Safety of one method of sputum induction in asthmatic subjects

To assess the safety of sputum induction in asthmatic subjects, we conducted a retrospective review of data from 351 sputum inductions in 78 subjects from our institution. The sputum induction protcol consisted of baseline FEV1, pretreatment with albuterol 180 micrograms, postbronchodilator spirometry 15 min later, the induction procedure itself (inhalation of 3% saline for 20 min), and postsputum induction spirometry. We found that sputum induction was usually well tolerated, although some subjects developed wheeze and dyspnea. Overall, 11 of the 78 subjects (14%) had a fall in FEV1 of > or = 20% from the postbronchodilator baseline ("excessive bronchoconstriction") during their first sputum induction (range: -20 to -69%); no subject developed refractory bronchoconstriction requiring hospitalization or emergency room treatment. Only one of the 54 subjects (1.9%) with a baseline prebronchodilator FEV1 > 80% had excessive bronchoconstriction, whereas 10 of the 24 subjects (42%) whose baseline FEV1 was < or = 80% predicted did so. The change in FEV1 during sputum induction was significantly correlated with the baseline prebronchodilator FEV1% predicted, the baseline postbronchodilator FEV1% predicted, the PC20 for methacholine, and the percentage of eosinophils in induced sputum. We conclude that 180 micrograms albuterol does not prevent excessive bronchoconstriction in all asthmatic subjects undergoing sputum induction, especially in asthmatic subjects with a low baseline FEV1. Pulmonary function should be monitored regularly during sputum induction in asthmatic subjects to monitor for excessive bronchoconstriction.