Capital & Coast DHB Respiratory Service
Bronchial Challenge (Provocation) Tests
This is a group of tests we do to see whether a person's lung air passages (the bronchi) are more sensitive than is normal. Over-sensitive bronchi are the problem in asthma and some other conditions. The ordinary breathing tests can be normal but if we provoke the bronchi with the right method the tests become abnormal as the air passages narrow down (called bronchoconstriction).
We can provoke bronchoconstriction in the right person either with a burst of exercise or by asking them to breathe in a substance that will have the irritant effect. The substances that can be used are:
- Methacholine, which is a chemical similar to the substance found naturally in the nerves of the bronchi. This is inhaled from a nebuliser in increasing amounts. We use this mainly to identify people with asthma.
- Hypertonic saline (salt water, a bit stronger than sea water) from a nebuliser. We use this especially in people who have had asthma in the past (but not currently) and who want to check that they are not running a high risk of trouble if they go scuba diving.
- Mannitol fine powder (a form of sugar) from a small inhaler device. This is not used by us at present but may be in the future.
- Some laboratories also use cold air for the same purpose.
- Exercise provocation tells us whether a person's shortness of breath after exercise is caused by asthma.
A number of factors may affect the bronchial challenge test results. The main one is inhaler medication, especially bronchodilators (e.g. Ventolin, Bricanyl, Combivent, Oxis, Serevent), cromoglycate (Intal, Vicrom, Tilade) and possibly antihistamines. Your appointment letter gives instructions on what to do if you are taking any of these medications. Also, acute viral infections, influenza and rubella vaccination can cause an increase in responsiveness to the test, so it is wise to call and reschedule your test if you are suffering with cold or flu symptoms, or have recently had a vaccination.