Exercise-Induced Bronchoconstriction: The New Guidelines

Laura A. Stokowski, RN, MS; Jonathan P. Parsons, MD, MSc


February 03, 2014

In This Article

Triggers and Risk Factors

Medscape: As we speak today, on the East Coast, it's 12°F outside. If I'm going to go outside and run today, what is it that might trigger EIB?

Dr. Parsons: It's not necessarily the temperature of the air; it's the humidity that really is a big deal. Typically, when it's really cold outside, the air is very dry. When you breathe relatively dry air compared with the air inside your lungs, sometimes it overwhelms the ability of your lung to humidify that air before it gets into the bottom of your lungs. It's the job of your lungs to get moisture into the air that you are breathing and to humidify it, because that's what your lungs need.

But if you're exercising outside in really dry air, the dry air overwhelms the ability of your lung to humidify it. Some of that relatively dry air gets down to the smaller airways of the lung and it irritates them, producing symptoms. If you went running out in the desert on a 90°F day when it was really dry out, you could have a similar phenomenon as if you were running in 12°F cold weather.

Medscape: Does it affect everybody?

Dr. Parsons: No, and if we knew why, we could probably prevent the disease itself from occurring. We don't know why it happens to certain people vs others, which is part of the big question with this diagnosis.

Moreover, sometimes the same person may be able to go out and run a half a dozen times in cold air and do fine, and then one time, for whatever reason, they have an episode provoked by cold air. Why it happened that time in that particular person is not clear.

Medscape: But EIB is more common in athletes, and so is that a risk factor that clinicians should be aware of? In particular, elite athletes or people who exercise every day -- should they be screened for EIB?

Dr. Parsons: That's a good question. There are 2 reasons that EIB may be more commonly found or more commonly diagnosed in athletes. One is that we have a higher index of suspicion in athletes. We are much more sensitive to it. By the nature of what competitive athletes are doing, we are more likely to look for EIB in a competitive athlete than in someone who is running on a treadmill recreationally.

The second reason is that simply by the laws of probability, competitive athletes are more likely to have an episode of EIB because they are exercising much more often than "normal" people. So the higher prevalence in athletes might be explained by the fact that they exercise more, and we look for EIB more.

We have looked at screening large populations of athletes and haven't found that it would be cost-effective, on the basis of the cost of testing, the risk for the disease, and the overall prevalence of the disease. Our studies to date don't support mass screening of athletes for EIB.


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