Tests and diagnosis

By Mayo Clinic Staff

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In addition to asking questions about your symptoms, your doctor will conduct a medical exam. He or she will also order tests to assess your lung function and rule out other conditions that may be causing your symptoms.

Test of normal lung function

Your doctor will likely administer a spirometry (spy-ROM-uh-tree) test to assess how well your lungs function when you aren't exercising. A spirometer measures how much air you inhale, how much you exhale and how quickly you exhale.

After you do the test, your doctor may give you an inhaled medication to open your lungs (bronchodilator). You'll repeat the test, and your doctor will compare the results of the two measurements to see whether the bronchodilator improved your airflow. This initial lung function test is important for ruling out underlying chronic asthma as the cause of symptoms.

Exercise challenge tests

An additional test that enables your doctor to observe and assess symptoms is an exercise challenge. You will run on a treadmill or use other stationary exercise equipment that increases your breathing rate. This exercise needs to be intense enough to trigger the symptoms you've experienced. If needed, you might be asked to perform a real-life exercise challenge, such as climbing stairs.

Spirometry tests before and after the challenge can provide evidence of exercise-induced bronchoconstriction.

Alternate challenge tests

As an alternative to the exercise challenge, your doctor may use an inhalation test that simulates the conditions that would likely trigger exercise-induced bronchoconstriction. If your airways respond to these stimuli, then the test should produce virtually the same lung function you have when exercising.

Again spirometry tests before and after the challenge test provide information about changes in lung function. These challenge tests include the following:

  • Methacholine challenge, the use of an inhaled agent that interacts with certain smooth muscle cells in airways and results in bronchoconstriction
  • Eucapnic voluntary hyperventilation (EVH) challenge, inhaling a mixture of dry air composed of oxygen, carbon dioxide and nitrogen that simulates the exchange of air when breathing is difficult
  • Mannitol challenge, inhaling a dry powder that can trigger water loss on the surface of the airways and switch on molecular activity that controls inflammation — conditions that cause bronchoconstriction in people with oversensitive airways

Ruling out other conditions

Your doctor may order additional tests to rule out other conditions with symptoms similar to those of exercise-induced bronchoconstriction. These conditions include:

  • Vocal cord dysfunction
  • Allergies
  • Lung disease
  • Irregular heartbeats (arrhythmia) or other heart conditions
  • Gastroesophageal reflux disease
Oct. 25, 2014

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