[Meanings of the clinical parameters of airway hyperresponsiveness]

Clinically, threshold concentrations of agonist causing 20% decrease in FEV1 (PC20 FEV1) or 35% decrease in airway conductance (PC35Gaw) are usually used as parameters of airway hyperresponsiveness. In this session, what do these parameters mean was discussed based on theoretical analysis, experimental data and clinical observations. Theoretically, using these parameters, it seems very difficult to distinguish whether hyperresponsiveness is due to the change in sensitivity or maximum responses. Experimental and clinical observations suggest that these parameters are affected by multiple factors, for example, genetic vs. acquired factors and functional vs. structural factors. There may be differences in the degree of contributions of each factors on clinical parameters of airway responsiveness between asthmatics and control, and mild and chronic severe asthma. Clinically, considering such differences may be important in interpreting the changes of these parameters.