# High psi effects on the body? **URL:** \ **Category:** Factual Questions\ **Created:** [September 17, 2006, 8:24am UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051 "2006-09-17T08:24:35Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Qwakkeddup](https://avatars.discourse-cdn.com/v4/letter/q/90ced4/32.png) [@Qwakkeddup](https://boards.straightdope.com/u/Qwakkeddup)\ **Post date:** [September 17, 2006, 8:24am UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/1 "2006-09-17T08:24:35Z")
Hello all. I have been reading (lurking) the SDMB for several years now. I have a pesky thought(s) running through my head that has been driving me nuts for about a month. When I google, I get lots of hits for altitude sickness, the bends, ect. I am hoping someone here is in the know or knows where I can look for a better chance of answering these questions. Boiled down to a nutshell… How many Atmospheres can the human body endure before needing mechanical assistance breathing? What would the “Crush Depth” beyond that be? How many feet below sea level would that come down to? A few facts that I have been able to look up. 1. -5000 feet below sea level in air equals just under 2 atmospheres. 2. The Deepest part of the world is around 7 miles in the Mariana trench. 3. I recall a History Channel show on the building of the Brooklyn(?) bridge and how the workers suffered some problems working under the water in huge structures that were sunk to the bottom of the river and pumped out so they could lay the foundations. I believe most of the problems were to do with depressurization though. So, How about it, any takers. BTW, this is purely a trivia type question for me. Just the fact that I formulated it and can’t find an answer on my own irks me to no end. I have spent probably 48 hours in the last couple of weeks googling and have come up with bupkiss. Thank you for any and all answers and I will keep my fingers crossed even though my typing may suffer. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [September 17, 2006, 9:28am UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/2 "2006-09-17T09:28:25Z")
The answer depends on what kind of gas you are breathing? Divers have different mixes depending on what depth they are going to, because each mixture has different problems and advantages/disadvantages - nitrogen, pure oxygen, helium etc. all act differently on the body under high pressure than under normal pressure. If you mean that the pressure would be too great to breathe in at all - my WAG is that, unless you are thrown out of a normal-pressure enviroment suddenly - you can have breathe normal as long as there is no pressure difference between your lungs and what you’re breathing. As for crushing - I would imagine (until somebody more knowledgeable comes along) that if the pressure is great enough to squeeze you flat (and you’re not wearing one of those full-body suits), then it would squeeze your whole body, not only the lungs. As for the workers - how long ago was that? Maybe they didn’t have the knowledge about using the right gases that we have now? If you want to read an interesting description of living in a deep-sea habitat, and the pressure/gas question, I found “Sphere” from Michael Crichton pretty entertaining. (Though I don’t know how accurate it is; it’s a novel, not a fact book; and there’s some story to wade through to get to the point.) ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [September 17, 2006, 9:41am UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/3 "2006-09-17T09:41:27Z")
[Here’s a wikipedia link for a start](http://en.wikipedia.org/wiki/Scuba_diving#Breathing_underwater) > [@](#): > > As one descends, in addition to the normal atmospheric pressure, water exerts increasing pressure on the chest and lungs - approximately 1 bar or 14.7 psi for every 33 feet or 10 meters of depth - so the pressure of the inhaled breath must exactly counter the surrounding or ambient pressure in order to safely and efficiently inflate the lungs. > > By always providing the breathing gas at ambient pressure, modern demand valve regulators ensure the diver can inhale and exhale naturally and virtually effortlessly, regardless of depth. … > > The diver must avoid the formation of gas bubbles in the body, called decompression sickness\* or ‘the bends’, by releasing the water pressure on the body slowly at the end of the dive. … > Nitrogen narcosis or inert gas narcosis is a reversible alteration in consciousness producing a state similar to alcohol intoxication in divers who breathe high pressure gas at depth. … > > …Oxygen toxicity or oxygen toxicity syndrome (also known as the “Paul Bert effect”) is severe hyperoxia caused by breathing oxygen at elevated partial pressures. The high concentration of oxygen damages cells. … > > \*This causes inert gases (mainly nitrogen), normally dissolved in body fluids and tissues, to come out of physical solution and form gaseous bubbles. … > > The original name for DCS (Decompression sickness) was caisson disease; this term was used in the 19th century, when large engineering excavations below the water table, such as with the piers of bridges and with tunnels, had to be done in caissons under pressure to keep water from flooding the excavations. Workers who spend time in high pressure atmospheric pressure conditions are at risk if they leave that environment and reduce the pressure surrounding them. > > DCS was a major factor during construction of Eads Bridge, when 13 workers died from what was then a mysterious illness, and later during construction of the Brooklyn Bridge, where it incapacitated the project leader Washington Roebling. ---
**Author:** ![Qwakkeddup](https://avatars.discourse-cdn.com/v4/letter/q/90ced4/32.png) [@Qwakkeddup](https://boards.straightdope.com/u/Qwakkeddup)\ **Post date:** [September 17, 2006, 6:10pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/4 "2006-09-17T18:10:41Z")
[QUOTE=constanze] The answer depends on what kind of gas you are breathing? Divers have different mixes depending on what depth they are going to, because each mixture has different problems and advantages/disadvantages - nitrogen, pure oxygen, helium etc. all act differently on the body under high pressure than under normal pressure. As for the workers - how long ago was that? Maybe they didn’t have the knowledge about using the right gases that we have now? [/QUOTE] For the first part, normal atmosphere at pressure. If you could go 7 miles below sea level in a normal atmospheric mix, would you be able to breathe without any mechanical assistance. Including anything to regulate your oxygen levels? Miners sometimes require filters because they are underground because of problems with methane and other gases. For the second part, I haven’t looked it up, but whenever the Brooklyn bridge was built, was just an example of what brought on the question. When you go too high, you require equipment to ensure you have oxygen, high altitude sickness, I am looking for the other side of that coin. I would assume at a certain depth air as we know it would take on different charicteristics. Thereby becoming unbreathable. I’ll abandon Crush depth for now as it may be confusing the point. ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [September 17, 2006, 7:24pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/5 "2006-09-17T19:24:37Z")
[QUOTE=Qwakkeddup] For the first part, normal atmosphere at pressure. If you could go 7 miles below sea level in a normal atmospheric mix, would you be able to breathe without any mechanical assistance. Including anything to regulate your oxygen levels? [/quote] Again, taking the simple [Wikipedia link](http://en.wikipedia.org/wiki/Nitrogen_narcosis) > [@](#): > > When breathing air, serious impairment due to narcosis starts at depths of about 30 metres (100 feet) or a nitrogen partial pressure of 3.2 bar. At depths of 90 metres (300 feet) or nitrogen partial pressure of 8 bar nitrogen narcosis leads to hallucinations and unconsciousness. Because normal air contains about 70% nitrogen and 20% oxygen. > [@](#): > > [Equivalent air depth](http://en.wikipedia.org/wiki/Equivalent_air_depth) is a commonly used way of expressing the narcotic effect of different breathing gases. Standard tables list conversion factors for narcotic effect: for example, neon at a fixed pressure has a narcotic effect equivalent to nitrogen at 0.23 times the pressure, so in principle it should be usable at four times the depth. Some gases have other dangerous effects when breathed at pressure; for example, high-pressure oxygen can lead to oxygen toxicity. Helium is the least intoxicating of the breathing gases, but it can cause high pressure nervous syndrome, a still-mysterious but apparently unrelated phenomenon. So the problems with normal air starts quite soon because the body reacts differently to the gases under pressure. You can’t breathe unpressurised gas for long: > [@](#): > > Early diving experimenters quickly discovered it is not enough to simply supply air in order to breathe comfortably underwater. As one descends, in addition to the normal atmospheric pressure, water exerts increasing pressure on the chest and lungs - approximately 1 bar or 14.7 psi for every 33 feet or 10 meters of depth - so the pressure of the inhaled breath must exactly counter the surrounding or ambient pressure in order to safely and efficiently inflate the lungs. > [@](#): > > Miners sometimes require filters because they are underground because of problems with methane and other gases. That isn’t related to pressure, but to the toxicity of those gases. > [@](#): > > For the second part, I haven’t looked it up, but whenever the Brooklyn bridge was built, was just an example of what brought on the question. Well, I’ll guess it was before the problem was known well enough to counter it, because with modern knowledge, suffering from decrompession sickness can be prevented. > [@](#): > > I would assume at a certain depth air as we know it would take on different charicteristics. Thereby becoming unbreathable. I’ll abandon Crush depth for now as it may be confusing the point. Yes, see the points above about oxygen becoming toxic and nitrogen acting like alcohol. ---
**Author:** ![Qwakkeddup](https://avatars.discourse-cdn.com/v4/letter/q/90ced4/32.png) [@Qwakkeddup](https://boards.straightdope.com/u/Qwakkeddup)\ **Post date:** [September 17, 2006, 9:08pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/6 "2006-09-17T21:08:09Z")
Ok, so now I think I am getting somwhere. Nitrogen Narcossis, for divers starts around 100 ft under water. 33ft under = approx 1 atmosphere extra pressure on the body. 100 ft under equals 3+ atmospheres approx. -5,000 ft = about 1 atmosphere in regular air. -15,000 would be a little under 3 atmospheres. ( I know sloppy math ) That does give me a range though. Breathing normal mix air at a dept of -15,000 on dry land could theoreticaly be the limit. below that you could need an air tank with tri-mix to limit nitrogen in your system. Since that is less than 7 miles that means walking the Mariana Trench in dry air without any equipment would still be improbable. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 17, 2006, 9:38pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/7 "2006-09-17T21:38:12Z")
> [@](#): > > 1. The Deepest part of the world is around 7 miles in the Mariana trench. Just a warning, here, to brace yourself for the inside jokes that are sure to crop up in this thread. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [September 18, 2006, 3:41am UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/8 "2006-09-18T03:41:50Z")
[QUOTE=Qwakkeddup] Hello all. I have been reading (lurking) the SDMB for several years now. I have a pesky thought(s) running through my head that has been driving me nuts for about a month. When I google, I get lots of hits for altitude sickness, the bends, ect. I am hoping someone here is in the know or knows where I can look for a better chance of answering these questions. Boiled down to a nutshell… How many Atmospheres can the human body endure before needing mechanical assistance breathing? What would the “Crush Depth” beyond that be? How many feet below sea level would that come down to? A few facts that I have been able to look up. 1. -5000 feet below sea level in air equals just under 2 atmospheres. 2. The Deepest part of the world is around 7 miles in the Mariana trench. 3. I recall a History Channel show on the building of the Brooklyn(?) bridge and how the workers suffered some problems working under the water in huge structures that were sunk to the bottom of the river and pumped out so they could lay the foundations. I believe most of the problems were to do with depressurization though. So, How about it, any takers. BTW, this is purely a trivia type question for me. Just the fact that I formulated it and can’t find an answer on my own irks me to no end. I have spent probably 48 hours in the last couple of weeks googling and have come up with bupkiss. Thank you for any and all answers and I will keep my fingers crossed even though my typing may suffer. [/QUOTE] The pressure differential between your lungs and the pressure pushing in on your ribcage can’t be very much. I stood on the bottom of a swimming pool with a snorkle tube about 8" long sticking out of the water a couple of inches and it was quite difficult to breath. That put my lungs on the order of 2.5’ below the surfact. That’s .08 atmospheres or about 1.1 psi differential pressure. As to crush depth, [free divers](http://en.wikipedia.org/wiki/Free-diving) have descended to depth of around 600 ft and that’s about 18.2 atmospheres or 267 psi. That must compress the air in the lungs to the same pressure. I can’t find any info on what the maximum air pressure without damage in the lungs would be. I suppose it could be tested on animals but that seems a little gruesome. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [September 18, 2006, 12:37pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/9 "2006-09-18T12:37:11Z")
> [@](#): > > . I recall a History Channel show on the building of the Brooklyn(?) bridge and how the workers suffered some problems working under the water in huge structures that were sunk to the bottom of the river and pumped out so they could lay the foundations. I believe most of the problems were to do with depressurization though. "Caisson disease is now thought to be the results of too rapid a decompression. Considering that they had huge numbers of workers going down and coming back up every day, and no knowledge or idea of the required decompression times, it’s amazing that more workers didn’t suffer from it. But it was widespread, and George Washington Roebling (son of Augustus Roebling, the original architect. GW succedded Augustus after the father died) was so crippled by it that he had to direct the building from his hotel room. See David McCulloch’s excellent book **The Great Bridge** on this. ---
**Author:** ![slaphead](https://avatars.discourse-cdn.com/v4/letter/s/e9bcb4/32.png) [@slaphead](https://boards.straightdope.com/u/slaphead)\ **Post date:** [September 18, 2006, 2:55pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/10 "2006-09-18T14:55:49Z")
[QUOTE=CalMeacham] "Caisson disease [/QUOTE] My brain is rasing some vague flags about bone necrosis/weakening due to prolonged working at pressure. No idea if this is related to facts or just too much coffee… I’m thinking your limiting factor is going to be [Oxygen Toxicity](http://en.wikipedia.org/wiki/Oxygen_toxicity). Presumably if you work out the lowest concentration of O2 you can breathe without dying and punch it into the formula for [maximum operating depth](http://en.wikipedia.org/wiki/Maximum_operating_depth) there will be some limit beyond which you can’t go without either suffocating from lack of oxygen or dying from toxicity. The table on that last link bottoms out at 523 metres - I believe the current scuba diving record is at something like 310 metres. ---
**Author:** ![Qwakkeddup](https://avatars.discourse-cdn.com/v4/letter/q/90ced4/32.png) [@Qwakkeddup](https://boards.straightdope.com/u/Qwakkeddup)\ **Post date:** [September 18, 2006, 5:52pm UTC](https://boards.straightdope.com/t/high-psi-effects-on-the-body/373051/11 "2006-09-18T17:52:38Z")
[QUOTE=Chronos] Just a warning, here, to brace yourself for the inside jokes that are sure to crop up in this thread. [/QUOTE] They wouldn’t really, would they???