Airway responses to antigen challenge in allergic rhinitis and allergic asthma

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The density dependence of the maximum expiratory flow-volume curve, functional residual capacity (FRC), and specific airwav conductance (SG aw ) were determined before and during bronchial provocation with ragweed extract in 27 subjects with ragweed hypersensitivity and a history of either bronchial asthma (16 subjects) or allergic rhinitis (11 subjects). Mean baseline SC aw was significantly lower while mean volume of isoflow (V iso ) and FRC were significantly higher in subjects with bronchial asthma. During antigen challenge, 10 of 16 subjects with bronchial asthma (63%) and five of 11 subjects with allergic rhinitis (45%) showed a greater than 35% decrease in SG w (“reactors”); mean relative decreases in SG aw from baseline were 46% and 53%, respectively. The remaining subjects showed a less than 35% decrease in SG aw (“nonreactors”) with mean relative decreases of 9% (allergic asthma) and 6% (allergic rhinitis). Mean V iso increased in all subjects with bronchial asthma and in eight of 11 subjects with allergic rhinitis. A significant increase in FRC (6%) was seen only in the “reactors” with bronchial asthma. Following antigen challenge, the beta adrenergic agonist, isoetharine, increased SG aw and decreased V o . We conclude that in asymptomatic subjects with ragweed hypersensitivity, (1) central and peripheral airway function is more abnormal in subjects with bronchial asthma than in subjects with allergic rhinitis, (2) subjects of both groups show quantitatively and qualitatively comparable airway responses during antigen challenge with a decrease in SG aw or an increase in V iso , possibly representing increase in central and/or peripheral airflow resistance, respectively, (3) V iso may be a more sensitive indicator of airway response to antigen challenge than SG aw , and (4) the bronchodilator effects of a beta adrenergic agonist on antigen-induced bronchospasm are similar in both groups.