fainting during methacholine challenge

[lynaha]

I am a 58 yr old female, non smoker. I recently had a methacholine challenge after having a persistant cough for 6 months and having a pulmonary function test that was inconclusive for asthma.  Following the fourth dose of methacholine I felt some tightness in my chest and became very light headed during the spiromitry portion.  Following the fifth dose, I actually fainted briefly during the spiromitry and feel against the side of the of the booth.  After that, the albuteral was administered, and I again briefly lost consciousness during the spiromitry.  The nurse who administered the test said she had only had one other person "go out" on her in the 12 yrs. she has been doing this testing and that I scared the "begeebees" out of her.  The test was done in a large medical facility where this nurse does nothing else but administer these tests.  I felt that she really pushed me beyond my means during the spiromitry, but she kept insisting that I keep blowing!!!  My question is why did this happen to me and what does it mean?