Help Advice on passing out/fighting SI

[february in alaska]

Sorry for spamming this forum lately haha, I need to get this right. The plan is to hang, and if all goes well my neck immediately, but I want to prepare in case that doesn't end up happening. I've heard all kinds of things for fighting SI or passing out beforehand, from xanax to hyperventilating to alcohol. The hyperventilating technique is sounding the most promising to me right now, can anyone speak towards that? Would that put me under long enough for the rope to do the rest of the work? I'm going to be standing on top, so passing out would make me drop automatically.