Interesting… I will look into that. Part of Wim Hofs teachings include breathing with an extremely long exhale while humming which sounds related. I’ve heard of research showing that any type of breathing with longer exhales than inhales activates a parasympathetic response, calming you down.

I suspect you’re missing something important- not surprising since Wim is a really unclear teacher. The low oxygen and/or high co2 causes your body to panic and you are supposed to use that as a stimulus to gradually train conscious control of your heart rate and stress response and calm yourself down. This is where the benefit comes from, not the short term physiological panic itself, whose symptoms you are describing. In fact, those symptoms should go away entirely when you learn to calm the panic and consciously control your autonomic nervous system. This then also primes you mentally to be able to go into ice water, which is also a large stimulus to learn to calm, plus trains your brain to more easily jump into anything difficult. All of this takes months or years of consistent practice to gradually develop a relatively permanent sense of calm and internal strength among other things, and is really just a simplified form of tantric tummo meditation.

Then again, Wim Hof costs you $0 and laughing gas gets expensive.