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Small, yet perfectly formed...
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Discussion Starter #1
So the question that arose whilstwe were trecking up volcanoes in Equador is this.

When you are at altitude it's really hard to breath because the air is thinner. it feels like it 's got no oxygen in it.

When you are 4800m above sea level what is the density of air relative to the air at sea level? and what would the PPO2 be? cos it feels really horrid.

I think I recall that you need something like 16% as the threshold of oxygen in air to susstain life so how close is it and at what altitude would the air become unable to sustain you?

I know it's not diving physics but it's climbing physics and Super really needs to know.

Jules
 

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Small, yet perfectly formed...
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Discussion Starter #2
I am sort of assuming that the percentage would still be 21% but there is just a lot less molecules of all the gases in a lungful due to the lower density.

but how much lower is it? feels like you got an elephant sitting on your chest!
 

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aka Chimp 1 or Mavis...
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Standard atmosphere is 1013.2mb at sea level and that level drops at 1millibar per 30ft or 10m so you can work it out yourself :)

700 millibars equates to approximately 10 000ft and 500 millibars at 18 000ft
 

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No longer open water diver
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density at 5000m is 0.74 kg/m3, and pressure 540 mB.

if i'm right, i think that gives a PPO2 of 0.11.
 

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The worlds slowest sailor.
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density at 5000m is 0.74 kg/m3, and pressure 540 mB.

if i'm right, i think that gives a PPO2 of 0.11.
the low pp means that gasses tend to absorb slowly into the tissues and bloodstream.
you can get knackered chewing a mars bar.
 

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Small, yet perfectly formed...
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Discussion Starter #6
density at 5000m is 0.74 kg/m3, and pressure 540 mB.

if i'm right, i think that gives a PPO2 of 0.11.
but wouldn't you be dead if the ppo2 was only 0.11?
 

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I recently(monday) had a BSAC nitrox instructor telling me that 13/30 trimix was hypoxic(give the man a biccy) and that any attempt to breathe that mixture at the surface would immeadiately render me unconcious! 10/50 meant I would be dead.
OK so the big yellow blender looks after things and I avoid any severe activity like surface swims...

But I have Skiied at over 3000M, and I dont recall taking it easy. Checking the link I was about on track with my maths, I`ve flogged my guts out at an equivalent of 13%O2, without rendering myself unconcious; more than once.

QED

He was talking bolloks.

Sort off!
 

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The worlds slowest sailor.
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altitude is a funny thing.
i took a single tiger to 14000 feet and felt fine for about 5 mins.
next time i saw the alt it said 10000.

mmmm....

life and stuff.
 

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No longer open water diver
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but wouldn't you be dead if the ppo2 was only 0.11?
people do die from high altitude induced illnesses - pulmonary oedema or cerebral oedema for example. as with the high PPO2s incurred during diving, the body can tolerate some exposure to low PPO2s but it can't survive at them for too long (hours or days). to answer your question, you may not die immediately, but you will die slowly.
 

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aka Chimp 1 or Mavis...
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I worked in the respiratory sector of the medical industrie and was always taught that we needed 17% to sustain life.

Rustferret
Very true but people adapt. Having seen the recent programme on Horizon about Doctors in the Death Zone ascending Everest to see what the physiological effects of a long term hypoxic environment were, I was very surprised at how much the body can adapt.

Although 16% is taken as the norm for required O2 content of a gas for man to survive, after the medical team had made their way to the top of Everest they took arterial blood samples, which were blue in colour, and then analysed them. The shock finding was that the ;lowest blood O2 figure was 3.5% (in arterial blood) and the consultant said that he had never seen a blood O2 level so low in a living human being!!

People can adapt.
 

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Small, yet perfectly formed...
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Discussion Starter #15
People can adapt.
But not very quickly...
I got tunnel vision and a thumping head ache and couldnt walk any further.

Still interested in a definitive answer on the PP02 and how that relates to low o2 mixes for diving. I think i read 16 or 17% being the lowest o2 content you can survive on..
 

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aka Chimp 1 or Mavis...
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But not very quickly...
I got tunnel vision and a thumping head ache and couldnt walk any further.

Still interested in a definitive answer on the PP02 and how that relates to low o2 mixes for diving. I think i read 16 or 17% being the lowest o2 content you can survive on..
I know of people who have tried a hard surface swim on 15/55 and found that they were light headed and had to submerge to push the ppO2 back up again. 16% is classed as a Normoxic trimix mix, anything less is hypoxic, more is hyperoxic, so it would appear that 16% is classed the norm...

The doctors on Everest took several months of acclimatisation to get where they were.
 

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aka Chimp 1 or Mavis...
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...and if you ascend rapidly to 18000 feet, you can develop a bend.
Which is why most of the decompression research recently has been carried out by NASA....

There was talk of high altitude pilot's blood fizzing in a decompression scenario, yep they were getting bent...
 
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