Here is a breathing exercise that 'the iceman' Wim Hoff recommends before getting in the cold bath or shower:
"In Becoming the Iceman, Wim Hof, in addition to gradual acclimatization, also advocates a specific breathing exercises:
Sit comfortably in a peaceful environment (bedroom, living room, back yard, in nature, whatever suits you). Then relax, consciously, and begin to breathe from the abdominal region, not too shallow, not too deep. Think of it like blowing up a balloon.Do this thirty times. Saturate the muscles and organs with extra oxygen. The goal is to let the oxygen saturate not only the lungs, but also all of the internal organs. It may feel like you are hyperventilating, but just remember that you have control.Whenever you feel saturation throughout your body, exhale completely (easy), then inhale until you can’t take in any more air (don’t force it), then exhale completely (easy) and hold your breath (easy).When the feeling telling you to breathe comes, it is because of the depletion of oxygen. At this point, you can inhale fully and hold it for ten seconds with lungs of air.When you complete that, you completed your first cycle!Repeat!
will keep you posted....