We look for a 20% drop in FEV1 (amount you blow out in one second forced breathing) for a methacholine/histamine challenge test to be considered positive. This is not a geographic thing. Other measures can be used but are not standardised. The following is from UpToDate - an excellent reference text for multiple medical subspecialties and refers to methacholine and then to exercise challenge testing:

To interpret a bronchoprovocation challenge test, a graph is drawn plotting the fall in the outcome indicator (eg, FEV1 or SGaw) versus the concentration of provocational agent (show figure 2). The effective concentration that would have resulted in a given change in the outcome indicator is determined by interpolation. This dose of provocative agent, eg, provocative concentration for a 20 percent fall in the FEV1 (PC20-FEV1), is used to interpret the test.

DIAGNOSIS — Laboratory testing for EIB conventionally involves six to eight minutes of ergometer or treadmill exercise, sufficient to raise the heart rate to 85 percent of the predicted maximum. Spirometry is checked prior to exercise, and every ten to fifteen minutes thereafter. A test is generally considered positive if the FEV1 falls by 20 percent or more. (See "Bronchoprovocation testing", section on exercise challenge).

With respect to the mechanism FYI:

Minute ventilation rises with exercise. EIB probably results from changes in airway physiology triggered by the large volume of relatively cool, dry air inhaled during vigorous activity [6,7]. This is supported by the finding that EIB is attenuated when the inspired gas is more fully humidified and closer to body temperature [8,9]. The effect of large-volume dry air inhalation on airway surface osmolality may be the primary stimulus responsible for bronchoconstriction [10]. Other relevant observations regarding EIB include

You've misunderstood. Most people with EIA also have other asthma symptoms, a small percentage just have EIA. By definition they do have a form of asthma, but may lack any other of the usual asthma symptoms and don't have what most laymen would consider 'asthma'. Your symptoms sound like that group with "just" EIA, usual caution about internet advice being worth what you pay for it to apply.

Cheers

OK, I've only had a collection of tests where I was sitting comfortably in a warm room, and as far as I know, I do not have asthma according to those tests.

Is it possible that my results would be different if I were to go through those same tests while I was exercising?

Also, if I don't have asthma, or EIA, what else might cause me to cough for hours after exercise, hacking things up? What else might cause me to rasp and wheeze while I'm cycling? And most importantly why do I hyperventilate when I'm really exerting myself?

very intelligent and helpful talk here. i'm sure that a meeting of the minds has us experimenting with different triggers and situations. if science hasn't figured it out yet, then what hope do we have as the 'bike forum asthmatics club'

I am trying to respond without getting into personal medical advice...take it for what it's worth. In my patients where the methacholine challenge has been done and is clearly negative, yet symptoms persist and are suggestive, I would 1) Do a trial of asthma medication, especially those used before exercise (actually I often do this first off....) sometimes even of routine use 2) Do a supervised exercise test either a full cardiopulmonary test or a simpler version with spirometry before and after exercise, along with observation of symptoms during the test.

Your mileage may vary, every case is different and you can't practise medicine online....

...dredging up an interesting thread, with a bunch of good info...

If I recall correctly, food sensitivities are related to excersize induced anaphalaxis. Severe attacks will USUALLY occur after excercise. I could see how (milder) attacks could occur during extended excersize (cycling, crosscountry running etc). Particularly if a mildly sensitive individual eats a gluten rich diet (wheat for example) prior to, or during strenuous excersize.

I don't know if excersize induced asthma, and excersize induced anaphalaxis are synonomous.

Hey, lungdoc.

Out of curiosity, is it possible for someone to be unreactive to the methacoline/histamine challenge yet still experience reduced lung capacity when exposed to cold, dry air?

I've never had a problem with reduced lung capacity other than when exercising in cold air. One would think that since I live in the Atlanta area (insanely high pollen counts, high ozone levels, the works) that something else would set it off if I had asthma.

BTW - I've got my inhaler now, so I'll try it out on my next coolish ride.

I have had asthma since I was 2 years old.. atleast that is when they finaly diagnosed it as asthma. My son also has asthma they have not officioly diagnosed it him yet at 8 years old though. I was told once it was for insurance reasons, so they just call it bronchial spasms. This thread has alot of good information in it, foods and other allergies can severely effect asthma. So can the weather, right before it is about to rain my allergies act up I get the runny nose sneezing etc.. Definately alot better then I was younger. I grew up back east in Virginia I was sick for 6 months of the year. Now I live in SoCal and I have a true asthma attack about every 3-4 years since I have been here. I don't consider slight weezing coughing a asthma attack and I am not currently on any medication. It might be worth while to have a allergy test taken it's possible there is something in your diet or might be a outside influence that is effecting you rather then just the cold. Only thing I did not like is someone calling it a handicap.

I do notice that the cold will bother me a bit, but out here a cold day is 50 degrees.. When I was young 2-7 years old. I would have bad asthma attacks doctors tried to put me on IV's.. in bubbles etc.. I was young did not listen hospital told my parents to take me home and advised wrapping me up in a warm blanket and driving around with the air conditioning on.. I can't give a you a good reason why this helped but it did. Nice steamy shower also did wonders at times, I remember turning on shower hot all the way on and laying on the cold floor a few times ..

Unlikely (very small percentage of patients) but it is possible as I may have noted above. An exercise challenge can be done if needed. Some difference in sensation can be simply normal, I have no asthma yet if it gets cold enough e.g. minus 30, I will cough and have some reaction to air that is that cold.

I have an appointment with my doctor on Sept 3. It was the soonest that I could get in. I'll continue to ride as usual but will walk the tough hill where I had the problem.

A lot of information here.