Inspiratory flow rate through a dry powder inhaler (Clickhaler) in children with asthma

Dry powder inhalers (DPIs) are increasingly being used to deliver drugs for the treatment of asthma. Both the aerosolization and delivery of the drug from a DPI to the lung are dependent on an adequate inspiratory effort from the patient, and it is well-known that the air flow achieved early in the inspiratory profile is important in determining particle size distribution from the inhaler. The present study assessed the peak inspiratory flow (PIF) generated through the Clickhaler DPI, and the early inspiratory flow at 150 mL of inspired volume (IF(150)), in asthmatic children. These measurements were made in a well-controlled setting, and two attempts were recorded to establish maximum achievement. Results were obtained from 57 children aged 6-17 years, showing a (mean +/- SD) best PIF of 60.5 +/- 18.7 L/min (range, 26.8-97.0). The mean PIF overall was 54.2 +/- 20.8 L/min (7.9-97.0). For children aged 6-8 years, the mean best PIF was 46.5 +/- 14.6 L/min (26.8-71.1); for those aged 9 years or more, it was >65 L/min (30.3-97.0). PIF values were unrelated to % predicted FEV(1) measurements. Best IF(150) (mean +/- SD) was 42.9 +/- 13.6 L/min (23.1-66.6) in children aged 6-8 years, and >55 L/min (28.0-86.4) for the older children, showing that high flow rates were achieved early in the inspiratory profile. These data indicate that children with stable asthma can generate adequate inspiratory flow rates to operate the Clickhaler effectively.