Investigative use of fibreoptic bronchoscopy for local airway challenge in asthma.

Local airway challenge has advantages over inhalation bronchial challenge as the response of the airway can be restricted and directly observed. It has been safely performed in subjects with mild or moderate asthma, either by the direct instillation of challenge solution to the selected segmental airways via a bronchoscope, or delivered to an airway segment isolated with a double-balloon catheter. However, these techniques carry potential complications, such as generalized wheeze, and due care is required in selection of subjects. Most investigators have used the method for studying the airway events following allergen challenge. Others have studied the airway changes following challenge with non-allergen provocation agents, such as hypertonic saline, adenosine 5'-monophosphate and cold dry air. The method has helped to define changes in the inflammatory cells and mediators in relation to early and late airway responses to allergen. Similarly, study of airway events following local challenge with hypertonic solution has provided useful knowledge in understanding the mechanisms of exercise-induced asthma. With more experience and an improved margin of safety, it will be possible to study local changes in airway physiology following local airway challenge. Finally, the techniques also have potential use for studying the airway events following provocation with a wide range of agents of potential relevance to the pathogenesis of asthma.