The pressure in your carbon dioxide cartidges are in the couple of thousands of pounds per square inch range. Atmospheric pressure is about 15 pounds per square inch, meaning, even if you go from sea level to outer space, you will only see about a 15psi drop in pressure.

So to answer your question, do you think your CO2 cartridge will mind holding in X,000 psi vs. X,015 psi?

Given this knowledge, one can also figure out whether one needs to "bleed off" the tires on a bike prior to loading on an airplane, regardless of whether the cargo compartment is pressurized.

Regardless, with air travel being such a hassle these days, it would be prudent to check with your favourite airline to determine if these are really air-transportable, even if they are technically so.