I got very close to passing out after hyperventilating in a squatting position for 30-40 seconds and then standing up quickly and blowing on my thumb. If I had hyperventilated for a minute I'm pretty sure I would have passed out.
But doing this with a rope around your neck would be tricky, because the placement of the rope is very important.
If you could make sure the rope is in the right position, it seems like a good method to me.