[Non-allergic factors of bronchial asthma]

The functional characteristic of all forms of asthma is the airway hyperresponsiveness to several stimuli. Airway hyperresponsiveness is always present in current asthmatics and can be also documented in some subjects during the symptom-free periods. The mechanisms of the spontaneous or induced increases of airway hyperresponsiveness are probably different from those responsible for stable airway hyperresponsiveness. The transitory increases in airway hyperresponsiveness are associated with an acute inflammatory response of the bronchial mucosa, whereas airway inflammation is not a constant finding in subjects with stable airway hyperresponsiveness. The mechanisms involved in the latter condition might be a functional and/or structural derangement of bronchial epithelium, a functional or structural alteration of airway smooth muscle or alteration in the function of the autonomic nervous system.