4 ms·

>Of these, the no-limits category presents FDs with the greatest challenge as they descend using a loaded sleigh and ascend using an air balloon. I thought tha

>Of these, the no-limits category presents FDs with the greatest challenge as they descend using a loaded sleigh and ascend using an air balloon. I thought that ascending too quickly could lead to issues (if I remember House correctly, "the bends")? Or does that only occur at greater depths than a freediver would reach? This seems even more dangerous than normal freediving, which seems pretty dangerous as-is. (I know nothing about diving).

gosub100 2y ago
They're not breathing in compressed air at depth (which could then expand in their blood upon surfacing), just what they brought in from the surface.
- ethbr1 2y ago
  It's not breathing compressed air that causes the problem, but rather that the gasses in your lungs are pressurized at all + rapidly lowering pressure on your entire body on ascent. In freediving, the air in your lungs is still pressurized equally at depth to what it would be with scuba, so the same thing happens. In scuba, you do replace the amount of problematic gas in your lungs as you breathe, which potentially leads to higher body saturation (as you're not just exhausting what's in one single lungful). But that's more about gas interchange at all than pressure. If you spend long enough at depth, even without breathing, you run into the same problem.
stonemetal12 2y ago
The bends are caused by accumulated nitrogen dissolving in tissue\blood. No breathing, means no added nitrogen, so no build up. Also it is a somewhat slow process, no breathing means they aren't under long enough for it to develop even if they had extra nitrogen. It is a problem caused by Scuba, and the fact that Scuba does what it is supposed to, extend the time you can spend underwater, is what causes the bends.
- itishappy 2y ago
  > It is a problem caused by Scuba, and the fact that Scuba does what it is supposed to, extend the time you can spend underwater, is what causes the bends. To expand on this a bit (pun intended), freediving after SCUBA is extremely dangerous, and this even includes shallow stuff like snorkeling. SCUBA adds dissolved gas to your blood, but once it's there decompression from any source puts you at risk for the bends. Repeated dives will have additional safety limits imposed due to the residual gas, which is managed by a complicated series of dive tables or a modern dive computer. https://www.naui.org/resources/dive-tables-review/ https://www.naui.org/resources/dive-tables-review/
  - Ostrogoth 2y ago
    To further expound on why snorkeling and freediving after scuba can be dangerous, it is helpful to understand that the greatest gas compression occurs in the first 10 meters underwater (Boyle’s law). Scuba divers are trained to ascend slowly (~10m/minute) in order to off-gas expanding nitrogen (and other gasses) and prevent bubbles from forming in tissue (which causes decompression illness). After scuba diving the human body still has a much higher residual nitrogen saturation, so even fairly shallow (less than 10m) rapid descents/ascents in the water column can cause bubbles to form.
  - knodi123 2y ago
    I was told that I shouldn't go scuba diving the day before an early-morning flight, because if the plane decompresses, I could get the bends while everyone else just gets a little hypoxic and uses their handy drop-down O2 supply.
    - Ostrogoth 2y ago
      There is also an increased risk of decompression illness simply because passenger aircraft typically maintain a lower atmospheric cabin pressure (US federal limits pressure equivalent to 8,000 ft elevation). Going from a high pressure environment (underwater) to a low pressure environment (8,000 ft equivalent elevation in aircraft cabin) too quickly can also cause the bends. Dive computers use algorithms to calculate when it is safe to fly post-dive.
nick238 2y ago
Yeah, the "no-limits" with weights/bags is very dangerous. After a 240m/800ft free-dive, Herbert Nitsch had severe decompression sickness and needed a hyperbaric chamber[1]. I thought AIDA stopped tracking WRs for it because of the absurd risk, but all I can find is that they stopped doing competitions for it, though the article is dated 2011[2]. At least if you swim yourself down, you have time to listen to your body. Note that these depths are absolutely insane for anything an ambient SCUBA diver would do, even for many technical saturation divers. If you want an actual breathing gas mix for that depth, using a mix of hydrogen, oxygen, and helium[3] may be the safest way (too much helium can cause HPNS). [1]: https://web.archive.org/web/20121105083822/http://www.deeperblue.com/herbert-nitsch-receiving-treatment-after-failed-record-attempt https://web.archive.org/web/20121105083822/http://www.deeper... [2]: https://gulfnews.com/uae/a-limit-on-no-limits-freediving-1.827009 https://gulfnews.com/uae/a-limit-on-no-limits-freediving-1.8... [3]: https://en.wikipedia.org/wiki/Hydreliox https://en.wikipedia.org/wiki/Hydreliox
- mannykannot 2y ago
  Until reading the first article, I was unaware that one could get decompression sickness from free diving. The Wikipedia article on this dive also says that Nitsch passed out from nitrogen narcosis (and specifically not oxygen starvation) towards the end of the ascent, something else that I was unaware of being a risk (not that I have any intention of trying deep free diving.) https://en.wikipedia.org/wiki/Herbert_Nitsch#Later_attempt_and_serious_injury https://en.wikipedia.org/wiki/Herbert_Nitsch#Later_attempt_a... With regard to the hydreliox mix, I see it has a scant 0.8% oxygen, and needs to be less than 5% to avoid having an explosive mixture. Even the latter figure, I think, would lead to hypoxia in most people at atmospheric pressure, so I imagine these ratios are adjusted with pressure, and probably that these mixtures are only used in saturation diving.
  - nradov 2y ago
    Don't believe everything you read. While an extremely high PPN2 can cause unconsciousness due to narcosis, it wouldn't be possible to definitively identify that as the cause. There could have been something else going on physiologically. Hydreliox has only been used in a few experimental or scientific dives, mostly with saturation procedures but at least once by cave divers. (It's possible that militaries could have done some secret dives as well.) https://indepthmag.com/hydrogen-dreamin/ https://indepthmag.com/hydrogen-dreamin/
foxyv 2y ago
It does happen, but usually it's not a problem if they don't do it too often. The amount of nitrogen in a single breath of air is pretty small and their time at depth is very short. Repeated dives can increase the amount of dissolved nitrogen though. This can be a problem especially if they have a heart defect called Patent Foramen Ovale which allows bubbles to bypass the lungs directly into arteries heading to the brain. For instance, for a 140ft dive, the no decompression limit for SCUBA (The amount of time you can stay at that depth without making stops at shallower depths to remove nitrogen) is 5 minutes. The typical no limits free dive is 2 minutes. They do experience a mild case of the bends on every dive but never notice it because it's so minor. https://www.mayoclinic.org/diseases-conditions/patent-foramen-ovale/symptoms-causes/syc-20353487 https://www.mayoclinic.org/diseases-conditions/patent-forame... https://divetables.com.au/dive-tables/ https://divetables.com.au/dive-tables/

gosub100 2y ago

They're not breathing in compressed air at depth (which could then expand in their blood upon surfacing), just what they brought in from the surface.

ethbr1 2y ago
It's not breathing compressed air that causes the problem, but rather that the gasses in your lungs are pressurized at all + rapidly lowering pressure on your entire body on ascent. In freediving, the air in your lungs is still pressurized equally at depth to what it would be with scuba, so the same thing happens. In scuba, you do replace the amount of problematic gas in your lungs as you breathe, which potentially leads to higher body saturation (as you're not just exhausting what's in one single lungful). But that's more about gas interchange at all than pressure. If you spend long enough at depth, even without breathing, you run into the same problem.

stonemetal12 2y ago

The bends are caused by accumulated nitrogen dissolving in tissue\blood. No breathing, means no added nitrogen, so no build up. Also it is a somewhat slow process, no breathing means they aren't under long enough for it to develop even if they had extra nitrogen. It is a problem caused by Scuba, and the fact that Scuba does what it is supposed to, extend the time you can spend underwater, is what causes the bends.

itishappy 2y ago
> It is a problem caused by Scuba, and the fact that Scuba does what it is supposed to, extend the time you can spend underwater, is what causes the bends. To expand on this a bit (pun intended), freediving after SCUBA is extremely dangerous, and this even includes shallow stuff like snorkeling. SCUBA adds dissolved gas to your blood, but once it's there decompression from any source puts you at risk for the bends. Repeated dives will have additional safety limits imposed due to the residual gas, which is managed by a complicated series of dive tables or a modern dive computer. https://www.naui.org/resources/dive-tables-review/ https://www.naui.org/resources/dive-tables-review/
- Ostrogoth 2y ago
  To further expound on why snorkeling and freediving after scuba can be dangerous, it is helpful to understand that the greatest gas compression occurs in the first 10 meters underwater (Boyle’s law). Scuba divers are trained to ascend slowly (~10m/minute) in order to off-gas expanding nitrogen (and other gasses) and prevent bubbles from forming in tissue (which causes decompression illness). After scuba diving the human body still has a much higher residual nitrogen saturation, so even fairly shallow (less than 10m) rapid descents/ascents in the water column can cause bubbles to form.
- knodi123 2y ago
  I was told that I shouldn't go scuba diving the day before an early-morning flight, because if the plane decompresses, I could get the bends while everyone else just gets a little hypoxic and uses their handy drop-down O2 supply.
  - Ostrogoth 2y ago
    There is also an increased risk of decompression illness simply because passenger aircraft typically maintain a lower atmospheric cabin pressure (US federal limits pressure equivalent to 8,000 ft elevation). Going from a high pressure environment (underwater) to a low pressure environment (8,000 ft equivalent elevation in aircraft cabin) too quickly can also cause the bends. Dive computers use algorithms to calculate when it is safe to fly post-dive.

nick238 2y ago

Yeah, the "no-limits" with weights/bags is very dangerous. After a 240m/800ft free-dive, Herbert Nitsch had severe decompression sickness and needed a hyperbaric chamber[1]. I thought AIDA stopped tracking WRs for it because of the absurd risk, but all I can find is that they stopped doing competitions for it, though the article is dated 2011[2]. At least if you swim yourself down, you have time to listen to your body. Note that these depths are absolutely insane for anything an ambient SCUBA diver would do, even for many technical saturation divers. If you want an actual breathing gas mix for that depth, using a mix of hydrogen, oxygen, and helium[3] may be the safest way (too much helium can cause HPNS). [1]: https://web.archive.org/web/20121105083822/http://www.deeperblue.com/herbert-nitsch-receiving-treatment-after-failed-record-attempt https://web.archive.org/web/20121105083822/http://www.deeper... [2]: https://gulfnews.com/uae/a-limit-on-no-limits-freediving-1.827009 https://gulfnews.com/uae/a-limit-on-no-limits-freediving-1.8... [3]: https://en.wikipedia.org/wiki/Hydreliox https://en.wikipedia.org/wiki/Hydreliox

mannykannot 2y ago
Until reading the first article, I was unaware that one could get decompression sickness from free diving. The Wikipedia article on this dive also says that Nitsch passed out from nitrogen narcosis (and specifically not oxygen starvation) towards the end of the ascent, something else that I was unaware of being a risk (not that I have any intention of trying deep free diving.) https://en.wikipedia.org/wiki/Herbert_Nitsch#Later_attempt_and_serious_injury https://en.wikipedia.org/wiki/Herbert_Nitsch#Later_attempt_a... With regard to the hydreliox mix, I see it has a scant 0.8% oxygen, and needs to be less than 5% to avoid having an explosive mixture. Even the latter figure, I think, would lead to hypoxia in most people at atmospheric pressure, so I imagine these ratios are adjusted with pressure, and probably that these mixtures are only used in saturation diving.
- nradov 2y ago
  Don't believe everything you read. While an extremely high PPN2 can cause unconsciousness due to narcosis, it wouldn't be possible to definitively identify that as the cause. There could have been something else going on physiologically. Hydreliox has only been used in a few experimental or scientific dives, mostly with saturation procedures but at least once by cave divers. (It's possible that militaries could have done some secret dives as well.) https://indepthmag.com/hydrogen-dreamin/ https://indepthmag.com/hydrogen-dreamin/

foxyv 2y ago

It does happen, but usually it's not a problem if they don't do it too often. The amount of nitrogen in a single breath of air is pretty small and their time at depth is very short. Repeated dives can increase the amount of dissolved nitrogen though. This can be a problem especially if they have a heart defect called Patent Foramen Ovale which allows bubbles to bypass the lungs directly into arteries heading to the brain. For instance, for a 140ft dive, the no decompression limit for SCUBA (The amount of time you can stay at that depth without making stops at shallower depths to remove nitrogen) is 5 minutes. The typical no limits free dive is 2 minutes. They do experience a mild case of the bends on every dive but never notice it because it's so minor. https://www.mayoclinic.org/diseases-conditions/patent-foramen-ovale/symptoms-causes/syc-20353487 https://www.mayoclinic.org/diseases-conditions/patent-forame... https://divetables.com.au/dive-tables/ https://divetables.com.au/dive-tables/