This sounds like part of what I learned in biofeedback. A few years ago when TOS was first suspected I was given a prescription for biofeedback. It was a clinical psychologist who connected electrodes to me to monitor whether muscles were tensed or relaxed. She taught muscle awareness, relaxation techniques, and diaphragmatic breathing. She had me record some of the relaxation sessions so I could play them back later (not really hypnotism, more like visualization). My insurance covered it (minus copay). I attended either 6 or 8 sessions. Ultimately, it turned out I was already breathing diaphragmatically (likely from being an athlete). It was a good experience but ultimately didn't prevent the need for surgery.