I deal with asthma also and my allergist has it well controlled. The suggestion to pay attention to breathing with the diaphram (post ?) is also right on. Even high altitude mountaineers do this. Additionally, I recently read an article, somewhere, that recommended breathing through the nose and gave many good reasons for doing so. I've been doing this for several weeks now even though I was sceptical. Usually I'm trying to maximize air intake. To my surprise, it works fine under almost all my climbing situations. The key though is still to draw air in with the diaphram and push it all out. This all takes a deliberate effort. I expect it to be even more effective in winter's cold dry air.