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Effects of hypoxia - interesting video (slightly disturbing - discretion advised)


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"I... I don't want to die" 

That was really interesting and not at all what I expected. I expected some confusion and clumsiness almost like when I've been awake for 36 hours, but despite looking reasonably conscious, he really had no idea what was going on. 

The chart he displayed said you'd have roughly 30 seconds of usable oxygen at 35k feet. I can last longer than that when I hold my breath, wonder if that's only if you're breathing?

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@SgtSomeone I think that is only if you're breathing, but I'm unsure. Maybe it have to do something with air pressure as well. Cause your brain con go some time without oxigen so...

Anyway, it was scaring when the doctor said, "Put your mask or you gonna die" and he just sat there smiling

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The problem is transferring gasses to and from your blood relies entirely on pressure.  If the pressure of oxygen in the air is less than the pressure of oxygen in your blood, then oxygen moves from your blood to the air in your lungs.  Above about 35,000 ft, the ambient pressure is low enough, that the time of useful consciousness becomes constant.  This is because there isn't enough air pressure to keep enough oxygen in your blood for you to remain conscious.  It then becomes a race of you using oxygen vs. oxygen and other gasses escaping in your lungs.  Holding your breath will not stop this because breathing also relies on relative pressure. 

If you have an FAA medical certificate, you can take a chamber ride for free at the Civil Aerospace Medical Institute

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18 hours ago, SgtSomeone said:

The chart he displayed said you'd have roughly 30 seconds of usable oxygen at 35k feet. I can last longer than that when I hold my breath, wonder if that's only if you're breathing?

The problem is that it is not the VOLUME of gas that you can fill your lungs with, it is the MASS.  You may be able to fill your lungs at sea level and hold it for over 30 seconds, but filling your lungs with the rarefied air at 35,000 feet will not give you sufficient oxygen to last more than about 30 seconds.

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On 7/23/2016 at 7:28 AM, SgtSomeone said:

"I... I don't want to die" 

That was really interesting and not at all what I expected. I expected some confusion and clumsiness almost like when I've been awake for 36 hours, but despite looking reasonably conscious, he really had no idea what was going on. 

The chart he displayed said you'd have roughly 30 seconds of usable oxygen at 35k feet. I can last longer than that when I hold my breath, wonder if that's only if you're breathing?

It's not the same as holding your breath because, at low pressures, gases spontaneously diffuse out of your lungs, so not only are you spending oxygen in your cells, you also lose it as it diffuses out of you.

 

12 hours ago, benzman said:

The problem is that it is not the VOLUME of gas that you can fill your lungs with, it is the MASS.  You may be able to fill your lungs at sea level and hold it for over 30 seconds, but filling your lungs with the rarefied air at 35,000 feet will not give you sufficient oxygen to last more than about 30 seconds.

Or, we could say it's the moles of oxygen we're losing. Its partial pressure is not high enough. :)

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While on the topic of why air pressure matters, does this mean the scene in Avatar where the Colonel opens the door on Pandora but holds his breath so he doesn't need a mask impossible? He holds his breath before the Pandoran air reaches him and air pressure on Pandora is supposedly very near earth pressure. From what I'm taking from this it would only matter if 1. He held his breath after breathing in the outside air or 2. The pressure difference was significant enough for the air to either be pushed in or pulled from his lungs even while holding his breath. 

Here is the scene I'm talking about for those that haven't seen the movie:

The part where he leaves is around 1:50

Spoiler

The part where he leaves is around 1:50

 

The atmosphere of Pandora is apparently 0.9 Atm of pressure with a composition of:

Nitrogen, Oxygen, Carbon Dioxide (over 18%), Xenon (5.5%), Methane and Hydrogen Sulfide >1%

I don't know if the pressure is low enough to not be able to be held back by lungs or not.

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9 hours ago, dharak1 said:

While on the topic of why air pressure matters, does this mean the scene in Avatar where the Colonel opens the door on Pandora but holds his breath so he doesn't need a mask impossible? He holds his breath before the Pandoran air reaches him and air pressure on Pandora is supposedly very near earth pressure. From what I'm taking from this it would only matter if 1. He held his breath after breathing in the outside air or 2. The pressure difference was significant enough for the air to either be pushed in or pulled from his lungs even while holding his breath. 

Here is the scene I'm talking about for those that haven't seen the movie:

The part where he leaves is around 1:50

  Reveal hidden contents

The part where he leaves is around 1:50

 

The atmosphere of Pandora is apparently 0.9 Atm of pressure with a composition of:

Nitrogen, Oxygen, Carbon Dioxide (over 18%), Xenon (5.5%), Methane and Hydrogen Sulfide >1%

I don't know if the pressure is low enough to not be able to be held back by lungs or not.

Sorta.

If you're in a plane or spaceship that depressurises it's a bad idea to hold your breath because the pressure in your lungs will dangerously over-inflate them without external pressure on your chest. And then once you've breathed out the zero/near zero partial pressure of oxygen in your lungs causes the oxygen in your blood to diffuse out down the pressure gradient and you've got 30s.

It's actually a similar situation if you find yourself in an atmosphere at sea level composed of pure nitrogen, carbon dioxide, or other composition with zero oxygen concentration. Breathing normally, that's still a zero partial pressure of oxygen which will suck the oxygen out of your blood by diffusion. 30s.

Unless you hold your breath. If you don't breath in the oxygen free atmosphere, then the air in your lungs maintains partial gas pressures not that different to that in your blood. It'll slowly deplete oxygen and accumulate CO2, but the driver is the gas concentrations in the blood. There's no sudden loss of partial pressure to suck the gasses out and you can last a lot longer.

So then you have Pandora. That's not a lack of oxygen or a lack of atmosphere. That's toxic gasses. If you breath normally, there's suddenly a partial pressure of toxins in your lungs that force their way into your bloodstream. But if you hold your breath, it's pretty much equivalent to holding your breath normally. The colonel wasn't in immediate danger unless he took a breath. No toxins in the lungs means none in the bloodstream.

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10 hours ago, dharak1 said:

The atmosphere of Pandora is apparently 0.9 Atm of pressure with a composition of:

Nitrogen, Oxygen, Carbon Dioxide (over 18%), Xenon (5.5%), Methane and Hydrogen Sulfide >1%

So what Im hearing is that the atmospher of Pandora is...farts with a bit of Xenon?

 

On topic:

There's tons and tons of data available with a bit of googling on what happens when a human is exposed to low pressure, low oxygen or vacuum environments. For low pressure/ppO2/vacuum exposure, you're not looking at more than 10-15 seconds of useful conciousness. There is at least one documented example (Soviet fatalities notwithstanding) of a human being explosively decompressed to vacuum, he lost conciousness in approx 10 seconds, was quickly rescued and made a full recovery. Said he could feel the saliva in his mouth boiling.

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Wasn't Pandora's atmosphere ridden with ammonia (NH3)? In any case, That much H2S is extremely dangerous and would lethally poison you in a few breaths (you'd die in minutes if you don't receive immediate help).

Hydrogen sulfide is more poisonous than hydrogen cyanide and, being a small molecule, it diffuses through skin so at those concentrations it would poison you by entering your blood via skin.

You could hold your breath but you wouldn't last for long even with the mask on. Kidney failure in case of ammonia and cell respiration failure (and suffocation) in case of hydrogen sulfide.

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3 hours ago, lajoswinkler said:

Wasn't Pandora's atmosphere ridden with ammonia (NH3)? In any case, That much H2S is extremely dangerous and would lethally poison you in a few breaths (you'd die in minutes if you don't receive immediate help).

Hydrogen sulfide is more poisonous than hydrogen cyanide and, being a small molecule, it diffuses through skin so at those concentrations it would poison you by entering your blood via skin.

You could hold your breath but you wouldn't last for long even with the mask on. Kidney failure in case of ammonia and cell respiration failure (and suffocation) in case of hydrogen sulfide.

Yet on screen evidence suggests it's safe enough to walk around in only a mask. That's either a goof or an indication that H2S is on the order of ppm.

LCL0 is on the order of 600ppm (inhaled?) for 30 mins, or 800ppm for 5min. Max US regulatory exposure is 20ppm (inhaled?). 

Lung surface area is approx 25 times greater than skin surface area (conservatively). It's also thinner and more readily diffused across. It therefore stands to reason that a lethal inhaled concentration of ~800ppm atmospheric equates to less than the regulatory equivalent skin dose.

Put another way, the concentration required to kill you if you're wearing a mask by diffusing through skin would be of the order 20,000ppm or 0.02%.

If Pandora's atmosphere is around 800ppm it should be safe to wear a mask and lethal in approximately the observed time frame without one. H2S is detectable at around 10ppb, so the smell of Pandora's atmosphere would be very, very strong.

Edited by RCgothic
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Time is the most important variable here.  Few minutes, few hours, perhaps, but more than that and you'd start feeling very bad.

The smell would be unbearing at first and would probably lead to laryingospasm or, at best, strong coughing and vomiting, but the smell would go away because H2S saturates the olfactoric nerve endings.

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So the problem is

#1) breathing in low O2 concentrations actively rids your body of oxygen.

#2) Holding your breath means that your lungs dangerously over inflate

#3) You normally can't hold your breath very long just on a whim. Before holding your breath for long periods of time, you typically hypervenitllate a bit in preparation. You get no warning

I think #2) isn't such a problem. #3 is the problem.

The pressure differential is only about 0.75 atmospheres, so the air in your lungs would inflate to about 4x the original volume.

https://en.wikipedia.org/wiki/Lung_volumes#Values

So how much does the volume of your lungs change between when you take a deep breath? According to that:

"Vital capacity: the volume of air breathed out after the deepest inhalation." - average adult male is 4.6 liters

"Total lung capacity: the volume in the lungs at maximal inflation," - 5.8

So if you took a deep breath and breathed out, that should leave 5.8-4.6 = 1.2 liters left .. ie the residual volume

1.2/5.8 = 0.2068

http://www.aerospaceweb.org/design/scripts/atmosphere/

Atmospheres at 35,000 feet: 0.23596

So if you just breathed out once and closed your mouth right at the end just before the decompression, your lungs wouldn't even fully inflate from the residual volume.

So... take some deep breaths, and at the end of the last one, breath out almost all you can (keeping in mind that you can have about 14% more air left in your lungs than the smallest residual volume to have your lungs equalize in pressure at the volume they were when you take your deepest breath... and if a little extra air is in them, the pressure differential at that point still won't be very high)

Now how long can you last before you need to breathe in again? Longer than 30 seconds I imagine. In the airplane, this would happen slightly sooner, because when your lungs expand, some O2 will diffuse out of your blood into your now expanded lungs... but I think this would be minimal.

Of course realize that when you need to breathe in at the end of this, on an airliner at 35,000 feet, opening your mouth and breathing only makes thigns worse, faster (well from an O2 standpoint, it will get rid of the CO2 buildup)

Now... set an alarm for a random time... and go about your business... when you hear that alarm, without drawing another breath, just immediately breath out as much as you can and hold your breath, and see how long you can last under those conditions. I suspect its much shorter.

Still, at 35,000 feet, breathing makes it worse, and holding your breath is probably the thing to do

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Except that when you hold your breath and that 14% residual volume expands 4x the pressure drops correspondingly to 1/4, which would then actively extract oxygen from your blood. Being a small volume, the partial pressures will equalise some, so it's not quite as bad as 3/4 of a total vacuum.

But 60-75% as bad is still pretty bad.

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An exception thats not an exception because it was already stated:

Quote

because when your lungs expand, some O2 will diffuse out of your blood into your now expanded lungs... but I think this would be minimal.

there.s only going to be a few liters of air for O2 to empty into from your blood. They shouldn't draw off too much O2 before the O2 partial pressures equalize. Its certainly better than the continuous escape.

But since you want to emphasize this point more, I looked into how much O2 would be stored in the blood, ready to diffuse out... the top answer here:

http://biology.stackexchange.com/questions/2841/total-amount-of-co₂-oxygen-in-bloodstream-in-humans

so the estimate is 1.67 kg of hemoglobin, in blood, which would be only 0.104 mols of O2... that is a lot lot less than I expected.

It seems that 98% of the O2 is in the RBCs, and only 2% dissolved in the plasma, so that guy was right to exclude that from the calculations: http://www.ncbi.nlm.nih.gov/books/NBK54103/

 

The partial pressure of O2 is normally 0.2 atms... 5.8 liters of O2 at 0.2 atms requires 0.0517 mols of O2.... seems like half your O2 would escape into your lungs before the O2 partial pressure reaches 0.2 atms Of course, as the pp of O2 drops in the blood, it will equalize earlier than 0.2 atmospheres.

But... http://www.ncbi.nlm.nih.gov/books/NBK54103/table/table2/?report=objectonly

P O2 in the alveolous is only 0.137 atmospheres (104/760 mm Hg) so now we really only need 0.0354 mols of O2 in the lungs, 1/4 of which was there to start with... so 0.0265 mols of O2 are needed in the lungs to prevent gas escaping from the blood in the alveolus to the space inside the lungs.... or 25.5% of the O2 dissolved in the blood... Ok, thats a lot more than I expected, but by keeping your mouth closed, you should be able to significantly limit the gas escape....

But why let it escape into 5.8 liters? a quick exhale then close means there should only be 1.2 liters left in the lungs to draw out O2... 1.2/5.8 ... mean that 25.5% of the O2 needing to leave your blood to equalize the PO2 is reduced to 5.28% of the O2 stored in your blood. So it comes down to how much O2 diffuses out during the brief period of time that you exhale and try to reduce your lung volume as much as possible. As the partial pressure of O2 in your blood still is far less than the ambient air pressure (about 0.24 atms vs 0.137) your lungs shouldn't be expanding as O2 diffuses into them.

 

Looking for another source on how much O2...

http://www.umich.edu/~projbnb/cvr/O2transport.pdf

"1.36 mL of oxygen per gram of hemoglobin" "Normally, the hemoglobinconcentration is about 15 g / dL." -> so 150g/ liter, 204 mL of O2 per liter of blood, 4.5 liters of blood... 0.918 liters of pure O2 at STP in blood... so 0.041 mols... Ok, this estimate is less than half the other estimate of 0.104 mols... that 5.28% best case scenario (instant exhale with no diffusion happening during the exhale) becomes 13.4% of O2 lost into the lungs. Fully inflated lungs... thats 64%... (although again... as the blood concentration drops, it will stop diffusing out as they equalize

According to this: https://courses.washington.edu/conj/resp/oxygen.htm

the estimate would be 206.3 ml O2/liter blood including the dissolved stuff... about 1% better.

Of course, 4.5 L is an average, and I was taking only the average male volume... the average adult female residual volume is 1.1... 9% better... do men have 9% more blood on average?

Its worse than I thought... but it still seems that not breathing is vastly preferable, because it limits the O2 loss.

My guess is that you'd last longest by exhaling as much as possible as fast as possible and then don't breath in.

Unless of course your lungs could survive a 0.76 atm pressure difference without bursting... in that case taking a deep breath and holding it would be best as the O2 in there would diffuse into your blood and not vice versa.

https://en.wikipedia.org/wiki/Orders_of_magnitude_(pressure)

"+19.3 kPa +2.8 psi High end of lung pressure, exertable without injury by a healthy person for brief times" * states citation needed - not clear if they mean some injury due to exertion (as by the diaphram) or just the internal lung pressure

"+13 kPa+1.9 psiHigh air pressure for human lung, measured for trumpet player making staccato high notes" * highest pressure generated by the diaphram doesn't mean the same thing as the highest pressure difference that the lungs can withstand.

19.3 kPa is only  0.191 atmospheres. If 19.3 kPa is the limit, then... well, that only gets one from .23 atmospheres to having .42 atmospheres in the lungs... but... at .42 atmospheres, thats 0.084 atmospheres of O2 in there... we only need 0.053 atmospheres of O2 more to stop O2 from leaving our alveolous.

.053 atmospheres in 5.8 liters is 0.307 liters of O2 at STP... 0.0137 mols of O2... ok... thats 33.% of our total O2 stores... thats better than the 64% for full lungs at equalized pressure.

It seems we'd need at least 0.685 ATM in our lungs at 20% O2 to prevent O2 from actively leaving our blood - at least when our blood is full saturated with O2.

This is clearly not a hard limit, as that occurs below 12,000 feet, and I can hike that high (although I did experience altitude sickness, going from nearly sea level to that high in 2 days was a big change... my uncle who lived in colorado was fine) - and for short durations I've taken my hnagglider up to 11km without any O2 (one should probably use O2 above 10km, definitely above 12km as reactions and reasoning are impaired, which are more important when flying than when hiking).

Indeed, people have climbed everest with no O2 - 29,000' or a mere 0.3 atmospheres. Of course, studies show they suffered brain damage... :/ and they spent a long time acclimating... and the measured blood O2 saturation levels were very low.

Anyway... asuming the maximum lung pressure differential (.19 atmospheres) then at 35,000', the air in your lungs can be like at 21,750' ... and in that air one doesn't pass out in seconds.

Based on all the numbers I see, holding your breath should be able to significantly extend your time of consciousness.

Edited by KerikBalm
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