5 ms·

The limits for other types of diving are interesting, too. All of the different gases you use for SCUBA diving have a maximum operating depth. At high pressure

The limits for other types of diving are interesting, too. All of the different gases you use for SCUBA diving have a maximum operating depth. At high pressures, various gases become toxic or cause side effects. Oxygen has a limit somewhere in the 1.2-1.6 bar range, and it becomes toxic. For deep dives, you need a lower percentage of oxygen in the mixture. Nitrogen causes nitrogen narcosis at higher pressures, so for deep dives, you need a lower percentage of nitrogen in the mixture. You need to add something else if you want to lower both nitrogen and oxygen, and that’s helium. At high enough pressures, helium causes high-pressure nervous syndrome, a.k.a. helium tremors. That’s normally the limit. Pretty much every gas is bad for you at these pressures. There is an experimental alternative, which is to use hydrogen gas for the deepest dives, but people are understandably cautious about breathing a mixture of oxygen and hydrogen.

VBprogrammer 2y ago
> people are understandably cautious about breathing a mixture of oxygen and hydrogen Wimps.
qayxc 2y ago
In principle liquid breathing is still an option. It's not great, but certainly better than oxygen + hydrogen.
- therein 2y ago
  Since we are talking about interactions with the nervous system, how do we go from the pressure at which these gasses were delivered to the alveoli to their behavior in the blood? I understand the practice GP is describing pretty well but when I try to simulate what is going on in my mind, it's not like these gasses are in gaseous form once they are in the blood. Are we just talking about the concentration that are reached because the pressure affects the diffusion gradient?
  - hbrav 2y ago
    You've got exactly the right image in mind: higher partial pressure of a gas in the lungs corresponds to a higher dissolved concentration of that species (H2, He, N2, O2, whatever) in the blood and tissue.
- nick238 2y ago
  Have there been any human trials of total liquid breathing? Hydreliox breathing has been tested a few times, and has the advantage that it's fairly compatible with existing technology (compressed air bottles, gas regulators, etc.). Yeah, it's hydrogen, hazardous to mix and handle, but so is acetylene, and that can explode all by itself if it's under too much pressure. Mess up the mix and you die, but if you mess up the mix for any breathing gas, you're pretty effed (the wrong N2/O2 mix can cause any of hypoxia, narcosis, seizures at various depths). Not many people have done a pure hydrogen/oxygen dive (vs. hydrogen/helium/oxygen), but from one who has on a rebreather: > “The first cautious sip of hydrogen just to activate the ADV was satisfying,” [Harris] said. Gas density was not subjectively improved, but Harris noticed an obvious benefit—the HPNS-induced hand tremors he typically experienced after 180 meters/590 feet disappeared. [1] [1]: https://indepthmag.com/n1-the-inside-story-of-the-first-ever-h2-ccr-dive/ https://indepthmag.com/n1-the-inside-story-of-the-first-ever...
  - qayxc 2y ago
    > Have there been any human trials of total liquid breathing? It's used on a somewhat regular basis in clinical settings (e.g. liquid ventilation). I'm not aware of any diving experiments, though. There might have been some classified military tests, but nothing official AFAIK.
    - nradov 2y ago
      Liquid ventilation has been used with some success as a salvage therapy for critically ill patients, especially preterm neonates. However, it carries serious risks of its own. And it requires an external mechanical pump to circulate the liquid; the human diaphragm isn't strong enough to move the liquid in and out. https://doi.org/10.5001%2Fomj.2011.02 https://doi.org/10.5001%2Fomj.2011.02 I think liquid breathing for human divers is going to remain science fiction forever. There just aren't any circumstances where it would make sense to do that instead of using an atmospheric diving suit (or an ROV).
      - shagie 2y ago
        In the realm of science fiction that has science... Timemaster by Robert L. Forward (who writes science papers with a plot - and that's a good thing). The main character wanted to get out to the asteroid belt in an accelerated time frame (not relatively accelerated but rather faster than the current slow methods) > "Sorry, sir," said Mary, the perky nose on her image twitching under her large glasses as she thought. "I'd be glad to turn over all the cable we've been making for the Mars rotovator, but by the time Bull's division could turn it into a cable catapult, you'd be there using the existing system." > "Can we push the gee limit higher?" asked Randy. > "Well... yes..." admitted Bull. "We have small express pods we use to send emergency cargo. We can accelerate those at ten times the normal three-gee launch acceleration and get them up to three hundred kilometers a second." > "How soon would that get me there?" asked Randy. > Bull, his fingers too large to operate a cuff-comp, pulled an hp pseudocray out of his shirt pocket, and did a short calculation. "Three weeks," he said. "But those capsules accelerate at thirty gees! You'd be squashed flat!" > Randy paused for a while as he thought. "I've read about deep-sea divers who survived at high pressures by breathing an oxygen-carrying liquid," he said. "If I floated in a tank of that, I could handle thirty gees easily." > Tony, Mary, and Bull each thought for a while; then all three nodded, although reluctantly. > "If I were you, I'd check with some medical and diving experts first," said Tony. "It could be hard on your lungs." --- Granted, that's science fiction and there are some real problems with that approach too... https://en.wikipedia.org/wiki/Liquid_breathing#Space_travel https://en.wikipedia.org/wiki/Liquid_breathing#Space_travel > Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15g to 20g. Extending acceleration protection beyond 20g requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. Effects will still be felt because of density differences between different body tissues, so an upper acceleration limit still exists. However, it can likely be higher than hundreds of G. > Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application. We're not at the point where we can launch at hundreds of Gs yet (and I'm not sure I would want them to be centripetal Gs initially either - that sounds very not fun) ... but when we get to the point were we want to launch a person into space in the direction of another planet at 10 or 20 or 30 Gs of initial acceleration, this is likely something to be revisited.
dylan604 2y ago
> people are understandably cautious about breathing a mixture of oxygen and hydrogen. That would be one heck of a case of indigestion. Maybe they can pre-mix it with the pink stuff. Maybe that explains the pink tint to the fluids in The Abyss??
- shagie 2y ago
  As an aside with the rat scene ... that wasn't special effects (though did have cuts). https://filmschoolrejects.com/the-abyss-breathing-fluid/ https://filmschoolrejects.com/the-abyss-breathing-fluid/ > The rat demonstration scene in The Abyss was unsimulated and used real-life oxygenated breathing fluid. Ed Harris, however, was tasked with pretending to breathe in his water-filled helmet. This was especially challenging during underwater shots, of which there were many. > ... > Supposedly, the only purpose for the cuts in the sequence was to avoid showing the rats defecating from panic. In total, the crew shot the scene five times with five different rats. Aftercare included holding the rats upside down to drain their lungs of fluid coupled with a vet visit. None of these efforts assuaged the concerns of the English censors, who cut the scene for UK distribution. https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 > Fluid breathing is a reality. Five rats were used for five different takes, all of whom survived and were given antibiotic shots by a vet. The rat that actually appeared in the film died of natural causes a few weeks before the film opened. According to James Cameron, the scene with the rat had to be edited out of the UK movie version because "the Royal Veterinarian felt that it was painful for the rat". James Cameron repeatedly assures that the rats used for this take didn't suffer any harm. --- Note that in https://en.wikipedia.org/wiki/Liquid_breathing https://en.wikipedia.org/wiki/Liquid_breathing the "Diving" section is under proposed uses. The human uses have been very limited to specific medical situations.
  - beAbU 2y ago
    I did not know about the rat breathing thing! I wonder if this was ever trialled on rats/mice in a more scientific environment prior to the movie, or do we as a species have the claim of a big scientific breakthrough in underwater breathing being done as a stunt for a movie.

VBprogrammer 2y ago

> people are understandably cautious about breathing a mixture of oxygen and hydrogen Wimps.

qayxc 2y ago

In principle liquid breathing is still an option. It's not great, but certainly better than oxygen + hydrogen.

therein 2y ago
Since we are talking about interactions with the nervous system, how do we go from the pressure at which these gasses were delivered to the alveoli to their behavior in the blood? I understand the practice GP is describing pretty well but when I try to simulate what is going on in my mind, it's not like these gasses are in gaseous form once they are in the blood. Are we just talking about the concentration that are reached because the pressure affects the diffusion gradient?
- hbrav 2y ago
  You've got exactly the right image in mind: higher partial pressure of a gas in the lungs corresponds to a higher dissolved concentration of that species (H2, He, N2, O2, whatever) in the blood and tissue.
nick238 2y ago
Have there been any human trials of total liquid breathing? Hydreliox breathing has been tested a few times, and has the advantage that it's fairly compatible with existing technology (compressed air bottles, gas regulators, etc.). Yeah, it's hydrogen, hazardous to mix and handle, but so is acetylene, and that can explode all by itself if it's under too much pressure. Mess up the mix and you die, but if you mess up the mix for any breathing gas, you're pretty effed (the wrong N2/O2 mix can cause any of hypoxia, narcosis, seizures at various depths). Not many people have done a pure hydrogen/oxygen dive (vs. hydrogen/helium/oxygen), but from one who has on a rebreather: > “The first cautious sip of hydrogen just to activate the ADV was satisfying,” [Harris] said. Gas density was not subjectively improved, but Harris noticed an obvious benefit—the HPNS-induced hand tremors he typically experienced after 180 meters/590 feet disappeared. [1] [1]: https://indepthmag.com/n1-the-inside-story-of-the-first-ever-h2-ccr-dive/ https://indepthmag.com/n1-the-inside-story-of-the-first-ever...
- qayxc 2y ago
  > Have there been any human trials of total liquid breathing? It's used on a somewhat regular basis in clinical settings (e.g. liquid ventilation). I'm not aware of any diving experiments, though. There might have been some classified military tests, but nothing official AFAIK.
  - nradov 2y ago
    Liquid ventilation has been used with some success as a salvage therapy for critically ill patients, especially preterm neonates. However, it carries serious risks of its own. And it requires an external mechanical pump to circulate the liquid; the human diaphragm isn't strong enough to move the liquid in and out. https://doi.org/10.5001%2Fomj.2011.02 https://doi.org/10.5001%2Fomj.2011.02 I think liquid breathing for human divers is going to remain science fiction forever. There just aren't any circumstances where it would make sense to do that instead of using an atmospheric diving suit (or an ROV).
    - shagie 2y ago
      In the realm of science fiction that has science... Timemaster by Robert L. Forward (who writes science papers with a plot - and that's a good thing). The main character wanted to get out to the asteroid belt in an accelerated time frame (not relatively accelerated but rather faster than the current slow methods) > "Sorry, sir," said Mary, the perky nose on her image twitching under her large glasses as she thought. "I'd be glad to turn over all the cable we've been making for the Mars rotovator, but by the time Bull's division could turn it into a cable catapult, you'd be there using the existing system." > "Can we push the gee limit higher?" asked Randy. > "Well... yes..." admitted Bull. "We have small express pods we use to send emergency cargo. We can accelerate those at ten times the normal three-gee launch acceleration and get them up to three hundred kilometers a second." > "How soon would that get me there?" asked Randy. > Bull, his fingers too large to operate a cuff-comp, pulled an hp pseudocray out of his shirt pocket, and did a short calculation. "Three weeks," he said. "But those capsules accelerate at thirty gees! You'd be squashed flat!" > Randy paused for a while as he thought. "I've read about deep-sea divers who survived at high pressures by breathing an oxygen-carrying liquid," he said. "If I floated in a tank of that, I could handle thirty gees easily." > Tony, Mary, and Bull each thought for a while; then all three nodded, although reluctantly. > "If I were you, I'd check with some medical and diving experts first," said Tony. "It could be hard on your lungs." --- Granted, that's science fiction and there are some real problems with that approach too... https://en.wikipedia.org/wiki/Liquid_breathing#Space_travel https://en.wikipedia.org/wiki/Liquid_breathing#Space_travel > Acceleration protection by liquid immersion is limited by the differential density of body tissues and immersion fluid, limiting the utility of this method to about 15g to 20g. Extending acceleration protection beyond 20g requires filling the lungs with fluid of density similar to water. An astronaut totally immersed in liquid, with liquid inside all body cavities, will feel little effect from extreme G forces because the forces on a liquid are distributed equally, and in all directions simultaneously. Effects will still be felt because of density differences between different body tissues, so an upper acceleration limit still exists. However, it can likely be higher than hundreds of G. > Liquid breathing for acceleration protection may never be practical because of the difficulty of finding a suitable breathing medium of similar density to water that is compatible with lung tissue. Perfluorocarbon fluids are twice as dense as water, hence unsuitable for this application. We're not at the point where we can launch at hundreds of Gs yet (and I'm not sure I would want them to be centripetal Gs initially either - that sounds very not fun) ... but when we get to the point were we want to launch a person into space in the direction of another planet at 10 or 20 or 30 Gs of initial acceleration, this is likely something to be revisited.

dylan604 2y ago

> people are understandably cautious about breathing a mixture of oxygen and hydrogen. That would be one heck of a case of indigestion. Maybe they can pre-mix it with the pink stuff. Maybe that explains the pink tint to the fluids in The Abyss??

shagie 2y ago
As an aside with the rat scene ... that wasn't special effects (though did have cuts). https://filmschoolrejects.com/the-abyss-breathing-fluid/ https://filmschoolrejects.com/the-abyss-breathing-fluid/ > The rat demonstration scene in The Abyss was unsimulated and used real-life oxygenated breathing fluid. Ed Harris, however, was tasked with pretending to breathe in his water-filled helmet. This was especially challenging during underwater shots, of which there were many. > ... > Supposedly, the only purpose for the cuts in the sequence was to avoid showing the rats defecating from panic. In total, the crew shot the scene five times with five different rats. Aftercare included holding the rats upside down to drain their lungs of fluid coupled with a vet visit. None of these efforts assuaged the concerns of the English censors, who cut the scene for UK distribution. https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 > Fluid breathing is a reality. Five rats were used for five different takes, all of whom survived and were given antibiotic shots by a vet. The rat that actually appeared in the film died of natural causes a few weeks before the film opened. According to James Cameron, the scene with the rat had to be edited out of the UK movie version because "the Royal Veterinarian felt that it was painful for the rat". James Cameron repeatedly assures that the rats used for this take didn't suffer any harm. --- Note that in https://en.wikipedia.org/wiki/Liquid_breathing https://en.wikipedia.org/wiki/Liquid_breathing the "Diving" section is under proposed uses. The human uses have been very limited to specific medical situations.
- beAbU 2y ago
  I did not know about the rat breathing thing! I wonder if this was ever trialled on rats/mice in a more scientific environment prior to the movie, or do we as a species have the claim of a big scientific breakthrough in underwater breathing being done as a stunt for a movie.