The use of expiratory forced flows for determining response to bronchodilator therapy.

Two hundred seventeen patients were studied before and after administration of isoproterenol by IPPB. In 35 patients, lung specimens were examined within 12 months after the study. Patients with elevated bronchial gland-bronchial wall ratio (Reid index showed significantly more improvement in forced expiratory flows after bronchodilator therapy, as compared to patients with normal Reid index. There was no difference in response to therapy in patients with emphysema of less than 20 percent, as compared to patients with emphysema of more than 20 percent. Patients with severe reduction in lung recoil pressure had lesser improvement after therapy in forced expiratory flows, as compared to patients with moderate reduction in recoil pressure or normal recoil pressure. In 39 patients inspiratory pulmonary resistance and forced expiratory flows were measured before and after therapy. In all these 39 patients, airway resistance showed comparable improvement regardless of the value for recoil pressure. The lack of response in expiratory flows is attributed to the increased collapsibilirv of the large airways and not to lack of response to therapy.