Buteyko Breathing Technique

My boyfriend just started learning Buteyko (spelling?) breathing technique. It's aimed mainly at asthmatics, but according to the guy who came up with this, 90% of people over-breathe, typically breathe very shallow, or stop breathing for periods of time, then gulp for air to catch up, without realizing what we're doing. I know very little about it, but it's got something to do with the idea that the lungs are supposed to have a certain amount of carbon dioxide stored all the time, and that the average breathing pattern doesn't allow for that. It's a totally different technqique than the deep belly breathing thing they teach in yoga, etc., but my boyfriend thinks, based on what he has read and practiced so far, that it's a sound technique that makes a lot of sense, in terms of re-training your breathing patterns. He's a bodyworker and spends most of his time on this kind of stuff, so I tend to trust his opinion. I think when you breathe properly, it affects the whole nervous system, hormone/cortisol production, the fight-or-flight state that most of us chronically stressed out people are in, etc. Might be worth looking into! I'm going to start practicing it, myself, since my breathing is really bad.