Level of lung function also correlates with other factors known to be associated with bronchial responsiveness such as cigarette smoking and age. Finally, level of lung function and increased airway responsiveness may be related because they are both manifestations of chronic airway inflammation. Although the majority of patients with chronic obstructive lung disease have both asthma and reduced levels of lung function, the converse is not true. Many asthmatic subjects have normal levels of lung function but are impaired by virtue of other epidemiologic criteria listed in Table 3.
Degree of Bronchial Responsiveness
Because bronchial responsiveness is a defining characteristic of asthma, it is difficult, if not tautologic, to relate it also to disease severity. Population-based studies clearly suggest that subjects with increased bronchial responsiveness are more likely to have lower levels of pulmonary function and a greater occurrence of respiratory symptoms.
Clinical studies have yielded equivocal results regarding the relationship of airway responsiveness to asthma severity. Some investigators have argued that reductions in responsiveness are the principal aim of therapy. Studies have conclued that the level of airway responsiveness is related to asthma severity as measured by symptoms in the past year, variability in peak flow, and medication requirements. However, other studies have reported no relationship to symptoms.
Tags: Airway responsiveness, Asthma, bronchial responsiveness, lung function, smoking