Abstract
Effective use of a dry powder inhaler (DPI) requires an optimal inhalation flow pattern. However, practical devices for providing instructions on flow pattern are currently unavailable. We recorded inhalation flow patterns through DPI's in 9 asthmatics (6 concurrently using Diskus, and 3 using a pMDI, -pressurized metered dose inhaler) using a new flow pattern visualizer (Visual Trainer) that displays time related changes in inspiratory flow.
Data acquisition and recording from a single DPI took 10 s, permitting ordinary clinical practice. Flows were classified into the following three patterns: an initial steep rise reaching a peak inhalation flow (PIFR) at < 0.6 s, followed by a gradual decrease with total inhalation time > 1.0 s / an initial steep rise with inhalation time < 1.0 s / an initial slow rise reaching PIFR at > 0.6 s with total inhalation time > 1.0 s. Inhalation patterns for Diskus and Turbuhaler use were evenly distributed among the three classifications. The PIFRs from Diskus tended to be higher than those from Turbuhaler in the same subjects. PIFRs using Diskus exceeded 60 L/min in all subjects, while 3 of 9 failed to reach this level using Turbuhaler. When inhaling from either DPI, PIFR appeared at > 0.6 s in 4 of 9 subjects. Inhaled volumes from Diskus were < 1 L in 3 of 9 subjects, and in 5 with Turbuhaler use. Both Diskus and pMDI users were included in the insufficient group.
In conclusion, patients using DPIs regularly do not always inhale with adequate flow patterns. The Visual Trainer may be a useful adjunct in the outpatient setting.
