Feo, I'm really glad to hear of your success regarding anxiety!
I've had anxiety attacks caused from deep breathing (immediatly) and from Buteyko breathing (hours later). Cohearent breathing, aka Heartmath seems to work best for me. Heartmath, ( I use the em wave device) has been a big help. But unfortunately I've been crashing and having anxiety issues lately. I think it may be linked to my supplements, so I'm taking a break from the vitamins.