Accuracy of three electronic monitors for metered-dose inhalers.

Background: Prior studies indicate that some devices used to monitor metered-dose inhaler (MDI) use are not accurate.

Objective: To assess the accuracy of the Doser CT (NEW-MED Corporation; Waltham, MA), the MDILog (Medtrac Technologies; Lakewood, CO), and the SmartMist (Aradigm Corporation; Hayward, CA) in a bench-top study.

Design: One, two, and four puffs of fluticasone propionate MDI (Flovent; GlaxoWellcome; Research Triangle Park, NC) were actuated twice daily for 30 days with two units of each device. The date and time of each actuation were recorded in a log and then compared with the output of the device. The percentage of doses recorded accurately was compared by analysis of variance.

Measurements And Results: The SmartMist was 100% accurate, while both the Doser CT and MDILog devices occasionally recorded spurious actuations. The Doser CT also had missed actuations after the counter had prematurely reached zero secondary to the spurious recordings. The accuracy (mean plus minus SD) was 94.3 plus minus 2.9% for the Doser CT and 90.1 plus minus 6.9% for the MDILog (p = 0.21). The dose regimen actuated and duration of use did not significantly affect accuracy.

Conclusion: All three devices are sufficiently accurate to monitor adherence in most clinical settings.