R2D Rebreather: Hypoxia and at what point would the damage be irreversible?

[Wrennie]

How long does it take for hypoxic brain damage to occur? Is it possible that irreversible damage could have already happened to you before the device succeeds at rendering you unconscious? I remember reading on a random medical website that 3 minutes without oxygen would be enough to cause irreversible brain damage, but it takes 3-7 minutes of being conscious while using the Rebreather before passing out. Does that mean that even if you decide not to follow through with it, if you've been breathing through the 'closed loop' for that specific amount of time that your brain would already be screwed? I had always been under the impression that the real damage started once consciousness was lost.

 

[Thanatonaut]

Simply put, if there's enough oxygen for you to still be conscious, you're not likely to experience brain damage. You might be in a closed loop, but there's still oxygen there for the time being. Really, the clock starts ticking on brain damage once you're unconscious.

 

[Wrennie]

Simply put, if there's enough oxygen for you to still be conscious, you're not likely to experience brain damage. You might be in a closed loop, but there's still oxygen there for the time being. Really, the clock starts ticking on brain damage once you're unconscious.

I truly hope that this is the case. I'd like to think you can back out at any point in time without consequence, at least until your consciousness is ultimately lost.

 

[Thanatonaut]

I truly hope that this is the case. I'd like to think you can back out at any point in time without consequence, at least until your consciousness is ultimately lost.

Now, if it kept you in a period of low oxygen a lot longer, say a couple of hours, there could be consequences. Think about the problems with hypoxia people run into on top of Mt. Everest. But really, I still don't have much faith in the DeBreather. If that's the route you're looking to go, I would go with a nitrogen exit bag setup. It's faster and more reliable.

 

[Wrennie]

Now, if it kept you in a period of low oxygen a lot longer, say a couple of hours, there could be consequences. Think about the problems with hypoxia people run into on top of Mt. Everest. But really, I still don't have much faith in the DeBreather. If that's the route you're looking to go, I would go with a nitrogen exit bag setup. It's faster and more reliable.

I personally have zero faith in my ability to construct an exit bag. I know I'd mess up somehow. I'm aware that the Debreather hasn't been available for very long and there haven't yet been any user accounts of experimenting with the newly released version to verify whether the design modifications improved its efficacy. I'm just going to wait until there's some more documentation before I invest in purchasing one. Thankfully it's affordable.

 

[Wrennie]

I emailed Richard Avocet about my concerns regarding hypoxic brain injury and this was his response:

Two aspects to address in your question: (1) You cannot suffer brain damage using the ReBreather unless you have already lost consciousness. If you are conscious after 5 minutes or more it is because your Oxygen level is still way too high to cause any damage, i.e., there is probably a leak somewhere. (2) If you lose consciousness using the ReBreather, the device is working as designed, and you will not regain consciousness unless someone intervenes to remove the mask (and you are able to be revived). Since death should occur within approximately 10-15 minutes of losing consciousness, that window of opportunity for intervention is really quite small.

Remember that you lose consciousness because the O2 level is too low to allow you to remain conscious. But that is just the first stage, because although you are unconscious you are still breathing. And each breath you take depletes and lowers the level of oxygen in the closed loop. Death is the result of the continuing decrease in O2 until you reach a point where life is not sustainable at such low levels of oxygen. That is when respiration fails completely and death follows quickly thereafter.

I hope this helps explain the process.

Best wishes,
Richard