To practice Buteyko breathing for sleep:
Sit in bed with your mouth gently closed (not pursed) and breathe through your nose at a natural pace, for about 30 seconds.
Breathe a bit more intentionally in and out through your nose, once.
Gently pinch your nose closed with your thumb and forefinger, keeping your mouth closed as well until you feel that you need to take a breath again.
With your mouth still closed, take a deep breath in and out through your nose again.
Many people don’t realize that they are hyperventilating. This exercise helps you to reset a normal rhythm of breathing.