Asthma without airway hyperresponsiveness to carbachol

Abstract

Generally, asthma is closely associated with hyperresponsiveness to bronchoconstrictor agents. However, we have observed three patients who initially had symptoms of asthma but no hyperresponsiveness. Responsiveness to carbachol was assessed by specific airway resistance (SRaw) measurement after bronchodilatators had been discontinued. The carbachol challenge was repeated 6-18 months later. Initially, no change in SRaw was observed after inhalation of 3 mg carbachol (cumulated dose). On the second occasion, carbachol responsiveness increased into the asthmatic range while the baseline values of SRaw were not different. Since we have used the SRaw measurement, the bronchodilatator effect of maximal inspiration is not the explanation for the failure to demonstrate hyperresponsiveness. These observations suggest that airway hyperresponsiveness is not a necessary condition for induction of asthma and symptoms of asthma may precede the appearance of airway hyperresponsiveness.