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> The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate. > Unless you have something specific to correc
by aix1 5y ago
> The volume would decrease rapidly with depth but the available oxygen per breath would increase to compensate.
> Unless you have something specific to correct?
Firstly, how would you bring the highly buoyant bubble of air underwater, in a controller manner?
But let's say, for the sake of argument, that you could.
Even though the volume of the bubble would indeed decrease with depth (e.g. it would halve at 10m), the volume of each breath would remain roughly unaffected by depth. This is the reason scuba divers deplete their air supply faster the deeper they go.
The amount of available oxygen per breath is irrelevant. Even at sea level the exhaled air is about 16% oxygen (down from 21%). Giving the body access to more oxygen per breath won't make the air supply last longer[*].
[*] Interestingly, there's a point at which oxygen becomes toxic. The circumstances in which this happens is well outside the parameters of this discussion, however. https://en.wikipedia.org/wiki/Oxygen_toxicity#Underwater https://en.wikipedia.org/wiki/Oxygen_toxicity#Underwater
- lb1lf 5y ago> Even at sea level the exhaled air is about 16% oxygen (down from 21%). Giving the body access to more oxygen per breath won't make the air supply last longer[*]. -Incidentally, in the survival suits we wear when helicommuting in the North Sea contain a rebreather device - which is simply a small bag in the suit's lining with a mouthpiece and a valve. The idea is that when getting underwater is imminent, you take a few deep breaths. When you exhale into the bag, you can then draw the spent air back in for another gulp or two of air. The idea being that in a couple of breaths you'll either be in the clear or dead - so a couple of extra breaths is all you realistically need. (Ever the cynic, I suspect part of the reasoning behind it is to keep you busy and un-panicked in your last few seconds alive, but anyway...)
- Retric 5y agoI am not saying it’s practical or their going to spend time at significant depth. The utility might have been a simple game of who could stay under water longer. That said, spending noticeably longer at 5-10m with an air filled bag weighted down by stones is a very long way from oxygen toxicity or the bends. As to available oxygen, removal of CO2 is major limitation in the long term and that’s limited by partial pressures so having more available oxygen doesn’t help in the long term. However, the world record for holding your breath is 22 minutes on pure oxygen so if we are talking a 7 minute vs 12 minute dive CO2 is going to be irrelevant.