SITE OF ACTION OF IPRATROPIUM BROMIDE AND CLINICAL AND PHYSIOLOGICAL DETERMINANTS OF RESPONSE IN PATIENTS WITH ASTHMA

In normal subjects inhaled anticholinergic agents may have a preferential dilating effect on large central airways. Patients (21) with asthma were studied to see if response to inhaled ipratropium bromide was related to the initial central or peripheral site of major airway narrowing. Of 21 patients with asthma, 14 increased their .ovrhdot.Vmax [maximum ventilation] > 10% after ipratropium, but when assessed by air and He/O2 flow-volume curves, responders and non-responders to He/O2 breathing were divided equally between those who benefited from the drug and those who did not. There were no significant differences in percentage improvement in .ovrhdot.Vmax between initial responders and initial non-responders to He/O2 breathing. Furthermore, the results from air and He/O2 flow-volume curves suggest that, contrary to some previous reports (not in asthmatics), inhaled ipratropim has a generalized action throughout the airways. There were no differences in severity of airflow obstruction, nor in age, sex, smoking history or atopic status between those who benefited from ipratropium and those who did not. Those improving after the drug had a significantly longer history of asthma than those who did not.