Bronchial component in chronic obstructive lung disease

Possible changes in the responsiveness of the airway to nebulized isoproterenol were studied in 69 patients evaluated retrospectively over an average period of 29 months and in 65 additional patients evaluated prospectively over a period of 6 months. Airway resistance (R_aw) decreased more than 15 per cent in 91 per cent of the patients studied retrospectively and in 97 per cent of the patients studied prospectively. Approximately 25 per cent of the group showed significant increases in vital capacity (VC) and maximum expiratory flow rate (EFR_max). Evidence of airway refractoriness was not observed. The variable physiologic response to isoproterenol suggests separation of patients into resistance-reactive, flow-reactive and vital capacity-reactive groups indicating differential response of the functional segments of the airway in chronic obstructive lung disease. Failure of EFR_max to increase after the inhalation of isoproterenol should not be taken as evidence of an unresponsive airway.