From a study on “The physiological effects of slow breathing in the healthy human“:

“Slow breathing practices have been adopted in the modern world across the globe due to their claimed health benefits. This has piqued the interest of researchers and clinicians who have initiated investigations into the physiological (and psychological) effects of slow breathing techniques and attempted to uncover the underlying mechanisms.”

I spend a hour a day (sometimes 90 min) on the meditation cushion and it’s pretty much just follow the breath. I experience both psychological and physiological benefits. My BP can drop as many as 15 points after a 15 minute session.

“While changes in the cardiovascular system can induce changes in respiration, the influence that respiration has on the cardiovascular system is reportedly stronger. Studies in healthy humans have found that controlled slow breathing, particularly at 6 breaths per min, is associated with an increase in fluctuations of both blood pressure and heart rate, compared to breathing at a typical rate.”

I average about four breaths per minute during a typical session.