Trouble breathing when running...

SoDamnHungry

I can normally run 3 miles without too much trouble, but last night on the treadmill at the end of my second mile, I started to have serious breathing trouble. My chest was so tight it felt like I wasn't getting any air in at all. I ended up walking for a minute and then stopping altogether. Then I hopped on the bike for a slow ride since I was a little dizzy and when my heart rate drops really fast, I feel like I'm going to pass out (so I wanted to keep it up and lower it slowly). I was only planning to ride a couple of minutes until my heart rate was down, but suddenly I started feeling way better, and the breathing trouble went away. Has this happened to anyone? Did you figure out a cause? If it happens again I'll go to a doctor, but in two years of running on a semi-regular basis, this is the first time it's happened. Anyway, it was quite scary and I don't wish to repeat the experience.

A little background info:

-I have asthma. But I had just taken my inhaler beforehand, and after I stopped, I didn't even need to take my inhaler because it got better so quickly. It just didn't feel like asthma. No wheezing. (ETA:) Also, it's regular asthma, not exercise induced. Most of the time I'm fine when I work out because the endorphins open the airway. If I have trouble it isn't until after I'm done working out and cooling down.

-I also get really bad post workout hypoglycemia, but it doesn't set it until about half an hour after I'm done working out, and it never causes breathing problems. Just really bad nausea and a headache, which I prevent by quickly drinking a few ounces of juice after I'm done.

-The only difference from my normal running this time is that I was trying to take it easy, so I walked for two minutes after my first mile instead of just doing two straight miles.

_Waffle_

This sounds like some sort of asthma event to me. I've had some runs where I was a bit sick or out of energy but all I ever feel is that my heart rate is easily spiked and breathing is quicker but I never feel like I can't breathe. I really don't know what to tell you other than that. It doesn't sound normal to suddenly be unable to breathe. Normal is just running out of energy, feeling hot, high heart rate.