Membrane impermeable to $N_2$ but permeable to $CO_2$ and $O_2$?

I'm looking for a way to bypass the bidirectional diffusive gas exchange that happens in human alveoli, to allow aquanauts to breathe a standard Nitrogen-Oxygen air mix at very high pressures (up to 300 atmospheres) found in ambient pressure deep submarine habitats. Being able to use ambient pressure habitats at this depth would be great from a structural engineering standpoint, but nitrogen narcosis would be absolutely deadly so I'm wondering if anyone knows a way of stopping nitrogen from diffusing into the bloodstream.

I'm disregarding High Pressure Nervous Syndrome (HPNS) here, on the assumption that since whales have found a workaround, a similar sort of neurochemical alteration would also be viable in humans.

edit: A quick clarification on nitrogen narcosis vs HPNS.

Nitrogen narcosis is just one of a number of different gas narcoses, any inert gas will cause narcotic effects past a certain pressure as it diffuses into the brain and (as best eh boffins can tell) physically interfering with the process of chemical signaling in the brain. Thus replacing nitrogen with another inert gas (ie: helium) is a no-go.

High Pressure Nervous Syndrome on the other hand is not a function of breathing gas (there is some confusion about this, as the Wikipedia article refers to it as occurring with helium based breathing mixes, however subsequent research has revealed that it's actually something that occurs due to pressure distorting biochemical enzymes in the body, particularly in the nervous system. The best guess in the field of cetacean neurology right now (from what I can tell) is that deep diving whales use neurochemical transmitters that are less susceptible to this pressure induced distortion in function.

You can also assume that the relative concentration of atmospheric O2 and C02 in the high pressure habitat has been altered to create partial pressures equivalent to those at sea level - that is nitrogen makes up a larger overall percentage of the local breathing mix.

posted over 5 years ago

Algebraist‭

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