Science 411
Nicholas Heath
Effect of breathwork on stress and mental ...

To date, this is probably the most significant study ever published on breathing.

Science 411
Nicholas Heath
Influence of a 30-Day Slow-Paced Breathing ...

Fifteen minutes of slow breathing (6 breaths per minute) before bed for 30 days improves sleep quality and increases vagal tone.

Science 411
Nicholas Heath
Heart rate variability biofeedback in chronic ...

HRVB (and, hence, slow breathing) is a powerful adjunctive therapy for managing a wide variety of chronic diseases. To be effective, it should be practiced for a minimum of 10 min/day (but probably 20+ for best results—see next section). More broadly, this study supports using slow breathing at around 5-6 breaths per minute in people with chronic diseases.

Science 411
Nicholas Heath
Deep Breathing Practice Facilitates Retention ...

We can use slow alternate nostril breathing immediately after learning a skill to improve that skill's short and long-term retention. More broadly and simply stated, this study supports using ANB after a task for enhanced learning.

nitric oxide

A pilot study on the kinetics of metabolites and microvascular cutaneous effects of nitric oxide inhalation in healthy volunteers (2019)

For the first time, it has been shown that metabolites of inhaled nitric oxide enter the blood stream and are carried systemically throughout the body in forms that can convert back to bioactive NO. This provides a mechanism for how inhaled NO has distant effects.