IMO Deep breathing is not the same as Overbreathing/hyperventilation. Deep breathing should be done in calm and controlled manner. There is no tension/stress in

IMO Deep breathing is not the same as Overbreathing/hyperventilation. Deep breathing should be done in calm and controlled manner. There is no tension/stress involved with Deep breathing as in hyperventilation. Deep breathing increases the amount of oxygen in the blood and brain. In my meditation practice I do 10-20 mins of Deep breathing and than the breath gets extremely shallow very easily after that. There is no need to hold or restrict the breath at that point. It naturally slows to 1-2 breaths per minute. Which induces great calmness.