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Does anyone know how survivable rapidly surfacing from 30 meters would be? Wolfram Alpha has the pressure down there at almost 400 kPa (compared to 100 kPa) so

by jlgreco 13y ago

Does anyone know how survivable rapidly surfacing from 30 meters would be? Wolfram Alpha has the pressure down there at almost 400 kPa (compared to 100 kPa) so my suspicion is "not at all", but I'm not really familiar with the tolerances and life expectancies with the bends. 30 meters is just agonizingly close to the surface though, well within what most adults could do horizontally (particularly if their life depended on it.) Being that close to the surface, but still so far away, must be absolutely awful.

fletchowns 13y ago
Probably not very survivable, given that they stuck the guy in a decompression chamber for 60 hours.
- jlgreco 13y ago
  Well yeah, but even a slight chance would be worth attempting if you were in such a position, even if it were just a 5% chance of survival, compared with the 100% chance they were probably shooting for with the 60 hour decompression. Of course if attempting it meant certain but excruciating death, then taking a shot at it would not be the way to go.
- ars 13y ago
  They left him in there for so long because he was in the water for so long. (i.e. plenty of time for nitrogen to dissolve). If he had swum up right away he would not need decompression. I imagine in the dark he would have been too scared of not being able to find the way out in the cluttered sunken vessel.
  - jlgreco 13y ago
    He probably also didn't know how close to the surface he was.
Udo 13y ago
It depends on how long you've been down there. If you have just been dragged under water with your boat, it's probably safe to make a rapid ascent (don't hold your breath though) - in fact, diving school teaches emergency ascents for situations where no other options apply, even if the diver is in need of decompression. However, after about half an hour it becomes a serious problem that gets worse over time as gases start to infuse into the tissue. If rescue (and access to a pressure chamber) is available right away, I'd make that ascent immediately even after being down there for a longer time. It beats drowning or CO2 poisoning. Dive tables illustrate pretty well how the relationship between depth and time works: http://www.naui.org/tables.aspx http://www.naui.org/tables.aspx
- simias 13y ago
  Do you really have to pay attention not to hold your breath while ascending? I'd have thought you'd feel your lungs expanding and you'd have the reflex to let the air go away. Although on the other hand it's probably not a situation common enough for us to have evolved an inate reaction to it.
  - Udo 13y ago
    Yes and no. If you relax your breathing apparatus, air will escape naturally. However, if you actively hold your breath, the mounting pressure can actually lead to a tighter block. Rapidly expanding lungs are not something that falls within the daily experience of most humans, so it's best to be aware of the complications. Especially when panic sets in (and the journey upward from 30m will be quite long) it can cost a lot of self control to force yourself to exhale.
    - jbri 13y ago
      Especially since if you're doing an emergency ascent, it's quite likely that it's due to having problems with getting air from your cylinder (if your air supply was fine, you'd probably be doing a controlled ascent instead). It's very difficult to avoid holding your breath when you know you won't be able to breathe in again until you reach the top.
arethuza 13y ago
The Royal Navy has a 30m deep "pool" (more of a water filled tower) that they use for submarine escape training: http://en.wikipedia.org/wiki/Submarine_escape_training_facility http://en.wikipedia.org/wiki/Submarine_escape_training_facil... So it must be fairly survivable.... Maybe it's staying for a long time at that pressure that causes the problem?
- gaius 13y ago
  They no longer use it - too many people were dying in the training, and modern submarines go much deeper anyway. If you want to have a go, you can go to Nemo33 in Belgium still.
  - Timshel 13y ago
    The too many seems to be 2 death in 60 years with up to 4500 trainee a year during the 60s/70s. Cf : http://www.worldnavalships.com/forums/showthread.php?t=3787 http://www.worldnavalships.com/forums/showthread.php?t=3787 http://www.subescapetraining.org/History1.html http://www.subescapetraining.org/History1.html
- Terretta 13y ago
  Florida has inland freshwater springs with depths to 240 feet / 73 meters. I did my first deep water scuba cert in Ocala: http://www.adventuresunderthesea.com/scuba-class-information/local-dive-sites http://www.adventuresunderthesea.com/scuba-class-information... The deeper you go, the less time you can stay there before you have to control your ascent. Even a mild case of the bends can be excruciating, not something you can tough out: http://en.wikipedia.org/wiki/Decompression_sickness http://en.wikipedia.org/wiki/Decompression_sickness
- dedward 13y ago
  Time at pressure is the key, without question. The longer you breathe at pressure, the more time there is for gas (nitrogen, mainly) to saturate your system (until you are at equilibrium, anyway). Release the pressure, and it's like opening a can of soda... all that dissolved gas can't stay dissolved any longer. It takes time to get out of your system as you reduce pressure, so a gradual decompression is the only safe way out once you are saturated. In a typical submarine, air pressure is maintained at standard atmosphere, relying on structural integrity to keep all that pressure from crushing the ship. That means they can surface any time without risk. Another neat thing when diving is that if you are down at 30 meters, you can take a breath from your regulator, spit it out, open your airway gently (say "AAAAH" quietly to yourslef basically) and then ascend, you feel like you have an endless supply of air, because that breath you took is expanding on your way up. (That's part of recreational diving.. you can ascend from 30 meters on a breath of air and not get stressed out about it)
ars 13y ago
Completely survivable. It's really not that deep (breath hold free divers do it routinely), and any sickness he would have could be easily treated in a pressure chamber (most large hospitals have them). It's not necessary to get into the chamber instantly - symptoms don't start for 1 to 48 hours.
- thornjm 13y ago
  Free divers actually avoid the decompression problem altogether. They breathe in air at surface pressure, it compresses as they dive down, and uncompresses to the same size as they rise up. The air cannot bubble out of their blood. The problems arise when you breathe in high pressure air down deep and bring that air up with you.
  - AaronBBrown 13y ago
    While it is highly unlikely that a single free-dive would cause a symptomatic decompression injury, there is a high incidence of decompression-related injuries amongst free-diving fisherman due to repetitive and deep free-diving. The probability of decompression sickness occurring is related to time and depth. Here's a link that provides a number of references: http://www.thediveforum.com/dive-medicine/3706-long-term-physiological-impact-repetitive-frequent-free-diving.html http://www.thediveforum.com/dive-medicine/3706-long-term-phy...
  - damoncali 13y ago
    I don't think this is exactly true in extreme cases. You go down deep enough and weird things happen.
  - ars 13y ago
    That's actually not why they avoid the problem. It's a matter of time and volume - it takes time for nitrogen to dissolve and they are not down there long. And they only have a single lungful of air, so there is not a lot of volume to dissolve. But, if they do repeated dives, each one will dissolve more and more nitrogen until they do have problems.
wazari972 13y ago
At 30 meters the pressure is 4bars (10m of water a 1b plus the atm). Your lungs contains ~7l of air, so with Mariotte lawsm you've got: 7l4b = cte = 28l1b. This means that if you don't expire when you swim up to top ... your lungs will contain 28l of air ... and explode! That's a common diving danger, and the cook certainly didn't know it.
- anonymous 13y ago
  If only nature designed our lungs with a hole that can be used to fill and empty them, rather than the completely hermetically sealed ones we have!
  - Filligree 13y ago
    If you're holding your breath, which a naive swimmer likely is, then it's perfectly possible to rupture parts of your throat when the pressure differential grows too large. I'm not sure if that'd be fatal or not, but it'd definitely be dangerous. The pressure differential, in this case, was three times that between normal pressure and vacuum.
    - Symmetry 13y ago
      The pressure differential for vacuum isn't enough to be dangerous by itself. The dangerous thing about vacuum exposure is that at that pressure your blood will boil at body temperature.
    - damoncali 13y ago
      That's what they teach in diving class, but I've always wondered if the pressure wouldn't cause an impulse to exhale at some point?
      - dedward 13y ago
        Nope - the impulse to exhale comes from carbon-dioxide levels, not pressure in the lungs. You'll go from feeling fine to acute pain to very dangerous damage pretty much momentarily.
steve19 13y ago
A few weeks ago I was on a navy submarine. They explained the escape procedure and I asked how survivable it was. Apparently nobody has much faith in it, but its better to try than certain death by drowning. ... I did wonder how painful a fast ascent from the bottom of the ocean would be once the bends kicked in, but had enough sense not to raise this question with about a quarter of the crew in earshot.
- AaronBBrown 13y ago
  The insides of submarines are at roughly 1 BAR. Unless there is a breach of the integrity of the submarine and you manage to stay in a compressed air pocket for a sustained amount of time (unlikely, at best) prior to ascent, you will not have gas disolved into your tissues and thus won't get bent.
  - damoncali 13y ago
    No, but 1 bar air in your lungs can be quite a proposition at any significant depth. Not for the faint of heart.
    - jessaustin 13y ago
      Can you clarify what you mean by this? As I type this comment, I have about that density of air in my lungs, and it doesn't particularly trouble me.
      - ISL 13y ago
        One atmosphere in your lungs, ten atmospheres outside your lungs --> scrunch. For an approximate simulation, imagine what removing 90% of the air from your lungs might feel like.
        jessaustin 13y ago
        That's not how flexible containers work. In the presence of increased pressure, the guts press against the diaphragm, which compresses the lungs. I don't have to imagine what removing air from my lungs feels like: that is part of breathing! Anyway, this guy seems to do OK compressing his lungs even more: http://competition.the-french-job.com/spread-the-world-record/ http://competition.the-french-job.com/spread-the-world-recor...
damoncali 13y ago
It would be inadvisable if you were down there for any length of time, but survivable.
dedward 13y ago
30 meters is around the commonly accepted limit for recreational scuba diving. If you are diving you can take a breath of air from your regulator at 30 meters and then, keeping your airway open, ascend to the surface on a single breath. Because you are ascending, the air in your lungs expands as you go up, and you get to the surface with a full breath of air, even though you've been blowing bubbles all the way up. At 30 meters you limit your dive to 20 minutes... beyond that you risk decompression sickness. At 10 meters the limit is around 3 hours. In both cases, if you were down for a couple of days, you'd need decompression. The deeper you go, of course, the more dangerous it is as there is more dissolved gas.

by jlgreco 13y ago

fletchowns 13y ago

Probably not very survivable, given that they stuck the guy in a decompression chamber for 60 hours.

jlgreco 13y ago
Well yeah, but even a slight chance would be worth attempting if you were in such a position, even if it were just a 5% chance of survival, compared with the 100% chance they were probably shooting for with the 60 hour decompression. Of course if attempting it meant certain but excruciating death, then taking a shot at it would not be the way to go.
ars 13y ago
They left him in there for so long because he was in the water for so long. (i.e. plenty of time for nitrogen to dissolve). If he had swum up right away he would not need decompression. I imagine in the dark he would have been too scared of not being able to find the way out in the cluttered sunken vessel.
- jlgreco 13y ago
  He probably also didn't know how close to the surface he was.

Udo 13y ago

It depends on how long you've been down there. If you have just been dragged under water with your boat, it's probably safe to make a rapid ascent (don't hold your breath though) - in fact, diving school teaches emergency ascents for situations where no other options apply, even if the diver is in need of decompression. However, after about half an hour it becomes a serious problem that gets worse over time as gases start to infuse into the tissue. If rescue (and access to a pressure chamber) is available right away, I'd make that ascent immediately even after being down there for a longer time. It beats drowning or CO2 poisoning. Dive tables illustrate pretty well how the relationship between depth and time works: http://www.naui.org/tables.aspx http://www.naui.org/tables.aspx

simias 13y ago
Do you really have to pay attention not to hold your breath while ascending? I'd have thought you'd feel your lungs expanding and you'd have the reflex to let the air go away. Although on the other hand it's probably not a situation common enough for us to have evolved an inate reaction to it.
- Udo 13y ago
  Yes and no. If you relax your breathing apparatus, air will escape naturally. However, if you actively hold your breath, the mounting pressure can actually lead to a tighter block. Rapidly expanding lungs are not something that falls within the daily experience of most humans, so it's best to be aware of the complications. Especially when panic sets in (and the journey upward from 30m will be quite long) it can cost a lot of self control to force yourself to exhale.
  - jbri 13y ago
    Especially since if you're doing an emergency ascent, it's quite likely that it's due to having problems with getting air from your cylinder (if your air supply was fine, you'd probably be doing a controlled ascent instead). It's very difficult to avoid holding your breath when you know you won't be able to breathe in again until you reach the top.

arethuza 13y ago

The Royal Navy has a 30m deep "pool" (more of a water filled tower) that they use for submarine escape training: http://en.wikipedia.org/wiki/Submarine_escape_training_facility http://en.wikipedia.org/wiki/Submarine_escape_training_facil... So it must be fairly survivable.... Maybe it's staying for a long time at that pressure that causes the problem?

gaius 13y ago
They no longer use it - too many people were dying in the training, and modern submarines go much deeper anyway. If you want to have a go, you can go to Nemo33 in Belgium still.
- Timshel 13y ago
  The too many seems to be 2 death in 60 years with up to 4500 trainee a year during the 60s/70s. Cf : http://www.worldnavalships.com/forums/showthread.php?t=3787 http://www.worldnavalships.com/forums/showthread.php?t=3787 http://www.subescapetraining.org/History1.html http://www.subescapetraining.org/History1.html
Terretta 13y ago
Florida has inland freshwater springs with depths to 240 feet / 73 meters. I did my first deep water scuba cert in Ocala: http://www.adventuresunderthesea.com/scuba-class-information/local-dive-sites http://www.adventuresunderthesea.com/scuba-class-information... The deeper you go, the less time you can stay there before you have to control your ascent. Even a mild case of the bends can be excruciating, not something you can tough out: http://en.wikipedia.org/wiki/Decompression_sickness http://en.wikipedia.org/wiki/Decompression_sickness
dedward 13y ago
Time at pressure is the key, without question. The longer you breathe at pressure, the more time there is for gas (nitrogen, mainly) to saturate your system (until you are at equilibrium, anyway). Release the pressure, and it's like opening a can of soda... all that dissolved gas can't stay dissolved any longer. It takes time to get out of your system as you reduce pressure, so a gradual decompression is the only safe way out once you are saturated. In a typical submarine, air pressure is maintained at standard atmosphere, relying on structural integrity to keep all that pressure from crushing the ship. That means they can surface any time without risk. Another neat thing when diving is that if you are down at 30 meters, you can take a breath from your regulator, spit it out, open your airway gently (say "AAAAH" quietly to yourslef basically) and then ascend, you feel like you have an endless supply of air, because that breath you took is expanding on your way up. (That's part of recreational diving.. you can ascend from 30 meters on a breath of air and not get stressed out about it)

ars 13y ago

Completely survivable. It's really not that deep (breath hold free divers do it routinely), and any sickness he would have could be easily treated in a pressure chamber (most large hospitals have them). It's not necessary to get into the chamber instantly - symptoms don't start for 1 to 48 hours.

thornjm 13y ago
Free divers actually avoid the decompression problem altogether. They breathe in air at surface pressure, it compresses as they dive down, and uncompresses to the same size as they rise up. The air cannot bubble out of their blood. The problems arise when you breathe in high pressure air down deep and bring that air up with you.
- AaronBBrown 13y ago
  While it is highly unlikely that a single free-dive would cause a symptomatic decompression injury, there is a high incidence of decompression-related injuries amongst free-diving fisherman due to repetitive and deep free-diving. The probability of decompression sickness occurring is related to time and depth. Here's a link that provides a number of references: http://www.thediveforum.com/dive-medicine/3706-long-term-physiological-impact-repetitive-frequent-free-diving.html http://www.thediveforum.com/dive-medicine/3706-long-term-phy...
- damoncali 13y ago
  I don't think this is exactly true in extreme cases. You go down deep enough and weird things happen.
- ars 13y ago
  That's actually not why they avoid the problem. It's a matter of time and volume - it takes time for nitrogen to dissolve and they are not down there long. And they only have a single lungful of air, so there is not a lot of volume to dissolve. But, if they do repeated dives, each one will dissolve more and more nitrogen until they do have problems.

wazari972 13y ago

At 30 meters the pressure is 4bars (10m of water a 1b plus the atm). Your lungs contains ~7l of air, so with Mariotte lawsm you've got: 7l4b = cte = 28l1b. This means that if you don't expire when you swim up to top ... your lungs will contain 28l of air ... and explode! That's a common diving danger, and the cook certainly didn't know it.

anonymous 13y ago
If only nature designed our lungs with a hole that can be used to fill and empty them, rather than the completely hermetically sealed ones we have!
- Filligree 13y ago
  If you're holding your breath, which a naive swimmer likely is, then it's perfectly possible to rupture parts of your throat when the pressure differential grows too large. I'm not sure if that'd be fatal or not, but it'd definitely be dangerous. The pressure differential, in this case, was three times that between normal pressure and vacuum.
  - Symmetry 13y ago
    The pressure differential for vacuum isn't enough to be dangerous by itself. The dangerous thing about vacuum exposure is that at that pressure your blood will boil at body temperature.
  - damoncali 13y ago
    That's what they teach in diving class, but I've always wondered if the pressure wouldn't cause an impulse to exhale at some point?
    - dedward 13y ago
      Nope - the impulse to exhale comes from carbon-dioxide levels, not pressure in the lungs. You'll go from feeling fine to acute pain to very dangerous damage pretty much momentarily.

steve19 13y ago

A few weeks ago I was on a navy submarine. They explained the escape procedure and I asked how survivable it was. Apparently nobody has much faith in it, but its better to try than certain death by drowning. ... I did wonder how painful a fast ascent from the bottom of the ocean would be once the bends kicked in, but had enough sense not to raise this question with about a quarter of the crew in earshot.

AaronBBrown 13y ago
The insides of submarines are at roughly 1 BAR. Unless there is a breach of the integrity of the submarine and you manage to stay in a compressed air pocket for a sustained amount of time (unlikely, at best) prior to ascent, you will not have gas disolved into your tissues and thus won't get bent.
- damoncali 13y ago
  No, but 1 bar air in your lungs can be quite a proposition at any significant depth. Not for the faint of heart.
  - jessaustin 13y ago
    Can you clarify what you mean by this? As I type this comment, I have about that density of air in my lungs, and it doesn't particularly trouble me.
    - ISL 13y ago
      One atmosphere in your lungs, ten atmospheres outside your lungs --> scrunch. For an approximate simulation, imagine what removing 90% of the air from your lungs might feel like.
      - jessaustin 13y ago
        That's not how flexible containers work. In the presence of increased pressure, the guts press against the diaphragm, which compresses the lungs. I don't have to imagine what removing air from my lungs feels like: that is part of breathing! Anyway, this guy seems to do OK compressing his lungs even more: http://competition.the-french-job.com/spread-the-world-record/ http://competition.the-french-job.com/spread-the-world-recor...

damoncali 13y ago

It would be inadvisable if you were down there for any length of time, but survivable.

dedward 13y ago

30 meters is around the commonly accepted limit for recreational scuba diving. If you are diving you can take a breath of air from your regulator at 30 meters and then, keeping your airway open, ascend to the surface on a single breath. Because you are ascending, the air in your lungs expands as you go up, and you get to the surface with a full breath of air, even though you've been blowing bubbles all the way up. At 30 meters you limit your dive to 20 minutes... beyond that you risk decompression sickness. At 10 meters the limit is around 3 hours. In both cases, if you were down for a couple of days, you'd need decompression. The deeper you go, of course, the more dangerous it is as there is more dissolved gas.