Singers with asthma ?

Hi everybody. If you have been following my posts you know that I suffer from asthma and a few weeks ago I had an attack that almost killed me. I have been singing as a form of excercise to strengthen my lungs. Were it not for the benefits I doubt I would be here right now. I am told that I do have a good voice which encourages me to keep going. Some days my asthma is so bad that I cannot hold a note for really any length of time. Are there any professional singers who have asthma and sinus problems? And if so how do you get around it?