This is probably the best form of execution possible. Your body doesn’t know that there’s a lack of oxygen, but it does notice a build up of carbon dioxide. Nitrogen poisoning is not noticable until you’re already “drunk” and falling asleep. That’s why it’s so deadly to divers.
That’s what we did, it just turned out that we were together for 7 years before everything fell in to place. We got out of college, got our careers in order, and bought a house. Then married the next year.