I'm going to assume you meant low air or high CO2.. perhaps I've read you wrong.
It is high CO2 that makes them gasp. If you hold your breath, it is high CO2 in your bloodstream, not low O2, that creates that "suffocating" feeling.
If you somehow created a low oxygen, low CO2 environment, your fish would drift peacefully off to sleep (and possibly not wake up). This is not easy to do, you'd probably need to be aerating the tank with nitrogen to do this.
Some fish naturally suck air at the surface, ie: gouramis and betas are labyrinth fish, so this is normal for them.
Last edited by mattinmd; 11-17-2014 at 01:32 PM.
Reason: added my assumption of OR not and.