What happens when you suffocate long enough to pass out?

[one_raven]

What happens when you suffocate long enough to pass out?
Let's say you had the self control to hold your breath long enough, or if you smothered yourself for long enough, to lose consciousness.

How long will the unconsciousness last if you weren't revived?
Will you wake up with a headache or some hangover-type symptoms (not an actual hangover, obviously, because you suffocated, not dehydrated)?
Could it do any permanent (or semi-permanent) damage provided that you don't crash down and break something?
What state of mind would you be in while unconscious? Similar to sleeping? Would you dream? Would you remember it?

On a related note...
What about other ways of forcing yourself into an unconscious state?
Such as doing that head-rush trick? (If you don't know, you stand bent over with your head down for a minute or so, then quickly straighten up to a standing position. If you do it right, you will lose consciousness. Good party trick )
How would the effects differ from asphyxiation?

 

[Monique]

You'd pass out because the lack of oxygen going to the brain. Once passed out, normal breathing happens again, oxygen levels rise and a conscious state will be the result. Certain types of divers are able to hold their breath for an incredibly long time when they try to set record depths without the supply of oxygen. There are people with sleep apnea, where due to an obstruction in the throat have trouble breathing while asleep. It can happen that no breath is taken for 2 min, after they retreat out of their sleep state, take a breath and fall asleep again.

Why you ask this though, getting into kinky stuff? 500-1000 people die annually in the US because of auto-erotic asphyxiation.

 

[one_raven]

No, no kinky stuff at all.
(Thanks for the "just in case" warning, though)
Isn't that how Michael Hutchence died?

I ask for two different reasons, actually.
I have recently begun a type of meditation during which you don't breathe (you don't hold your breath, but it is a method of keeping the airways open and allowing air to pass freely) and I was just checking to see what concerns I may or may not need to address before getting to a place where I am in a state of altered consciousness and not breathing.

The other reason is that I have suffered with bouts of insomnia for a long time (since I was a kid) and always wondered in the back of my mind (but never really looked into it) what would happen if I was really tired, but couldn't sleep, and held by breath until I passed out. I was curious whether I would just stay sleeping until my alarm went off if I was tired enough when I did it.

 

[Monique]

Ok, well, I don't think meditating without breathing is a smart idea. Air doesn't diffuse that fast to say that keeping your airways open, it allows the air to pass freely. Rather I would look into a kind of meditation technique where you conciously slow down your rate of taking breaths and change the way how deeply you take them. By doing that you can slow down your heart rate, but it takes a lot of effort to get to the point where minimal breathing is required. The same with the divers I mentioned.. they probably spend 10-15 minutes modulating their breathing to a very slow and deep rhythm. By doing that their heart slows down to a very slow pace and also their metabolic activity must decrease. You can't just stop breathing.

And on the insomnia: I mentioned the sleep apnea example, from which it is clear that sleep is prevented at low oxygen concentrations. These people have a lot of trouble going into a deep sleep, they can sleep for 8 hrs and still be exhausted when waking up. Also, passing out is not similar to sleeping at all. It is an emergency measure the body takes to preserve the little energy that it left for basic survival. The body shuts down all the brain areas that are not required for survival: you pass out because of that. The brain stem this way is still able to regulate breathing, body temperature, heart beat etc. Sleeping is a state where the brain is still very active.