause gas bubbles to form in our blood and tissues, leading to serious health problems.

4. Can we survive in extreme pressure environments, such as the deep sea or outer space?

Our bodies are not able to survive in extreme pressure environments for extended periods of time. However, with the use of specialized equipment and training, we can survive in these environments for short periods of time. For example, deep-sea divers use pressurized suits to protect them from the high pressure of the ocean depths.

5. How does pressure affect different parts of our body?

High pressure can affect our bodies in different ways. For example, it can cause our eardrums to rupture or our lungs to collapse. Low pressure can also have serious effects, such as causing our blood to boil or our tissues to swell. Our bodies have different ways of adapting to these changes in pressure, but it is important to stay within a safe range for our overall health and survival.

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