Asthma Subgroups: Exercise Induced Bronchospasm (EIB)

The most common phenotype (subgroup) of asthma is Exercise Induced Bronchospasm (IB). It affects upwards to 90% of asthmatics and 10% of non-asthmatics. Here is all you need to know about this subgroup. 1,3

Why did I call it EIB?  Traditionally, this subgroup of asthma has been referred to as exercise induced asthma. However, because it also affects non-asthmatics, and because it does not induce asthma (is not the root cause), many experts prefer to use the acronym EIB. 1,3

So, this should explain why you’ll see both acronyms used.

What is it? It’s when rapid breathing during vigorous physical exertion, such as running or aerobic exercise, triggers chest tightness, coughing, wheezing, and shortness of breath.  It’s exacerbated (made worse) when inhaled air is cold or freezing, such as during the winter months. If not controlled, it can force you to quit exercising and to rest, and it usually resolves within 20 minutes to an hour after cessation of exercise.

A few asthmatics have reported late phase asthma episodes that are not quite as severe as the initial episodes, although harder to control. It can last up to 24 hours. 4,5
Does it affect high endurance athletes? Yes. About 50% of cross country skiers have been diagnosed with EIB, along with 17% of winter Olympians, including swimmers and ice hockey players. 7,10

What causes it? Your nose humidifies and warms inhaled air to body temperature. When you are rapidly inhaling during exercise, it is not properly humidified and heated. This is exacerbated by the fact that many runners breathe through their mouths while running, as this is the path of least resistance for inhaled air, and your mouth is not as effective at humidifying and heating inhaled air as your nose.

When the air inhaled is not adequately humidified and warmed, cells lining airways loan some of their heat and moisture to warm and humidify this air. This, in turn, irritates these cells in such a way as to initiate an abnormal immune response where your immune cells release proinflammatory mediators such as histamine, leukotrienes, and cytokines. 5,6,10

White blood cells called basophils and eosinophils are recruited to airways and release more proinflammatory mediators. Studies show this can occur even in non-asthmatics, perhaps explaining why so many winter athletes develop asthma. EIB in swimmers may be due to repeated inhalation of chlorine fumes. 10

Proinflammatory mediators cause tiny vessels lining your airways to dilate and release some of their fluid, causing airway inflammation. They irritate nerve endings causing that itching or burning feeling. They cause smooth muscles lining airways to spasm and constrict, causing bronchospasm and shortness of breath. They tell goblet cells to increase sputum production, thereby making you feel even more short of breath.

This may also induce a late phase response. Some cytokines leave the airways to recruit more proinflammatory cells, and they come into contact with airway cells about 3-4 hours after you exercise and release their contents, which include more proinflammatory markers. This late phase, when it occurs, is less severe although harder to treat.

Another theory I’ve read about is that when the airways are rapidly cooled due to inhaling rapidly, or rapidly inhaling cool, dry air, this causes a “reflex parasympathetic nerve stimulation,” and this causes the airwacoly smooth muscles to spasm and constrict, causing asthma symptoms.7

Should you avoid exercise if you have it? Absolutely not. There is an enormous collection of studies showing the benefits of exercising with asthma, including the benefit of improved asthma control. So, most experts recommend all asthmatics, no matter how severe their asthma is, exercise on a regular basis. The good news is EIB can be treated and prevented.

What is the treatment? The best treatment involves working with your doctor and taking efforts to prevent it.  What this entails depends on whether you have asthma, and, if you do have asthma, how severe it is. If you do not have asthma, or you have mild asthma, you may get away with not taking any medicine, and simply warming up 10-15 minutes prior to exercise. It may also be beneficial to pace yourself while exercising, as opposed to running as fast as you can.

Many studies have confirmed the effectiveness of taking 2 puffs of albuterol just prior to exercise. Some benefit from taking Singulair every day, or just prior to exercise. For those with moderate to severe asthma, corticosteroids work to reduce underlying airway inflammation to make your airways less sensitive (less twitchy) during exercise. Combination medicines like Advair, Symbicort, Dulera or Breo work to reduce airway inflammation and keep airways open, thereby making it possible to exercise without it triggering asthma.

It’s also important to exercise indoors when the air outdoors is cold, such as during the winter months. Or, if you do have to go outdoors, wear a scarf over your mouth and nose to aid the warming and humidifying of inhaled air.

Everybody should exercise, especially asthmatics?  By working with your doctor, EIB can be controlled and prevented, allowing most people who have it to exercise. If you continue to be unable to exercise, then it’s important to consider alternative exercises, such as jogging, walking, swimming, Martial arts, biking, canoeing, kayaking, and biking.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The Asthma.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.
View References

Comments

Poll