@wdlindsy Did the state get its idea from sci-fi?!?
I’ve read so many sci-fi novels/stories that have nitrogen hypoxia as a painless way to suicide when unretrievably lost in space. The body supposedly recognizes hypoxia by buildup of CO2 in the blood/lungs; as long as you can expel CO2, you never realize you’re suffocating.
Regardless of how well-researched the author’s story is, it’s no basis for doing it for capital punishment.