Exercise Induced Asthma

Author：佚名 Source：none Hits：120 UpdateTime：2008-10-19 0:43:41


Exercise Induced Asthma (EIA) or Exercise Induced Bronchospasm (EIB) refers to asthma that occurs only with exercise. The reported incidence of EIA varies between 5 of the general population.

During start of exercise pulmonary functions tends to be normal, but within 5 to 10 minutes symptoms of asthma such as wheezing, breathlessness, tightness of chest appear. Patient may also feel extreme fatigue. After a rest period, the symptoms subside. But sometimes symptoms may become worse for a longer time.

Hyperventilation and airway cooling are the two most important triggers of EIA. People with exercise induced asthma have airways that are sensitive towards changes of temperature and humidity.

Hyperventilation during exercise is the primary event which causes cascade of events leading to EIA. Hyperventilation causes drying of the airway surface epithelium where by causing dehydration of the airway cells and increased intracellular osmolarity. The increased osmolarity results in the release of mediators from mast cells and damage airway epithelial. The mediators released during EIA include histamine, leukotrienes, cytokines, etc. All these events are called inflammatory reaction which is the root cause of asthma.

Other but less important cause of EIA is the airway cooling that is found with hyperventilation during exercise. During rest we breath through nose. Nose has a temperature and humidity control mechanism that makes air humid and at body temperature. When we exercise we breath through mouth, our respiration becomes rapid (hyperventilation). This forces cold and dry air into the airways. After the exercise is over, the small bronchiolar vessels around the tracheobronchial tree warm up, and this reactive hyperemia leads to exudation of serum into the interstitial fluid and release of mediators that subsequently causes airway muscles to contract and also walls of airways become inflamed resulting in narrowing of airways.

Following are the common questions often asked by people suffering from EIA:

How is EIA diagnosed?

Diagnosis of EIA can easily be made symptomatic. Person is usually normal before exercise. During exercise he experiences shortness of breath and/or chest tightness, wheezing, and cough.

After a period of rest , the symptoms subside. Some times symptoms such as prolonged cough after exercise, chest pain and fatigue may last longer.

The diagnosis of EIB can also be confirmed by a variety of tests, such as exercise challenge, methacholine challenge, or eucapnic voluntary hyperpnea. The International Olympic Medical Commission recommends any or all of these tests, but in most cases the eucapnic voluntary hyperventilation (EVH) test is the easiest to perform. If exercise challenge is to be performed, then this should be done in the athlete's sport.

"Pure" EIA and persistent asthma with an exercise exacerbation can be differentiated by spirometry. During rest if the forced expiratory volume in 1 second (FEV1) is not normal, patient is administerd an inhaled beta-agonist and test is repeated after 15 minutes. If the FEV1 improves 12 to 85% of maximum, four or five times a week.

What are the exercises that are more suitable for me?

Aerobic exercises like swimming, running or biking or which exposes the exerciser to warm, moist air that tempers the effect on the airways are more suitable for asthmatic patients.

Yoga may help manage asthma. Sahaja yoga is a type of meditation based on yoga principals that was found to be somewhat effective in managing moderate-to-severe asthma.