I'm asthmatic myself which has to do with allergies. I also used to be a heavy smoker so it is not surprising that same as yourself, lungs usually give out before legs. People who play wind instruments as well as singers, are taught to breath using diaphram muscles. It is astonishing to me that opera singers with no microphone can fill a music hall with their voice. Basically on the inhale, suck air down into the belly like a fat buddah. The diaphram plus intercostal muscles produce an increase in volume of the chest cavity that air then fills. I learned about the mechanics of breathing from a book "Yoga Anatomy" which has detailed explanations and illustrations of how it all works.