Airway response to mannitol challenge in asthmatic children using impulse oscillometry.

Bronchial responsiveness to mannitol has been assessed using multiple forced expiratory maneuvers which are difficult for many children. We determined if responsiveness to mannitol can be assessed in children using effort-independent impulse oscillometry (IOS). Subjects with asthma, 8-21 years old, underwent a mannitol bronchial provocation test. IOS resistance (R5 and R20) values and FEV(1) were measured at baseline and after each dose of mannitol. The mannitol challenge was positive with a 15% fall in FEV(1) or a > or = 10% fall in FEV(1) between doses of mannitol. There was a significant correlation between the change in FEV(1) and the change in IOS R5. Subjects with a positive challenge had a mean decrease in FEV(1) of 18.4% +/- 5.9% had a mean increase in R5 of 34.8% +/- 15%. There was no significant change in R20. Subjects with a negative challenge had no significant change in FEV(1), R5, or R20 from baseline. Using effort-independent IOS to assess airflow obstruction with a mannitol challenge is a useful alternative to FEV(1) in patients that have difficulty with spirometry tasks. A > or = 25% increase in R5 indicates a positive challenge.