I have EIA and many times have ended up on the side of the road gasping for air. I've actually passed out while climbing on my mtb and woke up to a bunch of little kids circling me on their bikes saying "Is she dead??" After that, I had a profound fear of riding alone. That cut into my frequency of getting out and I figured I had to do something.
I found that taking Magnesium supplement on a daily basis helps with my asthma.
http://drsircus.com/medicine/magnesium/magnesium-asthma
I also will administer 2 shots of my inhaler 20 mins before riding. I was pleasantly surprised to learn that I can ride for longer times without any issues.