The bronchoprovocation test is usually administered either at a physician’s office or clinic on an outpatient basis.

Just prior to the test, patients undergo pulmonary (lung) function testing with a spirometer (a device which records the patient’s breathing capabilities). This establishes a patient’s fitness for the bronchoprovocation test, and provides a baseline measure to which test results will be compared.

The key measure of bronchoprovocation testing is force expiratory volume (FEV). FEV is the amount of air exhaled forcefully in a sustained breath over a given period of time. Fitness for bronchoprovocation testing depends on the patient’s force expiratory volume at 1 second (FEV1). Patients who fail to meet threshold standards for good respiratory health are unlikely to be allowed to participate in the bronchoprovocation test. Some factors that may exclude a person from taking the test include:

• Decreased ventilatory function as a result of withholding medication
  
  
• Adults with FEV1 readings of less than 1.5 liters and children with FEV1 readings of less than 1 liter
  
  
• A response of 10 percent or more to the substance used to dilute the reactive substance

If a patient can take the test, the main form of testing is through exposure to histamine or methacholine (methacholine challenge test). A nebulizer (a device that breaks down liquid medicine into an aerosol mist) is used to deliver the “challenge” substance to the patient at intervals based on one of two methods:

• Two-Minute Tidal Breathing Method
  
  
  • The patient first will be exposed to a substance (usually saline) used to dilute the reactive substance. Two minutes later, another pulmonary test will be performed. No effect on the patient’s breathing capacity should be detected. In this way, the saline acts as a placebo, ensuring that emotional or psychological factors are not playing a role in any reaction that might take place to the “challenge” substance.
    
    
  • Next, the lowest dose of the testing substance – either histamine or methacholine – is introduced. After two minutes, another pulmonary function test is performed. If the patient’s FEV1 has not fallen by at least 20 percent, a higher dose of methacholine is introduced (up to a maximum dose of 16 milligrams per milliliter [mg/mL]).
    
    
  • If the test does not provoke a 20 percent decrease in FEV1, the patient is not likely to have asthma.
    
    
• Five-Breath Method
  
  
  • The patient is exposed to the testing substance and uses five deep breaths to inhale it.
    
    
  • A pulmonary function test is performed and the patient’s FEV1 is checked to see if it has fallen by at least 20 percent. If it has not, the test may be repeated with higher doses of the “challenge” substance (up to a maximum dose of 16 mg/mL).
    
    
  • If the test does not provoke a 20 percent decrease in FEV1, the patient is not likely to have asthma.
    
  
  

Individuals may experience a variety of complications during the test, including severe coughing, dizziness, light-headedness and chest pain. Patients experiencing discomfort or breathing difficulties at any point during testing should alert the technician who is administering the test. 

At the end of testing, a bronchodilator (a medication that expands the airways and improves breathing) will be given to the patient to reverse any constriction of the airways that has taken place. The patient will undergo one last round of pulmonary function testing to ensure that lung capacity has returned to normal. The entire testing process takes about 90 minutes.

Exercise challenge tests are similar to the basic bronchoprovocation test but add a component of exercise. The patient undergoes baseline pulmonary function testing before exercising on a treadmill or exercise cycle for about 10 minutes. The exercise should closely resemble the form of activity that most often triggers the patient’s symptoms. Once exercise concludes, pulmonary function testing is again performed. The process is repeated until either the FEV1 level drops by more than 20 percent, or 30 minutes elapse.