This will not work. Thanks to basic biology.
Putting a bag over your head forces you to re-breathe your own carbon dioxide instead of fresh oxygen, which ultimately kills you. However, your body tells you to breathe because of carbon dioxide in your blood. If you are re-breathing carbon dioxide, your brain will just scream louder and louder at you to get air. Eventually, you will panic and pull the bag off of tour head.
You need to have incredible willpower to be able to do this.