title: Differential effects of methacholine and antigen challenge on gas exchange in allergic subjects.
abstract: In order to better characterize the differential effects of nonspecific and specific (antigen) bronchial challenge on gas exchange, seven ragweed-sensitive subjects with a history of asthma underwent progressive inhalation challenge with methacholine and ragweed extract on two different days. For comparable severity of bronchospasm (mean specific airway conductance 0.05 sec-1cm-1H2O for methacholine and 0.06 sec-1cm-1H2O for ragweed), there was a greater decrease in mean arterial oxygen saturation after ragweed (4.7%) than after methacholine challenge (2.7%) (p less than 0.05). While this was not accompanied by differences in static lung volumes, the density-dependent index decreased by 19% after ragweed (p less than 0.001) but remained unchanged after methacholine challenge. These results suggest that a greater involvement of peripheral airways in the bronchospastic response is, at least in part, responsible for the greater decrease in arterial oxygen saturation after ragweed challenge.
mesh_terms: D000328:Adult; D000941:Antigens / Q000008:administration & dosage*; D001249:Asthma / Q000503:physiopathology*; D001985:Bronchial Provocation Tests; D005260:Female; D006801:Humans; D008297:Male; D008688:Methacholine Compounds / Q000008:administration & dosage*; D010101:Oxygen Consumption; D012129:Respiratory Function Tests; D014692:Ventilation-Perfusion Ratio
chemical_list: D000941:Antigens; D008688:Methacholine Compounds