Specific Bronchial Hyperresponsiveness
Bronchial provocation studies are increasingly performed to establish specific causes of occupational asthma. Unlike the measurement of nonspecific hyperresponsiveness with histamine or methacholine, which is an exceptionally safe procedure, the measurement of specific bronchial responsiveness is potentially dangerous. There are 3 reasons for conducting such an investigation: to document a previously unrecognized cause of occupational asthma, to establish a specific etiologic diagnosis when this is in doubt, and finally, in circumstances when an individual is exposed to more than one potential pulmonary sensitizer.
The tests themselves are time-consuming and must be conducted with great care, in a hospital. It is advisable for the individual to be an in-patient during testing. A physician must directly supervise the provocation test itself, with full cardiopulmonary resuscitation facilities and adrenaline drawn up in a syringe available for immediate use. As other patients and staff personnel should not be exposed to the allergen being tested, the studies should be conducted in an exhaust-ventilated exposure chamber.
A variety of different methods for bronchial provocation testing have been described. Those allergens suitable for testing in solution may be nebulized according to standardized procedures so that reproducible amounts of allergen are delivered to the subject. Two different methods- have been widely used; both give acceptable results in terms of safety and reproducibility.