Yes, I suggest you look into the deceast Swami Rama for insight. He was observed at the Menninger Foundation in Topeka Kansas while he voluntarily stopped his heart.
The school he founded here in Minneapolis provided me with some valuable breathing instructions. I remember one and it was called Nadi Shodhan and it will show you how how to observe how restricted your breathing really is, hopefully not both nostrils, and how to relieve it Each nostril is predominant in breathing throughout the day and changing cyclically. You can check out there site, you may find it of some interest, and don’t forget your Neti Dish.
http://www.himalayaninstitute.org/