[Significance of a negative inhalation test in chronic obstructive lung disease]

To assess the bronchospastic component in patients with chronic obstructive lung disease, measurement of vital capacity and forced expiratory volume (FEV) before and after inhalation of a beta-agonist is a widely used procedure. In a minority of patients this simple inhalation test yields a negative result, suggesting the possibility of unresponsive airways. The purpose of this study was to explore th significance of a negative test result by examining pulmonary mechanics in 17 patients before and after inhalation. The results permit the following conclusions: (1) A significant broncholytic action of a beta-agonist can be determined by measuring vital capacity and FEV. As a rule, a negative test cannot be attributed to the alleged insensitivity of spirometric measurements. For clinicla purposes, the more demanding determination of specific airway conductance is not necessary. (2) A negative inhalation test does not imply a pure emphysema with out peripheral airway disease, any more than it does irreversible bronchiolitis. All it proves is the unimportance of bronchiolospasm at the time of examination. The true role of a spatic component in the course of the disease, and the benefit of regular inhalations, can be assessed on the basis of repeated controls only.