That’s the point you pull out and try to focus on? “Humane” executions always had a medical backing for why it world work.
Then the you try to say “is the best way of execution I can think of short of explosives near the brain.” oh really that’s the best you can think of? Shows how flawed and warped your understanding of this is. If you honestly want to make it as quick and painless in pretty sure the French figured that out back in 1789. But Ya let’s blow up people’s heads with c4.