I am currently researching the "Wim Hof Method" a big part of which is hyperventilation and breath-holding induced hypoxia.
In another answer on the topic on this site I saw the following study being mentioned:
This study apparently demonstrates brain damage in free divers and the brain damage is proportional to breath-holding times.
Of course this study is small and has its limitations, but I am wondering what other data there is about voluntarily induced hypoxia and brain damage?
If done correctly, the Wim Hof Method should never cause you to faint, but doing it is on the edge of passing out. Some people suggest, that it is not possible to damage ones brain by breath holding, because before brain damage can occure the person faints and normal breathing resumes. However what data is there to support this claim? Surely, if you get yourself to pass out often enough it would lead to some kind of damage?
I have seen videos on youtube of people doing the excercise with an oximeter.
During the hyperventilation phase the saturation seems to be either stable or go up. At the retention (breath hold) phase the saturation sinks down to in some examples 50, which is right where one would expect to pass out.
What data is there, to help me understand if daily excercises like this are likely to cause brain damage?